What happened
On November 17, 2015, at approximately 12:00 LMT, a Guimlam Cabri G2 helicopter was conducting training flights at EPDE Dęblin. The crew, consisting of an instructor and a student pilot, was performing circuit patterns as part of an autorotation simulation exercise.
During the maneuvers, the crew experienced three distinct instances of momentary engine power loss. The first two occurrences took place at an altitude of 1,100 ft before the second turn; these were described as subtle and were initially perceived by the crew as turbulence. However, a third instance occurred during the takeoff phase at an altitude of approximately 20-30 ft while the aircraft was accelerating. This third event was characterized by a short but very strong and dynamic jerk associated with the loss of power. Following this third event, the crew aborted the training task and landed safely at the departure aerodrome.
The investigation
The investigation focused on the mechanical performance of the engine power management system. Following the incident, the operator, Heli Invest Services, grounded the aircraft for inspection. The continuing airworthiness management organization (CAMO) directed a check of the engine governor system.
As a result of the technical analysis, the tachometric breaker was replaced with a new component. Subsequent flight tests and onboard system checks performed after the replacement showed no further irregularities. The manufacturer was also consulted for technical opinion, confirming that the observed disturbances in the governor system could have been caused by a temporary malfunction of the tachometric breaker.