What happened
On a scheduled domestic service traveling from Perth to Port Hedland in Western Australia, the crew of Flight 1750 departed Perth Airport at 0836 hours Western Standard Time. After receiving air traffic clearance, the pilot-in-command opted to follow the 030° radial of the Perth VOR toward Ballidu, planning to climb to FL 170. During the initial climb, the pilot reported encountering turbulence at 1,500 feet, which necessitated a lower airspeed of 155 knots compared to the planned 175 knots. The crew also updated their flight plan to cruise at FL 190.
The aircraft proceeded along its route, providing regular position updates to various flight service units. At 1114 hours, the crew reported being near Wittenoom Gorge and provided an estimated arrival time for Port Hedland of 1142 hours. Following a notification that the descent would begin shortly, the aircraft reported passing 7,000 feet while 30 miles south of its destination. However, after the flight service officer at Port Hedland transmitted weather and altimeter updates, the aircraft ceased all radio communication.
During this period of silence, two separate witnesses observed the Vickers Viscount performing a rapid and steep descent from significant distances. Due to high terrain, the impact was not visible to these observers. A search initiated by a Cessna 337 at 1212 hours located the burning wreckage approximately 28.1 miles south of Port Hedland Airport. The aircraft was completely destroyed, and there were 26 fatalities with no survivors.
Findings
The investigation determined that the structural integrity of the starboard inner main spar lower boom had been compromised. Specifically, the insertion of a flared bush at station 143 significantly reduced the fatigue endurance of the component, making it unable to reach its intended retirement life safely.