Amateur-built WAIEX N75654 accident near Washington, Georgia

Probable cause

The in-flight failure of the aircraft’s Y-tail attachment structure during maneuvering flight due to overload. Contributing to the accident was, the kit manufacturer’s use of 14 CFR Part 23, Appendix A design guidelines intended for a conventional tail airplane without a V- (or Y-) tail.

NTSB analysis

Radar and global positioning system (GPS) information showed that the sport pilot took off from his home airport and initiated a climbing left turn until an altitude of 4,700 feet mean sea level (msl) was reached. The experimental, amateur-built (E-AB) airplane then continued on a westerly heading until the GPS stopped recording data. The last recorded radar return with altitude information was at 4,300 feet. Before the last radar return, the airplane was in a slight descent and had accelerated to about 100 to 110 knots ground speed. Witnesses reported that the engine stopped running in flight, and the tail separated before the airplane collided with the ground. Examination of the wreckage revealed that the airplane’s fuel system was empty and the propeller showed no evidence of rotation at impact. The airplane’s “Y-tail,” which was essentially the same as a V-tail, was found about 550 feet from the main wreckage, which confirmed that the airplane broke up in flight. The breakup appeared to have initiated in the forward Y-tail attachment structure, which was an aluminum attach angle. The lower attach angle separated in tension along the right side and further separated with the fracture running from the right to the left. When the lower attach angle broke, the structure that formed the aft connection Y-fitting also fractured and separated. Due to a lack of GPS data and the typical sample rate of radar data, the exact circumstances, including precise airspeed and any maneuvering leading up to the breakup, are not known. It is likely that the pilot, distracted by the loss of engine power, allowed the airplane to enter an unusual attitude, and the tail separated during the pilot’s attempted recovery from the unusual attitude.

Although there were (and are) no required design standards or criteria for E-AB airplanes, the kit designer used a pre-1996 version of 14 Code of Federal Regulations Part 23, Appendix A, when he designed the airframe. The pre-1996 version stated that the design load criteria in the appendix were an approved equivalent for the certification of conventional, single-engine airplanes of 6,000 pounds or less maximum weight. The 1996 revision of Appendix A removed the reference to conventional airplane and added an expanded section defining the applicability of Appendix A. The expanded definition explicitly excluded using Appendix A criteria when designing the V-tail configurations of certified airplanes. In general, the surface loads on a V-tail configuration may be greater than the design loads expected on the surfaces of a conventional tail airplane. The airplane was designed in the 2002 to 2003 timeframe and the first plans were sold in 2004.

Text from the NTSB. Open the NTSB docket for ERA12FA018 for the full record.