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DHC6, en-route, Arghakhanchi Western Nepal, 2014
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|On 16 February 2014 a Nepal Airlines DHC6 attempting a diversion on a VFR flight which had encountered adverse weather impacted terrain at an altitude of over 7000 feet in a mountainous area after intentionally entering cloud following a decision to divert due to weather incompatible with VFR. The aircraft was destroyed and all 18 occupants were killed. The Investigation attributed the accident to loss of situational awareness by the aircraft commander and inadequate crew co-operation in responding to the prevailing weather conditions.|
|Actual or Potential
|Controlled Flight Into Terrain (CFIT), Fire Smoke and Fumes, Human Factors, Weather|
|Aircraft||DE HAVILLAND CANADA DHC-6|
|Type of Flight||Public Transport (Passenger)|
|Intended Destination||Jumla Airport|
|Take off Commenced||Yes|
|Origin||Bhairahawa/Gautam Buddha Airport|
|Approx.||Dihidanda, Masinalek, Arghkhanachi, Nepal (elevation for this position is 7190 feet amsl)|
|Tag(s)||Inadequate Aircraft Operator Procedures|
No Visual Reference,
VFR flight plan
|Tag(s)||Post Crash Fire|
Plan Continuation Bias,
Procedural non compliance,
|Tag(s)||In Cloud on Visual Clearance,|
|Damage or injury||Yes|
|Aircraft damage||Hull loss|
|Fatalities||Most or all occupants (18)|
|Causal Factor Group(s)|
On 16 February 2014, a De Havilland Canada DHC6-300 (9N-ABB) being operated by Nepal Airlines on a day scheduled domestic passenger flight from Kathmandu to Jumla via a planned refuelling stop at Pokhara on a Visual Flight Rules (VFR) Flight Plan was subsequently found to have crashed into terrain en route between Pokhara and Jumla in Instrument Meteorological Conditions (IMC) resulting in its destruction and a post crash fire with fatal injuries sustained by all 18 occupants.
An Investigation was carried out by an Aircraft Accident Investigation Commission (AAIC) established by the Nepal Government Ministry of Culture, Tourism and Civil Aviation on the day after the accident. The wreckage of the aircraft was located on a sloping hillside near Dihidanda, Masinalek in the Arghakhanchi District. Recorded data relevant to the Investigation was successfully downloaded from the 30 minute Cockpit Voice Recorder (CVR) but the aircraft was not fitted with an Flight Data Recorder (FDR). The GPS Unit carried and used for navigational assistance during the flight was found not to have the capability to store track data. The aircraft was not fitted with either weather radar or Terrain Avoidance and Warning System (TAWS).
No evidence of any pre-impact loss of airworthiness was found, nor was there any indication that aircraft performance had been impaired by the effects of flight in the icing conditions which it was considered would have existed during periods of flight in cloud undertaken despite operating on a VFR Flight Plan.
The 49 year old aircraft commander, who had been PF for the accident flight, was found to have joined the Operator only 2 years previously although he had accumulated over 8000 flying hours including substantial P1 time and had substantial experience of domestic operations. Although the 28 year old Co-pilot had been with the Operator for 5 years, he had only accumulated a total of 365 flying hours. However, it was found that both pilots were used to operating together.
The Investigation deduced from the CVR recording that:
"Communication between Captain and Copilot was found not optimal and not in accordance with the rule and practice. (The) Copilot does not acknowledge the Captain’s information, or instruction on several occasions. The Copilot seemed to be unconcerned and Captain not authoritative, especially when the latter needed feedback and advice from (the) non flying copilot as they were facing problem with weather, and concerned about icing."
It was established that the aircraft had been operating on a VFR Flight Plan and that the aircraft was being flown "entirely based on (the) GPS Navigation (Unit) that was (installed) in the aircraft". It was noted that the crew had been unable to obtain a forecast of en route weather prior to their departure from Pokhara with a fuel endurance of 2.5 hours for what would normally have been a 1 hour flight. However, the engineer who checked the aircraft at Pokhara reported that the aircraft commander had appeared optimistic that adverse weather in the area of the route to Jumla was "moving away to the east".
The Investigation found that upon leaving Pokhara CTZ, the aircraft commander had "realised that the (intended) direct track was not possible due (to) weather and decided to proceed (initially to the) south". Evidence that considerable alterations to both track and altitude had followed was found and it noted that "finally, being unable to penetrate the weather ahead (the aircraft commander) decided to divert to Bhairahawa". This airport - elevation 344 feet - was the nearest at the time, had a non precision instrument approach procedure and was one of the two nominated alternates.
