This led in the crash of Yeti Airlines Flight 691, which killed 72 lives.

On 15 January 2023, an ATR 72-212A was operating scheduled flights between Kathmandu (VNKT) and Pokhara International Airport (VNPR).

The same flight crew operated two sectors between VNKT to VNPR and VNPR to VNKT earlier in the morning. The accident occurred during a visual approach for runway 12 at VNPR. This was the third flight by the crew members on that day.

The flight was operated by two Captains, one Captain was in the process of obtaining aerodrome familarization for operating into Pokhara and the other Captain being the instructor pilot.

The Captain being familarized, who was occupying the left hand seat, was the Pilot Flying (PF) and the instructor pilot, occupying the right hand seat, was the Pilot Monitoring (PM).

The take-off, climb, cruise and descent to Pokhara was normal. During the first contact with Pokhara tower the Air Traffic Controller (ATC) assigned the runway 30 to land.

But during the later phases of flight crew requested and received clearance from ATC to land on Runway 12.

After both engines’ propellers were feathered, the plane lost thrust and crashed. It is unusual for the propellers of both engines to become feathered, according to the report.

“When the Air Traffic Controller (ATC) provided the clearance for landing…, the Pilot Flying (PF) stated twice that there was no power coming from the engines,” according to the investigation.

The aircraft’s engines were fully operational at the time of the crash. Flaps are rectangular panels on the wings that are stretched to expand their surface area and provide greater lift to the aircraft during slow-speed landing and takeoff.

The plane loses lift and crashes if the flaps are not extended before landing. During landing, bringing the engine to idle speed with no flaps extended is a very unstable arrangement.

When both propellers were feathered, the investigation team observed that both engines of 9N-ANC were running flight idle conditions during the event flight to prevent over torque.

As per the FDR data, all the recorded parameters related to engines did not show any anomaly. At 10:56:50 when the radio altitude callout for five hundred feet3 was annunciated, another “click” sound was heard4.

The aircraft reached a maximum bank angle of 30 degrees at this altitude. The recorded Np and Tq data remained invalid.

The yaw damper disconnected four seconds later. 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 whether to continue to descend and the PM responded it was not necessary and instructed to apply a little power. At 10:56:54, another click was heard, followed by the flap’s surface movement to the 30 degrees position.

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