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A Look At Auto Conversion Accident Statistics

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Wanttaja

Sky Savant
Joined
Sep 15, 2013
Messages
2,854
Location
Seattle, WA
There have been several threads lately on auto conversions and safety. I have a database of homebuilt aircraft accidents from 1998 through 2014. I have extracted the accidents involving auto-engined homebuilts. Further, I have identified the engines by general type.

Here's a summary of the overall results. "Engine Probs" are those accidents that involved either a known mechanical issue with the the engine, or loss of power due to undetermined reasons. "% Engine Probs" is the percentage of total cases involving homebuilts powered by that type of aircraft that involved loss of power.

EngineCases% of TotalEngine Probs% Engine Probs
VW & Derivatives18739.4%7339.0%
Subaru17536.8%5531.4%
Ford163.4%637.5%
GM (Liquid-Cooled)459.5%2044.4%
Corvair153.2%853.3%
Honda102.1%330.0%
Mazda173.6%952.9%
Eggenfellner51.1%240%
Other51.1%240%
Total475100%17837.5%


Note that about 37% of auto-engined homebuilts began with an engine failure. Given the small sample size for many of these engines, a few percentage points higher or lower aren't very significant.

It should be noted, though, that only about 18% of accidents involving certified engines are attributable to the engine.....

It's interesting to compare the fixed wing vs. rotary wing results. Most of the above engine types are involved with very few rotary-wing accidents, but 42% (74 out of 175) of the Subaru accidents involved gyros. However, the engine was involved in only 8.1% of the cases, vs. nearly half (48.5%) on the fixed-wing aircraft.

Ron Wanttaja
 
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