Airlines PNG Flight 1600

Airlines PNG Flight 1600 was a scheduled regular commuter passenger flight that made a forced landing in a densely forested and mountainous area near the mouth of the Gogol River, Papua New Guinea on 13 October 2011. 28 of the 32 onboard died. The aircraft involved, a de Havilland Canada DHC-8-100 (known as a Dash 8), was operating Airlines PNG's scheduled domestic service from Lae Nadzab Airport to Madang Airport. The crash site was over 40 km south of the destination airport.^[2][3]

It was the deadliest plane crash in Papua New Guinea^[4] and the third deadliest accident involving a Dash-8, as the first was the crash of Colgan Air Flight 3407 in New York which killed 50 people and the second was the crash of a Bangkok Airways Dash-8 in Koh Samui in 1990 which killed all 38 people on board. As of November 2015, it remains as the most recent air disaster with over 20 fatalities in Papua New Guinea's soil.

The investigation found the propellers oversped because the Captain pulled the power levers through the flight idle gate and into the ground beta range during flight. This was prohibited by the Aircraft Flight Manual. Although a 'beta lockout' mechanism did exist for DHC-8-100,-200, and -300 series aircraft which prevented the propellers from going into reverse even if the power levers were moved into the beta range during flight, this mechanism was only required by regulation to be installed in DHC-8 aircraft operating in the USA. It was not required to be fitted to DHC-8 aircraft in Papua New Guinea, and it was not fitted to MCJ. If a beta lockout mechanism had been installed on the aircraft, the double propeller overspeed would not have occurred when the power levers were moved below the flight idle range and in the ground beta range during flight. Installation of this mechanism is now mandatory on DHC-8 aircraft worldwide by 19 June 2016. If the pilots had followed the standard emergency procedures detailed in company manuals, they would have given themselves more time to manage the emergency, consider their options, and carry out the approach and forced landing.^[5]

History of flight

On the afternoon of 13 October 2011, an Airlines PNG Bombardier DHC-8-103, registered P2-MCJ, was conducting a regular public transport flight from Nadzab, Morobe Province, to Madang, Madang Province under Instrument Flight Rules (IFR). On board the aircraft were two flight crews, a flight attendant, and 29 passengers. Earlier in the afternoon, the same crew had flown from Port Moresby to Nadzab. The autopilot could not be used because the yaw damper was unserviceable so the aircraft had to be manually by the pilots.

The plane was refuelled when it landed in Nadzab and resumed to its destination to Madang Airport. Flight 1600 then departed Nadzab at 16:47 local time. The Captain, Australian nationality, was later identified as 64 years old Bill Spencer from Cairns, Queensland. The First Officer was 40 years old Campbell Wagstaff from Te Kuiti, New Zealand.^[6] Spencer was the handling pilot. The aircraft climbed to 16,000 ft with an estimated arrival time at Madang of 17:17. Once in the cruise, the flight crew diverted right of the flight planned track to avoid thunderstorms and cloud.

On this route, the descent to Madang was steep (because of the need to remain above the Finisterre Ranges until close to Madang) and, although the aircraft was descending steeply, the propellers were at their cruise setting of 900 revolutions per minute (RPM). Neither pilot noticed the airspeed increasing towards the maximum operating speed (VMO); as they were "distracted by the weather". When the aircraft reached VMO as it passed through 10,500 ft, with a rate of descent between 3,500 and 4,200 ft per minute, and the propellers set at 900 RPM, the VMO overspeed warning sounded.^[7]

Spencer asked Wagstaff to increase the propeller speed to 1,050 RPM to slow the aircraft when this occurred. He raised the nose of the aircraft in response to the warning and this reduced the rate of descent to about 2,000 ft per minute, however, the VMO overspeed warning continued.^[7]

Wagstaff recalled Spencer moved the power levers back "quite quickly‟. Shortly after the power levers had been moved back, both propellers oversped simultaneously, exceeding their maximum permitted speed of 1,200 RPM by over 60% and seriously damaging the left hand engine and rendering both engines unusable. The noise in the cockpit was deafening, rendering communication between the pilots extremely difficult, and internal damage to the engines caused smoke to enter the cockpit and cabin through the bleed air and air- conditioning systems.^[7]

The emergency caught both pilots by surprise. There was confusion and shock on the flight deck, a situation compounded by the extremely loud noise from the overspeeding propellers. 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.^[7]

The left propeller RPM reduced to 900 RPM (in the governing range) after about 10 seconds. It remained in the governing range for about 5 seconds before overspeeding again for about 15 seconds, then returned to the governing range. During this second overspeed of the left propeller, the left engine high speed compressor increased above 110% NH, becoming severely damaged in the process. About 3 seconds after the left propeller began overspeeding for the second time, the right propeller went into uncommanded feather due to a propeller control unit (PCU) beta switch malfunction, while the right engine was still running at flight idle (75% NH). Wagstaff then told Spencer that the right engine had shut down. He then asked to Spencer if the left engine was still working. Spencer replied that it was not working. Both pilots then agreed that they had "nothing‟.^[7]

