experiamental fighter jet style aircraft

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SVSUSteve

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Just a quick point here....I would like to correct something.
Sometimes the euphoria happens on the way down, due to nitrogen. But that is a completely different story and also totally off topic.
It is more likely to be due to either catecholamines or a drop in carbon dioxide from the hypoxia-induced hyperventilation associated with altitude rise. Nitrogen levels would not change significantly enough to produce narcosis with descent from a low concentration to a normal concentration like would you would see with someone who is diving deeper while breathing from a scuba tank (the "rapture of the deep").
 

rv6ejguy

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Comparing race engines to aircarft engines isn't fair. Race engines spend precious little time at any specific rpm, this means things like resonance don't really come in to play. Also, the faster the car, the less time is spent at full throttle. The mass of the engine and cooling system can handle peak loads, but are unlikely to handle sustained full power runs. "Stock" engines maybe, race engines, are a lot less likely. Even stock engines are on the edge of overcoming their own ability to reject heat from cylinder heads.



Thread drift is fortunate and necessary. If you only discuss, or answer the question someone ASKS, they will rarely get the answer they NEED. (In my line of work, if I only answered the questions people asked, nobody would ever get their problems solved.)

Threads are conversations. Conversations take turns, and wander, and explore. That's where real learning, and the changing of minds happens.

Splitting a thread when the direction changes, means the next person, with the same question, won't be able to follow the discussion to it's conclusion. ;-)
I am not sure where you get this idea from. Liquid cooled engines don't have issues like this with proper radiators and oil coolers, they can sustain full power continuously from a heat rejection standpoint. This is very well proven in the full throttle validation tests every OEM runs these days for several hundred hours as well as speed records such as the 1989 one mentioned with 3 Subarus running WOT for days on end at high rpm. There have been numerous other endurance speed records like this set with production vehicles over the last 20+ years. The OEMs run WOT on the dyno these days for between 200 and 1600 hours depending on what they are testing or proving.
 

Toobuilder

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We must be careful of over generalizations... "Full power" is not an absolute value. Using the LS series for example, there are versions of the all aluminum 6.2 ranging from 366 HP to 638 HP. Both models share almost identical basic architecture, both can be run at "full" power for days, but one version has significantly less thermal margin than the other. Bump that 638 up to 1000hp, and you may go negative on the margin.

Yes, automotive engines are getting better all the time, but overstating their capabilities is as non productive as understating them.
 

nerobro

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I am not sure where you get this idea from. Liquid cooled engines don't have issues like this with proper radiators and oil coolers, they can sustain full power continuously from a heat rejection standpoint. This is very well proven in the full throttle validation tests every OEM runs these days for several hundred hours as well as speed records such as the 1989 one mentioned with 3 Subarus running WOT for days on end at high rpm. There have been numerous other endurance speed records like this set with production vehicles over the last 20+ years. The OEMs run WOT on the dyno these days for between 200 and 1600 hours depending on what they are testing or proving.
Liquid cooled engines still have an ultimate heat rejection capability in the heads. Same as air cooled engines.

WOT is also not full power. I use WOT commonly on my car to get better fuel economy. ;-) But i'm only turning 2000rpm. The heat rejection capacity of the engine is hardly taxed at that level. If we're talking the engine at it's 6500rpm redline, it's a completely different story.

Would you consider a 1995 Nissan altima to be a modern car? That car couldn't hold full throttle for more than 10 minutes before it's cooling system was completely overwhelmed. I don't know if the ignition had been retarded yet.

Also, modern cars cover up for issues like head heating, and cooling issues by adjusting fueling and ignition timing to keep the motor running.

Without picking specific engines, this discussion won't go anywhere productive. Yes, you can pick example engines where their only limiting factor is block integrity. And I can pick engines where the heads are the limit. We'll both be right.

As toolbuilder said. Understanding where the limitations may come in, is much more important than generalizations of certain engines capabilities.
 

jlknolla

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As a person who loves experimental aviation but who makes a living as an engineer in aerospace/defense reliability/maintainability and safety, I have to say that I am less and less confident that any auto conversion, with a PSRU, above 150 hp can be made reliable enough. For the lower powered applications, I am not sure they are good for anything other than truly mundane low-stress straight and level use with a precious few very specific and notable exceptions.

