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gmcjetpilot
03-30-2008, 02:27 AM
In another thread "statistics" where brought up. It was implied Lycomings are falling apart and alternative engines are bullet proof, at least the bottom end. So I decided to look my self. The goal was to filter out as much as I could to find the number for LOSS OF POWER, for each engine type, Lyc, Subaru, Mazda, Chevy, Ford. The Mazda, Ford and Chevy are fairly easy to search since there are so few accidents. Subaru had the highest total accidents of the Alternative Engines, due to fleet size I assume.


Using the NTSB data I tried to find the answer. Of course fleet size and hours of utilization is hard to pin down. This is how I attacked it.

For the alternative engines I searched for the engine name and variations. Than I went through each probable cause to determine if the engine was the cause and what part.

I eliminated any Undetermined, WX, Pilot Error or Airframe issues, so if the math does not add up that is why.

For the Lycoming I could not just type that in. So I searched the reason or probable cause field with key words such as: Crankshaft, Connecting Rod, Rod Cap, Bearing - failure, fatigue and fracture. Than I went through the results and eliminated other engines and as with the alternative engines, undetermined, WX, pilot error and airframe. The data base seems to go back to 1985, although I searched back to 1970. So assume this is 22 years worth. If it was not in the database I did not included it. No claim of perfection her just a good broad swipe.

Accidents due to internal Engine Failure

Lycoming (all)
32 total accidents
17 crankshaft failure, fatigue & Fracture, 1 experimental
15 rod, rod cap, rod bolt, failure, fatigue & Fracture, 2 experimental

[Note: maintence or improper engine assembly, e.g., under torquing rod bolts was included. There where at least 6 due to improper maintenance or manufacture defect. 3 failures in Experimental's.]

Breaking the "32" down to just typical "RV" engines failure/fatigue/fracture:
360s 4 crank & 4 rod failure, fractures and fatigue - 8 total
320's 1 crank & 1 rod failure, fractures and fatigue - 2 total
235's 0 crank & 1 rod failure, fracture and fatigue - 1 total


Subaru
42 accidents
16 pilot error
8 Undetermined
18 total ancillary & mechanical failures:
12 Ancillary
1 Vapor lock
1 Cooling lines
1 Waste gate servo
2 Fuel / Pump failure
7 electical / ignition

6 mechanical
1 PSRU failure*
1 Bearing failure
1 Belt timing gear
2 valve train or exhaust valve
1 Connecting rod failure over temp
*Consider PSRU as part of the engine.

Chevrolet / General Motors
13 total accidents and (1) major engine failure, (2) fuel related and (1) reduction drive.
The following Chevy or GM engines used: 5-V8, 6-V6, 1-4 cyl, 1-corvair


Mazda
Total 7 accidents: (1) Cooling, (1) Lube System, (1) exhaust/prop, (3) Carb/Fuel sys


Volkswagen
36 total accidents: (2) cranks, (1) lube system, (3) Ignition, (3) Carb/fuel


Ford
Total 8 accidents: (1) Cool, (1) Lube external, (1) Ignition, (1) Fuel (carb ice)
(2) Model-A's, (6) V6

************************************************** *******

Totals - accidents due to core engine failure
Lyc 32 (11 for 235, 320 and 360's only)
Subaru 6
Chevy 1
Mazda 1
VW 3
Ford 0

The above ignored electrical, cooling, ignition, turbo, timing and fuel issues. Of the alternative engines, adding the electrical, cooling, fuel and misc, you would have this.

Total accident due to loss of power core + ancillary
Subaru 18
Chevy 4
Mazda 6
Ford 4
VW 9

The higher number for the Subaru & VW is no doubt related to a larger fleet size. It is clear that the ancillary items on alternative engines, electrical, cooling, fuel and misc cause more loss of engine power than rods and cranks. The VW had almost as many accidents as the Subaru, but most where undetermined, pilot or other.

This is not a PERFECT cut at it, only a broad brush approach. I could have missed other "core" causes of loss of power, but a good faith effort was made.

Of all the Lyc powered Experimental planes, there where only (3) hard engine failures.

I did not search for fuel issues, starvation, carb ice, vapor lock and so on with the Lyc but there are 100's of fuel related accidents, but I did not include fuel starvation or carb ice with any of the above.

The fleet size of the Lycoming and Continental is many times larger, 200 times (?) more than the alternative engine fleet, especially in the high performance fixed wing plane category.

There are 66 times more registered Lyc 320/360's than Subaru engines with the FAA and only 2 times the failures. HOURS FLOWN? I can only imagine that the Lyc flys more but that is hard to prove.

Do all the other Lyc's count in the statistics: 235, 290, 480, 540, 720 and radials count as well? There are near 65,000 to 80,000 Lycs on the books (I think) with the FAA, not including turbines. How many are flying I don't know, but the 80 core failures for all certified engines (Lyc, TCM, Frank, P&W, Wright.....) over approx 70 years is about one a year.

Many of the Subarus are the lower power E85's used on Gyrocopters, but you don't read about all engine failures in the NTSB database, since many just Gyro down; however many did make the list of 42 accidents for Subaru powered "planes".

It is safe to say Lycoming has no (or few) cooling lines, belt or electrical causes of power loss in the data base. Belts took down at least one or two Alt engine planes, since they drive "internal" timing or cams. I did not check the Lyc but belts tend not to be critical as in engines with a belt driven valve train.

Conclusion: Draw your own, But I don't see a systemic problem with Lycoming or Continental reciprocating lower end or valve train. Both Continental and Lycoming went through a Crank production QC debacle at one point in time. You can see from the data the Continental crank problem on the C210's, early 1990's, and on the Lyc, late 90's, when their crank issue appeared. There are a handful of crank failures due to manufacture defects. If not for this transient QC issue, there would be about 5 less crank failures. Some of the above crank/rod failures where due to prop strikes or poor maintenance clearly, a cause and affect. I did not remove them from the count. The lesson is proper maintence and overhaul.

Although my search only went to 1985 it included all the planes in service made before than till now. If you parse the data even further you will find may be a dozen real holly failures out of the blue or due to manufacture failures for ALL aircraft engines. That ain't bad. Against the fleet size and time in service (since 1960) that's acceptable.

Fleet size is hard to pin down but from a "FAA registered" data base got the following: Lyc 320/360's - 40,000 (at least 65k for all Lyc horz recips), Subaru - 609, Ford - 121, Mazda - 4 (sounds low), Volkswagen - 1,235, Chevy (none listed).

rv8ch
03-30-2008, 03:52 AM
Hi George,

Interesting and very valid analysis of the FAA data. One observation I would like to throw out there is that we all know that there are lots of engine failures that do not end up in the database.

Because of this, one could argue that we really don't have accurate numbers.

One thing is still clear to me - by far the main cause of accidents is the judgment of the pilot flying the aircraft.

David-aviator
03-30-2008, 07:26 AM
Interesting read, George. If anything it supports a conclusion that simple is better when considering a mechanical contraption like a general aviation aircraft engine. There are many old engines out there doing their thing very well year after year.

I am intrigued by and drawn to the Subaru engine because of its incredible design success in an auto but do wish it were a bit more KISS in an airplane. There are a gazillion electrons flowing to keep it humming and I keep hoping they all know where to go and what to do.

The difference from a magneto to the typical electronic ignition system in modern auto engines is fascinating. So far it has proven quite reliable - at least for me. The other systems needed to keep it running are getting more and more reliable also, so we just keep on doing it to to fix what is wrong and get it better. Same can be said for Lycoming over the years.

TSwezey
03-30-2008, 08:06 AM
Thanks for data George. As David stated KISS seems to be the key to reliable. Alt engines are not nearly as KISS as the Lyco. Will they be made 100 % bulletproof probably not. The best we can do is try to cover every angle that could possibly go wrong. If there are any failures find the problem and fix it. There are several potential areas of failure in my engine: Loss of electrical power, loss of coolant, loss of belt (not for timing but for the water pump), PSRU failure and computer failure. Only testing will truly evaluate how reliable these systems are. I plan to fly very conservatively for quite awhile.

rv6ejguy
03-30-2008, 11:11 AM
Wow George, you must have spent a few hours crunching that data! Very interesting.

I'm not quite clear on what you searched under , all or experimental but I spent about an hour counting 72 catastrophic failures in only 5 years by typing in only "connecting rod", searching all types and sifting the causal conclusions. I only counted the valid ones. I was surprised how many others were caused by improper assembly or bad maintenance- maybe 50%!:eek:.

My numbers don't agree with your's at all and at a quick glance again today, I only had to go back to Jan. 2006 to find 17 catastrophic failures caused by straight mechanical reasons. There were many others where an unexplained loss of oil during flight caused rod failures. I did not count any radial engine rod failures here. Failures were rods, cranks and valves.

There were 14 crank failures alone in the late '90s alone in the first Lycoming crankshaft debacle. I know of 3 catastrophic failures ( 2 broken rods and a jug separating from a cracked case- 2 Lycomings and 1 Continental) just on aircraft operating from my airport in the last 4 years. This is a very small sample and shows that there are a lot more than one of these happening per year fleet wide, in North America.

We can't blame the engine for failing due to overheating, lack of oil or poor maintenance/ overhaul procedures. As I sifted the stats, these came up again and again. This seems little different than the race car engine world. Some people just should not assemble or work on engines even if they appear or think they are qualified. Clearly some of the A&Ps doing work on engines are plain scary.

There are many ways to sift the data but I do agree with your basic conclusion that you are more likely to have a power loss condition using auto power than a Lycoming.

In 2008 so far, we've had 4 power loss accidents in RVs, 3 Lycoming and 1 Subaru. They do happen, stay up on your forced landing skills. The recent stat mentioned on VAF shows that a majority lose control after power loss. Keep the nose pointed down and don't turn back to the field unless you have a lot of altitude.

Jconard
03-30-2008, 11:42 AM
Ross,

Georges numbers would not include the Canadian stuff at all because the NTSB does not investigate those.

I am willing to assume that unreported accidents occure proportionally, hence eliminating that as a variable.

Not sure if georges numbers were restricted to the 320/360, but based on fleet size, I think they were, I believe the power outs you are describing are with the big sixes, based on your previous posts.

rv6ejguy
03-30-2008, 12:52 PM
Actually there are a number of crashes in the NTSB database which occur on foreign soil and no not even involve US registered aircraft. Not sure why that is. In fact, I stumbled on one yesterday that happened operating from our base where 3 were killed and a rod failure was the cause.

There are a number of other well publicized accidents where catastrophic failure was the root cause in other countries. The double engine failure on a Navajo in Australia a few years back comes to mind: http://www.warmkessel.com/jr/flying/td/jd/57.jsp

I too would agree that there are many other engine stoppages which go unreported and don't lead to an accident. This means there are a lot more happening than the NTSB stats show- all the more reason to be sharp with your engine out skills.

I'd also agree that there appear to be far more problems with high hp turbocharged six cylinder engines than 320/360 Lycomings.

TSwezey
03-30-2008, 02:18 PM
I believe the NTSB reports include any American made airplane regardless of its registry.

gmcjetpilot
03-30-2008, 02:52 PM
Ross, Not sure if georges numbers were restricted to the 320/360, but based on fleet size, I think they were, I believe the power outs you are describing are with the big sixes, based on your previous posts.Ahaa the usual brain trust responds, ha ha. :D Yea I am glad you enjoyed it. It did take time and I don't "own" it and feel free to add, comment or criticize. One piece of wisdom I'll parrot "It's only as strong as its weakest link." Clearly from the stats that weak link is the pilot, sorry to say. That includes just making the decision to take off with known issues. Clearly as pilots and builders we have more responsibility or I like to say control over our fate and our passengers fate.

No, the Lyc numbers where for ALL Lycs from 50hp (O-145 (http://www.prime-mover.org/Engines/Images/lycO145.jpg)) to 450hp Lycoming TIGO-541 (http://www.prime-mover.org/Engines/Images/tigo541.jpg)

But it is easy to break out the 235's, 320's and 360's. Breaking down the 32 total for all Lycs to typical RV Lycs:

360s - 4 crank & 4 rod failure, fractures and fatigue - 8 total
320's - 1 crank & 1 rod failure, fractures and fatigue - 2 total
235's - 0 crank & 1 rod failure, fracture and fatigue - 1 total
.
Total 11 out of the 32 for small disp 4 cyl Lycs

The stats are far from perfect. You have to than look at each one and evaluate the cause, such as prop strike, manufacturer defect, maintenance or the "surprise". The latter act of fate is more rare.

You could do some PhD thesis on NTSB statistics. There are holes in the data and accidents not reported for sure. For a broad brush I think it shows a few things.

One thing that jumps out is electricity is critical to planes that need it for the engine to turn. Not being sarcastic, but true right. There where 7 pwr loss events for the Subaru due to electrical wiring including one ECU going wacky. The other engines, VW, Ford, Chevy, Mazda all suffered at least one or more electrically related loss of power events (recorded). I suspect as more Lyc flyers go to dual electronic or FADEC, we'll see Lycs having electrical loss of power accidents.

Zero failures across the board would be nice but unlikely. For many reasons, regardless of the engine, zero failures is not likely. Safe to say, if starting with a good part, installed, flown and maintained properly your "statistics" improve drastically, provided you don't do a stupid pilot trick, which no pilot is immune from either.

