A 'beta lockout' mechanism that would have prevented the overspeed even in case of erroneous power lever setting was available but not installed on the accident aircraft.

The planned route required a steep descent into Madang and, although the aircraft was descending steeply, the propellers were left at their cruise setting of 900 rpm, causing the airspeed to increase.

Shortly after the power levers had been moved back, both propellers oversped simultaneously, exceeding by over 60% their maximum permitted speed of 1,200 rpm and seriously damaging both engines.

About four seconds after the double propeller overspeed began, the beta warning horn started to sound intermittently, although the pilots stated afterwards they did not hear it.

[1] The aircraft crash-landed near the banks of the Guabe River tail-first at 114 knots (211 km/h; 131 mph), with flaps and landing gear retracted.

Most of the passengers were parents trying to attend thanksgiving ceremonies ahead of their children’s graduation at Divine Word University in Madang.

The AIC found that the pilot in command pulled the power levers beyond the flight idle gate and into the ground beta range, while attempting to slow the aircraft down during descent in bad weather.

[1][12] The mechanism that alerts pilots that they are selecting beta range had been the subject of previous investigations and it was found that a manufacturer-approved service centre had a history of releasing defective parts back to operators.

The report also found that the crew had to deal with an overspeed of both propellers that caused large amounts of drag making the aircraft extremely difficult to control and that there was significant noise caused by the propeller tips exceeding the speed of sound and also smoke in the cockpit and cabin due to the damage to the engines and bleed air system.

The pilots shut this engine down and therefore lost the ability to use hydraulic and electrical systems that might have improved the survivability of the forced landing.

[13] It also quarantined a fuel depot at Lae Nadzab Airport from which the crashed aircraft was refuelled before departing on the accident flight.

[15] On 14 October 2015, 4th anniversary of the crash, a candlelight memorial was held at Divine Word University in Madang, as most of the victims were parents attending their children's Graduation Day.