The real question is this - what good would it be to have a capable plane but an engine you never fully trust? I am running through this thought process literally right now as I ponder a new design - I ultimately decided to go Lycosaur power for this concept to minimize design and integration challenges from an experimental engine, and to maximize reliability.

A 3rd Honda powered Titan T-51 Mustang suffered engine failure and went in just yesterday (2nd failure, on 2nd engine, for this particular plane all within the first 40 hours or so of operation). Aussie homebuilding phenom Terry Kronk was killed in his scratch-built LS powered P-51 just a couple months ago (reportedly PSRU failure). I remember when the Stewart S-51 Mustang was Sierra Hotel and it seemed like Jim's plane went down every six months or so to some kind of failure (oil, cooling and PSRU failures as I recall).

The PSRU and auto-based cranks are the weak link IMO, and I just don't see where we have made any significant progress with respect to reliability in nigh on 20 years now. I actually flew Dave Blanton's V-6 powered C-170 outside Wichita back in the day, sure was smooth but another idea that never really met the hype.

The Legend was a great idea but only became a great plane when they dropped a Walter 601 in it.

The original concept for the ViperJet was a mid-mounted piston engine driving a pusher-prop on a long shaft, it only became a good idea when they switched to turbine power, and it became a great idea when they moved to a semi-modern and reliable engine - but it is beyond most of us in terms of price.

I really wish that there were truly durable/reliable auto conversions in the 200+hp range, especially in a v-type engine for the Walter Mitty P-51 drivers in all of us, but it seems to be mostly snake-oil and only a few flying examples.

The LS series are truly amazing engines - for cars, boats and Boss Hoss motorcycles - but engine failures in those applications are a minor inconvenience compared to the result in something that is highly wing-loaded to allow high cruise speeds.

If you really want something with jet styling, use a proven, reliable engine, and get appropriate training - planes that look sexy typically are less forgiving when things go bad (higher stall and touch down speeds), so remove/reduce the likelihood that things can go bad (use good engines).

300 mph designs are fairly difficult to layout and power appropriately as can be seen by the extremely limited number of successful planes in that space (Lancair IV, hot rod Glasair III's, Thunder Mustang, Turbine Legend) and none of those that come to mind have used auto-power in more than one-off attempts. There was a super fast Chevy powered Lancair IV-P, but not sure that still has that engine in it.

The airplane part can be done for sure with the right help from qualified helpers, but the engine area just isn't there on the auto-conversion side, to my requirements anyway.
 

Head in the clouds

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As a person who loves experimental aviation but who makes a living as an engineer in aerospace/defense reliability/maintainability and safety, I have to say that I am less and less confident that any auto conversion, with a PSRU, above 150 hp can be made reliable enough. For the lower powered applications, I am not sure they are good for anything other than truly mundane low-stress straight and level use with a precious few very specific and notable exceptions.

The real question is this - what good would it be to have a capable plane but an engine you never fully trust? I am running through this thought process literally right now as I ponder a new design - I ultimately decided to go Lycosaur power for this concept to minimize design and integration challenges from an experimental engine, and to maximize reliability.

A 3rd Honda powered Titan T-51 Mustang suffered engine failure and went in just yesterday (2nd failure, on 2nd engine, for this particular plane all within the first 40 hours or so of operation). Aussie homebuilding phenom Terry Kronk was killed in his scratch-built LS powered P-51 just a couple months ago (reportedly PSRU failure). I remember when the Stewart S-51 Mustang was Sierra Hotel and it seemed like Jim's plane went down every six months or so to some kind of failure (oil, cooling and PSRU failures as I recall).

The PSRU and auto-based cranks are the weak link IMO, and I just don't see where we have made any significant progress with respect to reliability in nigh on 20 years now. I actually flew Dave Blanton's V-6 powered C-170 outside Wichita back in the day, sure was smooth but another idea that never really met the hype.

The Legend was a great idea but only became a great plane when they dropped a Walter 601 in it.

The original concept for the ViperJet was a mid-mounted piston engine driving a pusher-prop on a long shaft, it only became a good idea when they switched to turbine power, and it became a great idea when they moved to a semi-modern and reliable engine - but it is beyond most of us in terms of price.

