Summit L410 at Lukla on May 27th 2017, contacted trees and impacted ground before runway
Last Update: April 13, 2018 / 14:45:36 GMT/Zulu time
Incident Facts
Date of incident
May 27, 2017
Classification
Accident
Departure
Kathmandu, Nepal
Destination
Lukla, Nepal
Aircraft Registration
9N-AKY
Aircraft Type
Let L-410 Turbolet
ICAO Type Designator
L410
Nepali Police reported the aircraft touched branches of a tree, suffered technical problems and impacted ground about 3 meters below the runway level just before 14:00L (08:15Z).
The airport reported the aircraft collided with a tree while attempting to land in foggy conditions at 14:04L and subsequently impacted ground. It took rescuers some time to free the crew out of the damaged cockpit area, all three were taken to the Lukla Hospital alive, however, the captain died after arrival in the hospital.
The following day the hospital reported the first officer succumbed to his injuries during the night. The third crew member was diagnosed with minor injuries and is stable on the way to recovery.
On Jun 7th 2017 a surveillance video by Lukla Airport was released showing the aircraft came out of fog/cloud about 6 seconds prior to impact (about 3-4 seconds after start of video), descended below runway level and impacted ground.
On Dec 16th 2017 in a press conference the accident investigation committee reported the final report has been submitted to the Ministry of Transport (editorial note: the final report has not yet been published). The committee reported that nearing the Lukla valley the crew was informed about heavy rain at Lukla and was considering to return to Kathmandu, however, was told Kathmandu was overly busy with many aircraft in the holds. Shortly afterwards the crew was told the weather at Lukla had improved and the rain had stopped. The aircraft entered the Lukla Valley but entered dense fog as soon as it entered the Lukla Valley and remained in that fog for about 4 minutes. 64 seconds before impact the first officer sighted the runway, the aircraft was at 9100 feet MSL at that time (Lukla elevation 8900 feet MSL), the aircraft was about 15 degrees off the extended runway center line. The runway disappeared from view again, the aircraft descended to 8500 feet MSL, the captain attempted to correct the error and began to climb the aircraft, however, with the landing gear out the aircraft slowed, the stall warning activated 13 seconds before impact. The aircraft struck a small tree with its left hand wing before impacting ground about 130 feet short of the runway. The commission stated that even if the crew had attempted to go around, they would not have been aware of their position in the narrow valley due to the dense fog, the captain has no time to carry out a recovery procedure. Both the flight crew as well as the airport authority violated standard operating procedures. The airport authority should have monitored the weather situation and temporarily closed the aerodrome. The crew should not have flown into that weather fluctuating every few minutes. It can not be ruled out that the captain was affected by fatigue. The commission believes the traffic congestion at Kathmandu was a contributing factor into the accident and recommended to review the situation at Kathmandu Airport with respect to traffic congestion. In addition the commission reported the runway in Lukla could be extended by 100 feet and recommended to do so.
Goma Air rebranded into Summit Air on Mar 13th 2017.
On Apr 13th 2018 Nepal's Accident Investigation Commission (NAIC) released their final report concluding the probable cause of the accident was:
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:
- Critical terrain and rapidly deteriorating weather condition.
- Pilot's loss of situational awareness
- Improper pilot response to stall warning including failure to advance power lever to maximum at appropriate time.
- Voilation of SOP by the ATS and Pilot as well.
The NAIC described the sequence leading to the accident in the abstract: "While continuing approach, both cockpit crew sighted the runway at 9100ft. 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 8500ft whereas threshold height is 8900ft. The aircraft was too close to the threshold and in the meantime already 400ft below the threshold. In that situation flight crews had no other alternatives than to climb immediately. So, in an effort to climb and reach threshold in a landing configuration with landing gears down and on full flaps excessive drag was created resulting aircraft to stall. Subsequently its left wing first hit a small tree and then impacted the sloppy terrain 130 feet short of the runway."
The NAIC detailed further in the factual presentation:
Aircraft reported entering valley at 0816. CVR record showed that First Officer sighted the runway at 0817 (64 seconds before the impact). Instantly PIC acknowledged he had also the runway in sight. Aircraft was at 9100 ft(approx.) when the cockpit crews sighted the runway. It maintained 9000 feet (approx.) for further 21 seconds. At time 0817:12i.e. 48 seconds before the impact Tower gave the latest wind as Westerly 04 knots and runway was clear. PIC was still in doubt and asked whether there was rain. Upon confirmation of having no rain from the Tower the aircraft started to descend further. The PIC, who was also the PF, found to have lost situational awareness deviated to the right with continued descend. At 0817:35 (25 seconds before impact) when the flight was descending through 8650ft First Officer warned PIC that they were too low. PIC did not respond the F/O's call-out and continued descend. On reaching 8500ft. F/O again warned PIC in panic. Then PIC asked in panic where the runway was. F/O directed towards the runway. But it was already too low and too late. There was initially two short stall warning sound. Then a continuous stall warning sounded till the impact, which lasted for 13 seconds. The last words in CVR records was (tranlated: Do not pull too much).
Abrupt change in aircraft attitude in an attempt to climb and reach threshold height at 8900ft. (on Kathmandu QNH) in a landing configuration, with landing gears down and on full flaps, created excessive drag resulting the aircraft to stall. Subsequently, its left wing first hit a small tree branch 180ft. short of the threshold. Then impacted the sloppy terrain 100ft. short of the runway.After the crash aircraft engine was reported to be running for about a minute. But there was no postcrash fire. Aircraft was totally damaged by the impact.
