Twin Engine Corvair powered JAG-2

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lr27

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TFF

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Professional pilots are constantly tested on engine out flying. It's the weekend warrior that has trouble with twin ops. Years ago in Flying mag, I believe, they had the statistics of twin problems from the perfect pair. Bonanza and Barron. Bonanza pilots survived loosing their only engine more than the Barron guys loosing just one. Generally same airplane and same type of pilots. It's all about training and practice. Plenty of cases where the pilot secured the wrong engine, i.e. Shutting off the good one. Now you really have a problem. Side note at the airline I worked at, two pilots ferrying a plane stalled both engines at an extreme altitude they should not have been at. Locked both engines up so they were a glider. Had to get blown to 25,000 to start the APU. They destroyed both engines with a core lock. Of course crashed. One of the findings was there was no duel engine failure emergency checklist. Another set of pilots on a ferry flight in our old turboprop planes, got cute. Captain went to talk to the flight attendant and the copilot shut one of the engines down to surprise the capt. Of course it did but it freaked the FO out too. The restarts kept overspending the prop which shuts the engine down. Back and forth they would overspeed one and it would shut as they got the other started to just overspeed again. At least they survived and got it flying again at 1000 feet but the engines rolled the plane a couple of times on the way down. Of course they were seat of their pants chasing the plane and never got the checklist out to stop making their mistakes.
 

BoKu

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Prove to me by mathematical probability analysis that the chance of engine failure is doubled because it is a twin or even a tri engine, I triple dog dare you. No self respecting man can turn down a triple dog dare!
Nah. But if you want to show us a statistical analysis that bounds what the probability really is, that's cool.
 

proppastie

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I wouldn't be so certain. Mounting the engines on the wings provides inertia relief that reduces wing bending moment at the side of body. So the wing spars are likely fine as-is even with short tip extensions.
Estimated max gross: 2150 lbs
It started life as an RV-6A (Van's site: 965 lbs empty, 1600 lbs gross).

550 lb is a big jump......mounting the engines to the wings had to produce changes in the spars if they are mounted somehow to the spars.

Edit: looked at more pictures.....and it is not clear if modifications of the spar were made.
It still is quite an accomplishment, and given the scope and quality of the project one would surmise he did/had done the stress correctly.
 
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proppastie

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Prove to me by mathematical probability analysis that the chance of engine failure is doubled because it is a twin or even a tri engine, I triple dog dare you. No self respecting man can turn down a triple dog dare!
Depends how you analyze or frame the question. Anecdotally I had 1 pilot induced fuel starvation incident and one ice induced fuel starvation incident in about 3500 hr. Had I been in a twin, both engines would have quit? So in the hypothetical twin fuel starvation twice the number of engines failed in the same period of time.
 

lr27

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Unless there are a significant number of incidents in which one engine dies BECAUSE the other one is there, there can't be twice as many engine failure incidents in twins as there are in singles. Proppastie's post shows why. OTOH, I have no doubt the risk IS increased some.
 

blane.c

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I think it is likely you will have an engine problem, not as likely to have a failure. I also think it doesn't matter how many engines you have, you are still likely to have an engine problem but not on all of them at the same time (usually). I also think odds are for idiots. I have listened to the logic of turbine singles being so reliable and reading of a turbine single crashing in the Amazon because of engine failure. It doesn't matter the odds when it happens to you. I will give up some efficiency for multiple engines, it is better.
 

lr27

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I think it is likely you will have an engine problem, not as likely to have a failure. I also think it doesn't matter how many engines you have, you are still likely to have an engine problem but not on all of them at the same time (usually). I also think odds are for idiots. I have listened to the logic of turbine singles being so reliable and reading of a turbine single crashing in the Amazon because of engine failure. It doesn't matter the odds when it happens to you. I will give up some efficiency for multiple engines, it is better.
Careful. With that kind of philosophy, you may be susceptible to buying too many lottery tickets.
 

FritzW

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Prove to me by mathematical probability analysis that the chance of engine failure is doubled because it is a twin or even a tri engine, I triple dog dare you. No self respecting man can turn down a triple dog dare!
...a triple dog dare!!!!

An engine has X probability that it will fail during Y hours of operation. 2 engines have 2X probability that one of them will fail during Y hours. ...or 1X probability that one will fail in 1/2 Y hours.

A roulette wheel has a 1/38 chance of landing on a certain number in one spin. It has a 1/1 chance of landing on that number in 38 spins.

If you pick two numbers you have a 1/19 chance of hitting one of them in one spin or a 1/1 chance of hitting one of the numbers in 19 spins.

EDIT:
Even simpler answer. ALL parts have a chance of failing. If you double the number of parts you double the chance that one will fail.
 
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BJC

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Anyone know how it performs on a single engine with the fixed pitch propellers?

Reminds me of a blunt-nosed Wing Derringer.


BJC
 

Daleandee

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Anyone know how it performs on a single engine with the fixed pitch propellers?
No idea as I haven't seen any performance information or specifications given.

Here is a video of the landing when it was taken over to the paint shop:


Dale
N319WF
 

radfordc

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A roulette wheel has a 1/38 chance of landing on a certain number in one spin. It has a 1/1 chance of landing on that number in 38 spins.
Nope. Just because the chance of hitting a particular number is 1 in 38 doesn't guarantee that the number will appear in 38 spins. Conside a coin toss. The chance of heads is 1 in 2...but you can flip the coin a 100 times and it's possible that it will come up tails every time. Possible....not likely.
 

radfordc

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Anyone know how it performs on a single engine with the fixed pitch propellers?
I don't know...but I like the quote from the builder,
Remember, the glide ratio of ANY (properly flown) twin with an engine out is better than the glide ratio of ANY single with an engine out.
 

FritzW

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Nope. Just because the chance of hitting a particular number is 1 in 38 doesn't guarantee that the number will appear in 38 spins....
Of course it doesn't, if it did I'd be a rich man. I was just pointing out the basic idea.
 

FritzW

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Remember, the glide ratio of ANY (properly flown) twin with an engine out is better than the glide ratio of ANY single with an engine out.
True. But, unless the design has adequate single engine performance, you double the chance that your going to be gliding.

I'm all for multi engine, I've got 7,500 hours as a LoadMaster on the Lockheed Tri-Motor (C-130). The more engines you have, the higher the chance you'll have to shut one down.
 

FritzW

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I'd guess well over a 100. BUT... most of them weren't the "oh s#it!, shut it down!" type. Most we're just precautionary. And a lot were prop problems, not engine problems.

EDIT: when you have a fairly little airplane with four fairly big engines, it's best to shut down a questionable engine if you don't have a compelling reason to leave it running.
 
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