Greg Dillon
Active Member
I know it's a turboprop, but the Tupolev TU-95 has counter-rotating props and is expected to remain in service till 2040. Maybe the Russkies know something we don't about gearboxes and c/r prop systems?
Van's Air Force
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The Lycosaurus is actually a crocodile.
- Thread starter Captain Avgas
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RudiGreyling
Well Known Member
Yes, all the Rotax engines, but then the power rating is much less than typical RV needs with exception of RV12. From 50HP for Rotax 503 to 115HP for Rotax 914. On my little airfield in South Africa we have 5 with more than 1000 hours on them.
I guess the bigger the HP need, the bigger the gearbox problems.
Regards
Rudi
No Rudi, the Rotax 914 is certificated, not experimental, and as such was conceived with real engineering and thoroughly tested. It also employs a clutch mechanism which limits torsional vibration. Even with all this, I understand that the gearbox has many premature failures and overhauls.
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No, there have been some faults in the gear wheel metal lately. This is fixed with the newest SB.
IMO the Lycomings are great engines, superb engineering. However, the design is old, and what was superb 50 years ago is not that great compared to what is superb today, crocodile or not
My bet is that if the original designers of the common Lycoming variants we see today were to design a new engine from scratch, they would end up with a larger 4/6/8 cylinder versions of the Rotax 912 - with gear and liquid cooling.No, there have been some faults in the gear wheel metal lately. This is fixed with the newest SB.
IMO the Lycomings are great engines, superb engineering. However, the design is old, and what was superb 50 years ago is not that great compared to what is superb today, crocodile or not
I don't agree. After 105 years of aircraft engine developement, air-cooled, direct drive engines have proven to be superior. Let's not forget that most engines WERE watercooled in the 1910's and 20's and 30's. Most were geared during the 40's and 50's. If this technology was superior, don't you think it would be in wide use today? Not only are geared engines NOT in wide use, every manufacturer that tries has difficulty keeping them together.
Why keep trying to pound a square peg into a round hole? Embrace the beautiful simplicity of the aircooled, direct-drive engine.
captainron
Well Known Member
The 1911 Colt pistol, named after the year of its introduction, was also a superb design with great engineering. Ninety-seven years later, it is still being produced by Colt, and by dozens of other manufacturers including Colt's arch-rival, Smith & Wesson. If you can't beat 'em......I guess. Anyway, in some cases, you don't need to re-invent the wheel- it's perfect the way it is.
Why not use what Cessna, Piper and others count on as their best insurance for keeping the lawyers at bay. If they thought a cobbled together car engine derivative would reduce their liability, they would be all over it in a heartbeat!
Cessna is now installing Thielert diesel engines in their products. Liquid cooled, geared and automotive based. Times do eventually change. Customers must have wanted something other than Lycos and Contis or Cessna would not be offering these. They are certainly not cheaper.
I personally don't think that engines like these will replace direct drive Lycos for most GA aircraft until cost and weight comes down and they actually reach TBR on a regular basis but times are a changin'.
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I think you are mixing cause and effect and theology and engineering here
The lycomings are not great engines because they are direct drive, air cooled, low rewing, large displacement engines. They are great engines because they are extremely well engineered pieces of machinery utilizing all the benefits of direct drive, air cooled etc. But the thing is - you can say the exact same thing about air cooled VW engines and their conversions (Sauer and Limbach notably), and they were never even meant to be flying.However, for the big picture as aero engines goes, the Lycomings are tiny, cheap, simple and unreliable toys (or maybe small crocodiles
) compared with modern turbofan and turboprop engines in any case.I think the crocodile similarity is rather good, because there really is not much you can do to make a substantially better engine. I still believe that by starting from scratch today, the 912 approach is far better: better HP to weight ratio (higher engine RPM), better efficiency (engine and propeller), better reliability, less vibration, less bulky, much wider envelope of propellers for fast/slow airplanes while still maintaining optimum engine and propeller efficiency.
