Yeti Airlines Flight 691

Yeti Airlines Flight 691 was a scheduled domestic passenger flight from Kathmandu to Pokhara in Nepal. On 15 January 2023, the aircraft being operated on the route, an ATR 72 flown by Yeti Airlines, crashed while landing at Pokhara, killing all 72 occupants on board. It is the deadliest accident involving an ATR 72.

Accident

The flight took off from Kathmandu's Tribhuvan International Airport at 10:33 am NST. It crashed on the bank of the Seti Gandaki River while on final approach to landing at Pokhara International Airport. A video filmed from the ground showed the aircraft banking steeply to the left before crashing away. Another video was streamed live on Facebook by Sonu Jaiswal, a passenger on the plane, before and during the crash. The video shows passengers unaware of the situation until seconds before impact.

The crash occurred in Gandaki Province between the old Pokhara Airport and the new Pokhara International Airport, which was opened two weeks earlier and also where the aircraft was intending to land. The accident resulted in the deaths of all 72 people on board, and was Nepal's worst aviation accident since the crash of Pakistan International Airlines Flight 268 in 1992, the deadliest aviation accident in Nepalese domestic aviation, and the deadliest accident involving an ATR 72.

According to an official at the Pokhara International Airport, air traffic control cleared the flight to land on runway 30 heading from east to west, but the captain requested the opposing runway 12 heading from west to east, minutes before the crash. A Civil Aviation Authority of Nepal spokesperson said: "The weather was clear; according to preliminary information the cause of the crash is the technical issue of the plane."

Flight-tracking organisation Flightradar24 noted that during the flight the aircraft had been transmitting inaccurate speed and altitude data.

Aircraft

The aircraft involved in the crash was a 15-year-old twin-engine turboprop ATR 72-500, with serial number 754 and registration 9N-ANC. It was first delivered to Kingfisher Airlines as VT-KAJ in 2007. In 2013, it was transferred to Nok Air as HS-DRD before being delivered to Yeti Airlines in 2019. The aircraft was powered by two Pratt & Whitney Canada PW127F engines.

Passengers and crew

There were 72 people on board, of which 68 were passengers and four were crew members. Among the passengers were 37 men, 25 women, and six children, three of whom were infants. Seventy-one bodies were found. On 17 January, authorities began returning the victims' bodies (the majority of which were burnt beyond recognition) to their families. The United States Department of State announced that two U.S. citizens died in the crash, although Nepalese authorities did not report any American deaths.

The plane was under the command of senior captain Kamal KC with Anju Khatiwada as copilot. Khatiwada's husband, Dipak Pokhrel, who also worked for Yeti Airlines, died in the 2006 Yeti Airlines Twin Otter crash. Khatiwada was set to qualify as a captain upon the successful completion of the flight.

Aftermath

The airport was closed as authorities launched a rescue operation. The Government of Nepal summoned an emergency cabinet meeting following the crash. Prime Minister Pushpa Kamal Dahal said he was deeply saddened by the tragic accident. The Office of the Prime Minister declared 16 January to be a national day of mourning, and the flag of Nepal was flown at half-staff. Yeti Airlines cancelled all regular flights scheduled for the day.

Investigation

Experts noted that the video from the ground taken moments before the crash showed the aircraft's nose noticeably high before the left wing suddenly dropped, probably indicating a stall. Hours after the crash, a five-member committee headed by Nagendra Ghimire was set up to investigate the accident in conjunction with the French Bureau of Enquiry and Analysis for Civil Aviation Safety.

On 16 January, the flight data and cockpit voice recorders were found; the recorders were examined in Singapore and with assistance from Transportation Safety Board of Canada, Bureau of Enquiry and Analysis for Civil Aviation Safety, and Transport Safety Investigation Bureau of Singapore. About a month later, on 13 February, a preliminary report was released, which largely reproduced all relevant logs:

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.

At 10:56:54, another click was heard, followed by the flaps surface movement to the 30 degrees position.

When ATC gave the clearance for landing 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 then to the maximum power position. At 10:57:20, the PM (who was previously the PF) repeated again that there was no power from the engines.

The aircraft's propellers had been feathered for a minute prior to the crash, causing the engine to produce no thrust and lead the vehicle into a stall; the condition levers, which control the propellers, were discovered from the wreckage set to the feathered position. Seconds preceding the crash, the pilots discussed a total lack of power and even moved the power lever to the extreme but failed to recognize that the condition levers were wrongly set. That the condition levers and the flap lever are next to each other in an ATR 72, experts speculate that the monitoring pilot (Kamal KC) had inadvertently moved the former in place of the latter, when asked of by the flying pilot. While, about twenty seconds later, he would set the flap lever properly on his own, he failed to account for his previous mistake, implying that the landing checklist was not properly followed. The Master Caution chime was likely alerting to the loss of the "AC wild" propeller-driven generators and associated systems powered by the AC wild electrical system (namely the primary hydraulic pumps, ice protection systems, and some interior and exterior lights) when the propellers were feathered.

Due to the shortened final approach leg for runway 12 for this flight and another flight three days before it that landed on the same runway, the stabilization criteria for a visual approach which is important for a safe landing was not met at the height of 500 ft above ground level. This led the Aircraft Accident Investigation Commission to recommend the Civil Aviation Authority of Nepal (CAAN) conduct a comprehensive study for the determination of an appropriate flight path that allows a stabilized visual approach.

On 15 March, Government of Nepal extended the deadline by 45 days to the investigation commission for the final report of the accident. As of October 2023, no final report has been published.

See also

* List of accidents and incidents involving airliners by airline (P–Z)
* List of accidents and incidents involving commercial aircraft
* List of airplane accidents in Nepal
* TransAsia Airways Flight 235

Notes

References

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2023 disasters in Nepal
Accidents and incidents involving the ATR 72
Aviation accidents and incidents in 2023
Aviation accidents and incidents in Nepal
Filmed deaths in Asia
January 2023 events in Nepal
Pokhara
Yeti Airlines accidents and incidents
Airliner accidents and incidents caused by stalls