I didn't look closely enough at Balus, Volume 2. To quote Jim Sinclair Chapter 3, Page 121:
At 10.30am on 20th May 1970, the STOL Aztec C, VH-COB took off from Gurney airport on a routine administration charter flight of 20 minutes to Esa'ala on Normanby Island. The pilot, Ian Cornett, was 35 years old and had been flying in PNG for only 6 weeks. He had been endorsed onto the Aztec 2 weeks before and his total flying hours were 1,272. Cornett had flown the Gurney-Esa'ala route once only-and in only one direction. DCA requirements were for a pilot to make a minimum of five flights under supervision in each direction over a route before he was cleared for command.
There were eight passengers on the Aztec: Ray Hennessy, manager of the Electricity Commission power station at Samarai; John Lee, an education officer; Harry-Balfour-Ogilvie, a patrol officer, and his wife, Esther, and infant daughters, Deborah and Sandra; Dave Robertson, Assistant District Officer, Esa'ala, and Komas Duri, a Papuan mechanic.
Port Moresby control sensed that something was wrong with the Aztec when Cornett failed to call for the customary bid for a departure clearance, usually sought as an aircraft is climbing from the runway. (I think Sinclair means they, DCA, didn't get his departure report Gurney, not clearance as the airspace between Gurney-Esa'ala wouldn't require one). No further contact was made with the aircraft and search procedures were begun.
Eight aeroplanes had been called into the search by last light that day, five of them STOL owned. Over the following days the weather deteriorated sharply as a tropical storm raged through the Milne Bay region. As the weather cleared the search intensified. Two Caribous with army observers were called in and several helicopters. A DC6 (Twin Otter) with radar photographic equipment- on survey work in PNG joined the search.
Ten days after the disappearance, the pilot of a light aircraft found the wreckage of the Aztec on the side of a mountain about six kilometres from Gurney. There were no survivors.
The DCA investigators found that the engines of the Aztec were in poor condition at the time of the crash although they had only done about 40 hours since overhaul. The aeroplane had made a belly landing at Daru in February with major damage resulting to the propellers, flaps, wheel bay doors and air intakes. Repairs had been carried out at the Patair workshop in Port Moresby, at which time the engines and propellers had been replaced. But Ian Cornett had had difficulty starting the Aztec engines over the week preceeding the crash. The starboard engine gave trouble just before the last flight. The first take off run had been abandoned after the engine stopped, and it took three attempts before it would start again.
Normal prudence should have resulted in the abandonment of the flight at this point but Cornett took off, in an aeroplane that was 126 kilograms over max take off weight and carrying one more passenger than allowed by the regulations.
End of Quote.