The Lycoming is perhaps a crocodile, but the Rotax 912 is the animal the crocodile eventually evolved into (whatever animal that may be
)
w1curtis
Well Known Member
These are "better" only in that the allow the use of Jet-A fuel. As such they will only make economic sense in areas where avgas is not available or cost prohibitive. The may sell well in Europe (for a lot more Euros) where avgas is expensive in comparison to jet-A if available at all. But in areas where avgas remains available and is more cost effective (here in the US diesel is more expensive than mogas and Jet A is more expensive than avgas-I won't go into energy content), that Thielert diesel is a gold plated paperweight. With the price points for these Cessna equipped Thielert's however, it may make more sense to just buy expensive avgas.
Maybe some of us have round pegs!
I too don't see the benefits of the Thielert engines in North America at this time for most GA aircraft due to the scarcity of jet fuel at many small airports, cost of the engines and fuel and the lack of longevity demonstrated to date.
Merely countering the observations in another post here.
cawmd82
Well Known Member
I wish it were the same....
In Texas we have been seeing diesel average about 18-20%--sometimes 50 cents a gaallon--more than regular unleaded and the spread has, if anything, been increasing. It was back to near equal in the early summer of 2007 for the first time since pre-Katrina but that was short lived.
Stories I have heard:
Katrina damaged diesel processing plants worse than gas plants.
Agricultural useage, due to increased corn prices, is way up.
Military consumption supporting the war efforts is the culprit.
I have no idea which, if any, of these are real factors.
In Texas we have been seeing diesel average about 18-20%--sometimes 50 cents a gaallon--more than regular unleaded and the spread has, if anything, been increasing. It was back to near equal in the early summer of 2007 for the first time since pre-Katrina but that was short lived.
Stories I have heard:
Katrina damaged diesel processing plants worse than gas plants.
Agricultural useage, due to increased corn prices, is way up.
Military consumption supporting the war efforts is the culprit.
I have no idea which, if any, of these are real factors.
Hermanthegerman
I'm New Here
Only a few weeks back the founder of the LEKI company here in germany survived the crash of his Extra, but was burned alive in the ensuing fire. His copilot tried to get him out but was driven away by the flames.
That fire would not have happened with diesel fuel.
You might want to ask his wife what she thinks of AVGAS
The whole ACCIDENT would not have happened, since it involved mixing up the mixture lever with another one.
Over 60 years ago there were already single lever engine operations on complex high performance engines.
Lycoming and the likes are as adapt to their environment as the Dodo was...
Mike S
Senior Curmudgeon
Welcome to VAF!!!!
Herman, welcome to VAF
Don't be too sure of that, the physics of a crash can easily atomize the fuel into an extremely flammable air/fuel mixture and disperse it where it will do the most harm. There are a lot of videos of jet aircraft crash testing where they purposely rupture the fuel tanks, and the fireball is just as violent as avgas. I have been through training on this when I worked CFR at Orange Co (John Wayne now) airport.
http://www.dfrc.nasa.gov/gallery/movie/CID/Small/EM-0004-02.mov
http://msn.foxsports.com/nascar/story/Daytona-500-Juan-Pablo-Montoya-crash-ignites-huge-fire-022712
I suspect the resistance to change has a lot to do with the problems/cost of certifying any new changes with the FAA.
Herman, welcome to VAF
Don't be too sure of that, the physics of a crash can easily atomize the fuel into an extremely flammable air/fuel mixture and disperse it where it will do the most harm. There are a lot of videos of jet aircraft crash testing where they purposely rupture the fuel tanks, and the fireball is just as violent as avgas. I have been through training on this when I worked CFR at Orange Co (John Wayne now) airport.
http://www.dfrc.nasa.gov/gallery/movie/CID/Small/EM-0004-02.mov
http://msn.foxsports.com/nascar/story/Daytona-500-Juan-Pablo-Montoya-crash-ignites-huge-fire-022712
I suspect the resistance to change has a lot to do with the problems/cost of certifying any new changes with the FAA.
