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Final report: Let
L-410 stalled after descending below runway level on finals to Lukla, Nepal
Narrative: A Let L-410UVP-E20 operated by Summit Air (formerly known as Goma Air) was destroyed in an accident when it attempted to land on runway 06 at Lukla-Tenzing-Hillary Airport in Nepal. The aircraft operated on a cargo charter flight with 1680 kg cargo on board. It took off from Kathmandu at 07:44 UTC at flight 409, bound for Lukla. It was the 5th flight of the aircraft to Lukla and with the same set of crew. Lukla weather was cloudy, but visibility and ceiling was reported to be fine after an hour of heavy rain. On first contact flight 409 reported abeam Rumjatar descending out of 11300 ft at 08:10 UTC. Lukla Tower provided the latest weather at the airport, as well as enroute weather relayed by 9N-AGU, an AS350 helicopter that had departed Lukla for Kathmandu. Almost 4 minutes after the first contact, Tower informed flight 409 about the deteriorating weather. The right base leg was covered by lifting fog though there was no rain and the final approach area was still visible. Weather deteriorated further and Tower regularly updated the flight crew. About 30 seconds after flight 409 reported entering valley, Lukla Tower again informed about the latest status of the further deteriorating weather. Flight 409 then informed that they would come up to Bhatkeko Daada and then decide. The pilot also informed they could see some bright spots. While continuing approach, both cockpit crew sighted the runway at 9100 ft. That was 64 seconds before the impact. While continuing approach the aircraft deviated to the right by almost 15 degrees and erroneously descended too low to 8500 ft whereas threshold height is 8900 ft (on Kathmandu QNH, whereas per AIP it is 9200 ft). The flight crew attempted to climb and reach the threshold in a landing configuration. The aircraft pitched up to over 25°, the airspeed dropped and the aircraft stalled. Subsequently its left wing first hit a small tree and then impacted the sloping terrain 130 feet short of the runway. The captain and copilot both sustained fatal injuries.
Probable Cause:
Probable Cause: The Commission concludes that the probable cause of this accident was aircraft stall as a result of excessive drag created by sudden increase in angle of attack of the aircraft supplemented by low speed (below Vref) in an attempt to initiate immediate climb on a landing configuration (full flap and landing gear down) warranted by the critical situation of the final phase of flight. The contributing factors for the accident are: a. Critical terrain and rapidly deteriorating weather condition. b. Pilot's loss of situational awareness c. Improper pilot response to stall warning including failure to advance power lever to maximum at appropriate time. d. Voilation of SOP by the ATS and Pilot as well.
Accident investigation:
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