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Geared Drives LS1 for RV-10

Yes, its true, N730WL was damaged Thursday afternoon during a test flight and subsequent emergency landing. Pilot, Bud Warren and I were taking the 10 for a flight around the airport to check out a high operating temperature problem. We took off after a long taxi and climbed normally, however the engine temperature kept climbing even after leveling off. For unknown reasons the engine seemed to quit making power. Bud skillfully banked back toward the runways. Not a good situation. A discussion with Bud today leads me to believe that the high engine temperature may have exceeded an operating parameter in the ECM and the engine reverted to a low power setting. This has yet to be confirmed but obviously needs to be addressed if this is indeed the problem.

Bud managed to get the airplane back to the airport sacrificing altitude and speed without stalling. Incredible job by Bud to get us back to the runway. However, once over the runway, we were too slow and the plane mushed onto the runway rather hard. We bounced and skidded to a stop on the collapsed main gear. Fortunately, there was no fire and Bud and I were able to get out of the 10 without any injuries, Thank God.

Unfortunately, there was considerable damage to the main landing gear and the prop was destroyed. The steps kept the bottom of the fuselage off the runway while we skidded, so no noticeable damage to the fuselage skin or tail. The wings didn't hit the ground but there is some minor damage from the gear folding up. I haven't looked at the landing gear mounts yet or the spar. So I don't know at this ten seconds the full extent of the damage.

This project has been five years in the making and this is a tough pill for me to swallow. I really appreciate the concerns voiced. Will try and keep you posted on any new developments or findings.

Good flying getting the airplane as far as you did...mighty glad both pilots walked away from it.

I know the devastating feeling you have right now. In October 2003, I wrecked my airplane when Subby #1 quit. What a mess!

Thanks on behalf of all experimental aviators for your efforts in trying to get the GM motor to work. Seems like inadequate cooling is the greatest challenge one faces. The answer probably lies in a clean sheet and starting from the beginning. Trying to get a liquid cooling system to work within a former air cooled environment just doesn't do it. There is one guy in Europe who has moved the rads to the wings and he has had great success.
 
Thanks on behalf of all experimental aviators for your efforts in trying to get the GM motor to work. Seems like inadequate cooling is the greatest challenge one faces. The answer probably lies in a clean sheet and starting from the beginning. Trying to get a liquid cooling system to work within a former air cooled environment just doesn't do it. There is one guy in Europe who has moved the rads to the wings and he has had great success.

Yes, the saga of a local RV8, Subie, and cooling problems have continued around here for a year now. I wonder if they'll ever get it worked out..

L.Adamson --- RV6A
 
OEM ECU responses to out of limit programmed sensor outputs has been a major cause of many power loss incidents when these are applied to aviation powerplants. This has been especially true on Subaru and GM installations. I have written a couple of articles on these aspects.

The problem with OEM ECUs is not their basic reliability which is excellent but the different design philosophy and intended application. When faced with high coolant temps just as one example, some ECUs are programmed to enrich mixture or either reduce power through closing the throttle (with drive by wire), limiting spark advance, selectively cutting spark or fuel or shutting down the engine completely by shutting off the injectors, ignition or fuel pump relay.

There are many other sensor anomalies which might trigger a programmed ECU response which are not a big deal on the ground but a big deal when in the air. Many of these responses are there to save the engine and a warranty claim or big repair bill.

In the aftermarket ECUs we supply for aviation, our philosophy is to warn the pilot about out of range or failed inputs but keep the engine running as long as possible at near full power to let him/ her possibly get the aircraft on the ground. The engine is expendable, the airframe and occupants are not.

While reprogramming software for OEM ECUs is widely available, the sheer complexity of the code (up to millions of lines of code today) and the tie in with chassis control and monitoring in many cases may blur or disguise critical commands. OEMs have historically not been keen about releasing all their secrets and very few people understand every nuance of every line of code whether they think they do or not. In the case of several Subaru ECU related accidents, a time vs. road speed sensor input triggered the limp mode function resulting in forced landings. These were not failures of the ECU. They were merely responding to their programming. Chassis control and monitoring software may equal or exceed the actual engine control software these days in many cases making ECU responses even less predictable by people reprogramming units for aviation use.

