Accident Data for Homebuilt "EZ" Type Aircraft
April 1996
RAF recently received a summary of all reported accidents during the period from 1983 to 1989 for various selected homebuilt aircraft. This document was put out by the NTSB and is indeed a very sobering document.
Since there are more EZ's flying than any other type of homebuilt, it was expected that there would be more EZ accidents during this time period. According to this report there have been 71 accidents during this time period. Of these, 24 of them were fatal accidents (33.8%). Mechanical failures of one kind or another caused 33 accidents, while 38 were caused by pilot error.
Pilot error accidents are to be expected. Even factory built, certificated aircraft accidents are mostly caused by pilot error. The unsettling thing is the very high rate of accidents caused by mechanical failures. In certificated (factory built) aircraft mechanical failures account for only 1.6% of all accidents. In homebuilt aircraft (not only EZs, but all homebuilts) mechanical failures account for 19% of the accidents. With the EZ-type aircraft, 47% of all reported accidents from 1983 to 1989 were caused by mechanical failures.
While it will always be difficult to control the pilot error-type accidents in any type aircraft, as responsible builders of homebuilt aircraft, we need to be more aware of the things that can cause mechanical failures and possibly lead to accidents.
Some of the mechanical reasons pointed out in the NTSB report are as follows: mud wasp plugged fuel tank vent-, contamination in float bowl; Teflon tape in float bowl; propeller failure/loss; water in fuel; drain not installed in lowest point; carb ice/carb heat inadequate; throttle spring failure; canopy not latched; grip came off control stick; crankcase breather kinked (blew all oil overboard), in-flight fire; improper wing incidence; landing gear improperly installed (attach tab); excessive connecting rod bearing wear.
You will note that only one of the above was an actual mechanical failure of the engine. All of the rest were simply caused by mistakes made by the builder and, essentially, all could have been eliminated by a careful, systematic approach to the important tasks of building and flying your own aircraft.
The only pilot oriented reasons called out by the NTSB report were: careless hand propping; lack of training (familiarity with type); fuel mismanagement; and failing to extend land gear.
From our own investigations of EZ-type accidents we know that low flying, buzz jobs and low-level aerobatics account for an abnormal number of accidents.
Reprinted from CP 57
As we have discussed previously in the Canard Pusher and as has been reported by Aviation Consumer magazine, the experimental homebuilt airplanes have an accident record that is worse than that experienced with certificated, factory-built aircraft. This is due to a number of factors. There are more chances for non-conformality to occur, thus each airplane built is actually a new, experimental, research, high-risk article.
This new research aircraft is often tested by pilots who have very little time in type and who often do not follow careful flight safety procedures in their testing. Also, because these aircraft are more fun to fly and have higher performance, many accidents are the result of improper aerobatics or other high-risk flying.
To report accidents and incidents
Write: Rutan Aircraft Factory
1654 Flightline
Mojave, Ca 93501
or Fax: (805) 824-4174
Attention RAF
As always, we publish information of this nature in the hope that it may help prevent more accidents.
As reported in CP 47, seven of the eleven Long-EZ accidents occurred during low altitude buzzing or acrobatic maneuvers. Because many individuals, including those who may purchase one of these aircraft or may ride in one as a passenger, may not be aware of the risks involved we included a plans change in newsletter 57 requiring placarding the aircraft and the owner's manual with the following announcement:
WARNING!
STATISTICS INDICATE THAT AMATEUR BUILT AIRCRAFT ARE MORE LIKELY TO HAVE AN ACCIDENT, INCLUDING A FATAL ACCIDENT, THAN FAA CERTIFICATED, MANUFACTURED TYPES. WHILE STRICT ADHERENCE TO OPERATING PROCEDURES CAN REDUCE THIS RISK, THE HAZARDS ARE SIGNIFICANT PARTICULARLY DURING INITIAL FLIGHT TESTING OR WHEN OPERATED IN A NONCONSERVATIVE MANNER.