Accident Summary
A Yakovlev Yak-52, being used for a familiarization flight, impacted an open field in a residential area after a pilot transmitted a distress call on the Unicom frequency. The aircraft descended vertically, and witnesses reported the engine was developing full power. The flight's purpose was for one pilot, a retired military pilot and airline captain, to familiarize the other with the aircraft. The aircraft was destroyed on impact.
Wreckage Examination
During wreckage examination, a brass nut was found inside the crushed skin of the empennage. The nut was determined to have come from an air hose assembly used for pneumatically operated systems such as engine start, flap, and landing gear extension and retraction. On one end of the assembly was a brass adapter that consisted of a nut and fitting. According to a partner of Squadron 52 LLC, the adapter portion was always connected to and integral to the hose assembly. The hose assembly, though not normally carried in the aircraft, was typically taken on cross-country trips to allow jump-starting the engine if the air tank developed a leak.
The nut exhibited numerous gouges. It was found positioned between the elevator bellcrank and housing. When investigators moved the bellcrank by hand, full up and down elevator control could not be achieved due to the nut's presence. The gouges on the nut were consistent with contact from the elevator bellcrank. Scrape marks were also observed on the underside of the bellcrank housing. It could not be determined how or when the adapter assembly separated from the hose, nor how the nut came to be in the empennage.