Unfortunately new windows into these secrets are often found the hard way through an event triggering a power loss.

So this is something to be aware of and another reason to perhaps extend the test flight period longer when using alternative engines and components.
Also keep those engine out procedures and skills well polished and have things thought out on the ground first before each flight. Things can and do happen developing new engine packages.

As a side note, flaps are optional on my checklists for use after power loss. Too many pilots are conditioned to using full flaps for every powered landing and may automatically lower flaps during a no or low power forced landing. Flaps on an RV will increase sink rate and reduce glide ratio by something like 50%. I would use flaps only when the field is made for sure to reduce touchdown speed or avoid an overrun. Over 50% of my powered landing are done clean to keep those skills current. Pre-takeoff briefings with both pilots in both front seats should always include a plan about aborts, glide speeds, duties of the other pilot to reduce the captain's workload- maybe throwing switches, monitoring airspeed!!!!!!, changing tanks, lowering flaps on command or securing exits and systems prior to and after touchdown in case of incapacitation. Not pleasant things to think about but treating these possibilities as real each time, improves your chances for a happy outcome.

The important thing in any forced landing is that you walk away from it. If the damage is repairable or nil, better still. Bud did a good job in getting it down safely. There is almost always something we can learn in hindsight on how we could have done better and nothing teaches you better or shakes complacency more than the real thing- an unfortunate truth.:(
 
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Very interesting concept. Any links of other info? I Googled it and found nothing.

Here's a copy of an exchange I had with Hans Teijgeler regarding an article in the Experimenter on liquid cooling. I believe Hans is flying a RV-8.




> -----Original Message-----
> From: [email protected] [mailto:[email protected]] On Behalf
> Of David Domeier
> Sent: vrijdag 19 juni 2009 5:03
> To: [email protected]
> Subject: [subenews] Re: Any comments/experience on this latest article in
> the Experimenter?
>
>
> There is something I don't understand with regard to liquid cooling.
>
> Why are people trying to re-invent something that was quite well worked
> out and settled back in WWII? Liquid cooling and radiators worked in
> those days, why don't we do it the way the Germans, British and Americans
> did it when they were shooting at each other?
>
> Seems to me they used a plenum with a mild diffusion to slow down the air
> before the radiator and a reverse diffusion in an exit duct to speed it
> up. It worked. Granted, you could not sit on the ground all day but
> neither can one do that with an air cooled engine. All this effort
> chopping up radiators and welding them back together and no diffuser
> plenum - I don't get it.
>
> Speaking of air cooled engines, for the first time in over 4 years of hot
> weather flying, I took off today with a heat soaked engine in 92F weather
> and climbed to 12,500' without a level off for cooling on the way up.
>
> Seemed like something was not quite right. :)
>
> dd

LOL

Like I get with mine you mean. A copy of a spitfire installation with two
rads in pods inside the wings. I can idle on the ground all day with no
temperature issues and climb to your mentioned 12,500' on full power without
even seeing temperatures raising one degree. 185F coolant and 220F oil.
Always.

So yes, I agree. The WWII guys had it right. Copying them is not easy, as
our aircraft were never designed with that cooling system in mind, but if
you manage to do it, it really works.

Hans
 
Cooling...