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Hermanthegerman
I'm New Here
The atomisation only takes place in the instance of impact.
In this case the fire broke out "long" after that...
drench yourselve in diesel or avgas, in wich situation would you rather strike a match ?
In this case the fire broke out "long" after that...
drench yourselve in diesel or avgas, in wich situation would you rather strike a match ?
Mike S
Senior Curmudgeon
Neither of course.
Either fuel will kill you.
Kinda like asking a condemned criminal if he wants to be hung, or shot.
Actually, avgas would probably get it over quicker, and would definitely not smell as bad as diesel-----specially when you consider that you usually die from inhaled fumes and not actually burning up.
Consider the fire that killed Amanda Franklin. Smoke oil, not avgas fed.
One more video. http://www.youtube.com/watch?v=enaS7BPw0Lg
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Geico266
Well Known Member
I suggest you take a rag soaked in diesel and light it before you advocate it being safe.
Anyone that has started a charcoal fire using a match and lighter fluid knows how easy it is to light.
I am sorry for the loss of any pilot, but AVGAS should not be blamed. If he grabbed the wrong control knob it was pilot error pure and simple. I was taught that if you move a lever and the engine quits undo what you just did!
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Here is an interesting difference between diesel (Jet fuel) and gasoline. Gas has a very high vapor pressure, so it pushes most of the air out of an enclosed fuel tank. As a result, sparks inside the tank will not ignite the fuel because there is no oxygen available for the reaction (I don't recommend trying it at home, however). That is why the automotive industry has no issues with all of those electric fuel pumps mounted inside the fuel tanks with exposed ire connections. Don't get me wrong, sparks aren't happening in there, but the risk is also very low. Diesel, on the other hand, has a relatively low vapor pressure, so the environment inside fuel tank is ripe for ignition with a nice mixture of fuel and oxygen available for the reaction.
On the flip side, the same vapor pressure properties makes it so that outside of an enclosed container, exactly the opposite is true. Gas will ignite with very little spark, but diesel requires quite a bit of encouragement for ignition to happen. They are both ignition hazards, just different hazards.
The most public example of jet fuel igniting like this inside of an enclosed tank was the 747 that went down over Long Island. The cause was a shorted, sparking wire inside the fuel tank.
Tim
On the flip side, the same vapor pressure properties makes it so that outside of an enclosed container, exactly the opposite is true. Gas will ignite with very little spark, but diesel requires quite a bit of encouragement for ignition to happen. They are both ignition hazards, just different hazards.
The most public example of jet fuel igniting like this inside of an enclosed tank was the 747 that went down over Long Island. The cause was a shorted, sparking wire inside the fuel tank.
Tim
LYCOMING VS AUTO
When I'M in the airplane cruzin over the Bob Adams wilderness area, or the Beartooth wilderness area I want an old proven engine purring away cuz if youall go down you ain't nuthin but bear bait or fish food.....
Does any one out there know why one should file the front sight off your big pistol when in grizzly country?????
When I'M in the airplane cruzin over the Bob Adams wilderness area, or the Beartooth wilderness area I want an old proven engine purring away cuz if youall go down you ain't nuthin but bear bait or fish food.....
Does any one out there know why one should file the front sight off your big pistol when in grizzly country?????
Hermanthegerman
I'm New Here
Lighter fluid is not Diesel....And no its not SAFE, but safer ...
Incidentally a rag soaked in linseedoil will also eventually selfignite when thrown into a heap of sawdust, but that is beside the point.
Well first, it was not he who pulled the lever, second it was close to the ground.
Third i am always in awe whe i meet someone who has never made a mistake and can thus preach from an elevated position.
When the designer of the FW 190 enginge control box was asked what a pilot would make when confronted with a high workload situation, when having to deal with enemy, power, mixture, cooling and his wingmen his answer was : "a mistake"
Hermanthegerman
I'm New Here
rv7boy
Forum Peruser
Be Nice!
