Aviation safety investigations & reports

de Havilland Canada DHC-6 SERIES 320, VH-HPY

Investigation number:
Status: Completed
Investigation completed


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The crew were operating a de Havilland Canada DHC-6 Twin Otter aircraft in Exercise Highland Pursuit 2/97. The purpose of the exercise, which was conducted by No. 173 Surveillance Squadron, 1st Aviation Regiment, Australian Army, was to provide tropical mountainous flying training in Papua New Guinea. There were three trainees and one training pilot on board the aircraft.

On Sunday, 9 November 1997, the third day of flying operations in Papua New Guinea, the crew were conducting a flight from Madang and return via a number of airstrips in the central highlands. When haze and cloud prevented them flying the flight-planned direct track between the Koinambe and Simbai airstrips, they decided to fly north-west via the Jimi River valley and one of its tributaries. Two of the trainees were occupying the cockpit seats, one as flying pilot and the other as navigating pilot using a 1:1,000,000-scale chart. When the crew turned the aircraft to follow a tributary off the Jimi River, the training pilot was in the aircraft cabin.

A few minutes later, their discussion regarding the progress of the flight attracted the attention of the training pilot. By this time, however, the position of the aircraft in the valley, and its available performance, were such that an escape from the valley was not possible. The aircraft collided with trees before impacting steeply sloping ground.

It was subsequently established that when the crew turned from the Jimi River, they entered the wrong valley. Calculations based on the manufacturer's performance data showed that the aircraft did not have sufficient performance to outclimb the increase in terrain elevation from the Jimi River valley to cross the Bismarck Ranges via this valley. There was a low level of experience and corporate knowledge within the Army regarding the operations of fixed-wing aircraft such as the Twin Otter in tropical mountainous areas.

Against this background, deficiencies were identified in the planning and preparation for the exercise, including risk assessment and the selection and briefing of the training pilot.

Download Final Report
[Download  PDF: 515KB]
General details
Date: 09 November 1997   Investigation status: Completed  
Time: 2357 hours UTC    
Location   (show map): 9 km SW of Simbai in the Bismarck Ranges - Papua New Guinea    
State: International   Occurrence type: Collision with terrain  
Release date: 25 July 1999   Occurrence category: Accident  
Report status: Final   Highest injury level: Serious  

Aircraft details

Aircraft details
Aircraft manufacturer de Havilland Canada  
Aircraft model DHC-6  
Aircraft registration VH-HPY  
Serial number 706  
Type of operation Military  
Damage to aircraft Nil  
Departure point Madang  
Departure time 2214 hours UTC  
Destination Simbai  
Crew details
Role Class of licence Hours on type Hours total
Pilot-in-Command ATPL 706 10803
Other Pilot ATPL 900 2460
  Crew Passenger Ground Total
Serious: 1 3 0 4
Total: 1 3 0 4
Last update 13 May 2014