As soon as I read here that the ECU possibly went into "limp home mode" I thought back to the article on Ross's home page for the SDS system that he sells. It deals with the possibility that the "automotive type" ECUs would execute a "limp home" when certain situations are encountered as he has stated in this forum. This is REALLY bad news in an airplane.
Also in this vein, I recall that Ross had talked about the need to eliminate the thermostat altogether. I wonder if Bill's -10 could possibly had a stuck or partially stuck thermostat and that was causing the overheating? I can still remember very vividly replacing a stuck thermostat in my car and the brand new one was also defective. The car got really hot and exploded a radiator hose and the hot steam almost wiped out my face and vision. I've distrusted the things ever since! :mad:
I was just sick when I read that Bill's plane had gone down. I have been following his progress with great interest. You can always replace "stuff" but people are not replaceable. Bill, glad you and Bud are OK.
 
Wing cooling

Here's a copy of an exchange I had with Hans Teijgeler regarding an article in the Experimenter on liquid cooling. I believe Hans is flying a RV-8. ...
Hans has helped get several aircraft flying. The one with the wing radiators is a Jodel.

 
As soon as I read here that the ECU possibly went into "limp home mode" I thought back to the article on Ross's home page for the SDS system that he sells. It deals with the possibility that the "automotive type" ECUs would execute a "limp home" when certain situations are encountered as he has stated in this forum. This is REALLY bad news in an airplane.
Also in this vein, I recall that Ross had talked about the need to eliminate the thermostat altogether. I wonder if Bill's -10 could possibly had a stuck or partially stuck thermostat and that was causing the overheating? I can still remember very vividly replacing a stuck thermostat in my car and the brand new one was also defective. The car got really hot and exploded a radiator hose and the hot steam almost wiped out my face and vision. I've distrusted the things ever since! :mad:
I was just sick when I read that Bill's plane had gone down. I have been following his progress with great interest. You can always replace "stuff" but people are not replaceable. Bill, glad you and Bud are OK.

Many people are flying with thermostats successfully however they do occasionally fail in the closed position. I've seen a few in 30 years or so of working on cars and aircraft. For the most part they are very reliable and if they fail, it is in the partially open position.

With bypass type thermostats on the inlet side of the pump which most engines have used for the last 20 years, 10-20% of the coolant flow never reaches the rads even with the 'stat fully open however. This is somewhat wasteful and requires more radiator area to compensate. Not having a 'stat requires some type of radiator shutters or flow valve to regulate coolant temps in varying OAT conditions. It is interesting to note that most WW2 liquid cooled engines did not use coolant thermostats but rather manual or automatic radiator exit doors.

Certainly if the 'stat is not there, it cannot fail.

It takes time to sort out new cooling systems on aircraft through flight testing. I believe that Bill's RV10 uses a very different rad setup than Bud's Wheeler did and Texas is a hot place this time of year. I do hope that Bud can get to the bottom of the power loss and cooling issues. I'd love to see what this engine can do in an RV10. Power to Bill and Bud to continue development and testing.:)
 
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Same Hans from the Airsoob list way back when? I recall Hans as a sharp guy, a physicist, and quite qualified for fundamental design. I'd pay careful attention to whatever he might have to say about anything.
 
Hans is a very friendly and sharp dude and has worked on many liquid cooled aviation projects in Europe. He is well known by the experimental world over there and here for that matter through various forums. He readily admits that his twin under wing rad setup cools very well mainly because it has a lot of rad area. Other pluses to this layout are superior ground cooling due to good wetting of the rad faces by the outer portion of prop arc where velocities are better than at the prop shank and more duct length for better pressure recovery in flight.

Wing rads can be done very well but present a lot of structural and line routing problems with the fuel tank location on RVs unfortunately.
 
I got an email yesterday from Bud that says they were NOT using a thermostat in Bill's -10. Too bad as that removal might have been an easy partial fix to the heating problem. Oh well.
I hope to talk at length with Bud at Oshkosh as I have already put my deposit down on his psru before the accident. I have faith that it will eventually get worked out and I have some ideas to discuss with him.




