The Crew Dynamics

Yeti Airlines Flight 691's crew comprised two captains, each playing a vital role in the operation of the flight.

The Pilot Flying, who was on the verge of becoming a captain, was familiarizing herself with landing at Pokhara. With a wealth of flying experience, she was at a crucial juncture in her career, seated in the left-hand seat and responsible for the aircraft's navigation from Kathmandu to Pokhara.

In the right-hand seat was the Pilot Monitoring, a seasoned instructor tasked with overseeing and advising the Pilot Flying. This role is essential during training flights, ensuring adherence to safety protocols. The Pilot Monitoring's responsibilities included observing, advising, and intervening when necessary to ensure the flight's smooth operation.

The route from Kathmandu to Pokhara is frequently traveled, with pilots accustomed to the landscape's transition from urban areas to the scenic beauty of Pokhara. However, this route demands meticulous attention and skill, as it involves navigating some of the world's most challenging terrains, particularly the Himalayas.

On this flight, the crew had successfully completed a round trip between Kathmandu and Pokhara earlier that same day.

As Flight 691 approached its destination, the pilots prepared for landing, a phase that necessitates coordination and strict adherence to procedures. The routine tasks of extending the landing gear and adjusting flap settings are crucial for ensuring a safe landing. It was during this phase that a critical error occurred.

The Countdown to Disaster

Following the initial descent, the Pilot Flying disengaged the autopilot, a standard procedure in preparing for landing.

Next, she aimed to increase the flap setting to 30 degrees, a vital adjustment for slowing the aircraft and ensuring a smooth touchdown. The Pilot Monitoring acknowledged this request, confirming that the flaps were being set as required. However, data from the Flight Data Recorder (FDR) disclosed a different scenario.

Instead of the flaps being adjusted, the propeller rotation speed of both engines decreased significantly, falling below 25%. This indicated that the propellers had entered a feathered state, meaning they were not producing thrust. Consequently, the aircraft's engines were essentially idle, providing no power for the critical final approach.

Faced with this unexpected situation, the pilots attempted to regain power. The Pilot Flying slightly increased the power lever angle from 41% to 44%, yet this action failed to influence the engine torque, which remained at zero, indicating that the engines were unresponsive.

As the aircraft continued its approach, altitude decreased further, reaching a critical level where swift decisions were imperative. At 500 feet, the Pilot Flying sought guidance from the Pilot Monitoring regarding whether to maintain the left turn as part of the landing procedure. The Pilot Monitoring advised to continue the turn, indicating that the focus was still on completing the landing.

However, as the plane descended further, its speed and altitude were misaligned with the standard parameters for a safe landing. The pilots were in a precarious situation, trying to manage an aircraft that was not responding as anticipated while navigating towards the runway.

The Critical Error

The issue revolved around the aircraft's propeller system, specifically the condition levers, which are crucial for managing engine power. The incorrect positioning of these levers was the key factor leading to the loss of engine power at a critical moment.

During the final approach, the Pilot Flying correctly requested an increase in the flap setting, a standard procedure for slowing down for landing. However, instead of adjusting the flaps, the Pilot Monitoring mistakenly altered the condition levers. This error placed the propellers in a feathered condition, minimizing air resistance, but also ceasing thrust production.

In normal operations, this setting is used when engines are shut down, not during an active flight phase, especially not during landing.

As a result of this mistake, the aircraft's engines ceased to provide the necessary thrust for landing. The FDR data revealed that despite attempts to increase power, torque remained at zero, indicating no output from the engines. Unaware of the incorrect lever positioning, the pilots faced an increasingly dire situation as the aircraft continued to lose altitude without means to regain control.

During these critical moments, altitude dipped dangerously, raising immediate concerns for a safe landing. At 500 feet, both pilots were engaged in crucial decision-making, trying to navigate the aircraft safely while unaware of the underlying issue that rendered their efforts futile.

Seeking Answers

The aftermath of the Yeti Airlines Flight 691 crash prompted an extensive investigation led by aviation experts and authorities.