++++++++++++++++++++++++++++++++++++++++++++++++++ +++++++++++++++++++++++++++++++++

BLAST FROM THE PAST? (pics from PrimeMover.Org (http://www.prime-mover.org/Engines/Pictures.html))

You want water cooled? 1,200 HP flat 12 cyl O-1230 (http://www.prime-mover.org/Engines/Images/lyco1230.jpg)

1,200HP not enough, two SO-1230's put into a "H" configuration thru a gear box for 2,300HP XH-2470 (http://www.prime-mover.org/Engines/Images/lycoh.jpg)

Still not enough liquid cooled power? How about the XR-7755 (http://www.prime-mover.org/Engines/Images/lycXR7755.jpg),
From 7,755 cubic inches (bore of 6.375", stroke of 6.75") and 7,050 lbs it gave 5,000 horsepower in 1944; 7,000 horsepower was the target. Nine liquid cooled in-line four cylinder engines about a common crankshaft. Two contra-rotating prop shafts. The camshafts each consisted of two sets of lobes. One set of lobes for takeoff, the other for economy cruise. The camshafts were shifted axially to switch lobe sets. 580 gallons of fuel per hour at takeoff power, BSFC of 0.43 at cruise. It was aimed for the B-36 but political pressures caused the B-36 to be fitted with the Pratt & Whitney R-4360 instead. Smithsonian's Garber facility has the last survivor. PIC (http://www.prime-mover.org/Engines/Images/xr7755a.jpg) and one more Picture PIC me in goggles (http://www.prime-mover.org/Engines/Images/xr7755b.jpg) (kidding not even born, but cool pic huh)
If there where as many GA planes as cars today or jets come later, you wounder what recip engines would have be developed for planes. It's fair to say from the highly experimental XR-7755 to the first O-360's and soon after 540's over a decade later, they knew how to make complicated engines. In the 1930's Lycoming was making supercharged water cooled V-12's (http://www.prime-mover.org/Engines/Images/Lyc1.jpg).

A new light weight version of the Continental O-200 (http://en.wikipedia.org/wiki/Continental_O-200) going back to the 1947 (C-90) is new again. It will be put into Cessna's first new GA plane, their C-162 LSA Sky catcher (is that a good name?). Can't they come up with something better (name and engine)? Apparently not. May be this still is a good configuration, flat 4 air-cooled direct drive?

What happened to CoolJugs (http://www.liquidcooledairpower.com/cj-techspecs.shtml)? Last I heard they had dyno and manufacturing vendor issues. But is it the inertia of air cooled engines that restricts new technology, or is it that new technology (current state) has not earned its way onto planes? Clearly going from air-cooled to liquid means finding a place for the radiator'(s). If there was some skin technology that would be good, but pressure loss from running long small tubes plus weight would be a challenge. Combing the heat exchanger and engine in one saves space and weight (ie air cooling). Of the liquid cooled engines there where 3 accidents from three different engines. It's not the core of the engine but its a factor like electrical.

Lycs in a way, indirectly have been taken down by cooling, by pilots overheating the engine and causing failures, even later failures from residual damage. If not causing outright failure, a Lycs life span is reduced by two things: inactivity and overheating. I think a car's reputaion is in part due to being driven daily and not overheated.

Clearly a Lyc is for trained pilots not "mini van soccer mom" (no offense) simple, turn the key and drive it. Some see the future aircraft engine as turn the key and drive, go to jiffy lube once twice a year, simple. Even jets need some care. Jets now have "FADEC" that protects the engine during start and operations. Early jets could be turned into melted junk very easy if the pilot did not watch temps like a hawk. Electronics can help, but total dependence is another issue. Jet engines can go into a fail-safe mode with less protection (ie "Jurassic" mode) but still run. Jets once started run on their own if supplied fuel. They can even suction feed with their own mechanical pump at reduced power. There use to be cables running out to the engine, now just wires? Progress or opening door to more or different problems? To me farm tractor technology has its charm. I love electronic gadgets, but I know they run on smoke and mirrors. If you ever burn up electronics what comes out? Smoke. Therefore smoke is the power that runs electronics. :D I know how electronics work, but I know how a push pull cable work even better.

May be they (Lyc) learned stuff in the 40's. It is clear before jets the P&W radials where and still are working well. Into the 60's most regional airlines had pistons and some are still winning races at Reno. I am amazed. Personally when it comes to furniture, I like modern, danish, not antiques. Actually antiques creep me out a little. But antique engines I love? Go figure....:D Pick your poison Gents.

rv6ejguy
03-30-2008, 04:21 PM
Ahaa the usual brain trust responds, ha ha. :D Yea I am glad you enjoyed it. It did take time and I don't "own" it and feel free to add, comment or criticize. One piece of wisdom I'll parrot "It's only as strong as its weakest link." Clearly from the stats that weak link is the pilot, sorry to say. That includes just making the decision to take off with known issues. Clearly as pilots and builders we have more responsibility or I like to say control over our fate and our passengers fate.


You could do some PhD thesis on NTSB statistics. There are holes in the data and accidents not reported for sure. For a broad brush I think it shows a few things. One is electrical is critical to planes that need it for the engine to turn. Not being sarcastic, but true right. There where 7 pwr loss events for the Subaru due to electrical wiring including one ECU going wacky. The other engines, VW, Ford, Chevy, Mazda all suffered at least one or more electrically related power loss events. I suspect as more Lyc flyers go to dual electronic or FADEC, we'll see some Lycs having electrical loss of power accidents.

Zero failures across the board would be nice but unlikely. For many reasons, regardless of the engine, zero failures is not likely. Safe to say, if starting with a good part, installed, flown and maintained properly your "statistics" improve drastically, provided you don't do a stupid pilot trick, which no pilot is immune from either.[/INDENT]



I agree with the electrical thing being the most likely cause to bring an auto conversion down and I stated this yesterday. My accident was caused by a bad Denso clone alternator and my inattention to monitor the charging system- so pilot error really. Second was my improper evaluation/ design of the electrical system, thinking that if the alternator failed, I'd notice it and land so why did I need a backup battery?

Lessons learned-

1. A low voltage light on the panel is useless in direct sunlight.

2. Install a backup battery just is case everything else goes wrong.

3. Install an aural warning device for low voltage.

4. Use only genuine Denso parts.

4. Pay attention, dummy.

I think we already saw a dual EI failure last year on a Lycoming RV didn't we? Luckily it turned out ok and does not appear in the NTSB database.

gmcjetpilot
03-30-2008, 04:52 PM
I agree with the electrical thing being the most likely cause to bring an auto conversion down and I stated this yesterday.As I said electronics are run by smoke and mirrors, and may be the work of dark evil forces? The push pull cable is divine farm tractor technology, easily understood by the dumb pilot, me. ha ha :D.

Yep if it takes electrons to turn the engine you better make sure you have it as much as gas. Like I said as Lycs go to FADEC or dual electronic ignition will see some loss of power with Lycs due to lack of electrons.

Even a Lyc with magnetos can benefit from all your wise advice. I agree with you, the low volt idiot light is a must have idiot light, may be second low oil pressure, than high temp (CHT or water) and may be low fuel pressure? The EIS4000 does all that and more of course, as many engine monitors do, which is "good" electronics. :D

(The problem with dumb idiot lights is they are on sometimes normally when all is well; with advanced engine monitor they can look at say RPM and suppress alerts, like lower oil pressure at idle. It idiot lights go on too much it's like the boy crying wolf, it gets ignored.)

The truth is pilots don't watch or scan system gauges like they should. From student pilot days I laughed at the small gauges across the panel or along the knee cap, well below the windscreen where you are suppose to look for traffic VFR. The accuracy of old gauges where also suspect, especially fuel gauges that "only read correctly when empty". Thanks! Cessna did have a low volt light but ironically it was kind of dim in bright light. So I joke when I say electronics is evil. Heck a J3 Cub had a cork with a wire in pooking up through the gas cap; much better than many fuel gauges I've seen.

All new jets have a EICAS (eye-cass) - Engine Indication Crew Alert System. If any thing goes wrong a BIG yellow alert light (some times red if warning) comes on with or with out an aural tone, beep or horn, depending on the level of importance. Even old ones had this in some basic form.

Jconard
03-30-2008, 08:54 PM
Did some research:

According to GAMA, last year and roughly the same for the last 5 years, the piston single GA fleet flew:

17 million hours. per year or 85 million hours.

So, assuming that each of the current 600 subaru powered craft alternate planes flew 100 hours per year (generous) thats 600,000 hours per year, sa 5 assuming that such a large number flew that frequently for the last 5 years, it would equal 3.0 million hours for the comparison period for sube power.

32 engine failures out of 85 million hours equals one failure in 26,562,500 fleet hours for certified single engine. (not including piston helicopters).

By the same token, 25 crash causing power failures for the subaru fleet equals one power failure leading to a crash in 120,000 hours fleet wide average.

This means you are 221 times more likely to suffer a crash caused by power failure with a subaru than with a certified engine. This is being very generous with the flight time for subes...my guess is that very few of the 600 get 100 hours per year, and this represents an assumption of double the flight time for the fleet.

Shall we calculate it for Egg who accounts for less than half the subaru fleet but more than half the crashes/failures?

rv6ejguy
03-31-2008, 12:41 AM
Did some research:

According to GAMA, last year and roughly the same for the last 5 years, the piston single GA fleet flew:

17 million hours. per year or 85 million hours.

So, assuming that each of the current 600 subaru powered craft alternate planes flew 100 hours per year (generous) thats 600,000 hours per year, sa 5 assuming that such a large number flew that frequently for the last 5 years, it would equal 3.0 million hours for the comparison period for sube power.

32 engine failures out of 85 million hours equals one failure in 26,562,500 fleet hours for certified single engine. (not including piston helicopters).

By the same token, 25 crash causing power failures for the subaru fleet equals one power failure leading to a crash in 120,000 hours fleet wide average.

This means you are 221 times more likely to suffer a crash caused by power failure with a subaru than with a certified engine. This is being very generous with the flight time for subes...my guess is that very few of the 600 get 100 hours per year, and this represents an assumption of double the flight time for the fleet.

Shall we calculate it for Egg who accounts for less than half the subaru fleet but more than half the crashes/failures?

I won't beat this one much more but there have been a lot more engine failures than 32 over the last 5 years and anyone who wants to sift through NTSB data can do it themselves. It is complete nonsense, not to mention incorrect math that a certified engine fails only every 26 million flight hours or even every 2.6 million hours. The turbofan manufacturers would love to have reliability like this.

There were 1798 forced landings in this period and you can bet at least 50% were caused by some engine malfunction. A quick search within the 5 years shows 278 engine failures, 144 rod failures and 195 power loss incidents mentioned.

gmcjetpilot
03-31-2008, 02:54 AM
I won't beat this one much more but there have been a lot more engine failures than 32 over the last 5 years and anyone who wants to sift through NTSB data can do it themselves. It is complete nonsense, not to mention incorrect math that a certified engine fails only every 26 million flight hours or even every 2.6 million hours. The turbofan manufacturers would love to have reliability like this.

There were 1798 forced landings in this period and you can bet at least 50% were caused by some engine malfunction. A quick search within the 5 years shows 278 engine failures, 144 rod failures and 195 power loss incidents mentioned.

Ross I don't know what you searched?

I tried to mach it and got 143 hits with ["connecting rod" and Lycoming] since 1985 or 22 yrs not 5 yrs. If I do 5 yrs I only get 44 hits. Many hits don't apply. I didn't read them all, but many are NOT connecting rod failures.

Some "hits" in the 143 have no reference to connecting rod failure at all. In the text it may say "connecting rod all check OK". In a another spot it the word failure appears. The search will flag it even though the rods are fine.

Ross you have to read the report. It's a good chunk to check. There may be some I missed, but of the 143, many are included in my 32 (now 49, see below). Even if my number is triple, it still will be a good failure rate based on hours flown. If we could only get pilots from running out of fuel and flying into bad WX.

I did see some lubrication failures, oil pump failures that should be included. There was an AD on sintered metal oil pump impellers +10 yrs ago. Oil pumps do fail than the engine fails. Even including lubrication failures, I still get a much smaller number.

[B]Here are some categories I didn't not look which should be in there.

Dropped valves? I did not account for them. They are "major internal parts"; Since 1985 there where 14 Lycoming valve failures, (1) experimental, (5) helicopters and (1) spark plug failure causing valve damage/failure (included). Of the (14), 360/320's accounted for (11). So the (14) goes to the (32) for a total of (46) big things causing loss of power.

Pistons? Only three found for Lycoming since 1985, two are marginal, more cause & affect like this PA-28R-200 (http://www.ntsb.gov/ntsb/GenPDF.asp?id=CHI84LA050&rpt=fi). Is improper assembly Lycs fault? There where two Experimentals with Lycs: Great Lakes (http://www.ntsb.gov/ntsb/GenPDF.asp?id=LAX96LA023&rpt=fi). The pistons fault? LongEz (http://www.ntsb.gov/ntsb/GenPDF.asp?id=SEA94LA125&rpt=fi). No reason given for the failure. One Rotax popped up, Piston - Failure. So the new total is 49.


************************************************** *******

Checking "LOSS OF ENGINE POWER" and LYCOMING for experimental only since 1/1/1985 brought back 39 hits.
I didn't check them all. A few where not Lycoming. Random checks showed many where fuel issues.

Checking "LOSS OF ENGINE POWER" and LYCOMING for ALL planes since 1/1/1985 brought back 333 hits.
Again a quick check, many accidents where caused by WX, Fuel, Pilot Error, Airframe and so on. A jet aircraft was in there so? I didn't have time to read & analyze them. Spot check showed many where covered in my original number. Also spot check showed loss of power due to Magneto. Some models of Lycomings had dual magnetos with a single drive. The gear sheared. Fortunately its an odd ball engine. Only RV's with 320-H2AD's need to worry about this. I don't think mags are a major cause of loss of power, but there is at least one.