Gentlemen,
this thread has taken a vector in a different direction from its original intent. As a moderator, I am getting an itchy finger to "moderate" this thread.
Please review Doug's Forum Rules before continuing this thread.
Thanks.
Gentlemen,
this thread has taken a vector in a different direction from its original intent. As a moderator, I am getting an itchy finger to "moderate" this thread.
Please review Doug's Forum Rules before continuing this thread.
Thanks.
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If you have not read the actual investigation on the TWA flight you should take a look. I don't think the jury is out at all. The facts are self evident when you see the chain of events. It was the usual combination of many factors forming a long chain with the accident at the end. The good news is that the lesson learned caused many changes in procedures on similar aircraft and have without a doubt prevented 1 or more accidents caused by the same events.
George
Buggsy2
Well Known Member
Reading this thread for this first time this got my attention. I wonder what the author is trying to say. Newton figured out that Force = Mass * Acceleration, so the statement
is not true.
rv7boy
Forum Peruser
Read it again...
"Rate of acceleration" is not the same as "acceleration."
I'd have to dust off my old engineering books and think awhile to see if he is technically correct.
But IIRC Velocity has units of distance over time;
Acceleration has units of distance over time squared;
And Jerk has units of distance over time cubed.
I think he is speaking of "Jerk" here. (Please, everyone, no jokes about "Jerks" will be appreciated.)
"Rate of acceleration" is not the same as "acceleration."
I'd have to dust off my old engineering books and think awhile to see if he is technically correct.
But IIRC Velocity has units of distance over time;
Acceleration has units of distance over time squared;
And Jerk has units of distance over time cubed.
I think he is speaking of "Jerk" here. (Please, everyone, no jokes about "Jerks" will be appreciated.)
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Buggsy2
Well Known Member
Yes, rate of [change] of acceleration with respect to time is the jerk. But given that he equates speed with jerk "if you double the speed or more accurately the rate of acceleration" I doubt he carefully selected jerk in his statement.
Too bad, since I think the writer is trying to say something of value and I wanted to follow it. Not trying to nitpick or embarrass him, rather would like a clearer explanation.
Too bad, since I think the writer is trying to say something of value and I wanted to follow it. Not trying to nitpick or embarrass him, rather would like a clearer explanation.
Diesel and jet fuel burn too. Ever seen what happens when a jet crashes? I saw a diesel bus on fire last year too. Diesel is fuel, designed to burn and as such, dangerous as well when an ignition source is present.
Captain Avgas
Well Known Member
Well Herman, the Dodo was actually a bird that was so overweight that it couldn't get off the ground which is what ultimately led to its extinction.
So in that regard it would appear that all of the obese GA aero-diesel engines that have appeared and then promptly become extinct in recent decades have more in common with the Dodo than the excellent power to weight ratio Lycoming which is still very much alive and thriving.
DCat22
Well Known Member
Lycodile evolution
Evolution takes time.
I must agree with the Lycodile analogy.
For the few shortcomings of the highly evolved Lycoming
no other, imitation or alternative has come even close to today's Lycoming.
It has even adapted well to a new diet of ethanol mogas.
Even according to an old post by rv6ejguy, the alternative engine does not like leaded gas and needed a top end overhaul at less than 400 hours.
Just wanted to bring this exciting thread back on its track.
Evolution takes time.
I must agree with the Lycodile analogy.
For the few shortcomings of the highly evolved Lycoming
no other, imitation or alternative has come even close to today's Lycoming.
It has even adapted well to a new diet of ethanol mogas.
Even according to an old post by rv6ejguy, the alternative engine does not like leaded gas and needed a top end overhaul at less than 400 hours.
Just wanted to bring this exciting thread back on its track.
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Buggsy2,
Yup, F = MA.
And, A = dV/dT
"Rate of acceleration" is somewhat imprecise, but what the author likely meant, considering he was discussing inertial strain in an engine, is that tensile strain increases as the square of RPM. When RPM is doubled, dV is doubled, and dT is halved.
