Incident Description
On September 18, 2016, at EPSC airport, an EC 135 P2+ helicopter experienced an anomaly during the start of engine No. 2. The pilot observed that the engine directly reached FLIGHT parameters even though the start switch was positioned to IDLE. The commander aborted the engine start and reported the malfunction to the technical service. The helicopter was subsequently grounded.
Maintenance Actions
Technical personnel from the SOT in Szczecin diagnosed the issue. They identified a malfunction of the Switch Unit 20VE. The switch unit was replaced with a new one. Following the replacement, a functional test was performed without engine operation, in accordance with AMM 31-11-20, 5-1 steps 1-12 (Rev. 21). The test was completed without any remarks. Subsequently, a functional test was conducted with the engines running, per AMM 31-11-20, 5-1 steps 13-20 (Rev. 21), resulting in a positive outcome. The helicopter was then deemed airworthy and returned to service.
Probable Cause
The probable cause of the incident was operational wear of the ENG 2 start switch of the Switch Unit 20VE.
Safety Recommendations
No safety recommendations were issued by the Polish State Commission on Aircraft Accident Investigation (PKBWL) following the investigation.