Hevilift DHC6 near Port Moresby on Sep 20th 2014, impact with terrain
Last Update: September 9, 2015 / 19:37:33 GMT/Zulu time
Incident Facts
Date of incident
Sep 20, 2014
Classification
Accident
Airline
Hevilift
Departure
Woitape, Papua New Guinea
Destination
Port Moresby, Papua New Guinea
Aircraft Registration
P2-KSF
Aircraft Type
De Havilland DHC-6 Twin Otter
ICAO Type Designator
DHC6
Papua New Guinea's Accident Investigation Commission (PNGAIC) have opened an investigation into the accident estimating a preliminary report will be released in 30 days. The AIC reported: "Of the nine persons on board, four including the two pilots, did not survive the impact."
On Oct 14th 2014 the NTSB reported that both pilots and two passengers were killed, one passenger received serious injuries and four passengers minor injuries, when the aircraft impacted a steep jungle-covered terrain below the summit of Mount Lawes.
No weather data are available for Port Moresby, the weather was generally described as poor with low cloud and has not been ruled out as a factor into the accident.
On Sep 8th 2015 Papua New Guinea's Accident Investigation Commission (PNGAIC) released their final report concluding the probable causes of the accident were:
- The flight crew continued the descent in instrument meteorological conditions without confirming their position.
- The flight crew’s assessment of their position was incorrect and they had lost situational awareness
- The flight crew deprived themselves of the “Caution” and “Warning” alerts that would have sounded about 20 sec and about 10 sec respectively before the collision, by not deactivating the EGPWS Terrain Inhibit prior to departure from Woitape.
The PNGAIC reported the captain (60, ATPL, 19,290 hours total, 5,980 hours on type) had undergone the last ILS proficiency check 11 months ago, therefore was not current and not permitted to fly an ILS approach, the captain was pilot monitoring. The first officer (25, CPL, 432 hours total, 172 hours on type) was pilot flying.
The aircraft entered the Port Moresby control zone under visual flight rules and received clearance to descend to 6000 feet visually and track for a left base for runway 14R. The aircraft was subsequently cleared for a visual approach tracking for a left base runway 14R, they should contact tower at 10nm DME. The crew subsequently reported being 9.5nm out descending through 4000 feet MSL and stated "we're running into a bit of cloud, we might as well pick up the ILS if it’s OK", tower replied instantly (without referring to the ILS portion): "roger, continue approach runway 14 right, report on left base."
The captain instructed the first officer to track to the right to pick up the localizer. A short time later the aircraft impacted Mt. Lawes at 1600 feet MSL, just below the summit, about 4.5nm left of the localizer (140 degrees) on a track of 177 degrees.
There were no system malfunctions prior to impact. The cockpit voice recorder revealed that there were no EGPWS warnings and the crew did not see the ground until about 1 second prior to impact.
An examination of the EGPWS revealed that the warnings had been inhibited on approach to Woitape and had remained inhibited throughout the following sector. On approach to Woitape, about 25 seconds prior to touch down, the EGPWS had issued two terrain cautions, the alerts were subsequently inhibited. The PNGAIC stated: "The Terrain Inhibit switch is intended to be used to prevent nuisance warnings when the landing airport is not in the EGPWS terrain database."
A helicopter pilot living near the crash site and hearing the impact sounds of the aircraft reported, that about 35 minutes prior to the impact it had been raining, there were 8 octas of cloud ceiling 1000 feet MSL, and the cloud cover had not changed at the time of impact.
The PNGAIC analysed:
The investigation found that the flight progressed normally after takeoff from Woitape, and the on-board video recorded data showed that the descent to 6,000 ft was commenced at 29 nm (53.7 km) from Port Moresby when the aircraft was clear of cloud. About 10 nm (18.5km) from Port Moresby, when the aircraft was in broken cloud the descent rate was increased. The pilot in command (PIC) told the tower controller that they were ‘running into a bit of cloud’ and said ‘we might as well pick up the ILS’ [instrument landing system approach]. However, the PIC did not request an ILS approach.
The Port Moresby Aerodrome Terminal Information Service (ATIS), current while P2-KSF was approaching Port Moresby had been received by the flight crew. It required aircraft arriving at Port Moresby to conduct an ILS approach. The PIC’s last ILS proficiency check was about 11 months before the accident flight.
The PIC did not meet the currency requirements specified in the PNG Civil Aviation Rule 6.807 in order to exercise the privileges of his Instrument Rating for Instrument Landing System (ILS) approaches. It is likely the reason the PIC did not request a clearance to intercept the ILS from 30 nm (55.6 km) to fly an ILS approach to runway 14 at Port Moresby.
During the descent, although the PIC said ‘we know where we are, keep it coming down’, it was evident from the recorded information that his assessment of their position was incorrect, and therefore the descent should not have been continued. The PIC and copilot had lost situational awareness.
The Enhanced Ground Proximity Warning System (EGPWS) did not provide Terrain alerts or warnings prior to the collision with the terrain. From correlation with the CVR, the investigation determined that the Terrain Inhibit was activated about 25 sec before touchdown at Woitape and after two Terrain Caution alerts had already been generated.
By not deactivating the EGPWS Terrain Inhibit prior to departure from Woitape, the crew deprived themselves of the “Caution” and “Warning” alerts that would have sounded about 20 seconds and about 10 sec respectively before the collision.
Incident Facts
Date of incident
Sep 20, 2014
Classification
Accident
Airline
Hevilift
Departure
Woitape, Papua New Guinea
Destination
Port Moresby, Papua New Guinea
Aircraft Registration
P2-KSF
Aircraft Type
De Havilland DHC-6 Twin Otter
ICAO Type Designator
DHC6
This article is published under license from Avherald.com. © of text by Avherald.com.
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