What happened
On March 3, 2018, a crew from the Warsaw branch of a medical rescue service was preparing for a rescue flight. While performing startup procedures using a ground power unit, the pilot successfully started the left engine without issue. However, during the attempt to start the right engine, the pilot noted that the engine spool failed to accelerate. Simultaneously, the pilot observed an increase in exhaust gas temperature and heard an abnormal noise coming from the starter motor.
In response to these indications, the pilot aborted the start sequence and shut down the functioning left engine. The technical coordination center was immediately notified of the situation.
The investigation
Following the incident, the EC 135 P2+ was removed from service for technical inspection. The investigation focused on the mechanical failure encountered during the engine start sequence. Maintenance personnel at the Warsaw-Babice technical station conducted a diagnostic assessment of the engine components.
During the inspection, it was determined that the drive shaft of the right engine's starter motor had sheared. To rectify the issue, technicians replaced the damaged starter motor (S/N P2501) with a functional unit (S/N P1366) in accordance with the Aircraft Maintenance Manual (AMM). After the replacement, a functional test was performed, which showed the starter motor operating normally, allowing the helicopter to return to service.
Findings
- The investigation established that the primary cause of the incident was the shearing of the starter motor drive shaft.
- The failure of the shaft was attributed to operational wear and tear.