I really wish that there were truly durable/reliable auto conversions in the 200+hp range, especially in a v-type engine for the Walter Mitty P-51 drivers in all of us, but it seems to be mostly snake-oil and only a few flying examples.

The LS series are truly amazing engines - for cars, boats and Boss Hoss motorcycles - but engine failures in those applications are a minor inconvenience compared to the result in something that is highly wing-loaded to allow high cruise speeds.

If you really want something with jet styling, use a proven, reliable engine, and get appropriate training - planes that look sexy typically are less forgiving when things go bad (higher stall and touch down speeds), so remove/reduce the likelihood that things can go bad (use good engines).

300 mph designs are fairly difficult to layout and power appropriately as can be seen by the extremely limited number of successful planes in that space (Lancair IV, hot rod Glasair III's, Thunder Mustang, Turbine Legend) and none of those that come to mind have used auto-power in more than one-off attempts. There was a super fast Chevy powered Lancair IV-P, but not sure that still has that engine in it.

The airplane part can be done for sure with the right help from qualified helpers, but the engine area just isn't there on the auto-conversion side, to my requirements anyway.
On the subject of auto engines converted for aircraft use the above is one of the most level-headed posts I've seen.

A couple of things I've noticed in just about any auto-engine conversion discussion -

Consider the dedicated air-cooled aircraft engine, especially the so called 'dinosaurs' (but which everyone keeps on installing because they're relatively reliable) an 0-360 for example is 180hp an 0-540 is 270hp and so in, in general. So they're producing about 30hp/lt so they are effectively 'de-rated'. And their overall reliability as a powerplant is increased because they don't need a PSRU since they are low revving long-strokers.

Whenever the discussion moves into the arena of auto conversions then everyone starts talking about how much power can be dragged out of them, hardly anyone considers anything less than 100hp/lt to be acceptable and 200hp/lt gets talked about with glee. Then add a PSRU because they're high revving short-strokers and is it any wonder that they're unreliable?

If folks were realistic then they'd be aiming for no more (or perhaps less) power from an auto engine than it produces in its standard auto use, and the penalty when compared with a dedicated aero engine would be extra weight, the advantage would be much less cost. Using a lower power output from an auto engine (lower than as used in the car) could be partially compensated for by the use of a different cam which was optimized for good torque at lower revs and so the engine could be used with a simple external thrust bearing instead of a PSRU, and then perhaps the reliability and longevity of a modern auto engine might actually exceed that of the dinosaur air-cooled aero engine.

With the above taken into account, and if it's a reasonable account, then it demonstrates what a remarkable job Rotax have done with the 912, being capable of producing at least 67hp/lt all day long with long TBO and excellent reliability regardless of running a PSRU.
 

StarJar

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As a person who loves experimental aviation but who makes a living as an engineer in aerospace/defense reliability/maintainability and safety, I have to say that I am less and less confident that any auto conversion, with a PSRU, above 150 hp can be made reliable enough. For the lower powered applications, I am not sure they are good for anything other than truly mundane low-stress straight and level use with a precious few very specific and notable exceptions.

The real question is this - what good would it be to have a capable plane but an engine you never fully trust? I am running through this thought process literally right now as I ponder a new design - I ultimately decided to go Lycosaur power for this concept to minimize design and integration challenges from an experimental engine, and to maximize reliability.

A 3rd Honda powered Titan T-51 Mustang suffered engine failure and went in just yesterday (2nd failure, on 2nd engine, for this particular plane all within the first 40 hours or so of operation). Aussie homebuilding phenom Terry Kronk was killed in his scratch-built LS powered P-51 just a couple months ago (reportedly PSRU failure). I remember when the Stewart S-51 Mustang was Sierra Hotel and it seemed like Jim's plane went down every six months or so to some kind of failure (oil, cooling and PSRU failures as I recall).

The PSRU and auto-based cranks are the weak link IMO, and I just don't see where we have made any significant progress with respect to reliability in nigh on 20 years now. I actually flew Dave Blanton's V-6 powered C-170 outside Wichita back in the day, sure was smooth but another idea that never really met the hype.

The Legend was a great idea but only became a great plane when they dropped a Walter 601 in it.

The original concept for the ViperJet was a mid-mounted piston engine driving a pusher-prop on a long shaft, it only became a good idea when they switched to turbine power, and it became a great idea when they moved to a semi-modern and reliable engine - but it is beyond most of us in terms of price.

