What happened
On May 7, 2016, a Cessna T207A was conducting a skydiving flight in the vicinity of the Białystok-Krywlany (EPBK) aerodrome within the TRA59 reserved area. During the climb from FL80, the two-person crew observed a brief low-voltage warning. While the warning initially subsided after the crew reduced the electrical load, the low-voltage indication returned continuously after the skydivers had exited the aircraft. The crew noted a progressive drop in battery voltage on the EDM 700 digital indicator. Following established checklist procedures, the crew disconnected the alternator, allowing the aircraft to land safely at EPBK without further incident.
The investigation
The PKBWL investigation focused on the mechanical state of the aircraft's electrical system. A technical inspection of the aircraft following the landing revealed significant physical damage. Investigators found a large gap between the two halves of the alternator housing and discovered that the ground wire had broken due to vibrations. Additionally, an accumulation of metal shavings was found within the engine compartment.
Findings
- The primary cause of the incident was an alternator failure due to undetermined reasons.
- Vibrations caused the alternator housing to separate and led to the breakage of the ground wire.
- The presence of metal shavings in the engine compartment suggests internal mechanical degradation of the alternator component.