On the order of Spencer, Wagstaff made a mayday call to Madang Tower and gave the aircraft's GPS position. However, instead of checking emergency checklists and procedures, their attention turned to where they were going to make a forced landing. The aircraft descended at a high rate of descent.^[7]

As they tried to control the plane, Wagstaff opined that they should ditch the plane in the mouth of Guabe River. Spencer said that they should land the plane right beside the river, as there were large boulders in the river bed. Sadly, neither place were good as there were large boulders hidden by vegetations on land. The aircraft impacted terrain with tail first at 114 knots with the flaps and the landing gear retracted. During the impact sequence, the left wing and tail became detached. The wreckage came to rest 300 metres from the initial impact point and was consumed by a fuel-fed fire. The front of the aircraft fractured behind the cockpit and rotated through 180 degrees, so that it was inverted when it came to rest. Of the 32 occupants of the aircraft only the two pilots, the one and only flight attendant, and one passenger out of twenty nine survived by escaping from the wreckage before it was destroyed by fire.^[8]

Aircraft

The aircraft that crashed was a de Havilland Canada DHC-8-102. The aircraft was first flown in 1988.^[1]

Passengers and crews

The plane was carrying 29 passengers and three crews, summing up a total of 32 people on board. The crew consisted of a captain, a flight officer, and a flight attendant. The captain was a 64-years old Australian Bill Spencer from Cairns, Queensland. He had logged in 18.200 hours of flying experience, which 500 of them were in the Dash-8. The First Officer was a 40-years old New Zealander Campbell Wagstaff from Te Kuiti. He had logged in a total flying time of 2.725 hours, which 391 of them were on the Dash-8. The rest of the passengers reported to be Papua New Guineans, with one reported to be a Malaysian-Chinese national (the only surviving passenger). Most of the passengers were parents tried to attend thanksgiving ceremonies ahead of the graduation of their children at Divine Word University in Madang.^[9]

Investigation

An investigation was carried out by the Accident Investigation Commission of Papua New Guinea and the Australian Transport Safety Bureau.^[10] Investigators located and retrieved the cockpit voice recorder and the flight data recorder.^[11]

The final report was issued on 15 June 2014. The investigation found that the Pilot-in-Command pulled the power levers to enter the ground beta range whilst attempting to slow the aircraft down whilst descending in bad weather. Ground Beta (the propeller's reverse pitch range) should only ever be used for slowing the aircraft whilst on the ground as at airborne speeds it can cause uncontrollable propeller overspeed and damage to the engines. 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 that caused the alerting device to not function correctly. Also, following a number of previous incidents of inadvertent selection of Ground Beta range on Dash 8 aircraft in service with other operators Worldwide, that resulted in serious damage to engines, the U.S. Federal Aviation Authority mandated that an additional safeguard was required to be fitted to aircraft operated by U.S. airlines. This system, called a Beta Lockout, was developed by the manufacturer and completely prevents inadvertent selection of Ground Beta range whilst airborne at high speeds but operators outside the U.S. were not notified or required to fit the modification. 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 report criticised the pilots for their failure to control the aircraft's rate of descent and speed both before and after the overspeed and noted that one engine was still capable of providing some accessory services during the forced landing even though it could not provide propulsion. 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.

Aftermath

After the crash, Airlines PNG decided to ground its entire fleet of 12 Dash 8s pending investigation.^[12] It also quarantined a fuel depot at Lae Nadzab Airport from which the crashed aircraft was refuelled before departing on the accident flight.^[13]

Following release of the initial accident findings, Airlines PNG added the Beta Lockout mechanism as a modification to all their Dash 8s meaning that inadvertent selection of Ground Beta whilst airborne at speed is no longer possible. Subsequently, Transport Canada in conjunction with the aircraft manufacturer released an Airworthiness Directive making it a mandatory requirement that all operators Worldwide make these modifications.^[14]

On 14 October 2015, 4th anniversary of the crash, a candlelight memorial was held at Divine World University in Madang, as most of the victims were parents attending their children Graduation Day. The memorial service was attended by staffs and students from the university. ^[15]

See also

• Austral Líneas Aéreas Flight 2553
• List of aircraft structural failures

References

External links

• Papua New Guinea Accident Investigation Commission
  • Preliminary Report (Archive, Alt, Archive, Doc format, Archive)
  • Final Report
• "Assistance to PNG AIC – Forced landing of Bombardier DHC-8-103, (Dash 8), P2-MCJ, 33 km south east of Madang, Papua New Guinea on 13 October 2011." (Archive) Australian Transport Safety Bureau