I really wish that there were truly durable/reliable auto conversions in the 200+hp range, especially in a v-type engine for the Walter Mitty P-51 drivers in all of us, but it seems to be mostly snake-oil and only a few flying examples.

The LS series are truly amazing engines - for cars, boats and Boss Hoss motorcycles - but engine failures in those applications are a minor inconvenience compared to the result in something that is highly wing-loaded to allow high cruise speeds.
Good points, but I have a friend who has had a 'Robinson' LS conversion in his RV-7, for 8 years and it runs great. Robinson is now offering a higher output version, so my friend bought a Queen Air, and is putting a pair in it. My jury is still out on that move. But my point is, we need to weed out what does work, and what doesn't.
 

rv6ejguy

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I already listed several successful V8 conversions which have over 1000 hours each and listed multiple examples of many other ones in previous threads so the premise that auto engines can't work well and reliably is just silly conjecture.

The big problem is most people don't know what they are doing, they are not engine people, they are not engineers, they have little field experience and they break the basic rules of engine building, tuning, design and operation. You can expect failure in these cases almost every time.

Really, I just see completely ignorant posts here about this continuously. Please, go read the SAE papers and test standards on how modern designs are validated by all the OEMs these days. Every one is subjected to testing FAR in excess of what the FAA requires to certify an aircraft engine. I've repeated this so many times it's tiresome now.

Nobody with sanity and knowledge is suggesting we run an engine at maximum power (or modified for higher than stock output) continuously in aircraft but what I'm saying is that almost anything built in the last 10-20 years has had multiple examples run exactly that way for thousands of hours collectively and single examples at 200-600 hours without failure. Modern designs are very well engineered and very overbuilt. Cooling is absolutely not an issue on any design I am aware of at stock power outputs as far as rejection of heat to the coolant (see above). As an example, I built multiple turbocharged Toyota road racing engines from 1.3 to 1.9L with 5 times the stock hp output (over 200hp/L). These had the factory water pump and zero mods to anything in the cooling system or cooling path other than the thermostat was removed. Never had any cooling problems either on the dyno (load type) or being flogged down a 3/4 mile straight. These engines were super reliable running thousands of laps collectively winning several championships against naturally aspirated engines with up to double the displacement. I have no doubt they could run at their stock 70hp output for thousands of hours. The race engines all had the stock crank, block and rods. Yes, every engine has its thermal limits, some are higher than others but no modern liquid cooled design is going to be challenged at stock hp levels- pure nonsense with everything in proper working order. Now, do I think a stock block Lycoming 360 would last at 1200hp (200hp/L) for even 1 minute? Nope. I know from working at Reno on one of the Gold Championship winners how thermally and mechanically challenged traditional aircraft engines are when pushed past stock (safe) limits.


We see many auto engine conversions have problems somewhere in the package and have failures and crashes- absolutely true. I am involved with this on a daily basis (my business) and I've assisted in crash investigations and reviewed plenty of accident stats. The common thread is almost never the core engine (unmodified) but rather supporting systems- PSRUs, electrical systems, fuel systems, cooling systems, ECU tuning or out of parameter OEM ECU protection responses etc. NONE of these have anything to do with the core engine that the OEM, designed, engineered, tested and validated. Please don't blame every failure of an auto powered aircraft on the engine- get to the facts on where and what system failure precipitated the incident.

The Robinson V8 conversions I've mentioned have done everything right and have the incident free flight time (around 4000 hours now) to prove it can be done, you just need the right people working on the project. The wrong people will make it a disaster like so many before. Most of the successful conversions have been done by experienced gearheads and engineers.

With stuff like PSRUs and engines, everything must be done right or you are going to have problems.

BTW, the Thunder Mustang uses an automotive based Falconer V12, rather successfully.

Broken cranks can almost always be tied back to TV issues with the PSRU design. The better automotive cranks are forged alloy steel, heat treated, nitrided with rolled fillets- state of the art and they are usually better supported with more main bearings in most non-V8 designs.

As far as detailing which auto engine designs have head cooling problems at stock hp- please fire away. I've worked on all the popular ones used to power aircraft and many others like the Nissan A, L, KA, VG series as well. Never seen a problem with any of these at power levels far above stock.

