Description

On 11 August 2009, a De Havilland Canada DHC-6-300 being operated by Airlines PNG on a scheduled domestic passenger flight from Port Moresby to Kokoda impacted terrain in day IMC while transitng the Kokoda Gap, approximately 6nm south east of the intended destination. The aircraft was destroyed by impact forces and all 13 occupants were killed

Investigation

An Investigation was carried out by the Papua New Guinea Accident Investigation Commission with assistance requested and provided by the Australian Transport Safety Bureau (ATSB). The wreckage was found in a forested area at an altitude of 5780ft amsl.

It was noted that the aircraft was not equipped with an Flight Data Recorder (FDR) or a Cockpit Voice Recorder (CVR) and neither of these were required by NAA Regulations. However, the aircraft was fitted with a Global Positioning System (GPS) - based tracking system which was independent of aircraft GPS navigation equipment and which was used by Company operations for flight following purposes. The non volatile memory chip from this equipment was recovered from the accident site, successfully downloaded and used to obtain position information which would not otherwise have been available.

The Investigation found no evidence of any airworthiness deficiency which might have caused or contributed to the accident. It was established that, prior to impact, the aircraft had been manoeuvring within the Kokoda Gap and it was considered that this had probably been in an attempt to maintain visual flight in reported cloudy conditions.

It was noted that in accordance with normal practice, an Instrument Flight Rules (IFR) FPL had been filed for the flight. This apparently meant that once clear of Port Moresby, the flight was intended to be conducted using visual procedures which allowed the crew to operate below applicable MSA of 13,700 ft in Visual Meteorological Conditions (VMC) because there were no radio navigation aids at Kokoda. Circumstantial evidence indicated that the aircraft had probably been in cloud at the time of impact.

There was some doubt about the extent of use of the installed GPS equipment for navigation purposes and it was noted that the First Officer had not been instrument rated. A different view was found to have been held by the NAA (CASA PNG) and the Operator (Airlines PNG) as an instrument rated First Officer was required for an IFR FPL to be filed under applicable Regulations. It was also found that the Airlines PNG SOP in respect of inadvertent entry into IMC whilst intending flight by visual reference was “ineffective in preventing Controlled Flight Into Terrain (CFIT)”.

The Investigation concluded that the accident was probably the result of controlled flight into terrain: that is, an otherwise airworthy aircraft was unintentionally flown into terrain, with little or no awareness by the crew of the impending collision.

A number of ‘factors’ were identified by the Investigation which it was considered had both led to an increased safety risk for the accident flight and were considered to have the potential to affect the safety of future similar flights:

• the crew of the aircraft
• the weather conditions affecting the flight
• crew training
• the conduct of the flight.

The ‘Contributing Safety Factors’ were listed in the Findings of the Investigation as

• Visual flight in the Kokoda Gap was made difficult by the extensive cloud coverage in the area.
• The crew attempted to continue the descent visually within the Kokoda Gap despite the weather conditions not being conducive to visual flight.
• It was probable that while manoeuvring at low level near the junction of the Kokoda Gap and Kokoda Valley, the aircraft entered instrument meteorological conditions.
• The aircraft collided with terrain in controlled flight.

‘Other Safety Factors’ were listed as:

• The copilot was assessed during normal proficiency checks for instrument approach procedures but was not qualified for flight in instrument meteorological conditions.
• The operator did not have a published emergency recovery procedure for application in the case of inadvertent flight into instrument meteorological conditions.
• The Civil Aviation Safety Authority Papua New Guinea surveillance of the operator did not identify the operations by the operator in contravention of (applicable rules).
• The lack of a reliable mandatory occurrence reporting arrangement minimised the likelihood of an informed response to Papua New Guinea-specific safety risks.
• There was no qualified Director (or similar) of Aviation Medicine in Papua New Guinea
• The lack of both flight data and cockpit voice recorders adversely affected a full understanding of the accident by the investigation.
• The investigation was unable to discount the possible incapacitation of the copilot as a factor in the accident.
• Although not required by the aviation rules at the time of the accident, the adoption of threat and error management training for flight crews, and of the methodology by operators would provide a tool to identify and mitigate operational risk as follows:
  • by flight crews, when flight planning and during flight; and
  • by operators, when developing their operational procedures.

It was noted that since the accident, both Airlines PNG and the CASA PNG had taken various safety actions in respect of DHC6 aircraft operations in general and operations into Kokoda in particular. One Safety Recommendation was made as a result of the Investigation:

• That the Civil Aviation Safety Authority PNG review the requirements affecting the installation of cockpit voice recorders in PNG-registered aircraft that are certified to carry 18 or more passengers, with the intent of implementation.

The Final Report of the Investigation was released on 31 March 2011 by the ATSB on behalf of the AIC PNG.

Related Articles

• Controlled Flight Into Terrain (CFIT)
• CFIT Precursors and Defences
• Terrain Awareness
• Pilot judgment and expertise (OGHFA BN)
• Situational Awareness (OGHFA BN)