The Papua New Guinea Accident Investigation Commission (AIC) released the final report on Air Niugini Flight 73, a Boeing 738 that crashed into Chuuk Lagoon while attempting to land at Chuuk Int’l Airport in bad weather. The plane came to rest on the water, and passengers were rescued by local fisherman and US Navy divers. One passenger was killed. A flight engineer seated in the cockpit jumpseat filmed the final moments of the flight. The video has no sound, and stops shortly after impact.
Basically, once the crew disabled the autopilot, they had no idea what they were doing and ignored every single alarm that was alerting them to the botched approach. They didn’t realize their predicament until seconds before impact. Below is an animation created of the accident sequence constructed from the flight data, and an excerpt from the synopsis of the investigation.
The investigation determined that the flight crew’s level of compliance with Air Niugini Standard Operating Procedures Manual (SOPM) was not at a standard that would promote safe aircraft operations.
The PIC intended to conduct an RNAV GPS approach to runway 04 at Chuuk International Airport and briefed the copilot accordingly. The descent and approach were initially conducted in Visual Meteorological Conditions (VMC), but from 546 ft (600 ft) the aircraft was flown in Instrument Meteorological Conditions (IMC).
The flight crew did not adhere to Air Niugini SOPM and the approach and pre-landing checklists. The RNAV (GPS) Rwy 04 Approach chart procedure was not adequately briefed.
The RNAV approach specified a flight path descent angle guide of 3o. The aircraft was flown at a high rate of descent and a steep variable flight path angle averaging 4.5o during the approach, with lateral over-controlling; the approach was unstabilised.
The Flight Data Recorder (FDR) recorded a total of 17 Enhanced Ground Proximity Warning System (EGPWS) alerts, specifically eight “Sink Rate” and nine “Glideslope”. The recorded information from the Cockpit Voice Recorder (CVR) showed that a total of 14 EGPWS aural alerts sounded after passing the Minimum Descent Altitude (MDA), between 307 ft (364 ft) and the impact point. A “100 ft” advisory was annunciated, in accordance with design standards, overriding one of the “Glideslope” aural alert. The other aural alerts were seven “Glideslope” and six “Sink Rate”.
The investigation observed that the flight crew disregarded the alerts, and did not acknowledge the “minimums” and 100 ft alerts; a symptom of fixation and channelised attention. The crew were fixated on cues associated with the landing and control inputs due to the extension of 40° flap.
Both pilots were not situationally aware and did not recognise the developing significant unsafe condition during the approach after passing the Missed Approach Point (MAP) when the aircraft entered a storm cell and heavy rain. The weather radar on the PIC’s Navigation Display showed a large red area indicating a storm cell immediately after the MAP, between the MAP and the runway.
The copilot as the support/monitoring pilot was ineffective and was oblivious to the rapidly unfolding unsafe situation. He did not recognise the significant unsafe condition and therefore did not realise the need to challenge the PIC and take control of the aircraft, as required by the Air Niugini SOPM6.
The Air Niugini SOPM instructs a non-flying pilot to take control of the aircraft from the flying pilot, and restore a safe flight condition, when an unsafe condition continues to be uncorrected.
The records showed that the copilot had been checked in the Simulator for EGPWS Alert (Terrain) however there was no evidence of simulator check sessions covering the vital actions and responses required to retrieve a perceived or real situation that might compromise the safe operation of the aircraft. Specifically sustained unstabilised approach below 1,000 ft amsl in IMC.
The PIC did not conduct the missed approach at the MAP despite the criteria required for visually continuing the approach not being met, including visually acquiring the runway or the PAPI.
The PIC did not conduct a go around after passing the MAP and subsequently the MDA although:
- The aircraft had entered IMC;
- the approach was unstable;
- the glideslope indicator on the Primary Flight Display (PFD) was showing a rapid glideslope deviation from a half-dot low to 2-dots high within 9 seconds after passing the MDA;
- the rate of descent high (more than 1,000 ft/min) and increasing;
- there were EGPWS Sink Rate and Glideslope aural alerts; and
- the EGPWS visual PULL UP warning message was displayed on the PFD.The report highlights that deviations from recommended practice and SOPs are a potential hazard, particularly during the approach and landing phase of flight, and increase the risk of approach and landing accidents. It also highlights that crew coordination is less than effective if crew members do not work together as an integrated team. Support crew members have a duty and responsibility to ensure that the safety of a flight is not compromised by non-compliance with SOPs, standard phraseology and recommended practices.