I'll comment on some other misconceptions here; most auto engines require a PSRU not because of their stroke but because they are generally smaller displacement than traditional aircraft engines and best power is made at elevated rpms, not conducive to good propeller efficiency. Short stroke at higher rpm usually results in similar piston speeds to traditional aircraft engines so reliability as far as bottom end components goes is similar. No different than a Rotax 912 compared to a Conti O-200. There is nothing remarkable here, specific output is directly related to mass flow on a given engine design. Run a 1.5L engine at 5000 rpm or a 3L engine at 2500 and you are going to make about the same power. Camshaft changes will have minimal effect on the hp curve of most modern auto engines below 3500 rpm. The VE is already very good here.


Most successful conversions have derated the cruise rpm and therefore the max continuous hp substantially from the factory ratings. Running flat out simply burns a lot of fuel because the engine must usually be run very rich to survive and high rpm frictional losses are substantial. In cruise, depending on the engine type and airframe, most piston auto engines are running around 3500-4800 rpm. Not really taxing an engine that has a 6000ish rpm redline which is pretty common among the average Subaru, Suzuki, Honda, LS etc.
 
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jlknolla

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Sorry it is not opinion nor ignorance, just math.

Of over 200,000 registrations, with tens of millions of GA hours per year, there are, relatively speaking, only a handful of auto-conversion powered aircraft, flying typically lower than average hours per year, with higher than average failure rates (anecdotally, since the number of flying conversions is statistically insignificant).

It is also inarguable that integration of auto-conversions is significantly more difficult than aircraft engines, and reliability is incomparable. There are nice looking packages out there, and as I mentioned, a few notable well-engineered exceptions with lots of run time on individual installations (mostly V6 with belted redrives in glider tow operations), but the math is not even close in terms of real world reliability across what are relatively small fleets. Peruse any builder's forum like Van's or the Titan board, the excellent Corvair sites, etc., and bearing, crank, PSRU, ECM, fuel delivery, exhaust, cooling and other issues/failures are the rule, not the exception.

In the case of the Titan Mustang that just went in, it was an engine built by Titan, and it was the 2nd such engine installed in that individual plane - the first one having failed within days of the aircraft getting its' pink slip. Pilot was OK but plane flipped on the forced landing and was damaged. Several of the 'Mini-Merlin' V6 Suzuki conversions have also failed - and don't misconstrue my intent, I like what John and the guys are trying to do with the Mustangs in OH (love their Whirlwind props too). Terry Kronk's Mustang had a Geared Redrive system installed and reportedly the PSRU failed (no detailed investigation due to government budget).

The ratio of failures per hour (MTBF) for auto-conversions (based on anecdotal evidence as described above) is astronomically low by comparison - they are literally orders of magnitude worse than for aircraft engines.

I am familiar with the Robinson package, and I like how it looks - I also really like Belted Air's Chevy system for the RV's and William Wynn's work with Corvairs (plus the 5th Bearing guys) - but of all my EAA acquaintences with auto-conversions (I would estimate maybe 8 or 9 of the hundreds of Chapter members I have met/flown with over the last 20 or so years) not one was really happy and this covered Subies, Vortec's, a 3.8L Ford or two, 2 rotaries and an LS - most would not repeat, and more than one eventually removed the conversion and installed a certificated engine. None flew cross-country or acro.

I know that a few guys have the dedication and persistence to make it work, and I am happy for them. And I really do appreciate a clean auto-conversion installation, the Engine-Air turbo-Vette powered Lancair was a work of art in person - but there is so much distance between an auto conversion and a certificated engine that they are simply not in the same universe in terms of reliability and therefore safety.

The real issue is how this combines with the OP's question about high-performance aircraft, where we see people combining experimental engines with highly loaded wings and the result is unfortunately predictable when there are engine failures.

Doesn't mean people shouldn't do it, doesn't mean there aren't some successful well-designed installations, just means I won't use one.
 

T-51ls1

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Does anyone know why the automotive engine's fail vs aircraft engines? Is it the engine its self or is it the reduction gear set up? If it's the engine then thats a fairly easy fix but will cost more in parts to buff it up to handle longer sustained run's. If it's the gear set up that connect's to the prop then i'm guessing its an engineering issue still maybe or other problems. I'm just wondering because i'd really like to use an automotive engine in my homebuilt plane when i get the money for it.
 

