Here is an email that I received on another group. Might help you guys in
this debate.
> > A while back, I posted the result of a cursory look at the accident
> > statistics for aircraft powered by auto engine conversions. It *was*
an
> > awful shallow pass, and at the time I promised to look into the issue
> > deeper.
> >
> > I have since obtained the NTSB accident databases for the years 1998,
> 1999,
> > and 2000, and am ready to provide more exact figures.
> >
> > The nice thing about the accident databases is that they usually
describe
> > the type of engine that powers the aircraft. Unfortunately, the FAA
> > registration database is a lot more vague. A lot homebuilts are merely
> > described as having experimental engines; a number don't even have an
> > entry. So we can't do the classic "x% of auto engined-airplanes have
> > accidents every year vs. y% Lycont-powered planes."
> >
> > Instead, we can take another tack: We can catalog the number of each
type
> > of engine in accident aircraft, then take a look at how often a loss of
> > engine power was a factor in the accident. The figures don't include
> cases
> > where the cause was traced to carburetor ice or the pilot running out of
> > fuel.
> >
> > Presentation of data:
> >
> > The "ENGINE" column describes the general category of the engine, one of
> > four types:
> >
> > "Certified" Engines include Continentals, Lycomings, Franklins,
Pratt
> > and Whitney, Jacobs, Vendeyev, LOM, and Walter.
> >
> > "Auto" Engines include those identified as Subarus, Suzukis, Fords,
> > Volkswagens, Revmaster, Chevrolet, GM, Mazda, Honda, Stratus, or NSI.
> >
> > "Non-C/4" are four-cylinder, non-certified, non-auto conversion
> > engines. They include the Rotax 912 series, the Jabiru, and the
Rotorway.
> >
> > "Two-Stokes" include Rotax 4* and 5* series, Yamahas, KFMs, Hirth,
> 2SI,
> > and Cuyuna.
> >
> > The next column is "ACC". This is the number of accidents in the
> 1998-2000
> > timeframe that involved each category of engine
> >
> > "PCT" is the percent of the total accidents where that category of
engine
> > was installed.
> >
> > "LOP" are the number of accidents where loss of engine power was
involved.
> >
> > "LOP%" is the percentage of cases where accidents involving aircraft
> > mounting that category of engine suffered an engine-related loss of
power.
> >
> > -
> > The Results:
> >
> > ENGINE ACC PCT LOPLOP%
> > -- --- --- ---
> > Certified 332 51% 57 17%
> > Auto95 15% 27 28%
> > Non-C/4 70 11% 13 19%
> > Two-Strokes13421% 46 34%
> >
> > Of primary interest here, I think is the percentage of accidents where a
> > loss of engine power occured...17% for certified-engine-powered planes,
> vs.
> > 28% for auto-engine conversions. Two-strokes were even higher; almost a
> > third of their accidents involved a power failure.
> >
> > It's interesting to note the non-certified four strokes are doing
> > practically as well as the certified engines. The Rotax 912/914 series
> > alone does even better... a LOP% value of 13%.
> >
> > An interesting side note: Lycomings outnumbered Continentals by nearly
> > four to one
