Alternative Engine Real World Experience?
 

What is the real world experience for all you alternative engine users out there?

How much total time since overhaul do you have on your engines?

Or maybe a better question is: Do any of these alternative engines with gearboxes ever make it past 1000 hours before they need major service?

David T.
Lancair Legacy
TCM IO-550

Yes
 

Sure PSRU's go past 1000 hours. Yes, alternative engines have made it past 1000 hours. Under what circumstance and how many, I don't know for sure. Data & statistics are hard to come by. I'm sure some will chime in with testimonials of their favorite high time alternative engine airplane.

With your Cadillac IO-550 engine/plane, I'm guessing you're not ready to yank it out and install an alternative engine; you're just curious. I'm then same way. As Lyc guy, I've followed alternative engine development for planes with great interest since 1985. They have come a long way. The group has more experience, parts support and PSRU availability, for a wider variety of engines. The most popular alternative engines for RV's: Mazda, Subaru and Chevy V6, all have been flying for over a decade or two. How many hours total I don't know. (Model T Ford engines, 25-65 hp, where used in the 30's. It's not a new idea.)

A true-isms the most passionate alternative engine enthusiast will not argue with, the core engine tends to be fairly reliable. Most 'issues' are with the ancillary systems. Even if you got 1000 hour between TBO with your Alt. Eng, overhaul would be cheaper than on a Lyc/TCM, no doubt. On the other hand despite what you might read, Lycs/TCM's make TBO and beyond routinely, however sitting for extended periods is death for them. Regular flying, reasonable normal maintence and operation in the green is critical to making TBO. Cars are driven regularly, soccer Mom's drive in the green and going to jiffy lube is usually needed. Abuse a car engine and it will not last.

PSRU's (belt drive, planetary or spur gear drive) enjoy a pretty good reputation. However the community has been shook lately with recent failures of Rotax and Eggenfellner PSRU's. Also new RV-10 using alternative power crashed with loss of life; the cause has yet to be determined but was tragic. This was on the heals of a Wheeler Express going down. The cause was a fuel line, not the V8 auto engine or PSRU itself.

There are high time PSRU's with more than 1000 hours, but the question is why does one PSRU go +1000 hours and another (same design) fail? That is what is on peoples minds. BTW, PSRU's have tear-down and/or inspection requirements set by each manufacture.


Obviously Lys have way more service history and no doubt always will. Engine choice is based on putting your faith in that power-plant. There is enough information to research to make intelligent choices. Nothing man made is failure proof.

The most hardcore "Lycoming only please" builder would switch to alternative power if it was: more efficient, higher performance with less weight and drag, while increasing reliability & lowering maintence. That is the Holy Grail. Even if it cost more people would switch. We can only support the pioneers and hope they achive a quantum leap. IMHO, a totally new technology will be needed, technology we don't have today, to best the Lyc/TCM across the board and raise the bar. My motto, there are no free lunches. Aviation design is full of compromises and trade-offs. A piston engine is a piston engine. A Wankel is a Wankel, with it's own inherent Pros and Cons. Turbine and Diesel are not the answer for small GA planes either, at this time.

To get philosophical, what will get you in the air sooner, with max fun, reasonable cost with out compromise in safety? (FILL IN THE BLANK HERE) Your milage may vary. Have fun and be safe.

At Eggenfellner we have more PSRU's flying than anyone. Over 20 years, we have had 2 failures. One failure could be traced back to a severely backfiring engine after the customer installed the wrong cam belt. The other is not known. It is known that not all pilots treat the machinery in the same way. Many do not follow such simple instructions as to have the propeller balanced. It does not matter how well the unit was built / designed, if it is not cared for. That being said, we usually see the opposite where the builder love his engine and is in tune with all maintenance. It is very easy to determine the condition of these gear drives by monitoring the temperature trends and sending in oil analyses samples to be recorded in the logs

We are 90% sure the Eggenfellner Engine was not the cause of the RV-10 crash. NTSB has not finalized the reports and they have the right to keep the information until they are ready to post it.

