What happened
On 9 November 1997, a de Havilland Canada DHC-6 (Twin Otter) operated by No. 173 Surveillance Squadron of the 1st Aviation Regiment was conducting Exercise Highland Pursuit 2/97. The mission was designed to train three pilots in mountainous tropical operations within Papua New Guinea. The flight crew consisted of a highly experienced training pilot and two trainees.
After performing landing and takeoff maneuvers at Koinambe, the crew decided to alter their planned route to Simbai due to heavy haze and cloud cover. A disagreement occurred regarding the specific path to take; the training pilot suggested following the Jimi River and a tributary, while the navigating pilot proposed a shorter route via a different valley. The crew ultimately chose the latter path.
During the en-route portion of the flight, the training pilot moved to the cabin to monitor the flight, leaving a trainee in the left cockpit seat as the flying pilot. While the crew attempted to navigate using a GPS and an ONC chart, the navigating pilot became disoriented. After performing orbits to re-establish their position, the flying pilot turned the aircraft into a valley that the crew believed was the correct route, though they failed to verify their heading.
As the aircraft entered the valley, the training pilot moved toward the cockpit and observed that the aircraft was at an extreme nose-high pitch. Despite the crew applying full power and flaps, the aircraft was unable to clear the rising terrain. The aircraft struck trees and crashed, resulting in 3 fatalities. The wreckage was located by a helicopter pilot approximately 9 km south of Simbai after an emergency locator transmitter signal was detected.
Findings
- The crew failed to perform a heading check to confirm they had entered the correct valley.
- The crew's decision to navigate through mountainous terrain without accounting for the significant increase in ground elevation led to the impact.