************************************************** *******

Lets say triple my current 49, so 150 hard engine failures & power loss accidents (not running out of gas) for 20 years. Assume 85 million hours (for 5 years). 56,666 hours MTBF. I think its better than that but that is a number.

Using John C Conard's analysis idea, with my 150 approx hard Lyc failures, the Subaru is 8 times as likely to have loss of power than a Lyc. To be fair I got (18) Subaru related loss of power, and that includes all engine/systems; my Lyc loss of power is more towards major mechanical, although I multiplied it by 3 to cover my bets. The bottom line statistics is like herding cats. You can justify, rationalize and quantify the reasons many ways.

The "TRUTH" is the Lyc fleet is large flying lots of hours. Also reading the details of many power loss accidents, even though the engine broke, it is clear there where extenuating circumstances that where not the engines fault, like poor maintenance.


Lyc crankshafts & rods are NOT life limited. They have infinite fatigue life. High time Lycs have gone 7 overhauls & are still going, with the same crank & rods. As long as they spec out, they go back in. With that said, no Alt power plant has 20,000 hour of aircraft service. Lycs with 10,000 hrs on major rotating assemblies are common in fleet service. Valves are always replaced at overhaul.

I was focused on lower ends, crank failures, rod/rod cap/rod bolt failures, big stuff, which seems to be a reasonable approach. What is a failure to you, loss of power? Than the Subaru does fairly poorly if you include electrical failure and other things like belts and turbo servos, which I ignored. Compare apples and apples.

There's this mind set Lycomings are crude, failure prone by the Alt Eng camp. When a Lyc fails Lyc opponents report w/ some satisfaction. Lyc failure stories makes it on sites promoting a particular "alternative".

I grant you, no Subaru crank failures could be found, but I know there's more than the one PSRU failure. I consider the PSRU as part of the crankshaft. The prop drive is a major portion of the power plant, as is the Lycoming crankshaft. It's like driving a car, if your engine doesn't blow up but your transmission explodes & all 4 wheels fly off, you are done.

What does my O-360 crank and rods have to do with a Continental or Franklin crank and rod? You can throw the kitchen sink at it, tally any crank failure up against the Lycoming. Lets be realistic, they are rare when you take out prop strikes, spurious manufacture defects and improper overhaul. Based against fleet size, age and time in service, it's a rare event. We are talking about almost 100,000 engines over 60 years and countless pilots under all kinds of conditions.

Most accidents are due to pilots not Lycomings. Look at the AOPA data for GA accidents. Mechanical is a small part. So we agree to disagree. However the data is the data.

The exercise was worth it, because it belays the urban legend that Lycoming "bottom ends" or cores are not robust. Yes sometimes oil pumps fail (due to bad maintenance) which have caused a few engines to fail. Some see the data and get another view, like a rorschach test. Regardless which blots of ink one sees, some always see the same thing. Still the most likely failure is sitting in the pilots seat by a wide margin.

If the reason to not buying a Lyc is fear of major engine failure, that's faulty logic, at least based on this data. The Lyc is a mature design, proven & improved, as it still is being refined. It just has a big head start.

My conclusion, Lycomings in experimental planes are more reliable & less likely to suffer inflight loss of power than ANY alternative engine, bar none. It does not mean "other engines" are not good? No, but they have to catch up to the mighty Lyc-o-saurus! Installation & "systems" are so critical to alternative engines; installation is key to reliability. Folks like Eggenfellner & RWS have a positive impact, with standard FWF kits and technical expertise.

Jconard
03-31-2008, 08:02 AM
Ross,

Strange that you didn't dispute my attributing a six hundred aircraft fleet for 5 years, even though there is no doubt that is extraordinarily generous, nor did you dispute my assuming one hundred hours per years flight as an average for the fleet although that is very generous....both of which lead to generous stats in favor of the Sube.

Of course no engine will go one hundred thousand hours....it is a probability statistic for the fleet.

I'm sorry you do not like the data. I just got sick of the reference to "sobering" data, so I went and got the data. At first you found a certain number of failures. Then when it became clear that those failures, which double the number of subaru's failures, occured across the span of a fleet more than 28 times larger (in flying hours), all of a sudden there are more power failures???

You wanted to go to the math.

The numbers are soundly against your repeated and unsupported claims and fear mongering.

Now you don't like the idea of using math....

In your recent epistle on Jan's site you decry the lack of historical support from the traditional aircraft crowd. You essentially say that all the coments on this site related to comparative reliability are unsupported rhetoric.

Well, here is the support. Now what would you like?

rv6ejguy
03-31-2008, 09:00 AM
I accept George's number from the figures that you are at least 8 times more likely to have an engine out in an alternative engined aircraft. He has crunched the numbers much more than I have.

I would say that most alternative or traditional powered aircraft do not put 100 hours per year on them so the fleet hours for the Sube are way too high.

I don't accept your math John. Here is what you said: "32 engine failures out of 85 million hours equals one failure in 26,562,500 fleet hours for certified single engine. (not including piston helicopters)."

If we take 85,000,000 and divide it by even George's 32, we don't come up with 26,562,500. Check your calculator. There is no way the the MTBF on piston engines is anywhere near this figure which is way better than the best commercial turbofans or the much respected PT6 (somewhere around around 300,000 hours for in flight shutdowns). My small sample that I personally know of with 3 failures- say each plane had 20,000 hours on it- that's 60,000 hours (really generous)- MTBF is 20,000 hours- several orders of magnitude different than your answer.

George's figure for Subaru was 18 engine related accidents- not 25.

Finally, total GA fleet hours do not equate to total Lycoming hours. You are stretching everything to suit your premise here. Even if 60,000 Lycomings flew the whole GA total of 85,000,000 hours in five years, that means that average annual flight time was 283 hours- not a true figure at all and we know that Lycoming does not power the whole GA fleet.

George's figures are believable, your's are not.

I'll still stand by my statement that the Subaru core has an excellent record for reliability. We have to work on all the other parts attached to it required to keep the prop turning to make the overall package more reliable. Clearly the Lycoming, as an overall package, has better reliability according the the stats.

Jconard
03-31-2008, 09:17 AM
Ross,

It is fleet probability of failure, not for any particular engine, so it is a comparative probability, and yess, I misplaced the commas...its one in 2.6 million, and 22.1 times more likely.

You say 18 sube failures, I added seven others that I knew of personally which I couldn't find in the database. Thats how I came up with 25.

You are correct that 5o hours per year is more reasonable, but by assuming one hundred, I actually made the subaru numbers look better, by granting them 50 hours of non incident use each year.

Finally, total GA fleet hours do not equate to total Lycoming hours.

Ross, 17 Million is for Piston Single only in GA. It is meant to include all the traditional engine hours. If you parce it further you will find that the 320/360 series flies well over half the total hours.

Even at 8 million hours per year times 5 (40 Million hours), with 32 failures the 320/360 shows one failure in 1.25 million hours over the period as opposed to one in 120,000 hours, or 10 to one in favor of the 320/360 series.

If I adjust to 50 hours per year for subes as you suggest it becomes one failure in 60,000 fleet hours over the last 5 years or 20 to one in favor of the traditional engine.

Sobering indeed.

Since you accept the eight to one as fact, will you be editing your marketing support material for Jan to reflect this fact?

rv6ejguy
03-31-2008, 11:26 AM
Even at 8 million hours per year times 5 (40 Million hours), with 32 failures the 320/360 shows one failure in 1.25 million hours over the period as opposed to one in 120,000 hours, or 10 to one in favor of the 320/360 series.

Since you accept the eight to one as fact, will you be editing your marketing support material for Jan to reflect this fact?

I think George's figures were for core failures not total power loss incidents from all causes (not including fuel exhaustion). Let us compare core failures to core failures or power loss accidents to power loss accidents.

You are welcome to believe that a Lycoming engine only stops every 2.6 million hours if you want. Quite obviously this is not the case. Just look at the Lyco RV accidents this year alone- 3 power losses. I don't think even the whole RV fleet of 5000+ Lycoming powered RVs have accumulated 7.8 million flight hours to date if we believe this figure, let alone these 3 aircraft. It is utter nonsense.

Root causes of failure have been identified in most Subaru accidents and corrective measures implemented plus information distributed through forums and media like Contact! Magazine. The Subaru engine as used in aircraft with supporting systems is not as mature as the Lycoming so numbers will get better with it and probably stay pretty static for the Lycoming.

The numbers are all here for people to see and believe what they want. I doubt that many will change their minds on engine choices. BTW, I don't do marketing for Jan, no matter how you perceive this.

gmcjetpilot
04-01-2008, 12:04 AM
Ross you know I respect ya, and you're like me, you don't like numbers that are unfair. Any one using raw numbers should take a BIG grain of SALT with it. I'd fly in anything you made with a Subaru or otherwise. There might be another home built made by someone else, not as talented, even with a Lycoming I might not fly in. It's the BIG PICTURE.

It was not meant to say mine is better. The idea is to learn what makes the fan stop turning. Sometimes the reports are "undetermined". The numbers where not meant to really divide and come up with MTBF. That is a little TOO FANCY.

Reading the reports reminds me to be careful. A lot can go wrong, but we have control over much of it. NTSB "numbers" don't tell the real story, but reading them can be an education. Some time reading the NTSB reports is time well spent, whether looking for engine, prop, airframe or pilot failures. The idea is to learn: NTSB (http://www.ntsb.gov/ntsb/query.asp)

WE HAVE CONTROL OVER OUR FATE. Those statistics are like pilot induced accidents. Some statistics don't mean a thing to me. I don't plan on flying in bad weather VFR or running out of gas, so my "stats" go up.

In a way each engine related accident stands by itself. A unique set of circumstances came together to cause it. At some point up stream there was a possible action which might have avoided it? If there is a trend, than yes a conclusion can be made. It's easier to "trend" lycs because of the size of the fleet. With small sample sizes who knows, but a wise man will take the data and apply it as best they can.

If we control what we can well, our stats will be WAY better than the general NTSB numbers.

rtry9a
04-01-2008, 09:35 AM
The problem with this thread is that it is a good example of garbage in, garbage out. The source material is flawed.

There have been what, three or four RV's down in the last couple of weeks now with engine problems- chances are, they have all been Lycs. It changes nothing, Lyc engines are reliable most of the time, as are well-designed alternative engines. We are really discussing aberations that can strike anyone, often only remotely related to engine design (fuel, bad maintenance, bad choices, etc), and tend to be unique to each aircraft.

If you all want to make this a decent thread, we have to look at, and reduce/eliminate all of the potential failure sources starting with the worst. Unfortunately, that means that we have to eliminate the pilot first:D.

rv6ejguy
04-01-2008, 11:06 AM
George, I spent 90 minutes last night re-sifting the data using "Forced Landing" as the search word and went back only to Mar. 2006. I did not count any power loss accidents which were undetermined for cause, nor fuel exhaustion or feed, nor poor maintenance. I counted 30 Lycoming powered accidents in this period. Causes were everything from carb ice, magneto and drives, oil loss, seal failures (not due to installation), rods, cranks, cam gears, barrel separation, vapor lock and cylinder bolts.

I searched "Subaru" over a 5 year period and found 23 total accidents (not all due to power loss. Again I threw out any undetermined ones and found only 7 which were actual defined mechanical / system failures- supercharger w/g, supercharger belt, ECU limp mode, ignition wiring, vapor lock, mechanical fuel pump and bad ignitor. No core failures.

You can sort any way you want but there are a lot more than 30 power loss Lycoming accidents over the 5 year period with a determined mechanical or system cause. The figure was about double or triple for both engines as far as undetermined causes went that still resulted in the plane coming down.

George, do you buy the 2.6 million hour MTBF? It is not logical by any stretch of the imagination from practical personal experience nor from just the first few engine outs this year on RVs alone.

I will give you the one where Lycomings are generally more reliable statistically than alternatives but we don't have data to know how much. Alternatives are improving all the time as we learn more.

Jconard
04-01-2008, 01:30 PM
Ross,

The MTBF is a fleet number, it is not meant to, nor is it used to imply that any engine would go that far....it is a way to average failure over the entire in fleet experience. If you want to change the label to feel better that's fine, but it is number of failures fleet wide, as a function of hours flown, fleet wide.

I will give you the one where Lycomings are generally more reliable statistically than alternatives but we don't have data to know how much. Alternatives are improving all the time as we learn more.

We do have the data, the hours are out there, even granting huge favorable assumptions toward the alt...it is 10-20 times as likely to fail as certified. Visit the GAMA site for the hours flown.

Your sifting has obviously missed a number of alt crashes...there is one famous one in the NTSB that was a rod failure from previous overheating...not counting fuel exhaustion there are way more than 7 from power failure....and are we back to "core engine" again? As long as you count as core the tings between the fuel tank and making the prop spin...it is a useful exercise in comparing the engines in aircraft application.

You would agree, I assume, that the goal is to spin a propeller...right?

I agree that fuel exhuastion shouldn't count in either case, nor should carb ice, but even so the failure rates are so disparate that the gap will not be markedly narrowed.

Ross, you continually talk about the one or two cases you personally know about, but just do not get the big picture....17 Million hours each year.....more than 60,000 flying examples.....you are talking about drops in a swiming pool.

flytoboat
04-01-2008, 01:45 PM
Ross,
Ross, you continually talk about the one or two cases you personally know about, but just do not get the big picture....17 Million hours each year.....more than 60,000 flying examples.....you are talking about drops in a swiming pool.

