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 LOP LOP% > > ------ --- --- --- ---- > > Certified 332 51% 57 17% > > Auto 95 15% 27 28% > > Non-C/4 70 11% 13 19% > > Two-Strokes 134 21% 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....
