Early in 2023, world witnessed to one of the worst accidents in the aviation industry's history when a civilian aviation aircraft ATR-72...
Early in 2023, world witnessed to one of the worst accidents in the aviation industry's history when a civilian aviation aircraft ATR-72 belonging to Yeti Airlines in Nepal crashed about a kilometer to the touchdown nearing its destination.
Nearly 5 months later, investigations are nearing completion, and one of the aviation industry expert TheFlightChannel has come up with a simulated reconstruction of the entire event in a well explained video.
The reconstruction sequence captures as below,
- Pre-flight Preparation
- Passengers and Crew
- Captain Anju
- Flight Attendants
- Departure from Kathmandu
- Approaching Pokhara
- Deadly Error
- Engine Feathering
- Turning onto the Airport
- Crash (Real Video)
- Investigation
On 13 February, a preliminary report was released. According to the committee, the data recorders indicated the aircraft's propellers had been moved to feathered position prior to the crash. Feathering a propeller causes the engine to produce no power, and it is only done in flight after an engine failure, to minimise drag caused by windmilling. The propeller feathering occurred after the pilot flying (PF) ordered flaps set to 30 degrees; the flight data recorder showed the flaps didn't move while the propeller speed fell below 25% and engine torque fell to 0%.
One theory is the pilot monitoring inadvertently moved the condition levers, which control the propeller, to the feather position instead of moving the flap lever as intended (the flap and condition levers are next to each other in the ATR 72).
From the preliminary report:
At 10:56:27, the PF disengaged the Autopilot System (AP) at an altitude of 721 feet Above Ground Level (AGL). The PF then called for "FLAPS 30" at 10:56:32, and the PM replied, "Flaps 30 and descending". The flight data recorder (FDR) data did not record any flap surface movement at that time. Instead, the propeller rotation speed (Np) of both engines decreased simultaneously to less than 25% and the torque (Tq) started decreasing to 0%, which is consistent with both propellers going into the feathered condition. On the cockpit voice recorder (CVR) area microphone recording, a single Master Caution chime was recorded at 10:56:36. The flight crew then carried out the "Before Landing Checklist" before starting the left turn onto the base leg. During that time, the power lever angle increased from 41% to 44%. At the point, Np of both propellers were recorded as Non-Computed Data (NCD) in the FDR and the torque (Tq) of both engines were at 0%. When propellers are in feather, they are not producing thrust.
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