17,000,000 hours divided by 60,000 flying examples is 283 hours per plane per year. That's a big story to go along with your big picture...

rv6ejguy
04-01-2008, 02:48 PM
John, do you believe that Lycoming power loss forced landings only happen every 2.6 million hours? We ARE calculating an MTBF here and my calculator does not show this at anything near 2.6 million hours even for core failures let alone total power loss accidents.

I include carb ice accidents in the Lycoming totals as this is part of the system, irregardless whether the pilot did or didn't use carb heat correctly. Still caused the plane to go down and won't affect an EFI Subaru. The carb is part of the total system on a Lycoming and a potential liability just like the PSRU on a Sube.

I'll let you add the previous Sube over temping failure if I can add 17 more to the 2 year Lycoming total where the bottom ends failed due to overheating parts and unexplained oil loss in flight. That would be 47 power losses for the Lycoming in only 2 years. Remember I only searched the term "forced landing" here. I did not cross check, crankshaft, connecting rod, power loss or engine failure to see if there were more in the period not caught on the first search term.

Your basic numbers don't hold up to logical scrutiny. How many RV guys here fly 283 hours per year? We've already had 4 Lycoming power loss incidents this year alone on RVs. You conveniently ignore this.

Walter Klatt
04-01-2008, 05:48 PM
Here is another twist to the question. Which engines are more tolerant of abuse?

I think we all agree that most engine failures are caused by faulty installation, maintenance or operation. For example, if you run your Lyc at 500degrees CHT constantly, you are not going to make TBO on your cylinders. Or if you run out of coolant on your Sube, you will soon be looking for a place to land.

In the Ultralight world, it is well know that 2 strokes are more prone to sudden stoppage due to seizures, crank failures, etc. Yet there are those that insist that 2 strokes are just as reliable (not longevity) as 4 strokes if properly maintained and operated. But they mostly agree that 2 strokes are less tolerant of abuse, such as going to full power before proper warm up, or high EGTs.

With alternative engines, I understand they are designed to run with tighter tolerances, but they have water cooling to allow for that. So what happens if your are mixture is too lean, or you get some predetonation? Will things quickly melt down? On Lycs, the engines won't last for long with extreme abuse, but they don't seem prone to sudden stoppage.

Just another perspective to consider on this queston of reliability...

Walter

Jconard
04-02-2008, 06:38 AM
Ross,

I believe that the failures you mention are best measured as spread over the fleet time. You have a basic misunderstanding of probability here...to determine that any one engine could go 2.6 million hours is the classic fallacy of decomposition. Nonetheless, this number is used in virtually every industry to get a sense for in field reliability of parts/systems.

17,000,000 hours divided by 60,000 flying examples is 283 hours per plane per year. That's a big story to go along with your big picture...

The annual hours number come from GAMA, a nationally respected organization. The fleet is much larger than 60,000 but the average will likely be quite high because a mathmatical average is always skewed by the highest number of cases...think of the aircraft in training and commercial ops that routinely put more than 1,000 hours on per year. If you average one training craft at 1000 hours with one hobby craft at 50 hours the average would be 525. This does not indicate nor is it meant to indicate, that both planes fly more than 500 hours.

As for carb ice...it is pilot error. Just like not figuring the buttonology on a prop controller leading to an inability to go around. Does it mean that a pilot should consider from a workload/systems choice...yes. It is not however a measurement of reliability.

I am not ignoring the 4 power loss incidents you talk about for RV's but in any fleet you could pick out a very short time frame when events happen all at once. Of course trying to draw any broad conclusions from such a small sample in time and universe would be faulty and unreliable at best. This is why the events are reviewed over a broad time frame and large universe of cases.

You can quible all you want over which events to use, but as previously demonstrated by George, even paring down sube failures to only 25, upping their flight time to include a 5 year fleet of 600 at 100 hours per year, and TRIPPLING THE KNOWN QUANITITY OF TRADITIONAL ENGINE FAILURES the numbers for fleet probability come to a result of roughly 10 to one infavor of the traditional engine.

It is interesting that according to the GAMA numbers, in the week we have been debating this, the single engine piston fleet has flown another 400,000 hours...

As to tolerance for abuse....as much as I hate to admit it, the engine most tolerant of abuse I have every seen is a rotary. When they fail, it is truly spectacular, but they will continue to run...at least a little, after horrible bouts of overheating and oil loss.

As to piston recips I have witnessed the teardown of a piper engine which broke the crank clean through, but the thrust faces kept the jagged edge mated and the pilot, though noting a severe vibration, continued on reduced power for 30 minutes to land.

As to subes and abuse, I know that Jan will not support a number of injection schemes because running them overlean can and will damage them, just as it will any engine....depending on power level and a host of other issues.

In the end that triffling certified test where max power, with max prop load with all temps at redline (including oil) for an extended period seems like a pretty good test of a thrust propulsion SYSTEM, doesn't it?

Sometimes I wonder why the numbers are so troublesome to the alternative engine crowd...it is as if the concept of Occam's Razor (the simple answer is always the best) is frightening. When relying on mission critical systems that are much more complex, you either have a rigorous replacement/inspection/design program, or the probabilities will stack up and you will have a higher failure rate.

I thought the complexity and its cousins were just fine and a known tradeof...afterall its smoother, and you aren't bothered with a red knob.

It seems that what the alt community really wants is to say "hey look here are 600 craft which have each put at least 300 hours on...and there's one or two with more than 700....it must be reliable." Then argument is made comparing this with the hundreds of millions of hours and many tens of thousands of traditional engines, and suggesting not parity but IMPROVED reliability.

It is truly good sales manship...I will sell you sometihing at 110% of the cost, with less speed for fuel burn, with more weight, with a whole host of new, lightly tested, mission critical systems, but it will work better...trust me

I will say it right here....if by the time I need an engine for my next plane there is a package that makes to the point where it is only HALF as reliable as a traditional engine, and only 125% as heavy, burning only 125% as much fuel for a given speed in a given airframe...I WILL BUY IT. Heck if one comes along before then which achieves parity...I will replace the engine I have.

rv6ejguy
04-02-2008, 10:15 AM
Like I said John, you don't answer the questions directly and skirt around them with feeble, illogical assumptions.

I'm through with this one.

Yukon
04-02-2008, 11:48 AM
Here's the answer boys, like it or not. Aviation as we know it started with liquid cooling 105 years ago. Gear reduction was stringently researched and applied between 50 and 70 years ago. Automotive proponents have been trying continuously to give us cheap, reliable power since the 1920's. Result......... aircooled aircraft engines in 2008 outnumber liquid-cooled engines 25 to 1. Gearboxes are STILL the huge pain in the a$$ they always were, coolant still leaks just as it did in Jenny's. High RPM's still spell heat and volumetric inefficiency. Simplicity is still king when it comes to light plane success.

Can't fight the numbers boys! Physics doesn't change. When are we going to learn?

flytoboat
04-02-2008, 12:36 PM
Can't fight the numbers boys! Physics doesn't change. When are we going to learn?

I really don't understand why all the naysayers are so adverse to change! Why don't we all go back to the model A Ford and not worry about making things any better? (I'm not saying Lyc = Model A) You are right that physics doesn't change, but technology changes, processes change, and new materials are developed. All this (with the proper innovation) leads to better products. IT CAN HAPPEN IN (EXPERIMENTAL) AVIATION TOO!
Go fly your lycomings and let the guys who want to "experiment" do that.
Yeah there have been some unscrupulous businessess out their hyping their products and selling snake oil, but we are (mostly) all adults here, and need to be responsible for researching the products we buy with our hard earned cash. You don't have to protect everyone from themselves. There are also some legitimate innovators out there trying to build a better mousetrap and someday, maybe, we can all benefit from their toils.
I am not an engineer and don't have the skills to put together an alternative engine package, but I sure appreciate those that do and enjoy reading about their successes and failures. Maybe liquid cooled automotive conversions are not the answer to a better GA powerplant, but it could be the next step in getting there. And if it turns out there is nothing better than a lyc, what is anybody hurting trying to prove different? I may end up with a trusty old lyclone in my RV, but I'll sure have a wishfull eye open for something better to come along...
=rant off=

Yukon
04-02-2008, 12:59 PM
Don,

I'm all for innovation, but the innovation has to WORK. Strapping car motors onto airplanes is not innovative. It has been done since 1929 when a Model "A" Ford was strapped onto a Pietenpol Aircamper. It was found to be heavy and unreliable. You see the occasional Subaru, Pinto and VW engine now on a Pietenpol, but mostly Continental 65. We have come full circle.

Rotary10-RV
04-02-2008, 02:34 PM
Don,

I'm all for innovation, but the innovation has to WORK. Strapping car motors onto airplanes is not innovative. It has been done since 1929 when a Model "A" Ford was strapped onto a Pietenpol Aircamper. It was found to be heavy and unreliable. You see the occasional Subaru, Pinto and VW engine now on a Pietenpol, but mostly Continental 65. We have come full circle.

Sorry John but you are incorrect,
Every turbofan jet flying has a reduction gearbox. Every Helicopter, Turbine, Lyc, or alternate engine. All the large and high power piston engines use reduction gearboxes, both air and water cooled. Watercooling was used on at least 1/2 of the high output aircraft engines prior to turbojets. The reason for the acceptance of large radials had nothing to do with efficiency, rather it was battle damage that was the discriminator between the two for the AAC. Even then the question was debateable since the most successful fighters in both theaters were watercooled, P-38s and P-51s. ALL piston engines declined in use with the acceptance of jets. The reason that Lycoming and Continental and Franklin became the engine of choice is through being at the right place at the right time. They were the only engines supplying the small engine market. The large engine market simply went away and nobody wanted to spend development money on a TINY market segment. The reason for Lyc and Conti dominating the market is apathy, not careful selection.
Bill Jepson

flytoboat
04-02-2008, 02:40 PM
Don,

I'm all for innovation, but the innovation has to WORK. Strapping car motors onto airplanes is not innovative. It has been done since 1929 when a Model "A" Ford was strapped onto a Pietenpol Aircamper. It was found to be heavy and unreliable. You see the occasional Subaru, Pinto and VW engine now on a Pietenpol, but mostly Continental 65. We have come full circle.

I agree that a viable commercial product has to "work", but innovation and experimentation may just lead you to the next better mousetrap. How many people tried to fly and failed before the Wright Bros? How many people ridiculed them and told them they were wasting their time? Just because auto or liquid cooled engines didn't become a commercial success in the past doesn't mean they never will. And if they don't, the experimentation may lead to something even better.
I am not an early adopter of the bleeding edge of new technology, but I do try to keep up with the things that interest me with great expectations of better/cheaper things to come. I don't want to be the shortsighted one standing back watching better things go by and saying "you can't do that because it has never worked before!" I want to see the innovators encouraged, and when I can no longer do that, I'll go fly my lyc and leave them alone to experiment till their hearts content.
For now, even though very smart people (much smarter than me) have come before and completed great work on these systems, I don't think that there is nothing more to learn. Thankfully people with the smarts and desire to tinker think so too.
There are some smart people building and flying airplanes with alternative engines that have not fallen out of the sky. People in this thread were using statistics to try to prove that alternative engines are more dangerous than traditional engines. There is a learning curve to everything and if you went back and run the numbers on early lycomings (I'm not a statistition and have no desire to do the research) but my guess is their early reliablilty was much worse than it is now. Hopefully things will improve with time.

Yukon
04-02-2008, 03:02 PM
Don, I agree. As long as the builder (and his family) understand the risks of powerplant experimentation.

Jconard
04-02-2008, 07:28 PM
Gee whiz,

I thought the title of the thread was which is more reliable....seems like a statistical fleet analysis is exactly the proper tool to evaluate this question.

Of all the things I have been accused of being feeble (in my thinking) or illogical has never been one of them. I suggest that you consider your position (credentials) when you go that direction.

I do not disagree with any of the folks who talk about experimenting. I think the disconnect is in the marketing. I woul not object to the hype if it were truthful. I just think that when people are sold on a "complete" "modern" FWF "solution" the implication is that it is a performance and reliability equivalent.

I am shocked at how offensive some find a numerical examination of those claims to be. This was a fine thread...when the numbers were "sobering" about the lyclone world....but not when the numbers went the other way...
just like the technical questions thread was fine until someone was asked to answer questions other than "how well these things run".

Are you interested in disclourse or not?

Yukon
04-03-2008, 12:47 AM
Sorry John but you are incorrect,
Every turbofan jet flying has a reduction gearbox. Every Helicopter, Turbine, Lyc, or alternate engine. All the large and high power piston engines use reduction gearboxes, both air and water cooled. Watercooling was used on at least 1/2 of the high output aircraft engines prior to turbojets. The reason for the acceptance of large radials had nothing to do with efficiency, rather it was battle damage that was the discriminator between the two for the AAC. Even then the question was debateable since the most successful fighters in both theaters were watercooled, P-38s and P-51s. ALL piston engines declined in use with the acceptance of jets. The reason that Lycoming and Continental and Franklin became the engine of choice is through being at the right place at the right time. They were the only engines supplying the small engine market. The large engine market simply went away and nobody wanted to spend development money on a TINY market segment. The reason for Lyc and Conti dominating the market is apathy, not careful selection.
Bill Jepson.

