What happened
On February 12, 2017, an EC 135 P2+ helicopter, operating as part of a Helicopter Emergency Medical Service (HEMS) mission, was flying toward Tuchola. Approximately eight minutes into the flight, the pilot activated the cabin heating and ventilation system and subsequently discovered that the installation was not functioning.
Despite the failure of the heating system, the pilot elected to continue the mission. Following the completion of the medical flight, the aircraft returned to the HEMS base in Bydgoszcz, where the crew reported the malfunction to the maintenance control center.
The investigation
Technical personnel from the SOT facility in Szczecin conducted a diagnostic inspection of the aircraft. The investigation established that the malfunction was caused by a failure in the electrically controlled mixing valve, which is responsible for blending engine bleed air with cabin air.
Upon identifying the faulty component, technicians replaced the defective valve (S/N: K 58905) with a new unit (S/N: 6251). Following the replacement, the heating system was tested in accordance with the Aircraft Maintenance Manual (AMM 21-00-00 5-2). The tests confirmed that the "Bleed air" message displayed correctly and that the system was fully operational during both ground and flight tests.
Findings
- The probable cause of the incident was the malfunction of the electrically controlled mixing valve due to component wear.