Dana

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Does anyone know why the automotive engine's fail vs aircraft engines? Is it the engine its self or is it the reduction gear set up? If it's the engine then thats a fairly easy fix but will cost more in parts to buff it up to handle longer sustained run's. If it's the gear set up that connect's to the prop then i'm guessing its an engineering issue still maybe or other problems. I'm just wondering because i'd really like to use an automotive engine in my homebuilt plane when i get the money for it.
There are problems with both. Redrives are "an engineering issue", but the fact that people are still having trouble with redrives despite the fact that some really smart engineers have been working on them for years means it's a really difficult engineering issue. As for the engine itself, it's not a matter of costing "more in parts to buff it up", the basic problem is that auto engines simply aren't designed for sustained high power running. Cooling and lubrication are two major issues, which can't be simply solved by upgrading parts; the engines just aren't designed for it. Likewise for crankshaft issues; driving a propeller on a short shaft puts very different loading on an engine that driving wheels via a transmission.

-Dana

Just remember -- if the world didn't suck, we would all fall off.
 

Toobuilder

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Yep, it's not any one thing that dooms auto conversions. But I would say that "core" engine failures are rare these days. This is usually the result of someone trying to get far more power out of the engine than it was ever going to see in a car. But the reall killer is the integration package as a whole. Cooling, exhaust, redrives, electrical, controls, etc, are all links in the chain. You can have an engine carved entirely out of billet, yet a blown radiator hose will drop the whole mess into a cornfield (or schoolyard). And the thing many people do, whether backyard mechanics or an engineering team, is "scope creep"... Complexity is a real dangerous thing here, and it is often hard for people to resist the lure of full digital controls, redrives with constant speed propellers, turbos, air conditioning, etc.

its no coincidence that the most successful conversions are usually the simplest.
 

rv6ejguy

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Sorry it is not opinion nor ignorance, just math.

Of over 200,000 registrations, with tens of millions of GA hours per year, there are, relatively speaking, only a handful of auto-conversion powered aircraft, flying typically lower than average hours per year, with higher than average failure rates (anecdotally, since the number of flying conversions is statistically insignificant).

It is also inarguable that integration of auto-conversions is significantly more difficult than aircraft engines, and reliability is incomparable. There are nice looking packages out there, and as I mentioned, a few notable well-engineered exceptions with lots of run time on individual installations (mostly V6 with belted redrives in glider tow operations), but the math is not even close in terms of real world reliability across what are relatively small fleets. Peruse any builder's forum like Van's or the Titan board, the excellent Corvair sites, etc., and bearing, crank, PSRU, ECM, fuel delivery, exhaust, cooling and other issues/failures are the rule, not the exception.

In the case of the Titan Mustang that just went in, it was an engine built by Titan, and it was the 2nd such engine installed in that individual plane - the first one having failed within days of the aircraft getting its' pink slip. Pilot was OK but plane flipped on the forced landing and was damaged. Several of the 'Mini-Merlin' V6 Suzuki conversions have also failed - and don't misconstrue my intent, I like what John and the guys are trying to do with the Mustangs in OH (love their Whirlwind props too). Terry Kronk's Mustang had a Geared Redrive system installed and reportedly the PSRU failed (no detailed investigation due to government budget).

The ratio of failures per hour (MTBF) for auto-conversions (based on anecdotal evidence as described above) is astronomically low by comparison - they are literally orders of magnitude worse than for aircraft engines.

I am familiar with the Robinson package, and I like how it looks - I also really like Belted Air's Chevy system for the RV's and William Wynn's work with Corvairs (plus the 5th Bearing guys) - but of all my EAA acquaintences with auto-conversions (I would estimate maybe 8 or 9 of the hundreds of Chapter members I have met/flown with over the last 20 or so years) not one was really happy and this covered Subies, Vortec's, a 3.8L Ford or two, 2 rotaries and an LS - most would not repeat, and more than one eventually removed the conversion and installed a certificated engine. None flew cross-country or acro.