Turbofans have reduction gearboxes? Says who? All fans I am aware of are direct drive, with the exception of the Garrett 731. Franklin, Continental and Lycoming all decided on aircooled direct drive because it was inferior to other technologies? I doubt it. Lycoming's largest engine is direct drive, Continental's GTSIO engines are timebombs, ask any operator..........just what exactly is the point of your post, because you have lost me.

JHines
04-03-2008, 01:25 AM
.

Turbofans have reduction gearboxes? Says who? All fans I am aware of are direct drive, with the exception of the Garrett 731. Franklin, Continental and Lycoming all decided on aircooled direct drive because it was inferior to other technologies? I doubt it. Lycoming's largest engine is direct drive, Continental's GTSIO engines are timebombs, ask any operator..........just what exactly is the point of your post, because you have lost me.

He's probably refering to the accessory gearboxes on turbofans.

Rotary10-RV
04-03-2008, 10:33 AM
He's probably refering to the accessory gearboxes on turbofans.

There are many reasons for gear boxes, both drive and accessory. These Lyc vs ?? threads always run far afield. It is interesting that when an arguement is made against any technology it is compared to something Lycoming or Contenintal got wrong, not to anything else done right. Here is one new example for everyone. www.sae.org/aeromag/techinnovations/1298t10.htm This shows that there are major advantages in some areas to using a reduction. This is the MAIN FAN reduction. Many of the large radials used a planetary. The Allisons and Merlins all used a spur gear reduction. This just degenerates into a opinionated arguement though. As John C. mentioned back to the original question, Which is MORE reliable? The answer is more difficult than the statistics imply. Statistically there is no question that Lycomings have more trouble free hours logged up. That doesn't mean that there aren't problems but to this point Lycs have been the engine of choice. The problem is when we begin to look statistically at the alternative engine choices. Do we compare to completely home built designs? Do we compare to comercial FWF systems? Some systems are flying in numbers, some were questionable to begin with and have gone out of business, some were vaporware to begin with. The success or failure of a given system usually lies with the capability of the builder, rather than the engine of choice or the layout. Some competent builders have hundreds of hours on unusual layouts done well, while others have had catastrophic failures using more conventional systems. For example look at the guys who flew a Long EZ to Osh from Venesula powered by 2 Suzuki 4 cylinders driving counter rotating props through V-belt drives! Now that's unconventional! Let me give an example of how incorrect assumptions and skewed statistics might snare the layman into a poor choice. Remember that many of the people getting into experimental aviation don't have degrees in mechanical engineering. OK here is the example. Press Release XYZ company. We at XYZ company are proud to release our new aircraft engine. The triple piston expansion (steam) engine. Are you skeptical? Let's show the reliability statistics of the thousands of Locomotives using steam power. Why steam? An expansion engine maintains its power at altitude. The steam engine also will make make maximum torque at nearly 0 RPM! Direct drive with the ability to drive a large diameter prop for maximum efficiency! ... OK I'll stop the example now. The interesting thing is that with modern materials it might be POSSIBLE to make a flying steam engine. Several manufacturers looked at re-introducing steam power to cars in a serious way because it IS efficient. The point is that the success or failure of this idea would totally depend on the people doing the design, not what had gone on in the past, reguardless of the number of times this system had been used in the past. Properly engineered it might work, but we would be skeptical, and justifiably so since the basic idea is so unconventional. Sticking to the point and veering back on-topic, George the original poster in this thread has mentioned that he would fly with some people in their alternative engine aircraft because he understands THAT PERSONS engineering expertise. THAT is why looking solely at the statistics for FAILURES that we miss the point. I have friends who are engineers that couldn't build their way out of a wet paper sack. If one of these guys welded up a copy engine mount for a Cessna 172 with a O-360 in it I would never fly in it. They can't weld to save their, or anybody elses life. I also know a couple of farmers that just finished high school who's creations I would ride, drive or fly with without hesitation. THE BUILDER IS THE KEY TO SUCCESS NOT THE POWER PLANT!
Bill Jepson

Rick_A
04-03-2008, 11:06 AM
I'm not an expert on engines or statistics but I understand that fact that most products are designed to work under certain operating conditions (I know about computer stuff and you don't want to use the same cheap h/w you get at Best Buy to run critical systems).

Most auto engines are not designed to work under high loads continuously. Boats and airplanes both stress engines in ways that cars do not. A big (gasoline) V-8 in car will go 150-200K miles - that same engine in a boat might need a re-build after 2 or 3 years.

If you could find an "endless mountain road", how many hours could the engine take climbing continuously? I don't know but that's what you're asking you airplane engine to do.

Not being an engineer, I opted for an engine designed to work under heavy loads for long periods.

Rotary10-RV
04-03-2008, 12:31 PM
I'm not an expert on engines or statistics but I understand that fact that most products are designed to work under certain operating conditions (I know about computer stuff and you don't want to use the same cheap h/w you get at Best Buy to run critical systems).

Most auto engines are not designed to work under high loads continuously. Boats and airplanes both stress engines in ways that cars do not. A big (gasoline) V-8 in car will go 150-200K miles - that same engine in a boat might need a re-build after 2 or 3 years.

If you could find an "endless mountain road", how many hours could the engine take climbing continuously? I don't know but that's what you're asking you airplane engine to do.

Not being an engineer, I opted for an engine designed to work under heavy loads for long periods.

Rick,
Duty cycle isn't a problem, really. All the auto manufacturers are running 400 HR continous full throttle cycles as a continous test. All the subsystems are much more of a worry than the duty cycle.
Bill Jepson

gmcjetpilot
04-03-2008, 08:43 PM
George, I spent 90 minutes last night re-sifting the data using "Forced Landing" as the search word and went back only to Mar. 2006. I did not count any power loss accidents which were undetermined for cause, nor fuel exhaustion or feed, nor poor maintenance. YOU HAVE TO SEE IT FOR YOUR SELF

Appreciate the time you took, I know how long it takes. For sure to get the most each individual should spend the time and read those babies (reports). What you learn is things can fail and ANYTHING that stops the FAN from turning is important, big or small.

I am not going to drive my plane out of gas or fly with known mechanical problems. I am not going to abuse, mis-use and dis-use my plane or engine. As well I plan no flights into know ice and thunderstorms. So statistics are interesting. To the Lyc side of the ledger, things have "popped up" only after decades and decades of use, such as the sintered metal oil pump impellers. It is that large fleet and documentation that is a plus, even if it shows a problem.

STUFF HAPPENS

The crankshaft debacle (both Lyc and TCM) in the 90's where due to long proven processes being changed willy-nilly and "outsourcing" to save a nickel. It was a bitter embarrassing pill for both manufactures, they would soon like to forget. Lessons re-learned, "If it ain't broke don't fix it".

Are 13B's or Subaru's weak or Subject to catastrophic failure? No not more than any engine, but stuff does happen.

Example, relying on rubber belts to drive pumps and cams is something car owners know well. It is the byproduct of overhead cams, which is cool but adds parts. That is something that should be inspected and replaced proactively, because its as important as the crankshaft (buts it made of rubber and bands of fiber.)

The rotary is very sensitive to its own issues, like foreign objects and oil issues. There are less parts and no valve-train to fail. My parents owned a Mazda RX3, one of the early rotaries in the US in the 1970's. I later bought as tired RX2 and fixed it as a kid. Seal issues where an issue back than. Less so now due to improvements, but not a trivial issue. Like a Lyc if built right and operated properly a very reliable engine.

Corrosion

Lycs? They are fairly low stress, but they are NOT tolerant of manufacture part defects, failure to assemble properly, operational abuse especially traumatic stoppage and probably most common DIS-USE. The Lyc cam is splashed lube. After sitting for weeks, months or years, it has corrosion. Start the engine dry with that corrosion and dry cam, it will be damaged. That is why flying every week is so critical. The solution? Lyc cams are now roller cams. :D It only took 50 years to incorporate them. There is a STC for optional oil squirters in the case to force lubrication on the cam lobes, but the corrosion issue is a big deal. Still this is refinement after 50 years. Is it needed? No if you fly everyday. Flying commercial or flight instruction in piston planes flown daily its not a problem. Cylinder coatings have improved from the Chrome that was state of the art as well.

I think cars being driven daily is a plus for them as well. It remains to be seen if a Subaru or Mazda not flown will be as prone to corrosion issues as the Lyc is.


EVEN A SMALL THING CAN STOP THE FAN AS MUCH AS A BIG THING

Every engine has a weak or vulnerable part. The Lyc gets high marks in its "Farm tractor" approach to vital support systems, ignition, fuel and cooling, all simple and / or mechanical.

The auto engines are all designed with water cooling and electronic ignition and or fuel injection. Many only have one plug per cylinder. With that in mind those systems are as important as the crankshaft or connecting rods. You have to make the wiring bullet proof and heavy duty.

The Belted Airpower guys (V6 conversions with flat cog belt reduction) tried to go more Lyc in their systems approach with carburation, mechanical fuel pump and simple points ignition. Looking at the accidents its hard to say but there where a handful of accidents with V-8's and V-6's. I don't know what approach they used. Their PSRU does not need gears or lube. It seems easy to inspect and may be not as subject to harmonics? With an aluminum block and heads you can come up with a light weight (relative to alternative engines) set up.


FAIR BALANCE APPLES AND APPLES

It is shocking that there are "loss of power accidents". Because of the huge Lyc fleet it's almost impossible to compare apples and apples to alternative engines, numbering in the few 100's, flown by amateur enthusiast, but if you turn on the Experimental only filter on the NTSB search engine, few Lyc issues come up. I think that's a more fair direct heads up comparison. Even limiting it to experimental aircraft only, the Lyc fleet is much larger than all the alternative engines together. The accident rate from loss of power due to "catastrophic" mechanical engine failure (fire and brimstone) is small. However even with a loss of power, survival is not impossible if you fly the plane.

The engine failure that got my attention, is the Aerosport/Lyc catastrophic engine failure in the Oregon RV-8 accident (http://www.ntsb.gov/ntsb/GenPDF.asp?id=SEA99FA113&rpt=fi). It spewed oil and made landing the plane difficult, may be impossible with a fuel fed fire. Fortunately these scenarios are very rare. If the engine just stops, at least you have a chance to make a forced landing under control. This is why I limited my search to crankshafts and rods; if they fail they can cause oil and parts to fly. Other issues like sucking a valve or burned piston are less typically less dramatic. Regardless of how an engine stops, it stops. If there is no fire or major oil leak you're doing OK. In the RV-8 Oregon catastrophic engine failure, the gascolator was damaged apparently.

The sobering thing to me, there's not a lot to learn from the above, except may be don't open the canopy with an engine fire. The engine was "high compression". If you modify your engine, you're reducing your margins. The factual said piston had peening damage? (from detonation?) I have no idea if HC pistons was a factor, just a comment. Detonation was not mentioned as a cause. I also have no idea how a rod fails in fatigue after 25 hours? The RV-8 and engine had 25 hours on it. Rare defect or improper assembly? I know it's not a design issue. Is this a good case for wearing a parachute during phase I or even always? It may have saved him. Bottom line, engines stop for many reasons and it means you are landing, soon. Some times "fate is the hunter". Factual (http://www.ntsb.gov/ntsb/GenPDF.asp?id=SEA99FA113&rpt=fa)

Yukon
04-03-2008, 10:01 PM
There are many reasons for gear boxes, both drive and accessory. These Lyc vs ?? threads always run far afield. It is interesting that when an arguement is made against any technology it is compared to something Lycoming or Contenintal got wrong, not to anything else done right. Here is one new example for everyone. www.sae.org/aeromag/techinnovations/1298t10.htm This shows that there are major advantages in some areas to using a reduction. This is the MAIN FAN reduction. Many of the large radials used a planetary. The Allisons and Merlins all used a spur gear reduction. This just degenerates into a opinionated arguement though. As John C. mentioned back to the original question, Which is MORE reliable? The answer is more difficult than the statistics imply. Statistically there is no question that Lycomings have more trouble free hours logged up. That doesn't mean that there aren't problems but to this point Lycs have been the engine of choice. The problem is when we begin to look statistically at the alternative engine choices. Do we compare to completely home built designs? Do we compare to comercial FWF systems? Some systems are flying in numbers, some were questionable to begin with and have gone out of business, some were vaporware to begin with. The success or failure of a given system usually lies with the capability of the builder, rather than the engine of choice or the layout. Some competent builders have hundreds of hours on unusual layouts done well, while others have had catastrophic failures using more conventional systems. For example look at the guys who flew a Long EZ to Osh from Venesula powered by 2 Suzuki 4 cylinders driving counter rotating props through V-belt drives! Now that's unconventional! Let me give an example of how incorrect assumptions and skewed statistics might snare the layman into a poor choice. Remember that many of the people getting into experimental aviation don't have degrees in mechanical engineering. OK here is the example. Press Release XYZ company. We at XYZ company are proud to release our new aircraft engine. The triple piston expansion (steam) engine. Are you skeptical? Let's show the reliability statistics of the thousands of Locomotives using steam power. Why steam? An expansion engine maintains its power at altitude. The steam engine also will make make maximum torque at nearly 0 RPM! Direct drive with the ability to drive a large diameter prop for maximum efficiency! ... OK I'll stop the example now. The interesting thing is that with modern materials it might be POSSIBLE to make a flying steam engine. Several manufacturers looked at re-introducing steam power to cars in a serious way because it IS efficient. The point is that the success or failure of this idea would totally depend on the people doing the design, not what had gone on in the past, reguardless of the number of times this system had been used in the past. Properly engineered it might work, but we would be skeptical, and justifiably so since the basic idea is so unconventional. Sticking to the point and veering back on-topic, George the original poster in this thread has mentioned that he would fly with some people in their alternative engine aircraft because he understands THAT PERSONS engineering expertise. THAT is why looking solely at the statistics for FAILURES that we miss the point. I have friends who are engineers that couldn't build their way out of a wet paper sack. If one of these guys welded up a copy engine mount for a Cessna 172 with a O-360 in it I would never fly in it. They can't weld to save their, or anybody elses life. I also know a couple of farmers that just finished high school who's creations I would ride, drive or fly with without hesitation. THE BUILDER IS THE KEY TO SUCCESS NOT THE POWER PLANT!
Bill Jepson


Yes indeed, Bill, here we are in 2008, and P&W is pioneering a gearbox for a turbofan. Until now, it has been considered too problemmatic for airline service. Time will tell how well it works. Remember the the fond hopes for the Prop Fan??? Big gearboxes, big props, big problems, big R&D write-off.
I'll be long-retired before it makes it's way onto a 737.