Engine books the world over note this squared relationship between RPM and tensile strain. It's been tested with strain gauges.
Yup, F = MA.
And, A = dV/dT
"Rate of acceleration" is somewhat imprecise, but what the author likely meant, considering he was discussing inertial strain in an engine, is that tensile strain increases as the square of RPM. When RPM is doubled, dV is doubled, and dT is halved.
Engine books the world over note this squared relationship between RPM and tensile strain. It's been tested with strain gauges.
Hermanthegerman
I'm New Here
Errr,
the Dodo was a bird that could only evolve in such a fatal way because it had a MONOPOLY
Wich ist what Lycosaurus and the likes enjoyed thus far. When said monopoly ended.....
So far the monopoly is still being enforced through massive papwerork costs.
L.Adamson
Well Known Member
I wouldn't want an automated "mixture" control, if it was given to me. I've always flown from higher altitude airports, in which using the mixture knob is a way of life. I prefer making the adjustments that I want, versus a machine doing it from someone elses programmed..... thoughts.
L.Adamson
Captain Avgas
Well Known Member
I have observed that an opinion on VansAirforce tends to carry more weight when the author puts his name to his post.
I could be wrong but I think it might be Herman. And I think he might be German.
Captain Avgas
Well Known Member
I'm a great believer in the theory that if everyone put their name to forum posts we would in fact have a lot more civility and a lot less rash statements.
Captain Avgas
Well Known Member
It would even be better if everybody who posted on this forum also contributed $25 to Doug's Vans Airforce, don't you agree Captain?
Barry Ward RV6a F PRVM
I agree 100%, but $50 would be even better. A list of those who have contributed so far this year can be found here. http://www.vansairforce.net/2012_Donators.pdf
It's a bit off subject but a quick check of those who have contributed in 2012 indicates that only roughly 100 members a month are making a contribution (1200 for the year at that rate). That's a disgracefully low number considering that there are over 15,000 registered members. I don't think that Doug Reeves will be joining the Forbes 400 list anytime soon.
Barry
Well Known Member
Back to the original thread and in reply to our German friend Herman. Perhaps he is is not aware that several years ago the German car manufacturer Porche decided to get into the business of developing a replacement for the Lycoming engine .
Their engine which was a single leaver 200 power unit was installed in a specially developed Moony. In spite of the technical engineering excellence of Porche as well as their considerable finacial resources the whole thing turned into a fiasco. All the planes had to be reequiped with Lycoming or Continental powerplants.
Over the last 40 years or so vast summs of money have been invested in trying to build a better engine to replace either the Lycoming or Continental engine in the 150 HP or plus range and there has been little sucess. This is why Vans only recommends Lycoming engines for their aircraft.
Barry
Their engine which was a single leaver 200 power unit was installed in a specially developed Moony. In spite of the technical engineering excellence of Porche as well as their considerable finacial resources the whole thing turned into a fiasco. All the planes had to be reequiped with Lycoming or Continental powerplants.
Over the last 40 years or so vast summs of money have been invested in trying to build a better engine to replace either the Lycoming or Continental engine in the 150 HP or plus range and there has been little sucess. This is why Vans only recommends Lycoming engines for their aircraft.
Barry
Hermanthegerman
I'm New Here
I am painfully awarwe of that !
Mooney is not the only manucaturer who experienced this, but in fact a whole array of manufacturers over here were affected.
This brings us right back to my statement about protectionism.
Users of the engine loved it, but for PORSCHE the ac engine market was a comparatively small portion of their income and they were told that they had the choice between continuing to build ac engines OR selling cars in the US.
It sucks, but when you build cars....
Bob Kuykendall
Well Known Member
My favorite article on the topic by Alfred Scott, the man behind the F8L Falco kit airplane: Dead on Arrival: Porsche PFM
Thanks, Bob K.
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