What happened
On October 19, 2020, a Piper PA2-161, registration OY-JBF, was conducting a local instrument flight rules (IFR) training flight departing from Roskilde Airport (EKRK). While the aircraft was in a climb phase, the pilots activated the cockpit heating system. Immediately following this action, white smoke became visible within the cabin.
In response to the smoke, the crew deactivated the heating system, which caused the smoke to dissipate. The pilots subsequently issued an emergency message and decided to return to EKRK. The aircraft landed safely at the aerodrome without further incident. The flight took place during daylight hours under visual meteorological conditions.
The investigation
The investigation focused on the source of the smoke observed in the cockpit. A technical inspection conducted by the aircraft's maintenance facility identified that a small amount of brake fluid had leaked near one of the cabin's air heating vents at an earlier time.
It was determined that when the heating system was engaged, the heat caused this residual brake fluid to evaporate, resulting in the production of the white smoke. Following a thorough cleaning of the area, the maintenance team was unable to replicate the fault.