Investigation Summary
The accident began during the takeoff roll on runway 20. At approximately 70 knots, which was 13 knots below the calculated V1, the First Officer prematurely called for rotation. The aircraft struggled to become airborne, briefly lowering its nose before finally lifting off at 86 knots. CCTV footage revealed a flash in the right engine five seconds before rotation, and the pilot reported a bird strike to air traffic control shortly after liftoff. A Black Kite carcass was later found on the runway 408 meters from the intersection. Although the crew suspected a bird strike had disabled an engine, post-crash inspections found no bird remains inside the engines and no mechanical faults. However, the investigation determined that an 'insidious' power reduction occurred starting at 70 knots. The investigation revealed the aircraft was overloaded; while the load sheet indicated no luggage, surveillance showed 80 kg was loaded, correcting the takeoff weight to 5,914 kg, which exceeded the 5,899 kg limit. Because the crew did not feather the propeller of the malfunctioning engine, the resulting drag exceeded the thrust produced by the remaining engine. The aircraft reached a maximum altitude of 100 feet before decelerating into a stall.
Final Conclusions
The Nepal Aircraft Accident Investigation Commission (NAAIC) concluded that the primary cause was a reduction in thrust for undetermined reasons, resulting in drag that exceeded available power during a critical phase of flight. The investigation characterized the power loss as 'insidious' because it occurred gradually, making it difficult for the crew to recognize. A significant factor was that the flight idle fuel flow was incorrectly set too low, which caused the drag on the malfunctioning engine to be even greater than in a standard engine-out scenario. Contributory factors included the crew's failure to maintain V2 speed during the climb, the premature V1 call and rotation, and the decision to continue the takeoff despite the power loss occurring below V1. The investigation also highlighted that the crew failed to maintain the runway centerline, which eliminated the possibility of a forced landing on the remaining runway surface.
Photographic Evidence (1)
Video Analysis
Sita Air Crash 2012 | Pepsicola | Raw Footage — Raw footage and news coverage of the Sita Air Dornier 228 crash site near Kathmandu shortly after the accident on September 28, 2012.
If playback is blocked, the owner has disabled embedding — use the link above.
Airframe & Maintenance
Systems & Failure Modes
Garrett TPE331-10T-511D Engines
The twin turboprop engines were found to be producing low power at impact, but no internal mechanical failures were identified.
Propeller Feathering System
The propellers remained in the normal operating range; failing to feather the propeller on the malfunctioning engine resulted in over 350 kg of drag.
Interesting Facts
- 01The aircraft was slightly overloaded by approximately 80 kg of unmanifested luggage.
- 02A Black Kite bird carcass was found on the runway, but no remains were found inside the engines.
- 03The right engine propeller was not feathered, creating significant drag that the remaining engine could not overcome.
- 04The crew rotated the aircraft at 70 knots, well below the calculated V1 of 83 knots.
- 05The investigation could not determine the exact mechanical reason for the thrust reduction.
Safety Actions & Advisories
Weight and Balance Oversight
The investigation highlighted discrepancies in load sheets, leading to calls for stricter monitoring of passenger and luggage weights in Nepalese domestic operations.