During a turning descent considered likely to have been made in cloud and contrary to the recommendation of the Co-pilot not to descend, the aircraft violently impacted the sloping side of a ridge within a mountain valley at 7190 feet amsl and, after several secondary impacts had disintegrated. There were signs that fire, suspected to have been fuel fed, had affected some parts of the wreckage. The track followed by the aircraft is shown on the map below taken from the Official Report.
The weather conditions at the time were reported by the security guard of a telecommunication tower close to accident site (who had no formal training in weather observation) to have been as follows:
- Light rain and hail storm in the morning
- Snowing since around 10:00 AM
- Thunder, dark cloud, all around covered up and visibility was low.
The Investigation concluded that on the evidence available:
- Although the flight was continued from Pokhara in spite of the likelihood of adverse weather conditions en route, the crew were under no pressure in this respect from the airline management or from any of the passengers or from any other source.
- The aircraft commander's penetration of visible moisture without having proper anti-icing capability had been in violation of SOPs as well as contrary to the Aircraft Flight Manual (AFM).
- Although the aircraft commander had initially seemed to be confident and appeared to have demonstrated the quality of leadership, later in the accident flight, "his presence of mind about his position and dilemma in actions did not display good leadership".
- The aircraft commander had been "focused on completing the mission in spite of adverse weather".
- The aircraft descended below 8500 feet without the pilots having sufficient awareness of the terrain.
- The nature of accident was ‘Controlled Flight Into Terrain (CFIT)’.
The Investigation determined that the Most Probable Cause of the accident was the "losing (of) situational awareness on the part of PIC while flying into instrument meteorological weather condition to the extent of collision with terrain."
It was additionally determined that there had been two Contributing Factors:
- (A) deterioration (in the) weather associated with (the) western disturbance (which was) unstable in nature and contained embedded Cb.
- Inappropriate and insufficient crew coordination while changing course of action.
A total of 12 Safety Recommendations were made as a result of the Investigation as follows:
During the Investigation the following Recommendation was made:
- that Operators shall immediately develop and implement an appropriate surveillance mechanism to ensure the effective monitoring of the flying behaviours of the pilots and their adherence to SOP including the violation of the VFR rules.
Upon completion of the Investigation, the following 11 additional Recommendations were made:
- that the Ministry of Culture, Tourism and Civil Aviation (MoCTCA) should establish an independent and effective aircraft accident investigation mechanism with the provision of adequate resources under the Ministry of Culture, Tourism and Civil Aviation (MoCTCA) for the effective investigations and also for the continuous monitoring of the implementation and compliance-status of remedial safety measures.
- that the Department of Hydrology and Meteorology, in coordination with CAA Nepal, should develop a mechanism to obtain the weather data not only of the airport stations but also from other parts of the country for the information and analysis of en-route weather.
- that the Civil Aviation Authority of Nepal (CAAN) should further strengthen its surveillance and monitoring function, focusing on critical safety areas including the violation of SOP, proper application of Crew Resource Management, CFIT prevention and ensuring effective enforcement by collecting information on flight operation activities on a daily basis.
- that CAAN should ensure that all fleets operated by AOC holders are equipped with the appropriate Terrain Awareness Warning System (TAWS) in accordance with the provisions of Annex 6.
- that CAAN in coordination with Department of Hydrology and Meteorology should develop a mechanism to obtain the real time weather data not only of the airport stations but also from other parts of the country for the information and analysis of en-route weather.
- that CAAN should encourage airlines to install onboard aircraft equipment that will help for real time tracking of the aircraft in flight.
- that the Nepal Airlines Corporation should review and strengthen the training requirements on Crew Resource Management (ground and in flight), with special attention to the importance of close coordination and cooperation between PIC and Co-pilot and also emphasising the situations requiring interventions from Co-pilot.
- that the Nepal Airlines Corporation should, in view of the significant fleet expansion in progress, systematically identify the hazards, changes in system, operational environment and consequential safety risk especially in the process of recruitment and training of the operational and engineering personnel.
- that the Nepal Airlines Corporation should enhance the flight dispatcher's capability to enable them to fulfil their responsibility as per the provisions of company SOP.
- that the Nepal Airlines Corporation should develop special program and policy for the prevention of CFIT accidents.
- that the Nepal Airlines Corporation should review and further strengthen the effective implementation of Safety Management System process especially in the areas of improved reporting system, hazard identification and risk mitigation.
The Final Report was submitted by the AAIC to the Ministry of Culture, Tourism and Civil Aviation on 25 August 2014 and subsequently published n English but without the accompanying Appendices.
- Controlled Flight Into Terrain (CFIT)
- CFIT Precursors and Defences
- Flight in Mountainous Terrain
- Terrain Awareness
- Terrain Avoidance and Warning System (TAWS)
- Situational Awareness
- Safety Management System
- Management of Change
- Crew Resource Management (CRM)
- Continuation Bias
- Socio-Cultural Effects on the Flight Deck