As soon as I read here that the ECU possibly went into "limp home mode" I thought back to the article on Ross's home page for the SDS system that he sells. It deals with the possibility that the "automotive type" ECUs would execute a "limp home" when certain situations are encountered as he has stated in this forum. This is REALLY bad news in an airplane.
Also in this vein, I recall that Ross had talked about the need to eliminate the thermostat altogether. I wonder if Bill's -10 could possibly had a stuck or partially stuck thermostat and that was causing the overheating? I can still remember very vividly replacing a stuck thermostat in my car and the brand new one was also defective. The car got really hot and exploded a radiator hose and the hot steam almost wiped out my face and vision. I've distrusted the things ever since! :mad:
I was just sick when I read that Bill's plane had gone down. I have been following his progress with great interest. You can always replace "stuff" but people are not replaceable. Bill, glad you and Bud are OK.
 
As far as I know he was as of 2015. Last time I heard several years ago, he had 600+ hours on it. He doesn't post here much any more, preferring to just fly it and avoid the comments and questions.

There have been some gearbox oil seal troubles on some of the other LS/RV10 conversions which didn't turn out well. Causes found and fixes have been implemented now.
 
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Wet wing tanks and heat exchangers?

What cooling arrangement did the said 600 hour LS powered RV 10 use?

On business jets, the engines have a very small oil reservoir capacity. For example the P&W 615 and 617 family use only 4 liters per side:eek:
However the engine oil is cooled with a heat exchanger that circulates the cold fuel from the wings and trades heat with the engine oil.

I would think you could gain a fair amount of supplemental cooling with this method for an LS install.

Or for a TDI VW into an RV 4 or 9 you might get virtually all of your engine cooling using flat plate heat exchangers and the fuel in the wet wing tanks. The result would be zero cooling drag. Dan Horton and Dave Anders are you reading this?
 
As far as I know he was as of 2015. Last time I heard several years ago, he had 600+ hours on it. He doesn't post here much any more, preferring to just fly it and avoid the comments and questions.

There have been some gearbox oil seal troubles on some of the other LS/RV10 conversions which didn't turn out well. Causes found and fixes have been implemented now.

Thanks. I will try and reach out.
 
What cooling arrangement did the said 600 hour LS powered RV 10 use?

On business jets, the engines have a very small oil reservoir capacity. For example the P&W 615 and 617 family use only 4 liters per side:eek:
However the engine oil is cooled with a heat exchanger that circulates the cold fuel from the wings and trades heat with the engine oil.

I would think you could gain a fair amount of supplemental cooling with this method for an LS install.

Or for a TDI VW into an RV 4 or 9 you might get virtually all of your engine cooling using flat plate heat exchangers and the fuel in the wet wing tanks. The result would be zero cooling drag. Dan Horton and Dave Anders are you reading this?

I believe these are using large obliquely mounted rads in the cowling. These would be high drag but that doesn't matter so much with 350hp on tap.

You don't want to heat up fuel on piston engines with EFI. That's bad news for creating vapor lock problems.

The amount of heat to dissipate into the coolant is huge. Surface conduction heat exchangers would have to be gigantic and are impractical for everyday use for a variety of reasons. I've already demonstrated cooling THRUST in my conventional radiator setup on my RV6A.
 
What cooling arrangement did the said 600 hour LS powered RV 10 use?

On business jets, the engines have a very small oil reservoir capacity. For example the P&W 615 and 617 family use only 4 liters per side:eek:
However the engine oil is cooled with a heat exchanger that circulates the cold fuel from the wings and trades heat with the engine oil.

I would think you could gain a fair amount of supplemental cooling with this method for an LS install.

Or for a TDI VW into an RV 4 or 9 you might get virtually all of your engine cooling using flat plate heat exchangers and the fuel in the wet wing tanks. The result would be zero cooling drag. Dan Horton and Dave Anders are you reading this?

I assume, as fuel burns off you have less and less heat transfer media?
 
What cooling arrangement did the said 600 hour LS powered RV 10 use?

