Investigation Summary
The flight was marked by significant external pressure and a breakdown in standard operating procedures. The Pilot-in-Command (PIC) was initially hesitant to fly due to reports of deteriorating weather but was reportedly pressured by ground staff and the departure of a competitor's flight to proceed. During the flight, the crew encountered Instrument Meteorological Conditions (IMC) but attempted to maintain visual contact with the ground. Crucially, the TAWS 'Inhibit' switch was active. The investigation revealed that the crew had failed to enter the correct regional barometric pressure into the Air Data Computer, leading to incorrect altitude readouts and nuisance alerts. To silence these alerts, the crew inhibited the system, which ultimately prevented an audible warning before the collision. The investigation also highlighted a 'high crew gradient,' where the highly experienced PIC (17,500 hours) was paired with a junior co-pilot (520 hours) who did not effectively challenge the PIC's decisions.
Final Conclusions
The Aircraft Accident Investigation Commission concluded the primary cause was the crew's failure to maintain the proper course while inadvertently flying in IMC with the TAWS inhibited. Contributing factors included the failure to follow company SOPs, loss of situational awareness, poor Crew Resource Management (CRM), and the PIC's high workload as he performed both Pilot Flying and Pilot Monitoring duties simultaneously.
Photographic Evidence (1)
Video Analysis
No video analysis linked for this case file yet.
Systems & Failure Modes
TAWS (Terrain Awareness and Warning System)
A system designed to prevent CFIT; it was manually inhibited by the crew, silencing alerts as they approached the mountain.
V2 Tracker
A GPS-based tracking system used by the airline that provided the last known coordinates and flight path data for the investigation.
CVR (Cockpit Voice Recorder)
Captured the PIC's dissatisfaction with the weather and the decision-making process leading up to the impact.
Interesting Facts
- 01The aircraft (MSN 619) was manufactured in 1978, making it 44 years old at the time of the accident.
- 02The aircraft exceeded its Maximum Takeoff Weight (MTOW) due to a last-minute passenger addition.
- 03The TAWS system was found to be in the 'Inhibit' position, which suppressed audible terrain warnings.
- 04The Pilot-in-Command had over 17,500 total flying hours, while the co-pilot had 520 total hours, with only 315 hours on type.
- 05The wreckage was located at an altitude of 13,290 feet, roughly 7.7 nautical miles southwest of Jomsom.
- 06The flight was operated for Yeti Airlines, the parent company of Tara Air.
Safety Actions & Advisories
TAWS Policy Enforcement
CAAN issued directives to ensure TAWS remains functional and is not inhibited during en-route phases of flight, especially in mountainous terrain.
Weather Minimums
Stricter enforcement of VFR weather minimums for the Pokhara-Jomsom route, requiring clear visual reference for the entire flight duration.
Weight and Balance Oversight
Directives were issued to ground staff and operators to strictly adhere to load manifests and prevent unauthorized last-minute passenger additions that exceed MTOW.