The primary objective was to comprehend the sequence of events leading to the tragedy and to identify any underlying issues that could help prevent future incidents. The investigation focused on several key aspects, including the aircraft's mechanical systems, the pilots' actions, and the environmental conditions at the time of the crash.

Critical pieces of evidence in aviation accident investigations include data from the Flight Data Recorder (FDR) and Cockpit Voice Recorder (CVR). These devices provide essential information regarding the aircraft's performance and the pilots' interactions leading up to the crash. In Flight 691's case, FDR data revealed no movement of the wing flaps when the Pilot Flying called for "FLAPS 30." Instead, it indicated a simultaneous reduction in propeller rotation speed for both engines, confirming they were in a feathered state and not generating thrust.

The investigation scrutinized human factors, particularly the actions and decision-making processes of the flight crew. Understanding the dynamics in the cockpit, the crew's adherence to standard procedures, and their response to the emergency were central to piecing together the final moments of the flight. Investigators aimed to discern whether lapses in communication, judgment errors, or other factors contributed to the mismanagement of the aircraft's systems.

Additionally, the investigation included examining the visual approach procedures at Pokhara International Airport, assessing the challenges posed by the airport's location, the adequacy of approach paths, and protocols for the simultaneous operation of both national and international airports in the region.

The findings were highly anticipated by the aviation community, the victims' families, and the public. The objective was to gain a comprehensive understanding of the factors that led to the crash and to propose changes that could enhance flight safety. The final report was expected to offer detailed insights into the tragic accident, contributing to ongoing efforts to improve aviation safety standards globally.

Looking Beyond the Crash

The Yeti Airlines Flight 691 disaster brought to light broader implications for aviation safety, especially in Nepal and similar regions with challenging terrain. The event triggered a reevaluation of safety protocols, training standards, and the effectiveness of current regulations in ensuring passenger and crew safety.

Nepal's aviation sector, characterized by diverse topography and often unpredictable weather, presents unique challenges. Many airports are situated in mountainous regions, requiring pilots to navigate difficult approaches, making operational safety paramount. The Flight 691 incident underscored the necessity for rigorous pilot training, particularly in managing emergencies and understanding aircraft systems.

Furthermore, the crash accentuated the importance of effective communication within the cockpit. The misinterpretation of procedures between the Pilot Flying and Pilot Monitoring was a significant factor in the accident. This aspect of the tragedy highlighted the critical need for clear and precise communication, particularly during high-pressure situations.

Internationally, the incident contributed to ongoing discussions about flight safety, especially in regions with similar geographical and environmental challenges. Aviation authorities and airlines worldwide were reminded of the significance of continuous training, adherence to standard operating procedures, and the implementation of advanced technology to assist pilots in navigating complex flight paths.

The incident also drew attention to the role of regulatory bodies in maintaining and enhancing safety standards. It raised questions regarding the oversight of training programs, enforcement of safety regulations, and the adequacy of existing protocols to address the unique challenges faced by pilots in such environments.

Honoring the Lives Lost

The Yeti Airlines Flight 691 crash represented a profound tragedy that resonated beyond Nepal's borders, affecting communities worldwide. Among the 72 lives lost were individuals from various countries, including France, Nepal, Russia, Australia, South Korea, Argentina, India, and the United Kingdom.

The diversity of the passengers illustrated the interconnected nature of our world today. The tragedy united nations in mourning, transcending geographical and cultural divides. The sorrow experienced by the families and loved ones of those on board was shared by many globally, fostering a sense of unity in grief and empathy.

In Nepal, the crash had a particularly significant impact. Air travel serves as a vital lifeline, linking remote areas with the nation and the world. The incident raised serious concerns about aviation safety in a region known for its challenging flying conditions.

The international community also felt the repercussions of this tragedy. It heightened awareness regarding the necessity for rigorous training for pilots, especially in demanding conditions, and the imperative for constant vigilance in maintaining and enhancing safety standards.

The legacy of Flight 691 extends beyond the tragedy of its crash. It serves as a reminder of life's fragility and the need for collective efforts to ensure air travel safety. The memories of those lost in the crash will forever remind us of the pursuit of excellence in aviation safety, honoring their lives by striving for a safer future in air travel.