The Safety of Experimental Amateur-Built Aircraft

​​​​Experimental amateur-built (E-AB) aircraft represent nearly 10 percent of the U.S. general aviation fleet, but these aircraft accounted for approximately 15 percent of the total—and 21 percent of the fatal—U.S. general aviation (GA) accidents in 2011. Experimental amateur-built aircraft represent a growing segment of the United States‘ general aviation fleet—a segment that now numbers nearly 33,000 aircraft. 

The National Transportation Safety Board (NTSB) undertook this study because of the popularity of E-AB aircraft, concerns over their safety record, and the absence of a contemporary and definitive analysis of E-AB aircraft safety. The study employed several different methods and data collection procedures to carefully examine this segment of U.S. civil aviation. This comprehensive approach resulted in a detailed characterization of the current E-AB aircraft fleet, pilot population, and associated accidents. 

Four sources of data formed the basis of this study. First, the NTSB performed a retrospective analysis of accident and activity data over the last decade to compare the accident experience of E-AB aircraft with that of similar non-E-AB aircraft used in similar GA flight operations. Second, the NTSB conducted in-depth investigations of all E-AB aircraft accidents during 2011, which provided a case-series of accidents for more detailed analysis. Third, a broad survey of the community of aircraft owners and builders was conducted by the Experimental Aircraft Association (EAA) in July and August 2011, and the data were made available to the NTSB for analysis to understand the population of E-AB aircraft builders and owners. Finally, discussions with EAA representatives, Federal Aviation Administration (FAA) officials, E-AB aircraft builders and owners, kit manufacturers, and representatives of E-AB aircraft type clubs provided insights on E-AB aircraft safety issues and solutions.

​​The study compared the accident experience of E-AB aircraft with that of similar non-E-AB general aviation aircraft over the last decade. A detailed analysis was also conducted  of the 224 accidents, involving 227 E-AB aircraft, that occurred during 2011. These analyses revealed the following factors defining E-AB aircraft accidents:

• E-AB aircraft account for a disproportionate number of total accidents and an even more disproportionate share of fatal accidents when compared with similar non-E-AB aircraft conducting similar flight operations.
• Accident analyses indicate that powerplant failures and loss of control in flight are the most common E-AB aircraft accident occurrences by a large margin and that accident occurrences are similar for both new and used aircraft.
• Structural failures have not been a common occurrence among E-AB aircraft.
• In comparison with similar non-E-AB aircraft, a much higher proportion of accidents involving E-AB aircraft occur early in the operational life of the aircraft.
• A similarly large proportion of E-AB aircraft accidents occur shortly after being purchased by a subsequent owner. For example, 14 of the 224 study accidents during 2011 occurred during the first flight by a new owner of a used E-AB aircraft.

Through further analysis of the accident record and the results of an EAA survey of E-AB aircraft owners and builders, the study also found:

• The majority of E-AB aircraft are now built from commercial kits, rather than from purchased plans or original designs.
• Pilots of E-AB aircraft, whether involved in accidents or not, have similar, or higher, levels of total aviation experience than pilots of non-E-AB aircraft engaged in similar general aviation operations. 
• Pilots of E-AB accident aircraft, on average, had significantly less flight experience in the type of aircraft they were flying than pilots of non-E-AB aircraft.

Finally, study analyses identified the following key issue areas to explain these findings and recommended actions to improve E-AB aircraft safety.​

​​In response to the findings of this study, we issued 12 recommendations to the Federal Aviation Administration and 4 recommendations to the Experimental Aircraft Association. The recommendations include expanding the documentation requirements for initial aircraft airworthiness certification, verifying the completion of Phase I flight testing, improving pilots‘ access to transition training and supporting efforts to facilitate that training, encouraging the use of recorded data during flight testing, ensuring that buyers of used E-AB aircraft receive necessary performance documentation, and improving aircraft identification in registry records.​