Investigation Summary
The accident sequence began approximately 14 minutes after takeoff when the crew received reports of deteriorating weather at their destination, Lukla. While maneuvering to return to Kathmandu, the primary generator failed. Air traffic control initially diverted the aircraft to Simara Airport (VNSI) due to poor weather at Kathmandu, but this diversion was abandoned as Simara was also closed due to visibility. The captain attempted to engage the backup generator, but the switch was unsuccessful. In an attempt to manage the electrical load, the crew followed an outdated emergency checklist and attempted to 'recycle' the battery pack. This action, combined with the continued operation of non-essential systems, drained the battery in less than half its rated discharge time. As the battery died, the aircraft's attitude indicator and other critical flight instruments failed. Flying in heavy rain and thick clouds (IMC), the crew suffered spatial disorientation. The aircraft entered a steep, high-speed descent, impacting a rice paddy on a hillside at approximately 9,000 feet. Witnesses noted the engines were quiet just before impact, though investigators determined this was likely due to the high-speed dive rather than engine failure. The impact was so severe that it created a 3-meter deep crater and spread wreckage across a 100-meter area.
Final Conclusions
The investigation concluded that the primary cause was spatial disorientation of the pilot following the loss of the attitude indicator. This instrument failure was the direct result of a total electrical power loss caused by the failure of both generators and the subsequent rapid depletion of the battery. The investigation highlighted that the crew's use of an outdated checklist significantly accelerated the battery drainage. Contributing factors included the prevailing monsoon weather conditions which necessitated reliance on instruments and the crew's failure to declare an emergency, which might have prioritized their landing at Kathmandu.
Video Analysis
The Plane That Ran Out of Electricity | Agni Air Flight 101 — A detailed look at the technical and human factors that led to the crash of Agni Air 101 in the mountains of Nepal.
If playback is blocked, the owner has disabled embedding — use the link above.
Airframe & Maintenance
Systems & Failure Modes
Attitude Indicator
A critical flight instrument that provides the pilot with information about the aircraft's pitch and roll relative to the horizon; its failure in IMC led to spatial disorientation.
Electrical Generation System
Consisted of two generators; the failure of the primary and the inability to engage the backup forced the aircraft to rely solely on battery power.
Emergency Checklist
The crew utilized an obsolete version of the checklist, which provided incorrect instructions for managing a dual generator failure, leading to rapid battery exhaustion.
Interesting Facts
- 01The aircraft was a Dornier 228-101 built in 1984 (MSN 7032), though some sources like BAAA-ACRO list the year of manufacture as 1985.
- 02The crash site was located approximately 18 nautical miles (33 km) south-southwest of Kathmandu, though some reports placed it 30 km southeast.
- 03The flight crew did not declare a formal emergency (Mayday) despite the technical failures.
- 04Both the Cockpit Voice Recorder (CVR) and Flight Data Recorder (FDR) were recovered undamaged.
- 05The aircraft created a crater 3 meters deep upon impact due to the high vertical velocity.
Safety Actions & Advisories
Checklist Standardization
The investigation emphasized the need for all operators to ensure that only the most current, manufacturer-approved checklists are available in the cockpit.
Emergency Declaration Training
Recommendations were made to improve pilot training regarding the timely declaration of emergencies to ensure priority handling by ATC during technical failures.