On business jets, the engines have a very small oil reservoir capacity. For example the P&W 615 and 617 family use only 4 liters per side:eek:
However the engine oil is cooled with a heat exchanger that circulates the cold fuel from the wings and trades heat with the engine oil.

I would think you could gain a fair amount of supplemental cooling with this method for an LS install.

Or for a TDI VW into an RV 4 or 9 you might get virtually all of your engine cooling using flat plate heat exchangers and the fuel in the wet wing tanks. The result would be zero cooling drag. Dan Horton and Dave Anders are you reading this?

The trick with the jets is that, even at minimum fuel levels, you still have a lot more available mass to transfer the heat to. There are also concerns with jet fuel that it will start getting waxy and solidifying if it gets cold; circulating the heated fuel back to the tank mitigates that. We don't have that problem on our little airplanes. If anything, we want to keep the fuel cool.

For a water-cooled engine I think you're better off doing a P-51 style radiator scoop.
 
When you are out of fuel you are out of heat:D

However when low on fuel,
if the warm return line entered the tank at the high end, the heat would dissipate as the fuel run back down along the bottom wing skin, working its way around and through the ribs on its way back to the cool intake port at the wing root.

Nobody can take off with zero fuel and there would need to be a certain minimum fuel required. Perhaps better suited to Finland and Alaska.
I suppose a byproduct would be leading edge anti icing. Normally the tail plane LE and propellor collect ice before the main wings however.
 
I looked at this many years ago - the short story is that it won't work, there is way too much heat to get rid of. You can't dissipate it through the wing skin quickly enough. Crunch the numbers on it to your satisfaction, but it won't work.
 
Done in 1931 with 2300 HP

R J Mitchell did do it in 1931 with the supermarine S6 B with a Rolls Royce 2300 HP V12.

In that case the heat exchanger tubes were direct to the skin and they used most of the fuselage to do it.

https://en.wikipedia.org/wiki/Supermarine_S.6B

https://en.wikipedia.org/wiki/Supermarine_S.6B

No doubt that radiators are smaller with simpler plumbing and a smaller target for bullets. -not so much a factor in an RV.
 
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There are numerous examples of surface conduction cooling from the 1930s on race aircraft. In most cases the fuselage, floats and sometimes wings had embedded cooling tubes covering many dozens (hundreds?) of square feet of surface area.

Now take an RV10. How will you install the coolant tubes all over the wing and fuselage skin? How will you ensure heat transfer from the tubes to the skin? How will you collect and route coolant from the engine to all those tubes? Will you give up 100 pounds of useful load in tube, manifolds and coolant weight? Are you ready for the leak potential of all those joints and connections? How will your ground cooling be on a hot day?

Ever wonder why nobody has done it since the '30s?

I've already flight proven the concept of the Meredith Effect on my RV and documented it here and in a Kitplanes article if you're looking for zero cooling drag.

Surface conduction cooling simply does not make sense on many levels for a GA application.
 
Is there any other unknown success story out there that a potential builder could look at. I know this is not a popular move around here.
 
Robinson aircraft has several LS engines flying in See Bee RC-3 amphibian AC, sometimes called
Vee Bee's with the Robinson V8 Conversion. Lots of total hours and proven cooling and propellor drives.

The Z-06 engine is supercharged and rated at 650 HP. See one on you tube by searching for "Republic RC-3 Seabee Engine Startup" Perfect for high altitude lakes where you can have sea level performance at 9000 ft.
The gear reduction and prop are part of the Robinson package and purpose engineered for the job in the see bee.

In the RV 10 realm, the biggest items are cooling and your chosen prop and drive units. A massive undertaking for those that have the desire, time and engineering support. A full price IO 540 and new prop will cost a lot less and provide years of reliable service and resale value at any point in time.
 
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Robinson aircraft has several LS engines flying in See Bee RC-3 amphibian AC, sometimes called
Vee Bee's with the Robinson V8 Conversion. Lots of total hours and proven cooling and propellor drives.

