Incident Summary
On April 3, 2018, a Eurocopter EC 135 P2+ helicopter, registration SP-HXZ, operated by Lotnicze Pogotowie Ratunkowe (Polish Medical Air Rescue) for HEMS (Helicopter Emergency Medical Service) missions, experienced an in-flight caution shortly after departure from its base at Sokołów Podlaski. The crew was responding to a medical emergency in Łuków.
Flight Details
The helicopter departed at 09:06 local time. During the acceleration phase, at an altitude of 700 feet, the Crew Alert Display (CAD) showed a FADEC MINOR caution for engine 1. At that time, engine parameters were within normal limits. In response, the aircraft commander decided to return to the base, where the helicopter landed safely at 09:13. The three crew members on board were uninjured. Weather conditions were reported to have no influence on the event.
Maintenance Actions
To identify the cause of the caution, a mechanic inspected the helicopter and performed resistance measurements on the P1 connector pins V and C of the power turbine speed (NPT) sensor, following the Engine Maintenance Manual (EMM) 72-00-02 Rev.36. The measurement on the warm engine exceeded the permissible limits specified in the engine maintenance documentation.
Consequently, in accordance with the helicopter's maintenance documentation (KCO 083/005/HXZ/1/1), the mechanic replaced the NPT (power turbine speed) sensor with a new unit, following EMM 77-11-00 Rev.36. After replacement, functional checks per EMM 71-00-00 Rev.36 were performed with positive results; the FADEC MINOR caution did not reappear on the CAD. The aircraft was then returned to service.
Cause
The direct cause of the FADEC MINOR 1 caution was a malfunction of the power turbine speed sensor.