I know that a few guys have the dedication and persistence to make it work, and I am happy for them. And I really do appreciate a clean auto-conversion installation, the Engine-Air turbo-Vette powered Lancair was a work of art in person - but there is so much distance between an auto conversion and a certificated engine that they are simply not in the same universe in terms of reliability and therefore safety.

The real issue is how this combines with the OP's question about high-performance aircraft, where we see people combining experimental engines with highly loaded wings and the result is unfortunately predictable when there are engine failures.

Doesn't mean people shouldn't do it, doesn't mean there aren't some successful well-designed installations, just means I won't use one.
You are quite right about the OVERALL dismal record of auto engine conversions from a per flight hour perspective. When we did a comparison using the NTSB database a few years back, depending on the criteria used, auto conversions were 6-8 times more likely to be involved in some sort of power loss (all causes) incident/ accident. This is not a good record. What I will say about this is that in almost none of the reviewed accidents was the core engine the direct cause of the accident.

In the case of the Titan power loss incidents, each one can be traced to too much timing or too lean AFRs or in the case with the geared PSRU failure, a propeller far outside the approved mass/inertia limits. One other involved an unapproved exhaust system mod which melted through ECU wiring. Early on, we issued a SB about incorrect timing procedures being used which resulted in detonation failures. Titan is now embarking on an improved ground testing program for the engines. I think this will show huge benefits. Lessons sometimes have to be learned the hard way, we've all done that. As we learn more, things should start to become safer.

I'll just state again for emphasis, most failures are the result of not doing things right to begin with- in other words it is generally well know to people in a a given field that this would be a bad thing to do. I'll qualify that in saying that much of this work is leading edge and development/ testing so there will be things learned that only this will uncover. This is more risky by nature. When you have good people working on a project like the folks at Robinson for instance, things turn out well the first time. Kudos to fine efforts like this.

I'm not sure why people are impressed with the Corvair projects. Someone in the field could see these multiple failures coming even before the first ones flew. I wrote about this a while back on HBA.

One big thing is the lack of standardization once a given FF package is proven. Ideally at this point, all subsequent packages should be identical. Minor changes can throw all the reliability out the window again

So, you are quite correct in saying there is much work to do with auto conversions but most work centers on supporting systems, not on the core engines which are generally very good. PSRU design in particular needs more engineering and scientific validation, especially with regards to TV. Right now, there are only a handful of PSRUs which have a proven track record. Many more have had multiple failures.

To comment on Dana's post, actually a single speed gearbox is not a hard thing to design and make reliable. The harder part is making it reliable driving a propeller under flight loads. To this end, few PSRU makers have applied much engineering to the problem, either in design or testing, hence lots of failures. The TV damping system is a huge part of the puzzle here and this can be expensive to test and prove. The last 5 years have seen a much bigger awareness in TV and some proper fixes being applied. This awareness was mainly caused by all the failures! The wrong way to approach the problem to be sure.
 

Toobuilder

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Does anyone know why the automotive engine's fail vs aircraft engines...
Not that we don't want to discuss this with you, but this topic has been discussed ad infinitum in a variety of threads. I'm not sure we need another round of that in this particular thread. A search will turn up plenty of facts, opinion, and conjecture from both "sides" of the subject.
 

jlknolla

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You are quite right about the OVERALL dismal record of auto engine conversions from a per flight hour perspective. When we did a comparison using the NTSB database a few years back, depending on the criteria used, auto conversions were 6-8 times more likely to be involved in some sort of power loss (all causes) incident/ accident. This is not a good record. What I will say about this is that in almost none of the reviewed accidents was the core engine the direct cause of the accident.

In the case of the Titan power loss incidents, each one can be traced to too much timing or too lean AFRs or in the case with the geared PSRU failure, a propeller far outside the approved mass/inertia limits. One other involved an unapproved exhaust system mod which melted through ECU wiring. Early on, we issued a SB about incorrect timing procedures being used which resulted in detonation failures. Titan is now embarking on an improved ground testing program for the engines. I think this will show huge benefits. Lessons sometimes have to be learned the hard way, we've all done that. As we learn more, things should start to become safer.

I'll just state again for emphasis, most failures are the result of not doing things right to begin with- in other words it is generally well know to people in a a given field that this would be a bad thing to do. I'll qualify that in saying that much of this work is leading edge and development/ testing so there will be things learned that only this will uncover. This is more risky by nature. When you have good people working on a project like the folks at Robinson for instance, things turn out well the first time. Kudos to fine efforts like this.