Even after all these years we only have about 5 individuals close to 1000 hr flight time. It takes a long time to get there with 75 hrs / year. Our latest, G3 PSRU has been designed for the life of the engine, possibly with an overhaul.

Jan Eggenfellner

1000 hour club
 

Thanks Jan. Looking at Tracy's Real World Solutions, Inc (RWS) web site, who specializes in Rotary engine conversion, in the FAQ section, he states their high time PSRU (in a fixed wing plane) was 1,400 hours as of mid 2004. Another of their PSRU's have 2,500 hours of service in a gyro-copter. It is interesting to note that RWS has also had made changes to their PSRU from their original design.

Shoot! I should have phrased my question differently! I was not being a smart**s really! I really want to know how long these engines typically go for.

Believe me, i am pulling for all the alternative guys - Jan, Innodyne, Deltahawk, all of them! I hate being held up by the Lyc-TCM duopoly, trust me!

So there are still two key questions:

What are typical operating lives?
What is SFC at cruise power?

The argument is that automobile engines are not designed for high continuous power settings. Average engine-life power settings for an auto engine are something like 15%, while they are 65% for the Lyc-TCM's. Big difference. Does this matter???

David T
Legacy

The power setting matters little as auto engines are validated to much higher WOT standards in development than aircraft engines require for certification. There is a strong correlation between piston speed and longevity however. For a 2000 hour TBO (no topping allowed), my current thinking and those of others in the know like to see piston speeds below 2500 ft./min in cruise and well below 3000 ft./min for takeoff and climb. Lower is better which is why I advocate short stroke turbocharged engines as having the best of all worlds. In light of this, max continuous rpm needs to be limited to about 75% of the factory redline for most designs.

A Lycoming/ Conti operates below 2000 ft./ min which is the reason behind their reliability long term in most cases as far as internal spinning components. Thermal issues cause most of the premature problems with air cooled engines primarily with head cracking. This is rarely an issue with liquid cooled engine where CHTs are low enough that the aluminum maintains most of its strength, unlike air cooled heads.

I would say that MANY air cooled engines go to TBO without topping and that Lycoming O-320/360 engines are among the most reliable if treated well however we certainly see more problems on some of the older, higher hp 6 cylinder engines with case and head cracking, exhaust valve and guide distress etc. It is rare to see a twin engined aircraft with say 4000 hours where both engines have gone the same amount of time without premature top end work or overhaul periods. The same applies to many of the higher strung Lycoming and Continental sixes used in the big Pipers and Cessnas where less than 50% make it to overhaul without topping. Some versions have been complete disasters- like the Malibu/ Lycoming combo for instance.

So, yes, things are progressing rapidly with better engines and better PSRUs coming onto the market. Soon I think auto conversions will be a more viable alternative to many pilots especially with the statospheric costs of 540/550 engines and parts used in high end kit planes. A company like EPI is quite capable today of doing the whole job right. It won't be cheap but neither is a new 550.:)

I flight plan using 162 MPH and 5.6 gph for economy cruise.
These are actual in-flight #'s. If we can have # by a 360 powered 7A, we would have a valid comparison. Not Van's #'s but an airplane built and outfitted with full IFR, interior, heat, etc.


OAT 89F, 30.06,at 6500 feet OAT 65F

RPM 1700 - 162 MPH, 5.6 gph
RPM 1800 - 165 MPH, 6.2 gph
RPM 1900 - 170 MPH, 7.1 gph
RPM 2000 - 175 MPH, 8.0 gph

Top speed is around 196 MP
Numbers are from (RV-7A, Andy Parrish)

Jan Eggenfellner

The power setting matters little as auto engines are validated to much higher WOT standards in development than aircraft engines require for certification.

Wrong, aircraft engines which are rated for full power are rated to run that WOT for full TBO. THERE ARE NO CAR ENGINE TESTS FOR 2000 HOURS AT WOT FULL POWER.

Before you go to the subaru race car example, it was around 400 hours, and the truth is the duty cycle for a car puts power at less than 30 percent for most of its life.

At Eggenfellner we have more PSRU's flying than anyone. Over 20 years, we have had 2 failures.

