REFLECTOR: alternative engines

Wed Dec 5 18:03:23 CST 2007

Without stepping too high up onto a soap box, there are many other installation issues relating to auto engine aero conversions, that left ignored (mostly because of inexperience; ignorance; or more thorough testing) could cause the engine to become silent - and completely ruin your day.
Those who have an engineering/or engine mechanic background excluded - there are reasons (backed by real world bad experiences) why buiders should be cautious about auto-engine conversions.  The engine itself is not the entire story.  A reliable engine + an unreliable propeller speed reduction drive = an unreliable power plant.  Same logic applies to exhaust systems; induction systems; engine mounts; cooling systems - all of which are customized to fit/work in an airplane environment.  Ryan Falconer, who is an accomplished racing boat engine builder, following the failure of a Falconer engine in the Papa-51 Thunder Mustang, is attributed to saying, "...aircraft engines really are different".  I personally know of three Velocity builders who have experienced crashed or emergency landings because of unanticipated problems with their auto engine installation (and not the engine).  Without naming names - I know of a Subaru powered Velocity that went down because the single ignition spark plug wires were routed too close to the exhaust; _all_ of the wires burned in half on the maiden flight; aircraft crashed; pilot survived; but years of hard work went down the drain.  Another Velocity (rotary powered) experienced not one, but several engine fires due to broken oil lines and oil cooler fittings - the spouce of the pilot said, "Either that engine goes - or I do".  Another (I believe it was a Subaru powered) Velocity recently had an engine fire on takeoff in Naples, Florida - the pilot and passenger barely escaped serious injury.  What I'm saying here is ... it is not just the engine that is important - it is the _complete_ engine installation; propeller speed reduction drive; and propeller and their related systems.  EVERYTHING NEEDS TO WORK.  And if you - as the builder - are not in a position to _know_ (with a very high degree of certainty) that everything WILL work - then maybe its best that you get some additional technical assistance - or think about a traditional aircraft engine.
The absolute _worse_ reason why the uninitiated should consider an automotive engine is, "It is less expensive than an Lycoming or Continental".  Bunk!  Talk with those who have installed auto conversions and ask what time and money they have invested in designing; purchasing; installing; and testing their engines.  Chances are it greatly exceeds the cost of a traditional aircraft engine (especially if one considers the time involvement).
In my opinion, one should consider an auto engine like one who enters the ministry ... do it because you are "called" to do so.

Hoping everyone catches the wonderful spirit of the season!
Scott B.

  ----- Original Message ----- 
  From: Alex Balic 
  To: 'Jim Agnew' ; 'Velocity Aircraft Owners and Builders list' 
  Sent: Wednesday, December 05, 2007 3:40 PM
  Subject: Re: REFLECTOR: alternative engines

  I might add that when I was doing my research before deciding on the Subaru, I found their test schedule- can't remember now, but they pull off of the line and test run engines at cycles up to 10,000 rpm for extended periods (hours) at a time to test for failure modes- My engine will be loafing at around 5600 rpm, but it is nice to know that that is not a strain - I have never heard of a crank failure in even a race version of a Subaru or Honda or Toyota engine- (yes I know the pro race versions are built differently)  did hear about a broken Honda valve once though on an F1 car, but that was running at about 22,000 rpm or so, (the FIA has recently limited rpm to a paltry 19,000 for safety reasons) so I can't really complain - not saying that it is not possible, but I will stand behind the Japanese quality control and design ability anytime- my design ability is another matter of course, but I have been very judicious in what I have done, and certainly will give it a good workout before getting airborne... I have no concerns about the mechanical ability of the engine to reliably produce power for the aircraft, but I will maintain a vigilant watch on my cooling and fuel systems, because if it does ever go quiet, it will almost certainly be because of one of those two things..

  Alex

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  From: reflector-bounces at tvbf.org [mailto:reflector-bounces at tvbf.org] On Behalf Of Jim Agnew
  Sent: Wednesday, December 05, 2007 1:07 PM
  To: Velocity Aircraft Owners and Builders list
  Subject: Re: REFLECTOR: alternative engines

  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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