What happened
On September 18, 2016, during the startup of the number two engine of an EC 135 P2+ helicopter at Szczecin Airport (EPSC), the pilot observed an irregular engine behavior. Despite the engine start switch being set to the "IDLE" position, the engine transitioned directly to "FLIGHT" operating parameters. Recognizing the malfunction, the pilot immediately aborted the engine start procedure and reported the issue to the maintenance department.
The investigation
The aircraft was subsequently withdrawn from service for technical evaluation. Maintenance personnel from SOT Szczecin conducted a diagnostic inspection of the helicopter's systems. The investigation established that the Switch Unit 20VE was malfunctioning. To rectify the issue, technicians replaced the faulty switch unit with a new component. Following the replacement, functional tests were performed in two stages: first, a ground test without engine ignition was conducted in accordance with the Aircraft Maintenance Manual (AMM-31-11-20, 5-1, items 1-12, Rev. 21), which yielded no issues. A second functional test was performed with the engines running (per AMM 31-11-20, 5-1, items 13-20, Rev. 21), which also resulted in a positive outcome. The helicopter was then cleared for return to service.
Findings
- The probable cause of the incident was the operational wear of the engine 2 start switch within the Switch Unit 20VE.
Safety action
- The operator has undertaken preventive measures to ensure that all technical and operational personnel within the facility are briefed on the details of this occurrence.