Investigators believe contact with jagged rocks at the Bulolo airstrip damaged a tyre on a Bombardier de Havilland Dash 8-200 before the tyre exploded inside its stowage well at cruise altitude.
The turboprop – registered P2-ANK, owned by Air Niugini and operated by Link PNG – had been operating a service from Port Moresby to Tari on 4 August last year.
After departing runway 14L the aircraft had been climbing through 20,000ft, some 39nm west-north-west of Port Moresby, the pilots heard a bang and felt the aircraft shudder.
The first officer initially believed the aircraft had suffered an engine failure, but a check on the instrumentation showed the powerplants were operating normally.
Papua New Guinea's Accident Investigation Commission says the crew opted to return to Port Moresby and burned excess fuel before landing at the airport.
"It wasn’t until the passengers and the crew disembarked, that the crew were advised by the engineers that panels were missing aft of the left exhaust nacelle," says the inquiry.
Further inspection found that one of the two tyres on the left-hand main landing-gear was deflated and damaged.
"It was apparent that, when the tyre blew out in the wheel well, it caused substantial damage to the main structure on the inside of the nacelle," the inquiry adds.
The investigation determined that the aircraft had originally arrived in Port Moresby from Bulolo, and an examination of the runway found that weather erosion and poor maintenance had left jagged rocks exposed on the surface.
Inspection of the tyre showed that it had suffered foreign-object damage which had probably been inflicted by a rock impact on the tyre's side wall during landing at Bulolo.
When the aircraft returned to Port Moresby from Bulolo the damage was not discovered during post- or pre-flight inspections, ahead of the service to Tari. None of the 31 occupants was injured during the event.