The Z-06 engine is supercharged and rated at 650 HP. See one on you tube by searching for "Republic RC-3 Seabee Engine Startup" Perfect for high altitude lakes where you can have sea level performance at 9000 ft.
The gear reduction and prop are part of the Robinson package and purpose engineered for the job in the see bee.

In the RV 10 realm, the biggest items are cooling and your chosen prop and drive units. A massive undertaking for those that have the desire, time and engineering support. A full price IO 540 and new prop will cost a lot less and provide years of reliable service and resale value at any point in time.

The Seabee setup solves all the setup challenges other engine installations would have to face. The placement of the radiator seems to be the hardest puzzle to solve otherwise, the PSRU/redrive does not appear to be the problem.
 
Jeff Ackland's P85 has had great success from the get go with his LS engine and Ballistic drive. http://altitudegroupllc.com/aircraft/p85/

I've mentioned the Australian glider tugs here a couple times. These worked very well in a hard environment, replacing 540 Lycomings which were not lasting very well. Unfortunately some of the links are no longer up.

Robinson has been doing the LS conversions for a long time but I talked to a fellow who had numerous problems with his and there was another one on a trip to the far north which required an engine change after some pistons went south. I don't know enough about the actual causes to comment much further. The Robinson gearbox is too heavy for an RV10 and would require tail ballast I believe. They're a little too heavy to be just the right fit here IMO although with a composite prop and the rad moved aft of the firewall, I believe it's doable. There is one more lurking up in Eastern Canada which flew but had a gearbox problem (not Robinson) and a forced landing which went smoothly. I suspect it will be flying again this year.
 
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The Robinson gearbox is too heavy for an RV10and would require tail ballast I believe.
Even with the shorter gearbox Robinson advertises? I believe the longer one was designed for prop clearance issues on the Seabee.
I agree that weight and cooling are the shortfalls.
 
Even with the shorter gearbox Robinson advertises? I believe the longer one was designed for prop clearance issues on the Seabee.
I agree that weight and cooling are the shortfalls.

We pretty much have the recipe for cooling figured out and proven.

The Ballistic airboat drive has no provision for a hydraulic C/S prop which would be desirable on a -10. You might be stuck with an electric MT or if you can wait a couple years, there is a new gearbox under development which may have a reasonable cost and weight for something like this.

The existing Auto PSRU, EPI and Robinson drives are worth about twice to 3 times what a crate LS3 goes for these days. That's a hard pill to swallow for most I believe.
 
We pretty much have the recipe for cooling figured out and proven.

The Ballistic airboat drive has no provision for a hydraulic C/S prop which would be desirable on a -10. You might be stuck with an electric MT or if you can wait a couple years, there is a new gearbox under development which may have a reasonable cost and weight for something like this.

The existing Auto PSRU, EPI and Robinson drives are worth about twice to 3 times what a crate LS3 goes for these days. That's a hard pill to swallow for most I believe.
Who are the collective "we" you refer to?

I am not sure I want a constant speed prop. The added weight significantly impacts performance I am told. Also, slow speed performance is horrible especially as you try to hold the nose up before touchdown.
 
Who are the collective "we" you refer to?

I am not sure I want a constant speed prop. The added weight significantly impacts performance I am told. Also, slow speed performance is horrible especially as you try to hold the nose up before touchdown.

We refers to the people who have been successfully flying auto conversions for a long time now. There is no real mystery to cooling efficiently with low drag. You can see some discussion here: http://www.vansairforce.com/community/showthread.php?t=103432&highlight=meredith+effect I have some decent rules of thumb for rad area, volume, piping diameters, inlet and outlet areas and duct designs if you're interested in pursuing something like this.

You'd probably want a C/S prop on an RV10 for the TO, climb and landing advantages although with 400+hp on tap, you might just get a fixed pitch prop to work ok on a -10.
 
The Corsair guy posted here a few times. Seems liability will prevent them from trying to certify it in the US.
 
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