I'm not sure why people are impressed with the Corvair projects. Someone in the field could see these multiple failures coming even before the first ones flew. I wrote about this a while back on HBA.

One big thing is the lack of standardization once a given FF package is proven. Ideally at this point, all subsequent packages should be identical. Minor changes can throw all the reliability out the window again

So, you are quite correct in saying there is much work to do with auto conversions but most work centers on supporting systems, not on the core engines which are generally very good. PSRU design in particular needs more engineering and scientific validation, especially with regards to TV. Right now, there are only a handful of PSRUs which have a proven track record. Many more have had multiple failures.

To comment on Dana's post, actually a single speed gearbox is not a hard thing to design and make reliable. The harder part is making it reliable driving a propeller under flight loads. To this end, few PSRU makers have applied much engineering to the problem, either in design or testing, hence lots of failures. The TV damping system is a huge part of the puzzle here and this can be expensive to test and prove. The last 5 years have seen a much bigger awareness in TV and some proper fixes being applied. This awareness was mainly caused by all the failures! The wrong way to approach the problem to be sure.
Great post! This is why I like this site, great exchange of info and opinion in a respectful manner.
 

rv6ejguy

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While I fly an auto conversion myself which I developed and this is part of my business, I want to be the first to say, this is not as easy as it looks and it should not be attempted in most cases by people who don't have the right experience and background. I too thought I was pretty smart when I started but I made plenty of mistakes myself and I'll probably still make some more.

Auto conversions are simply NOT for your average builder in most cases and it is true that there are very few proven reliable turnkey packages out there which will perform as reliably as a traditional aircraft engine. Too many people have stars in their eyes and believe all the marketing hype from companies offering relatively unengineered and untested products. There are many one offs done by people which have been very successful but there are many, many others which have not turned out well and many vendor packages which have also been failures. If this was easy and reliable, many more would be flying behind auto engines I believe.

Go into this with eyes wide open and realize you are a test pilot and will be for many hundreds of hours into it. If you don't want this, install a traditional, proven aircraft engine. I can assure you, your life will be a lot easier.
 

DangerZone

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Just a quick point here....I would like to correct something.


It is more likely to be due to either catecholamines or a drop in carbon dioxide from the hypoxia-induced hyperventilation associated with altitude rise. Nitrogen levels would not change significantly enough to produce narcosis with descent from a low concentration to a normal concentration like would you would see with someone who is diving deeper while breathing from a scuba tank (the "rapture of the deep").
Before trying to correct something/someone with unverified assumptions it would be wise to check the scientific facts first. As I replied in the private message you sent me, most of the information that you are interested in should be available if you check the biophysical effects on health of HAHO/HALO and diversion unit soldiers from the '70s of the last century til more recent days. Even though there are some interesting digressions in this thread it would be nice if we could allow it to follow the topic, experimental fighter jet style aircraft.

I mentioned the example of the BD-10 that was a brilliant idea in the late '80s yet suffered quite a few design and structural problems when the project started evolving in the '90s. Besides the video that is available on youtube is there more information on it's construction or 'behind the scene' story of that project? I am sure the author of this topic as well as others who are interested in the experimental fighter style aircraft would appreciate all details that others may have...

One detail is interesting, as the BD-10 project evolved the mass of the aircraft went drastically up (from the initial 725kg to 1025kg, around 300kg!) possibly due to changes which had to be made during the initial design phase. If I am not mistaken there was a test pilot who left the project, was it because the designers would not take his thoughts into consideration or for another reason? Because it seems that the project could have been a success if some changes would have been made on the fuselage. Does anyone have more info to share..?
 

nerobro

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What makes the BD-10 brilliant? (Your word, not mine.) I see a very conventional layout aircraft. A chibi F15.

It could be done better. :)
 

autoreply

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Typical development for light jets:
Underpowered, install more powerful engine, resulting in more engine weight and fuel weight, driving empty mass higher, requiring an even more powerful engine etc.

So select your engine before anything else and make it a realistic choice. Unless you're going for a jet-powered sailplane, a T/W (@ mtow) of 0.35 or so is the minimum...
 
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