Yeti Airlines Flight 691

Yeti Airlines Flight 691 was a scheduled domestic passenger flight flown by Yeti Airlines from Kathmandu to Pokhara in Nepal. On 15 January 2023, an ATR 72, the aircraft being operated on the route, stalled and crashed while landing at Pokhara. All 72 people on board died on impact.

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 65 m away. Another video of the crash was streamed live on Facebook from inside the plane by a passenger, Sonu Jaiswal, showing that the passengers were 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. Flight-tracking service Flightradar24 noted that during the flight the aircraft had been transmitting inaccurate speed and altitude data.

Aircraft
The aircraft involved was a 15-year-old twin-engine turboprop ATR 72-500, with serial number 754 and registration 9N-ANC. It first flew on 1 August 2007 and was first delivered to Kingfisher Airlines as VT-KAJ on 16 August. On 8 March 2013, it was transferred to Nok Air as HS-DRD before being delivered to Yeti Airlines on 26 April 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.

Preliminary report
About a month later, on 13 February, a preliminary report was released, which largely reproduced all relevant logs. (PF = Pilot Flying, PM = Pilot Monitoring): 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 [...]

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 this point, the Np of both propellers was recorded as Non-Computed Data (NCD) in the FDR and the torque (Tq) of both engines was 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 about a minute before the crash, causing the engine to produce no thrust and lead the aircraft 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 incorrectly 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.

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, the Government of Nepal extended the deadline by 45 days to the investigation commission for the final report of the accident.

Final report
On 28 December 2023, the final report was released. It reiterated the preliminary findings that the accidental change of position of both condition levers to the feathered position resulted in the loss of thrust, leading to the aerodynamic stall and crash. Some other contributing factors are also found, mostly human errors due to a high workload, lack of appropriate technical and skill-based training, ineffective crew resource management (CRM), lack of sterile cockpit discipline, and the non-compliance with standard operating procedures (SOP).