REFLECTOR: alternative engines

[Jim Agnew]

I'll add to Al's comments, you have never driven on the German Autobahns where the throttle is a binary device as in idle and flat out.
Or how about marine conversions that spend most of the time close to wide open.
 
Jim

 
James F. Agnew
Jim_Agnew_2 at Yahoo.Com
Tampa, FL
Velocity 173 Elite Aircraft Completed & Flying 



----- Original Message ----
From: Al Gietzen <ALVentures at cox.net>
To: Velocity Aircraft Owners and Builders list <reflector at tvbf.org>
Sent: Wednesday, December 5, 2007 1:19:51 PM
Subject: REFLECTOR: alternative engines


Gary wrote:
 
Also be aware that 
most insurance companies will not insure an auto conversion. With the 
limited companies writing experimental policies you may not get insurance. 
 
I wouldn’t argue against using a Lycoming, but I have not found insurance to be a reason to use one.  When I went to get insurance I had two quotes to choose from. And I was a relatively low time pilot (200 hrs) and had no canard time.
 
The fact is auto engines were designed to operate under a totally different 
environment. They typically work at 15% of their maximum power most of their 
lives. 
 
You’re right that the average duty cycle is low, although I think 15% is understating it a bit.  But if you look at the test programs that the engines are subjected to in development testing you’ll find that it is very rigorous, perhaps more severe than certified engines. Many hours of full throttle operation, and hundreds of full throttle simulated acceleration cycles.  
 
The aircraft engine is also derated by limiting its rpm to somewhere around 3000.  It’s peak power capability is somewhere considerably above that.
 
I have heard of more crankshaft, connecting rod and valve failures on aircraft engines than on auto engines; even when used in aircraft.  The vast majority of issues with auto engine conversions in aircraft are related to installation factors, and possibly the re-drive, rather than the basics of the engine.  These are the challenges for the builder.  Every conversion installation has some first-of-a-kind features.
 
My personal conclusion was that if the choice was limited to pistons, rods and valves; I may as well stick with a certified engine.  The rotary is a significant departure, and offers potential advantages; that’s my opinion FWIW. And if the issues truly are related to installation factors rather than the choice of engines; then perhaps it doesn’t matter.
 
I have 70 hours now on my rotary installation, and all is well.  A long way to go to 1500-2000 hrs; but I’m about past the ‘infant mortality’ kinds of issues, and I’d fully expect the engine to get there (definitely it will outlast me). Yeah; in warm weather my oil temps mean that, after the first couple thousand feet at well over 1000 fpm, I have to limit my climb rate to something more typical of a Cessna cool day. I know of ways to resolve that issue – and will when we get back toward summer, but that is not an issue unique to an alternative engine.
 
I recently gave a ride to a guy who flies a Baron and a Cozy.  In a followup e-mail he says: “I enjoyed looking at and flying your airplane.  The power, smoothness and sound of the rotary was very impressive.  I’ll take that.
 
Al


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