But let's keep our eye on the ball. It's the power pulses of a reciprocating engine that makes the gear reduction of car engines for airplane use so difficult. Turbines are apples and oranges.

rtry9a
04-04-2008, 10:37 AM
[/quote]
But let's keep our eye on the ball. It's the power pulses of a reciprocating engine that makes the gear reduction of car engines for airplane use so difficult. Turbines are apples and oranges.[/quote]

A pretty good argument for the other alternative motor, the Mazda rotary. I dont know of any PRSU failure with a rotary engine and planetary gearset.

With no valves and beefy over-engineered internal parts, the Rotary has the potential to have the best reliability of all the aircraft engines.:eek:

Yukon
04-04-2008, 11:49 AM
Indeed, gearbox issues seem to be fewer with the rotary/planetary installation, but then you have the 25% fuel burn penalty and the loud exhaust to deal with.

airguy
04-04-2008, 04:23 PM
Loud exhaust perhaps - and high EGT to worry a turbo if you're running one - but Mistral is saying their 75% power NA LOP operation is turning a BSFC of .44 in their latest (today/yesterday) releases. .44 is respectable no matter what engine your talking about, if it's true.

rtry9a
04-04-2008, 05:31 PM
Yukon, neither of your comments are necessarily true, but still seem to get passed around a lot by the Lyc boys trying to make biased comparisons.:rolleyes:

The modern versions of the Rotary (Renesis) use large side exhaust ports that are significantly quieter, less polluting, and more efficient than the older motors, and generally quieter than most of the unmuffled Lycs around. The loud motors generally come from the late '80's RX-7 recycled turbo engines, with turbos removed, that had peripheral exhaust ports and have had the exhaust dividers removed- and they can be brutal even with mufflers.

A .44-.46 BSFC is normal at cruise. A rotary burns fuel at the same rates as Lyc's under power, and probably a little less efficient at leaned-out cruise (but not 25%, more like 5-10%). The rotary engine cruises well at a 20:1 air fuel mixture, without detonation, with mogas. Not that it matters, the important measurement is really miles per dollar, not miles per lb/gal, and there the rotaries really shine.

FWIW, rotaries love turbocharging but need aftermarket turbos sized for full power operation. The stock OEM turbos tend to overspeed and fail in aircraft operations.

Yukon
04-04-2008, 06:03 PM
Yukon, neither of your comments are necessarily true, but still seem to get passed around a lot by the Lyc boys trying to make biased comparisons.:rolleyes:

The modern versions of the Rotary (Renesis) use large side exhaust ports that are significantly quieter, less polluting, and more efficient than the older motors, and generally quieter than most of the unmuffled Lycs around. The loud motors generally come from the late '80's RX-7 recycled turbo engines, with turbos removed, that had peripheral exhaust ports and have had the exhaust dividers removed- and they can be brutal even with mufflers.

A .44-.46 BSFC is normal at cruise. A rotary burns fuel at the same rates as Lyc's under power, and probably a little less efficient at leaned-out cruise (but not 25%, more like 5-10%). The rotary engine cruises well at a 20:1 air fuel mixture, without detonation, with mogas. Not that it matters, the important measurement is really miles per dollar, not miles per lb/gal, and there the rotaries really shine.

FWIW, rotaries love turbocharging but need aftermarket turbos sized for full power operation. The stock OEM turbos tend to overspeed and fail in aircraft operations.

Van's did a flyoff and found a huge fuel penalty associated with the rotary.
25% is my recollection. Ask Van's.

A rotary-powered RV used to fly over my house now and then. Unbelievably noisey. When it flew out of sight, you could still hear it on the horizon! Can only imagine what it was like to fly. Which model, I don't know.

If you guys want rotaries, diesels, fuel cells, I really don't care. Do it, but don't try to convince anybody they are better......just different.

gmcjetpilot
04-05-2008, 01:04 AM
Getting back to the thread Mazdas suffer the same achilles heel as other auto conversions, ancillary systems. The big turn off to me and one of the achilles heels is the lubrication. I personally don't want to mix oil with gas. Other wise an oil injector pump is needed and one more thing to deal with, including running out of oil. The Rotary fliers say its not a big deal. I am just set in my ways with the Lyc, check oil and add oil if needed, keep it at 6qts. I end up adding about 1 to 1.5 qts between oil changes. It's not that the Mazda is bad for using oil, its just preference on how you want to handle it. On a Lyc its not a separate deal to hassle with. If you mess up and forget to put oil in gas of fill the injector......My lyc could fly oil change to oil change with out any oil added. Also very subjective but seems to make sense in my mind, Mazda rotaries are sensitive to foreign object damage. I have seen piston engines suck stuff in and blow it out. I mean its a bad thing for any engnie but seals are critical on the Wankel.

I love rotaries and in many ways they are ideally suited for airplanes, compact, fairly light, reliable and less reciprocating mass (thus you would think smoother). The down side is they use more gas, oil and are louder than loud. Turbo'ing does cut noise, and with the turbo flying high (in the teens), you can get good econ fuel burn. The down side is you have to fly high sucking O2 to take advantage. Overall fuel burn will be higher. Of course a Lyc can be turboed, but than it needs inter-cooler and than you run into Vne issues..........it gets to be a viscous circle. I love the idea of turbos but for a daily driver or fly'er, I like normally aspirated.


Wankel Fuel Econ
The only way a Rotary, Wankel, 13B stock or modified, LOP or "closed loop" can match a Lyc's fuel burn is turbocharging and fly very high, in the teens. It's just a fact. Misteral says .44? At what airspeed and altitude? I don't believe that is a block fuel burn. Until there is an independent eval I'll remain sceptical. After all, it's core is a Mazda engine with some mods. I wrote in the Misteral thread the reason for poor gas burn is inherent in the design, a skinny, long, shallow combustion chamber. Rotor control porting causes very fast exhaust ejection speeds, which is wasted energy, but that makes it ideal for turbocharging. Turbos add weight complexity and cost but since it's already water cooled, you can use a water cooled turbo, which should be more reliable than an oil cooled one. However turbocharging means you need more radiator. Its a vicious circle proving the no free lunch rule.

rtry9a
04-05-2008, 10:35 AM
Yukon- The Vans test used old Powersport engines that had no ability to lean out the mixture- not really a fair comparison when the Lyc was leaned... The modern systems that use Tracy's engine mgmt system all have that ability. Id really like to see another flyoff with a newer setup- Vans location in Oregon doesn't help. It might be possible during one of Vans SnF visits to the southeast:confused:

Another problem is that the non-turbo Renesis engines produce power (~220-250hp) better matched with the O-540 class of engines, and there are not many fixed pitch RV-7/8s around with the bigger powerplants. On this point I believe George is also mistaken- Rotaries do not need turbocharging to compete with equivalently powered Lycomming engines.

GMCJet= Since this thread is about reliability, lubricating the engine rotors with a fuel/oil mixture allows the engine to continue to run after a failure that is often catastrophic in a conventional recip engine. That difference might allow a return to an airport under partial power.

Mixing oil can be a minor inconvience, but I find it a safety advantage. fwiw, it is also possible to keep the oem oiling system in place, but feed it 2-cycle oil through a separate oil tank instead of feeding synthetic oil in the crankcase. Most pilots prefer to remove it.

gmcjetpilot
04-05-2008, 03:15 PM
The rotary conversation is going on the Misteral thread, but I don't think I am wrong about the fuel econ of rotaries. I would love to be shown I'm wrong. My opinion is Wankel's are inherently not great on fuel econ, to put it mildly and why its a niche engine in the commercial mass market, but that is OK.

Builders put a Wankel's in their RV for many reasons, including to be different, the challenge, to have one of these unique engines, but one reason they are not used is to save gas money. I don't see a problem. There is nothing wrong with the Wankel, even if it is a little thirsty. No one engine has "IT ALL".

I am with you, I want to see another fly off. Tracy at RWS says the RPM was not right with the Van Power Sport fly-off. I don't get it. I also hear Lean O Peak mentioned. LOP, I don't see it. If LOP cruise econ is great, OK lets get the data. LOP = less power always. Here's my test based on Van's idea:

Two similar RV's take off (may be four, two pwr'ed by 13b's, two Lycs) - at cruise altitude, side by side, equal speed (Wankel's choice of speed from low to high cruise), switch tanks, fly for an hour or two side-by-side, than switch tanks back and land. Fill the cruise tank and let the data be known. The other way is a dash - side-by-side, switch tanks and make a run for a distant way point, time it, note lat-long position or dist relative to way point (coordinate with radio if not in sight), switch tanks and land. Again measure fuel used and distance flown. That is fair. I'll bet money the Lycoming will burn less and/or be faster. I can fly a Lyc pwr'ed RV slow at 45% power for lower FF. but we are talking REAL WORLD. I doubt a slow flight or max range/endurance contest would put the Mazda at an advantage either.

I hear about LOP with rotary? Have you ever seen that in practice. Just saying "Lean of Peak" equals less power (as it always does), and thus you get lower fuel burn. That is fine, a Lycoming can run LOP. There is no free lunch. You have to level the playing field with real world, side-by-side fly-offs. This also includes the affect of cooling drag and prop efficiency. That is fair right? It's the total package engine and airframe. I hear reasons for poor fuel Econ like: RPM, ECU, LOP and others. However atrocious fuel burns are common and known for a long time. It takes some good evidence to change that reputaion. I have an open mind.

The Van's Power Sport v Lyc fly-off really showed the Pwr Sports sucked gas. I'll grant you, may be they where not "tuned right". I'll grant you one Lyc had the FADEC, may be 4% to 6% better than stock carb or FI/magneto setup? May be not? However the difference is fuel burn was so large, like 20% to 40%.......ouch. No matter how you slice the numbers, the Wankels burned at least 17% more than the Lycoming. Something is up?

Flying high altitude with a turbo Wankel, I concede gives good MPG's and for good reasons. It makes sense both from an aerodynamic and engine stand point. It puts plane and engine (combo) at optimal advantage. With the mass waste of energy going out the exhaust of a wankel is more than a pistion IMHO, so turbocharging is a must to get Wankel efficiency, IMHO. I could be wrong about good low altitude fuel econ with normally aspirated Wankel's, but that is not what Wankel fliers tell me; if you run wide open with a Wankel you'll pay for it at the pump. I don't think high power is key to good economy with any engine; it makes no sense from an aero or engine stand point to me. Airframes and engines don't get significantly more efficient or thrifty when run at higher power or speeds.


Back to reliability, loss of power and catastrophic failures

I have not heard of a Wankel self destructing with part shrapnel in an experimental plane, but I have heard of it cars, granted race cars. They are spectacular. Even Tracy of RWS warns not to push power too much for sake of reliability. I personally melted down a Wankel in a RX3 Mazda in the late 70's. Wankel's will not tolerate overheating, but seals are much better today.

Sadly one of those gorgeous beautiful cool Power Sport RV-8's, Jim Clark's "Spitfire" had loss of power due to one lousy electrical switch!

http://www.ntsb.gov/ntsb/GenPDF.asp?id=LAX05CA310&rpt=fi

"Examination of the electrical system revealed that the "Master Power Switch" that was being used was an automotive keyed single pole single throw switch, and that the back was loose and coming apart, making the internal electrical contacts intermittent. This switch ties together power from the batteries and the alternator. Failure of this switch could result in the loss of ignition power to the engine."


Claimed HP and the Alternative engine

As far as claimed HP Mazda Motor company publishes, that is fine in a car if you wind it out to red line. Tracy of RWS races his RV-4 rotary in the 160HP class, even though the engine is rated at "180HP". The Power Sport Wankel's reported having 210HP, but they had the strong performance as a 180HP Lyc. Which is good!!!! My point is HP numbers mean nothing. I think you can expect at most 160-180 hp equiv flight performance for a typical installation, from my observations. Things can change of course.

Most alternate engine guys don't fly near the automotive rated red line or peak HP RPM. In a car that peak makes sense winding out the gears, "peaking" momentarily as you shift. However that is not how alternative engines are run in planes. Wisely most alt eng guys run well below red line, so factory HP numbers mean little if you're not running at those RPM's. Also PSRU's v direct drive & thicker wood props v thinner metal ones, cost HP and thrust efficiency.

HP is not the key to going fast. Sure its important up to a point, but at high speed drag reduction is key to gaining speed with our small planes. I suspect Wankel's do have more cooling drag and less prop efficiency, which might explain some shortfall. Its the total package. However the Pwr Sport RV8's had the best of the best IMHO. May be it needed some tuning but the performance was good, just fuel econ was abysmal. There is one surviving example, Gerry Gustfason's "Tiger" might do another fly-off? And we should get a Real World Solution Rotary in there of course.

