Event
On June 18, 2011, at approximately 1450 Pacific daylight time, an experimental Aerovodochody L-29 Delfin, registration N37KF, experienced a partial failure of the primary airframe structure that supports the airplane's rudder while in the air race pattern at Reno-Stead Airport, Reno, Nevada. The commercial pilot, who was the sole occupant, was not injured. The airplane, owned and operated by Raju Mann Ward, sustained substantial damage.
Aircraft and Flight
The local flight was conducted under 14 Code of Federal Regulations Part 91 as an air race qualification/training flight. It departed from Reno-Stead Airport approximately 20 minutes before the accident. Visual meteorological conditions prevailed, and no flight plan had been filed.
Failure and Damage
According to the Federal Aviation Administration (FAA) inspector who responded to the scene, while the airplane was in flight, part of the engine support structure—installed as part of a modification to accommodate a higher thrust engine—failed to hold the new engine in proper alignment. This failure allowed jet blast from the engine to be deflected onto a portion of the primary airframe structure. The melting of that structure affected the support and movement of the airplane's rudder.
Although the failure occurred in flight, it was not detected until the pilot was operating the rudder pedals during the landing roll. The pilot was able to keep the airplane on the runway by applying alternative or non-standard control inputs.
Investigation Findings
During the investigation, it was determined that at least five other L-29 airplanes had the same type of mounts, which were all designed and welded or manufactured by the same entity. According to the FAA inspector who examined these mounts, the welding was poor on some of them, and there was some degree of structural variation among a number of the mounts.