Propellers likely cause of PNG plane crash
Only four people survived the crash. (AAP: Scott Waide)
Investigators in Papua New Guinea say a plane that crashed killing 28 people got into trouble when its propellers began rotating too fast.
Only four people survived when the Airlines PNG Dash 8 crashed near Madang on October 13.
The Accident Investigation Commission's preliminary report says the plane's over-speed warning horn went off as it descended into Madang.
Shortly after, both propellers simultaneously over-sped and exceeded their maximum permitted revolutions per minute by 60 per cent.
The pilots then shut down both engines and conducted a forced landing near the Buang River.
The report says the plane burst into flames shortly after impact and the fire consumed most of the airport.
Senior investigator Sid O'Toole says the over-speed situation could have caused the engines' turbines to self destruct.
"If the over-speed is so high and that power turbine self destructs, there is no control over the propeller," he said.
Mr O'Toole says it is still too early to say if that is what happened and investigations are continuing.
The commission's preliminary report does not identify the cause of the crash; it only outlines the facts surrounding the incident.
Among the survivors was Australian pilot Bill Spencer and his New Zealand co-pilot Campbell Wagstaff.