Was grounding the fleet for upgrade an option then? I guess I got the impression the bulletin from your company made it mandatory.

Andy's numbers are definitely acceptable, but when I read the website he notes that his airspeed was reading high and his fuel flow was reading low.

Here are those two quotes:

Speeds are within a couple of knots and FF may be a little low
460 nm, flight time 3+21, fuel used 19.9 gallons with 0-5 knot tailwind.

Still works out to just under 140 knots at a little over 6 gallons per hour without accounting for the tailwind...not awful at all.

My numbers
 

When I run 75% at 7500', I can count on at least 201 TAS in my -6A, 0-360 carbed. Empty weight 1065# with a FP Catto, pitched for max cruise. At 2300RPM (engine and prop:)), I can putz around at 162-164mph.

Jan, you didn't say what your engine was turning to get 2000 prop RPM,

Regards,

stratospheric cost?
 

(Edit: Massave math error, started off with wrong price for both engines)

You can get a brand new shiny Lycoming 540 with roller tappets for $39,000 (corrected).

The "Complete 3.0 200 hp 6 cylinder firewall package" from Eggenfellner is $25,000 (corrected), so at first blush we're talking $14,000 (corrected) difference.

Looking down the list on the Egg site, a constant speed prop is $9,000 or $10,000. A constant speed Hyd control "BA" Hartzell is $6,500+$1,200 (Gov) = $7,700, so there is a ($1,300 to $2,300) (corrected) to the credit of the Lyc.

We could start talking about nickles and $1000's, but just off the bat, including the prop, we're looking at ($12,700 to $11,700) (corrected) difference.

Granted the Lyc needs an oil cooler, exhaust, electric fuel pump and baffle. Van's firewall kit for the RV-10/IO-540 is $4,710 ($5,910 minus the $1,200 prop gov I included above). **Assuming you don't need to buy anything else for the Eggenfellner, than the Lyc total FWF cost is about $17,900 (corrected) more.

** (From Eggs option list)
Hot water heater pkg $595
6-Port Fuel valve $495
High pressure filter $195
E-Cowl with Hardware $1,890
Alternator op (75A v. 35A) $490
Shipping Creating $1,400

To the Eggs credit side of the ledger goes credit for the standard Van's engine mount and cowl, but it may still be a net cost if Van's credit is less. With some of the Egg options, I suspect are needed, the difference between the Lyc IO-540 FWF v Egg 3.0 is less than $17,900 (corrected). If you go with the Egg turbo set-up ($7,000 more), so the Egg is about $10,000 less (corrected) coin.

(Deleted comment about Lyc 540 v Egg being close in price.) (corrected) One engine is 3.0 liter and the other is 8.85 liter (540 cu-in).

Time honored tradition of scrounging for a used Lyc core & rebuilding it, saves significant money, $10,000 for example. It's more of an option with the Lyc. Finding a used 3.0 Subaru will not save you that much money since most of the cost is in the Egg FWF kit itself.

I don't see the promise of significantly lower acquisition cost with commercial alternative FWF kits v. Lyc. (Well $17,900 is significant; I stand corrected.) They have to make a profit. There's nothing wrong with being more expensive, if you get what you pay for. The exceptions are builders who scratch build everything with a used engine. Most people don't have the skill or time for that. Those that do, save money with sweat equity, not to mention the pride of doing it yourself.


As far as performance, I would just like to see SIDE BY SIDE comparisons, like Van has done in the past, like what they did with the Power-Sport rotary engined planes, eg, where you fill the tanks and fly side by side (with Lyc power) and measure fuel burn. Also you do a 'timed' closed course flight plan (and tank check), as well as drag races & time to climb. That would take all the calibration of instruments out. Power-Sport did them self proud, but the higher fuel burn of Wankel 's was apparent. It's great to go as fast or faster but not at the expense of significant gas burn, with prices what they are. I think turbo-charging and flying high is where the alternative engines can shine, efficiency wise. However this adds cost, weight and complexity. It does require you to fly up into oxygen mask altitudes to get that bonus. One could also argue you can turbo a Lycoming and make up the ground again.