I mentioned the Lycoming Cons. There are some, as well as some Pros, pros over a Wankel or Subaru, just like 4-strokes v. 2-strokes have pros and cons. The Wankel has many things to recommend it, like a two stroke engine. The Lycoming has many things to recommend it, like a 4-stroke. Here is my post (http://www.vansairforce.com/community/showpost.php?p=212767&postcount=13) in the recent Mistral thread.

Rotary10-RV
04-07-2008, 03:47 PM
http://img382.imageshack.us/img382/4978/powerandfuelconsumptionen7.jpg
http://img241.imageshack.us/img241/9444/powerandtorquefo7.jpg

The reason for the comments about LOP operation is that the rotary has proven to run well LOP to an extent that piston engines won't even run there. Mistrals fadec is setup to lean in the cruise region, while still producing 168 HP. This is a perfectly reasonable cruise number fo a 200HP engine.
OK Thanks go to Moose for posting the images in the Mistral thread. These are the posted numbers from Mistral. They speak for themselves. They do need to be independently verified. When they publish for the FAA though they MUST be verified as they would be published to a POH and failing to meet their numbers would kill them with lawsuits. The idea of reliability isn't really effected by engine noise, rather just the need for a muffler. While George didn't actually call the rotary a 2 stroke, it might not be clear to some people that the rotary is indeed a 4 stroke, in a different external format. On the reliability front the differences, the lack of valves and connecting rods would have to be a plus for the rotary not a minus. Mistral is using a ceramic tip seal to address the one real wear area on the rotary. Modern materials have made these reliable since the second generation of rotaries, but the use of the expensive ceramic seals will allow a much longer TBO. They are already confident with a 2000 hr TBO, but if the tests prove what they are already seeing they may go to 3000 hr TBO which IS truely excellent. TBO is what we are talking about on a reliability thread right? I think that the rotary is the only engine I see comming to the market now with the potential to rival or surpass the Lyc or Conti durability in the GA marketplace. The manufacturer must cover all bases, that is the PSRU if used must be as good as the engine. The Mistral PSRU is purpose built and beautifully finished. There hasn't been a hint of trouble durring the certification testing for the G300. (300 HP 3 rotor)

Bill Jepson

gmcjetpilot
04-07-2008, 10:15 PM
http://img382.imageshack.us/img382/4978/powerandfuelconsumptionen7.jpg
http://img241.imageshack.us/img241/9444/powerandtorquefo7.jpg

The reason for the comments about LOP operation is that the rotary has proven to run well LOP to an extent that piston engines won't even run there. certification testing for the G300. (300 HP 3 rotor). I find it interesting that three rotors is only 200HP. So if two rotors is that 133 hp?

Bill JepsonBill I love your post and respect your opinion. Great info. That is cool info. I would make a few comments. The first being these numbers are unbelievably good, two or three rotor. Not that I don't believe them, just that they are fantastic numbers. I'd need to see it in a plane. Where did you get this. Is it on their web site?

For peak power @ 2250 RPM, ROP BSFC is 0.556 at 200hp or 18.5 gal/hr. 0.556 BSFC is great at peak power, actually better than a Lyc at peak power? I'd have to see it in a plane flying.

For ECON power @ 2100 RPM, LOP BSFC is 0.444 at 168 HP. WOW! A Lyc can run nominally at .42 econ but at 75% power. At 65% a Lyc can get 0.38 BSFC. Taking normal econ of .42 v .444, that is 5.7% worse for the rotor, which is better than the 10% difference I'd expect. But the Wankel G-200 is at 84% power! WOW! We shall see.

Second, they show at 2100 RPM (assume @ prop) for best LOP BSFC. At that RPM, from ROP to LOP, you get 16.8% better BSFC for 11.8% less HP! The .444 BSFC @ 168 HP is 12.5 gal/hr. That is crazy great. I would just have to see that in real world tests.

From the .556 (peak power @ 2250 rpm) to .444 BSFC (LOP @ 2100 rpm), gives 25.2%!!!!!!!!! That is incredible. I'd just have to see it. I hate to be suspect; these numbers are extremely fantastic! I wounder if the low RPM is an issue in the way Wankel pilots fly? It sounds like you need a prop designed to be efficient at 2100 RPM or 2250 RPM max? I see what Tracy was saying at RWS, about the Van's fly off, that RPM was too high for the Wankel. The Lyc can run low RPM's as well, which also helps a Lyc and it's prop efficiency wise.

Piston engines can run LOP very nicely but no where near 16.8% improvement from peak power to LOP at one RPM. LOP might give you 4% better BSFC in the Lyc. Fantastic numbers and hope they turn out to be true in real world flight.

You can see your overall block fuel econ can be shot, if you don't run ROP too much. Not leaning on either engine, Lyc or 13B, will cost you at the pump. The claim to fame I hear is the Wankel can run LOP all the time? OK.

The data is nice because it does show the difference in HP as I have said. People look at just less fuel burn but there is a cost in HP and of course speed. A Lyc can be dialed back to low power (65% or less) and leaned to just short or roughness or LOP for great econ.

HP for HP, LOP or not, I still think piston engine for all its oldness has some awesome properties. That is all I am saying. Clearly some fly offs are needed. Dan C's econ air race (http://www.rvproject.com/race.html) on April 5th was pretty good. Dave L's turbo wankel RV-6 made a nice show of it, but it was 7th out of 9 in fuel econ. Good yes but not better. The top half or 4 econ finishers (all Lycs) had an average GPM of 17.6 mpg. The rotary was 13.3 mpg. That is 32% difference! Somewhere there is a disconnect from data to real world and Mistral wants us to believe they have solved Wankel fuel inefficiencies. I hope my suspicion is belayed and I am wrong.

Again the caveat is racing is not real world flying but its good data, since most RV's fly their planes more aggressively then in econ mode.

Here is the basic numbers for the Lyc no magic LOP. If you believe the numbers above (which the took off their web site?) than the Wankel is better than a Lyc in every way. I don't believe their numbers, but I stand to be corrected. If they ever get any out to the market (cert or amateur) we shall see. If I was buying a new Mistral from my Piper I would get a lawyer to put it in writing for a guaranteed fuel burn.
http://img167.imageshack.us/img167/4205/lycspecseconfuelzd9.th.jpg (http://img167.imageshack.us/my.php?image=lycspecseconfuelzd9.jpg)

Rotary10-RV
04-08-2008, 02:25 AM
Bill I love your post and respect your opinion. Great info. That is cool info. I would make a few comments. The first being these numbers are unbelievably good, two or three rotor. Not that I don't believe them, just that they are fantastic numbers. I'd need to see it in a plane. Where did you get this. Is it on their web site?

These charts come direct from Francois the CEO of Mistral. He posted these charts in an e-mail to the aircraft rotary engine newsletter. Yes these numbers are great, and like you I want to see them verified in an independent test before I accept them as gospel. The Charts are for the G200 2 rotor. Francois says that the 3 rotor scales directly with just 50% more of everything. 300 HP in the 3 rotor, and corresponding increases in fuel burn. The 3 rotor actually compares a bit better power to weight wise, which is why I susppect they decided to certify it first. Since it will be up against Lyc 540's and other big sixes.

For peak power @ 2250 RPM, ROP BSFC is 0.556 at 200hp or 18.5 gal/hr. 0.556 BSFC is great at peak power, actually better than a Lyc at peak power? I'd have to see it in a plane flying.

<snip> for acceptable length sorry.

Second, they show at 2100 RPM (assume @ prop) for best LOP BSFC. At that RPM, from ROP to LOP, you get 16.8% better BSFC for 11.8% less HP! The .444 BSFC @ 168 HP is 12.5 gal/hr. That is crazy great. I would just have to see that in real world tests.

Correct, that is prop rpm. Their reduction is 2.82:1 so that corresponds to 5922 engine RPM. If you remember some of my other posts George I mentioned that the rotary has a "sweet spot" at 6000 RPM there the engine has been shown to make nearly zero bearing load, in instrumented tests. The balance, compression, and exhaust work best there. It makes sense that if you waste the least HP to friction that the BSFC should be best there, so that makes sense. High RPMS are no sweat for the rotary either so everybody is spinning the engine up. Using 7000 as a redline won't make much stress at all.

From the .556 (peak power @ 2250 rpm) to .444 BSFC (LOP @ 2100 rpm), gives 25.2%!!!!!!!!! That is incredible. I'd just have to see it. I hate to be suspect; these numbers are extremely fantastic! I wounder if the low RPM is an issue in the way Wankel pilots fly? It sounds like you need a prop designed to be efficient at 2100 RPM or 2250 RPM max? I see what Tracy was saying at RWS, about the Van's fly off, that RPM was too high for the Wankel. The Lyc can run low RPM's as well, which also helps a Lyc and it's prop efficiency wise.

Piston engines can run LOP very nicely but no where near 16.8% improvement from peak power to LOP at one RPM. LOP might give you 4% better BSFC in the Lyc. Fantastic numbers and hope they turn out to be true in real world flight.

You can see your overall block fuel econ can be shot, if you don't run ROP too much. Not leaning on either engine, Lyc or 13B, will cost you at the pump. The claim to fame I hear is the Wankel can run LOP all the time? OK.

The data is nice because it does show the difference in HP as I have said. People look at just less fuel burn but there is a cost in HP and of course speed. A Lyc can be dialed back to low power (65% or less) and leaned to just short or roughness or LOP for great econ.

HP for HP, LOP or not, I still think piston engine for all its oldness has some awesome properties. That is all I am saying. Clearly some fly offs are needed. Dan C's econ air race (http://www.rvproject.com/race.html) on April 5th was pretty good. Dave L's turbo wankel RV-6 made a nice show of it, but it was 7th out of 9 in fuel econ. Good yes but not better. The top half or 4 econ finishers (all Lycs) had an average GPM of 17.6 mpg. The rotary was 13.3 mpg. That is 32% difference! Somewhere there is a disconnect from data to real world and Mistral wants us to believe they have solved Wankel fuel inefficiencies. I hope my suspicion is belayed and I am wrong.

George, you aren't wrong at all. If you asked Dave Leonard if he had the most fuel efficient wankel running He would laugh and say NO WAY! Dave re scooped his cowl and put a none to clean chin scoop on it. It cools great, but Dave would admit it isn't even close to optomised for drag. Daves is a fine home garage engine job. He did eveything himself except re-trimming the turbo to make LESS boost. He does have Tracys EMS which does allow him to lean the engine. This ability to run lean seems to take advantage of the charge being forced infront of the plugs in sort of self stratification. Tracy says his was still running smooth at 18:1 air/fuel ratio on a wide band sensor. This was something truly unexpected. Mistral said it seems to corresopond to the "tuned" areas. This is an area that Mazda really hasn't put much work in because they are trying to get the engine to produce better HP and efficiency at LOW rpms for better mileage in a car. For aircraft we almost never see less than 50%. In a car the operational percentages are reversed. A street car rarely sees greater than 50% and then for only a few seconds.

Again the caveat is racing is not real world flying but its good data, since most RV's fly their planes more aggressively then in econ mode.

Here is the basic numbers for the Lyc no magic LOP. If you believe the numbers above (which the took off their web site?) than the Wankel is better than a Lyc in every way. I don't believe their numbers, but I stand to be corrected. If they ever get any out to the market (cert or amateur) we shall see. If I was buying a new Mistral from my Piper I would get a lawyer to put it in writing for a guaranteed fuel burn.
http://img167.imageshack.us/img167/4205/lycspecseconfuelzd9.th.jpg (http://img167.imageshack.us/my.php?image=lycspecseconfuelzd9.jpg)

George, I don't believe the wankel will be better in every way. I am skeptical of presented figures as you are. There are several areas in which the rotary WILL shine and one of those will be reliability once the ancilliaries are properly worked out. The other is power to weight which everyone expected anyway. The reason I believe Mistral has the best chance of any non-conventional engine company is because most of their Board of Directors are pilots, and they truly understand what is needed in an aircraft engine. Their work is truly professional, meticulous, and at the same time they are excited about the product. Francois said that they kept a bottle of champaign cold for the day the tuning of the 2 rotor started breaking 200HP without excessive RPMs. They have a VERY advanced EMS which helps to get those numbers up. Their castings for the intake are simply a work of art. When you look at one of the engine/PSRU combos sitting on the bench your mind says AIRPLANE ENGINE. I think these guys would do well if asked to optomize a conventional engine as well. Their purpose built gearbox is a solid design, using straight-cut gears made for this planetary. They are using a fairly high reduction 2.82:1 so they have a low prop RPM to get good efficiency. Again this shows their engineers know how to get more out of the combination. My rooting for Mistral is pretty greedy on my part. First I will probably use one of their PSRUs if I possibly afford it. Second, if and when they succeed in certifing the rotary, I'll be able to show my insurance company that my engie isn't unique and hopefully get lower insurance rates! My contention all along hasn't been that the rotary is better, rather that it is just as good in most areas and allows us another genuine choice for our aircraft.
Bill Jepson

gmcjetpilot
04-09-2008, 02:35 AM
I hear you Mr. Bill Jepson. The numbers are not fantastical unbelievable just really really really really good. If they can produce that in an airplane I will be very happy. I still think they face a issues with market, installation, cost and Lyc and TCM inertia. New small GA planes are pretty slim to nill. It really needs to be in a new plane installation. The idea of retro fitting an engine that cost $??,??? :eek: plus prop and installation will be hard. It's not like the Lycoming or Continent are terrible and parts hard or expensive to get.

