Incident Overview
On 2 October 2016, a Tecnam P2006T (registration SP-MAC) was conducting an LKE exam flight for the MEP(L) rating near Wyszków, Poland. As part of the exam, the crew performed an in-flight engine shutdown and restart exercise. The engine was shut down correctly, but subsequent attempts to restart it were unsuccessful. After several failed restart attempts, the aircraft's battery was depleted.
Flight and Landing
With one engine inoperative and no electrical power, the crew was unable to obtain landing gear position indications. They established contact with another aircraft, which relayed the situation to EPBC airport. The crew extended the landing gear using the emergency system and performed a low approach over runway 28 at EPBC to visually confirm gear deployment. The aircraft then landed on grass runway 10 without further incident.
Post-Flight Inspection
After taxiing to the hangar, the engines were shut down and an inspection was conducted. No anomalies were found. The engine that had been operating throughout the incident was started, and its alternator energized. The engine that had failed to restart in flight was then started successfully. Both engines were tested and performed normally. The aircraft operator contacted the Part 145 maintenance organization Bartolini Air, which authorized a ferry flight with the gear extended to EPLL for further checks. No faults were found, and the aircraft returned to service.
Probable Cause
The investigation commission did not establish a direct cause for the incident. The probable cause was suggested to be one or more of the following: the aircraft was in uncoordinated flight, the fuel valve was closed, the electric fuel pump was turned on, or the magnetos were not switched on.
Contributing Circumstances
The examiner involved in the flight regularly operates various P2006T aircraft, which differ in equipment. One variant includes an additional battery for engine starting. The aircraft involved (SP-MAC, serial number 66) has a single battery that serves both engine starting and avionics. The in-flight engine restart procedure requires turning off both power buses, which disables the alternator's charging capability and allows the battery to be drained during restart attempts.