I Love My AeroVee

[gammaxy]

Noel,

Some of the questions you raise about compression and exhaust valves of N12YX are answered in the docket found here:
https://dms.ntsb.gov/pubdms/search/docu ... mkey=93754

This document in particular lists measured compressions and the date and values at the previous compression test:
https://dms.ntsb.gov/public/60500-60999 ... 610329.pdf

[lutorm]

For those of you who believe that paying attention to detail during assembly will give you a reliable aerovee engine, how do you square that against the fact that two factory aircraft had their engines fail on takeoff with disastrous results?

That is a fair concern, but it should also be considered that the factory aircraft would also be the ones that are doing the testing. If any should have problems, it should be them. That's how the problems would be found before making it to the customers.

It's unfortunate it had to have such consequences, but I don't think that indicates anything except that they are actually testing the stuff they are developing. (I'm not familiar with the details and whether those aircraft had vanilla installations and how many hours, but it sounds like at least one was a turbo development platform.)

[lutorm]

For those of you who believe that paying attention to detail during assembly will give you a reliable aerovee engine, how do you square that against the fact that two factory aircraft had their engines fail on takeoff with disastrous results?

That is a fair concern, but it should also be considered that the factory aircraft would also be the ones that are doing the testing. If any should have problems, it should be them. That's how the problems would be found before making it to the customers.

It's unfortunate it had to have such consequences, but I don't think that indicates anything except that they are actually testing the stuff they are developing. (I'm not familiar with the details and whether those aircraft had vanilla installations and how many hours, but it sounds like at least one was a turbo development platform.)

[kmacht]

I can't speak to the accident with the turbo but the second accident had a stock aerovee in it. It was the plane they were using to give transition training in and actually failed while on a transition training flight with a customer aboard. It was not a flying test bed.

Keith
#554

[SonexN76ET]

Just Aircraft had a factory Super STOL with a Rotax 912 go down last year due to an engine failure. A couple of months ago the AOPA sweepstakes reimagined 150 with a remanufactored engine swallowed a valve and went down. Engine failures in aviation can and do happen to many. Sonex is not alone.

If it were not for the Aerovee I would not be able to afford an airplane.

Jake

[kmacht]

The difference is that both of those accidents had assignable causes. The Just Aircraft accidents were both traced to fuel contamination (one fiberglass fibers in the tank and the other water in the fuel). The AOPA plane because it swallowed a valve. Neither of the two sonex factory aircraft have an assignable root cause. I would have a far different opinion of the aerovee if it were announced that some major component was defective or that some assembly error were found to be the issue. At least those things could be inspected or corrected. Right now we are left flying with the knowledge that even the factory doesn't know how to keep their engines running but somehow we are supposed to know how to keep ours from stopping on takeoff. Everyone is free to make their own risk decisions and what I choose to accept will probably be different than what you do. I'm not denying that some have had success with their engines.

Keith
#554

[daleandee]

I can't speak to the accident with the turbo but the second accident had a stock aerovee in it. It was the plane they were using to give transition training in and actually failed while on a transition training flight with a customer aboard. It was not a flying test bed.

I want to thank Keith for his very tempered approach in pointing out a fact that is very relevant to this entire discussion. I admit that at first I didn't quite understand the depth of what he's driving at. I know many have had good service with their VW engines and I know that any engine can fail. But a failure of a factory training aircraft with out finding a cause is troubling. Knowing the cause means a fix can be found. If there is to be a shining example of the robustness and reliability of this particular VW conversion, surly it would be found on the factory assembled and maintained customer training aircraft.

Dale Williams
N319WF @ 6J2
Myunn - "daughter of Cleanex"
120 HP - 3.0 Corvair
Tail Wheel - Center Stick
Signature Finish 2200 Paint Job
168.7 hours / Status - Flying
Member # 109 - Florida Sonex Association
https://www.youtube.com/watch?v=1VP7UYEqQ-g

[achesos]

Lots of excellent points have been made in this string. Here goes my attempt:

As an AeroVee owner and also a test engineer at an engine manufacturer, I too am interested (maybe somewhat fascinated) in understanding root cause of failure. What we (pilots) may need to (re-) consider about the FAA published information is that (in my opinion) the FAA determines the cause of the accident - not necessarily the cause of the engine failure.

My point is we may all want to hear precisely what the actual root cause was, but we might need to consider the source and the intention of that investigation. What we really want to know is exactly the same thing that Sonex does -
But, that type of engineering analysis costs big money. I was just there (at Sonex) for a tour on January 19th, and it does not appear that this company is swimming in excess cash flow. They appear to me to be doing what they can within the limitations they have. I know of no legal requirement that they share anything and everything they have learned during their own investigations and test research, but appreciate it when they do.

These are experimental aircraft, with all the pros and cons that come with that category. As a pilot in command, I need to determine the airworthiness of the aircraft before I fly it.
Great discussion on how important engine health is to a flight ending with a controlled landing at the pre-determined destination. Engine health matters, independent of brand, but because it is an assembly of lots of parts, each with a tolerance, that get assembled by different people with different levels of skill, so engine health then must differ, right? It all adds up to something we might like to label as "Quality", but split the hair finely enough, and there are no two alike in the universe... I believe that this is our assumed risk in any powered plane.

[lutorm]

Right now we are left flying with the knowledge that even the factory doesn't know how to keep their engines running but somehow we are supposed to know how to keep ours from stopping on takeoff.

I'm not sure what you mean. Your engine can stop on takeoff. Any engine can stop on takeoff. Everyone has to accept that risk or they shouldn't fly. Anything else and I think you're deluding yourself.

I'm not going to say that I'm comfortable with the fact that no root cause was found, of course it would be better to know what went wrong. But that happens to certified engines, too. I just read this article about a TSIO-520 partial power loss on take-off where Continental themselves inspected the engine and concluded that it was a "failure for unknown reasons". (Mike Busch thinks he knows what happened, though.) And that was even though the factory could inspect the entire engine without additional crash damage.

Life is a numbers game. We accept certain risks in exchange for doing (or not doing) certain activities or spending more or less money. In this case it's most likely true that the risk of failure in an Aerovee is larger than in a certified engine installation. How much larger is hard to say. If nothing else, that's just from the vast number of hours accumulated on certified installs. You pay for that with a price that's about 4x higher. If you are really risk-averse, it might make sense to pay those 4x. Others may not be willing to able to do that and choose to accept the risk.

The real problem with making this trade-off is that we have such poor statistics on the reliability of experimental engines.

[John keith]

Just want to say after building and flying my plane and hearing and seeing other people struggle with there Aerovee that so Far I have nothing but good to say about my engine. Like any new engine install you'll have bugs to work out but as far as temperature issues especially I have had none. To be fair I have only flown spring and fall and my engine only has 10 to 12 hours on it so it's breaking in and will run hotter but hottest oil temp recorded after doing circuits was 190 degrees and hottest cylinder head was 390 and exhaust gas 1220, maybe running a little rich but so what. Just wanted to let people know the engine is great if it's set up right like any engine.