The captain (48, ATPL, 9,687 hours total, 1,897 hours on type) was pilot flying, the first officer (27, CPL, 1,311 hours total, 1,028 hours on type) was pilot monitoring.
The NAIC analysed the FDR data: "Referring to above charts, the aircraft was flying low during final moments of its flight. On the final minute IAS was significantly low which dropped below 50Kt during final few seconds then further down below 20 kt. Pitch attitude was at maximum during final seconds. Magnetic heading was abruptly changed in the last moment. Following comparative chart will further elaborate the final parameters of crashed flight and other two flights previous to the occurrence."
The NAIC analysed the last 267 seconds of the flight:
They entered Lukla valley at 9,200 ft. which normally should be 10,500 ft. That counted as a violation of SOPs (both GOMA AIR as well as Lukla Airport SOP). The flight crew were not able to see the final glide path for landing to runway 06 and they were informed about the rapidly increasing thick fog towards the left as well as the right base of runway 06. The pilot monitoring had spotted the runway at exactly 64 second before impact and so did the Captain 2 seconds later.
The flight crew had configured the airplane with flaps fully extended and landing gear down for landing 35 seconds ahead of the impact. The Pilot monitoring did not lose sight of the runway till impact but the Captain (PF) could not maintain the runway in sight during the last 25 seconds due to several reasons. The reasons might be lack of situational awareness, high workload, low visibility, a fixed mind-set to land due to high severity of risk produced by surrounding terrain, aircraft being lower than the runway threshold and still not being able to sight the runway and Captain's intention to climb to reach threshold height of 8900 ft. from 8500ft. (using KTM, QNH). During the last 10 seconds, both pilots took cross control of the aircraft. In their attempt to climb the aircraft in landing configuration to 8900 ft. from 8500ft. the aircraft lost a substantial amount of speed from 75 knots to 19 knots within the time frame of 13 seconds with continuous stall warning. The stall recovery procedure is to apply maximum engine torque, lower the nose and reconfigure the aircraft stepwise but the Captain only partially applied engine torque to 22%, 42% and 92% in the interval of 4.33 seconds, respectively, and the pitch rose from +6 degrees to +27.6 degrees. The airplane fell “behind the power curve” and then proceeded to stall and impact on the sloppy terrain 130 ft. short of the runway threshold. It came to rest 100 ft. below the runway threshold 06.
With respect to the flight attendant (3rd crew member) on the flight the NAIC analysed: "The Cabin Crew has been working with Goma Air for two years (since 18th Oct-2015). She sustained serious injuries during crash and was evacuated to Kathmandu. Her condition is stable, and she is recovering well. The commission met her on 26th June, 2017 (1 month after crash), but she was not in a condition to answer questions at that stage. The commission met her again on 14th July, 2017 (1 and ½ months after crash). She did not remember much about the actual crash but said that weather was not as normal as usual on that flight."
The NAIC analysed with respect to CG: "Upon physical inspection of the crashed aircraft, cargo position and latches were found to be properly done. So the commission ruled out the possibility of shift of CG to be the cause of accident."
Incident Facts
Date of incident
May 27, 2017
Classification
Accident
Departure
Kathmandu, Nepal
Destination
Lukla, Nepal
Aircraft Registration
9N-AKY
Aircraft Type
Let L-410 Turbolet
ICAO Type Designator
L410
This article is published under license from Avherald.com. © of text by Avherald.com.
Article source
You can read 2 more free articles without a subscription.
Subscribe now and continue reading without any limits!
Read unlimited articles and receive our daily update briefing. Gain better insights into what is happening in commercial aviation safety.
Send tip
Support AeroInside by sending a small tip amount.
Related articles
Fleet type match
Goma L410 at Pokhara on Jun 2nd 2015, nose gear did not extend
A Goma Air Let L-410, registration 9N-AKY performing a scheduled flight from Jomsom to Pokhara (Nepal) with 18 people on board, was on approach to…
Newest articles
Fleet type match
Delta A339 at New York on Apr 21st 2024, nose wheel steering fault
A Delta Airlines Airbus A330-900, registration N404DX performing flight DL-49 from Amsterdam (Netherlands) to New York JFK,NY (USA) with 295 people…
Fleet type match
Condor A320 near Lausanne on Apr 21st 2024, hydraulic problem
A Condor Airbus A320-200, registration D-AICA performing flight DE-1412 from Munich (Germany) to Fuerteventura,CI (Spain), was enroute at FL340 near…
Subscribe today
Are you researching aviation incidents? Get access to AeroInside Insights, unlimited read access and receive the daily newsletter.
Pick your plan and subscribePartner
A new way to document and demonstrate airworthiness compliance and aircraft value. Find out more.
ELITE Simulation Solutions is a leading global provider of Flight Simulation Training Devices, IFR training software as well as flight controls and related services. Find out more.
Your regulation partner, specialists in aviation safety and compliance; providing training, auditing, and consultancy services. Find out more.
AeroInside Blog
Popular aircraft
Airbus A320Boeing 737-800
Boeing 737-800 MAX
Popular airlines
American AirlinesUnited
Delta
Air Canada
Lufthansa
British Airways