Pondering Waiex engine choices

Bullet Proof?

While chasing that philosopher's stone of general aviation, the "bullet proof" piston engine, I ran across this stimulating post on aircraft engine reliability.

Based on the data posted, I estimated the fleet-wide odds.  Over a 25 year period this is the rough-order-of-magnitude fraction of aircraft engines (including automobile engine conversions) that experienced catastrophic in-flight failure:

Lycoming:         1 in 1000
VW:                  1 in 120
Ford/Subaru:     1 in 30
Mazda:              2 out of 3
Chevy:              4 failures each

This is based on actual NTSB accident investigations back to 1985, compared to aircraft fleet sizes currently registered (as of 2009).

The truth is probably significantly worse for the Subaru/Mazda because there were very few flying before 15 years ago or so.  People have been flying behind Fords since the 1930s (Model A) and the VWs since the 1970s and maybe earlier.  Chevy enthusiasts have been trying to fly the "big block" engines but most have been using the Corvair.  I am disappointed the Mazda engines did so poorly here, because I had/have high hopes for the Wankel (rotary) engine.

The VW conversions actually come out looking pretty good.  The Aerovee slated for use in our Sonex probably does better than above because the data includes ALL Volkswagen derivatives.

The poor record of the Chevy conversions may be slightly overstated, but then again maybe not, because if the author's data is to be believed, apparently there are currently NONE registered (I cheated and divided by one).  The first thought that springs to mind is that they all must have crashed or scrapped!

As a postscript, I will add that the engines that I found most often mentioned as "bullet proof" are the Lycoming O-235 and O-360.  That's encouraging news for our Bearhawk, which sports the latter.

Montana Feedback

I have excused myself from getting my hands dirty the last couple of days due to an apparent sinus infection.  Good times.

But Don did get an answer from the bearhawk builder in Montana, with responses to our earlier queries.

Key points:

• Project was started in 2000; owner is now selling due to medical issues.  Aircraft was built in the garage of an EAA technical counselor who was involved "from day one"  (Probably because it was the owner's first project.)  Very encouraging.
• No cargo door because it's not in the plans!  (I guess it was a later, builder initiated improvement).  Relatively straightforward to retrofit, but does involve some welding.  And removal of fabric covering (which is Stits process, by the way).
• The Airframe & Powerplant mechanic who did the evaluation rated the sheet metal work on the wings as "fair" due to some imperfect riveting (rivets not flush, or not bucked/crimped perfectly).  This is good news because it is not a dimensional issue (i.e. wings are straight!).  We will want to remove wing skins and redo some riveting.
• The same A&P rated the TIG-welded fuselage cage as "good."
• All material and hardware came from a known good supplier (Aircraft Spruce).  Except the engine, which was salvaged from a damaged aircraft (engine was not damaged, but was overhauled to zero time).  Also, project includes a constant-speed prop from same source.  Bonus!
• Building logs are not 100% complete, but should be OK.
• The landing gear is 4-6" longer than called for by the plans, a modification intended for rough fields/bush flying.

Overall, this is encouraging information and makes sense.  Slightly better than I was hoping, actually.

Questions for the Helena, Montana Bearhawk Builders.

Was the rear cargo door left off because the fuselage frame was modified?
How difficult do you think it will be to rework the fabric skin to include this door?
Why are you not completing the project?
Have there been any design updates issued that you have incorporated since your plans were issued?
Why do you think the inspecting A&P only rated the work on the wings as fair?
Who were your major hardware suppliers?
What is the total time on the O-360?
What is the history on the propeller?
What kind of building logs did you keep?
Was this your first aircraft build?
Did you have any help along the way from inspectors or mechanics?
What kind of welding did you use for the fuselage?
What was the most difficult part of the build process?
What fabric covering system did you use?
What did you use to paint your welded fuselage frame?
Do you have any jigs or fixtures that might be useful for completing the project?
How much longer is the landing gear than the standard bearhawk?
How far along is the wiring?
Were you going to set this plane up as a constant speed prop?