I have to admit a three rotor Wankel is pretty sexy. The Mistral with their smooth flowing induction, serious looking not home-brew looking PSRU and pro Mil Spec installation and wiring is fancy snazzy.

As an incurable selective cheap skate, it has to be better and cheaper to turn me on. Not better but more money, not so much a turn on. A lot better and more money, than yea sure. They have not crossed the A LOT better to cost threshold for me. If I had lots of money I would consider a three rotor job, if they made it available to us RV folks. It would make a nice RV-10 engine, a tad too much for two seat RV's.

You go back to 2004 they had delivery dates, prices and performance on the web site. To be fair bringing a new engine to market, is really hard. The road to engine certification is littered with lots of engine projects. It does not mean they where bad, just all the challenges I listed are expensive and time consuming. In the end price matters. If they can't sell an engine with as good performance or better for less or same money, it's going to be hard. Since retrofit means major mods to systems, engine mount, cowl to name a few, it will be a hard sale. Lycs and TCM are in production and fairly cheap, especially Lycs due to competition from Lyc, ECI, Supr.

If Mistral goes for the experimental market, that would be great! The problem is people can buy used 13b from a junk yard (buy two or three they are cheap) and overhaul them. Than buy a bunch of RWS stuff (ECU, PSRU, Mount....etc) and have an engine for less than $16k with out much guess work. The Mistral three rotor engine is in a different class. I would try and find a three rotor Mazda (rare right) and home brew it from the get go. A PSRU might be an issue? The two rotor 13b's are too small for a RV-10 IMHO. It will fly, just not with RV IO-540 performance. From Dan C's Econ 111 mile Air race, showed Dave L's RV6 rotor pwr'ed bird could fly with the big boys. So I hate to suck enthusiasm out of the sails of rotor enthusiast. I just want people to be realistic and know all sides before committing. The more informed and experienced know all the pros and cons.

A newbie might believe some of the hyperbole that Lycs are dangerous and Wankel's are perfect and superior in every way.

Rotary10-RV
04-09-2008, 12:25 PM
<snip>
I have to admit a three rotor Wankel is pretty sexy. The Mistral with their smooth flowing induction, serious looking not home-brew looking PSRU and pro Mil Spec installation and wiring is fancy snazzy.

As an incurable selective cheap skate, it has to be better and cheaper to turn me on. Not better but more money, not so much a turn on. A lot better and more money, than yea sure. They have not crossed the A LOT better to cost threshold for me. If I had lots of money I would consider a three rotor job, if they made it available to us RV folks. It would make a nice RV-10 engine, a tad too much for two seat RV's.
Hey George, guess what I have in my shop? Answer: A 3 rotor 20B and an RV-10 kit!

<snip>

If Mistral goes for the experimental market, that would be great! The problem is people can buy used 13b from a junk yard (buy two or three they are cheap) and overhaul them. Than buy a bunch of RWS stuff (ECU, PSRU, Mount....etc) and have an engine for less than $16k with out much guess work. The Mistral three rotor engine is in a different class. I would try and find a three rotor Mazda (rare right) and home brew it from the get go. A PSRU might be an issue? The two rotor 13b's are too small for a RV-10 IMHO. It will fly, just not with RV IO-540 performance. From Dan C's Econ 111 mile Air race, showed Dave L's RV6 rotor pwr'ed bird could fly with the big boys. So I hate to suck enthusiasm out of the sails of rotor enthusiast. I just want people to be realistic and know all sides before committing. The more informed and experienced know all the pros and cons.

A newbie might believe some of the hyperbole that Lycs are dangerous and Wankel's are perfect and superior in every way.

I think you are hitting the market nail exactly on the head George. I have long believed that the way to get acceptance of a new certified engine is to first sell to the experimental builders. After you gain acceptance and prove good performance figures regular aircraft companies will take you seriously.
I personally strive to keep the hyperbole to a minium. I have NEVER felt that Lycs and other certified engines are dangerous, quite the opposite, I feel that they have earned their placement in the market through long service. My focus is to educate some of our other people that a rotary engine, when properly engineered and installed ISN'T dangerous. My knowledge shows me that many engine types CAN work. We must approach the design work with our eyes open. I am always aware that my engine package will be an example, good or bad, for the use of alternate engines as a power source.

Bill Jepson

SHIPCHIEF
04-17-2008, 02:26 PM
Bill;
I agree with your last sentence about being an example that others will notice, particularly if something goes wrong.
I'm sensitive to the issue, as a builder of an RV8 with an 'alternative' engine, I hear comments. I observe reactions to aircraft taking off with 'alternative' engines, usually negative comments about the sound and then ad hominum insults etc.
If our planes fly fine we don't get alot of credit, but if we have any kind of failure, the 'alternative' engine will promptly get mentioned.
I do a lot of 'double-triple idiot checks' and have other open minded poeple look at my 'plant' for possible failure modes and poor engineering.
Mainly I get a lot of blank looks and glassy stares.

rv6ejguy
04-17-2008, 05:21 PM
Bill;
I agree with your last sentence about being an example that others will notice, particularly if something goes wrong.
I'm sensitive to the issue, as a builder of an RV8 with an 'alternative' engine, I hear comments. I observe reactions to aircraft taking off with 'alternative' engines, usually negative comments about the sound and then ad hominum insults etc.
If our planes fly fine we don't get alot of credit, but if we have any kind of failure, the 'alternative' engine will promptly get mentioned.
I do a lot of 'double-triple idiot checks' and have other open minded poeple look at my 'plant' for possible failure modes and poor engineering.
Mainly I get a lot of blank looks and glassy stares.

Quite true. I have had a number of ATC guys in the tower state how great my Subaru sounds however so there are a few open minded people out there. Show some traditional engine guys my engine and the blank stares and dumb questions fly- so it that the turbo? Ahhh, nope that's the air filter...:(

There are plenty of Lycoming powered RVs performing uncommanded descents to terra firma every year but when an auto engined one comes down- we get all the headlines. Gee thanks. Power loss accidents are never fun no matter which engine you fly. It's a good thing to learn what caused them alright but always best to wait for the official word before starting the finger pointing.

gmcjetpilot
04-18-2008, 08:14 PM
Quite true. I have had a number of ATC guys in the tower state how great my Subaru sounds however so there are a few open minded people out there. Show some traditional engine guys my engine and the blank stares and dumb questions fly- so it that the turbo? Ahhh, nope that's the air filter...:(

There are plenty of Lycoming powered RVs performing uncommanded descents to terra firma every year but when an auto engined one comes down- we get all the headlines. Gee thanks. Power loss accidents are never fun no matter which engine you fly. It's a good thing to learn what caused them alright but always best to wait for the official word before starting the finger pointing.Ross I don't have an opinion about fly-by engine sounds of an alternative engines. I guess its personal preference, but if someone doesn't care for it, than they're not open minded? :D


There are plenty of Lycoming powered RVs performing uncommanded descents to terra firma every year but when an auto engined one comes down- we get all the headlines. Gee thanks.

I don't follow the logic or sentiment. What happens to an engine and installation that has only a handful examples (or one or few 100 equivalent installations) flying, an incident or accident is a big deal. I would think you would want to know the reason why. Is it not part of the alternative engine joy, the fact they are rare, cool, different, custom? That also means alternative engines are often untested or involve new (custom) applications/installations. There is some risk that goes with that, if we are all being honest.

I disagree with your comment that there are plenty RV's with Lycs losing power every year. Do you have any facts? The NTSB data does not support that at all.

To be blunt, if I limit my search to Lycs in experimentals there are almost NO Experimental's that have lost power due to mechanical failure. Compared to all alternative engines, Lycs are superior statistically in experimentals, when it comes to loss of power. If you look at loss of power due to ancillary systems the Lyc is clearly superior statistically with its old fashion mechanical fuel and ignition systems.

The high time Alt engine & gear is my only be 500 hours. The highest time engines are in the 1000 hour or may 1,500 flight hour range. Lycs have millions and millions of flight hours as a fleet (every few years!). When it comes to standard, nothing is as standard as a Lyc and its installation. That's a big advantage. That's not a put down of Alt engines, which stands on their own ground and relative fleet size.

To mention Lyc in the same breath with Alternative engines as some reason or justification for alternative engine failures is faulty logic. It's not relevant to the safety of any alternative engine. Alternative engines need to stand on their own, not look to the Lyc. I understand the Lyc is the gold standard and a bench mark to aim for.

There's NO feeling good about any accident, alternative engine or not. Its just irrelevant to play the blame game on Lycs. So if a Lyc fails does that make it better for alternative engines? I just don't get it. Personally I don't point at any accident for a "Gotcha!". I look at it to learn.

The Egg engine and unique prop in a RV-10 airframe, a rare combo, was involved in a tragic accident. There aren't may of these six bangers flying much less in that airframe, so YES IT TAKES ON MORE IMPORTANCE IF A RARE BIRD GOES DOWN.

I guarantee if the first of new kind of Lycoming or Continental to come out in decades, had an engine related accident, it would make the news.

The new certified / prototype diesels that quit due to a battery issue in that "Diamond twin" made news. It's new and fairly untested so its big news. Let say in 20 years from now there are 20,000 diesel Diamond twins flying, it will not be big news if one falls out of the sky.

Alternative engine guys need to stop bashing Lycs to support a decision to fly what ever you want. Vice verse, the petty bashing of alternative engines is silly stuff you all should ignore as well. Personally I like the sound of a P&W radial the best. The main charter we all have is to make flying as safe as possible regardless of the engine we fly behind.

SteinAir
04-19-2008, 12:32 AM
George,

That is probably one of the most well reasoned posts I've seen regarding the whole "engine debate". I just stay out of it because I think people on both sides just get crazy stupid. People throwing data all over the place out of context and entirely useless (on both sides), so on and so forth.

I chuckle when I see people using "data" to support their decision either way. Pick your poison, stick with it and don't worry about trying to convince others. Do what is best for YOU - period. I fly behind a Lyco because it's best for ME, but not for everyone. Some people even choose to fly behind turbines, diesels, wankels, franklins, subies, etc.. They are still people, they are still homebuilders, they are still customers, pilots and some are even friends of mine. That doesn't make them bad people or me a bad person for not going alternative. It means we each chose something different. It means I don't have the patience, skill or courage that Ross does to research, design, develop and ultimately test my own setup. I'm barely a capable pilot with the stuff I fly behind now, much less trying to be a test pilot!

I always want to know what caused any crash, no matter what the engine because I have lost good friends who were flying behind both Certified type and Alternative engines. I do have to agree overall that regardless of the Lyco / Subie / Wankle sounds....nothing beats a nice round engine!

Anyway, good post.

Cheers,
Stein.

PS - Ross....I haven't seen that crazyweird congolmeration of Tempest /Napier /DC4 /Bristol "data" post again for a couple days now, aren't we due another post of it?!?!? All in fun, I promise! :)

rv6ejguy
04-19-2008, 10:35 AM
Stein,

You always post something well reasoned and usually amusing.

People sometimes do get upset about the smallest things. I was merely posting that there are SOME traditional engined guys who will admit that my Subie sounds ok, if different. Most seem genuinely interested- or perhaps amazed that it does work. Other pilots seem to have the view that the idea of a car engine in an aircraft is nuts or scary, much like the view some certified aircraft pilots have of our RVs. So I used the phrase "open minded" to describe those who don't fly auto conversions but can appreciate them.

When it comes to sounds, well that is subjective like looks for sure. An R-3350 pumped up to 80 inches rounding the pylons at Reno sounds good but doesn't make the hair stand up on the back of your neck like Strega's Merlin at 125+ inches and 3400 rpm- the nicest sounding engine in the world- IMO.

I can't say I'm fond of the sound a 4 banger Lycoming RV makes with twin pipes- kinda coarse but I do fancy the sounds of twin TIGO-541s in synch on a PA31P (fond memories) or the race Continental and Lycoming sixes in the Sport Class. That's good music!:)

My hangar neighbor next to me owned a beautifully clean Citabria for many years powered by an O-360 "fish boat motor" (his words). He is importing an RV7 to replace it next month from Texas as he has had RV envy really bad after watching me taxi by all the time and having a flight in the 6A. The RV7 will share his space with a Buick V8 powered, one off replica Spitfire which looks extremely authentic and sounds very close to the part too. I consider Tim open minded with his choice of aircraft and power plants. You certainly wouldn't have an O-360 in a Spitfire replica!:eek:

I can't wait to do some more formation work and shoot some pix and video when Tim gets the -7 up here. I'm glad that Tim has a "fish boat motor" powered RV so I have someone to play with- even if I won't be able to keep up with him.:(

It's the flying experience that counts for most of us, not what turns the fan up front. I know Tim is really going to enjoy his RV- not sure how much he'll fly the Spit now!

smokyray
05-06-2008, 10:12 AM
Is this considered an Alternative Powerplant?:)

http://www.youtube.com/watch?v=1PB4Fhge4oI

Rob Ray
F16,RV4ormerly
HR2

Yukon
05-06-2008, 10:23 AM
Is this considered an Alternative Powerplant?:)

http://www.youtube.com/watch?v=1PB4Fhge4oI

Rob Ray
F16,RV4ormerly
HR2

Yes Smokey, that is a PERFECT example of an alternative engine!

gmcjetpilot
05-07-2008, 01:47 AM
Is this considered an Alternative Powerplant?:)

http://www.youtube.com/watch?v=1PB4Fhge4oI

Rob Ray. F16,RV4ormerly HR2Yep defunct for the second time. Search the archives these forums for Innodyn or Google.