Nepal's Aircraft Accident Investigation Commission (AAIC) has released Preliminary Report on Yeti Airlines ATR 72 crash earlier in January.
The accident occurred during a visual approach for runway 12 at Pokhara International Airport which was the crews third sector for the day. The flight was operated by two Captains, one who was in the process of obtaining aerodrome familiarization for operating in Pokhara and the other Captain was the instructor pilot.
The Captain undertaking familiarization was occupying the left-hand seat and was the Pilot Flying (PF) and the instructor was occupying the right-hand seat as the Pilot Monitoring (PM).
On final approach at 700ft, PF disengaged the Autopilot and called for flaps 30 however the flight data recorder (FDR) did not record any flap surface movement at that time and instead the propeller rotation speed (Np) of both engines decreased simultaneously to less than 25% and the torque (Tq) started decreasing to 0% which suggests both propellers going into the feathered condition.
At 10:56:50 radio altitude called out five hundred feet with the aircraft reaching a maximum bank angle of 30 degrees at this altitude. The yaw damper disconnected four seconds later and the PF consulted the PM on whether to continue the left turn and the PM replied to continue the turn subsequently, the PF asked the PM on whether to continue to descend and the PM responded it was not necessary and instructed to apply a little power.
At 10:56:54 the flap's surface movement to the 30 degrees position was observed and as ATC gave the landing clearance at 10:57:07, the PF mentioned twice that there was no power coming from the engines.
At 10:57:11, the power levers were advanced first to 62 degrees and then to the maximum power position. It was followed by a “click” sound at 10:57:16. One second after the “click” sound, the aircraft was at the initiation of its last turn at 368 feet AGL, and the high-pressure turbine speed (Nh) of both engines increased from 73% to 77%.
At this point the PF handed over control of the aircraft to the PM at 10:57:18 and at 10:57:20, the PM (who was previously the PF) repeated again that there was no power from the engines. At 10:57:24 when the aircraft was at 311 feet AGL, the stick shaker was activated and a second sequence of stick shaker warnings was activated when the aircraft banked towards the left abruptly. The radio altitude alert for two hundred feet was annunciated, and the cricket sound and stick shaker ceased.
At 10:57:32, the sound of impact was heard in the CVR. The FDR and CVR stopped recording at 10:57:33 and 10:57:35 respectively.
This report suggests the likely hood of inadvertent selection of condition levers to feather position by PM when the PF called for flaps 30 which resulted in the aircraft stalling and subsequently crashing. As per the FDR data, all the recorded parameters related to engines did not show any anomaly.