19 Jul 2019 - Final report issued P2-PXE 737-800 landed short of runway at Chuuk, Micronesia 27 Sep 2018
On 27 September 2018, an Air Niugini 737-800, P2-PXE (33024/1688), was approaching Chuuk (PTKK), Micronesia, runway 04 in low cloud and rain showers. At 23:45 UTC (09:45 local time) the aircraft impacted the water of Chuuk Lagoon about 1,500 ft (460 m) short of the runway 04 threshold, during its approach to runway 04 at Chuuk International Airport. As the aircraft settled in the water, it turned clockwise through 210 degrees and drifted 460 ft (140 m) south east of the runway 04 extended centreline, with the nose of the aircraft pointing about 265 deg.
Flight ANG73 was enroute from Pohnpei to Port Moresby via Chuuk with 12 crew members and 35 passengers on board. Six passengers were seriously injured, and one passenger was fatally injured.
PTKK 282355Z 04007KT 3SM SHRA BKN000 OVC008CB 26/25 A2973 RMK CB ALQDS MOV SW SLP071 60186 8/3// T02610250 10261 20250 52015
A preliminary report was issued giving some factual information but all analysis and conclusions were reserved for the final report which was published 19 Jul 2019. Significant details are given below.
*** Updated 18 Apr 2019 ***
On 28 September 2018, at 23:24:19 UTC2 (09:24 local time), a Boeing 737-8BK aircraft, registered P2-PXE (PXE), operated by Air Niugini Limited, was on a scheduled passenger flight number PX073, from Pohnpei to Chuuk, in the Federated States of Micronesia (FSM) when, during its final approach, the aircraft impacted the water of the Chuuk Lagoon, about 1,500 ft (460 m) short of the runway 04 threshold. The aircraft deflected across the water several times before it settled in the water and turned clockwise through 210 deg and drifted 460 ft (140 m) south east of the runway 04 extended centreline, with the nose of the aircraft pointing about 265 deg. The pilot in command (PIC) was the pilot flying, and the copilot was the support/monitoring pilot. An Aircraft Maintenance Engineer3 occupied the cockpit jump seat. The engineer videoed the final approach on his iPhone, which predominantly showed the cockpit instruments. Local boaters rescued 28 passengers and two cabin crew from the left over-wing exits. Two cabin crew, the two pilots and the engineer were rescued by local boaters from the forward door 1L. One life raft was launched from the left aft over-wing exit by cabin crew CC5 with the assistance of a passenger. The US Navy divers rescued six passengers and four cabin crew and the Load Master from the right aft over-wing exit. All injured passengers were evacuated from the left over-wing exits. One passenger was fatally injured, and local divers located his body in the aircraft three days after the accident. The Government of the Federated States of Micronesia commenced the investigation and on 14th February 2019 delegated the whole of the investigation to the PNG Accident Investigation Commission. 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)4 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, overriding5 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 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. The investigation found that the Civil Aviation Safety Authority of PNG (CASA PNG) policy and procedures of accepting manuals rather than approving manuals, while in accordance with the Civil Aviation Rules requirements, placed a burden of responsibility on CASA PNG as the State Regulator to ensure accuracy and that safety standards are met. In accepting the Air Niugini manuals, CASA PNG did not meet the high standard of evidence-based assessment required for safety assurance, resulting in numerous deficiencies and errors in the Air Niugini Operational, Technical, and Safety manuals as noted in this report and the associated Safety Recommendations. The report includes a number of recommendations made by the AIC, with the intention of enhancing the safety of flight (See Part 4 of this report). It is important to note that none of the safety deficiencies brought to the attention of Air Niugini caused the accident. However, in accordance with Annex 13 Standards, identified safety deficiencies and concerns must be raised with the persons or organisations best placed to take safety action. Unless safety action is taken to address the identified safety deficiencies, death or injury might result in a future accident. The AIC notes that Air Niugini Limited took prompt action to address all safety deficiencies identified by the AIC in the 12 Safety Recommendations issued to Air Niugini, in an average time of 23 days. The quickest safety action being taken by Air Niugini was in 6 days. The AIC has closed all 12 Safety Recommendations issued to Air Niugini Limited. One safety concern prompting an AIC Safety Recommendation was issued to Honeywell Aerospace and the US FAA. The safety deficiency/concern that prompted this Safety Recommendation may have been a contributing factor in this accident. The PNG AIC is in continued discussion with the US NTSB, Honeywell, Boeing and US FAA. This recommendation is the subject of ongoing research and the AIC Recommendation will remain ACTIVE pending the results of that research.
The aircraft was fitted with a solid-state cockpit voice recorder (SSCVR) and a separate solid-state flight data recorder (SSFDR). The SSCVR (P/N: 980-6022-001 & S/N:04448) and SSFDR (P/N: 980-4700-043 & S/N: 17869) were manufactured by Honeywell Aerospace. The CVR was installed at the rear fuselage of the aircraft. The SSFDR was installed in the ceiling at the rear of the passenger cabin.
The SSFDR was recovered from its rack within the aircraft by local civilian divers.
After the auto-pilot was disengaged at 625 ft (677 ft), the aircraft’s descent rate increased from 750 ft/min and a groundspeed of 146 kts to 1,380 ft/min and a groundspeed of 149 kts, at 420 ft.
Heavy rain and IMC were encountered at the minimums and the crew activated the windscreen wipers.
The SSCVR was designed to record 30 minutes of audio on four channels (P/A, Co-pilot, Pilot, Cockpit Area Microphone/CAM) and 120 minutes of audio on 2 channels (combined crew audio & CAM).
Significant excerpts taken from the CVR are as follows:
Until 2 seconds before impact, the copilot did not give the PIC any oral cautions throughout the approach despite the excessively high rate of descent and the aircraft increasingly being flown below the glideslope in an unstabilised manner and in IMC. As the pilot monitoring, the copilot did not challenge the PIC (the flying pilot) as required in the Air Niugini Limited Crew Resource Management (CRM) procedures.
Wreckage and impact information
The initial examination of video taken by the divers showed that the main landing gear separated from the aircraft during the water impact. The rear fuselage behind the wing had fractured during the impact sequence. The aircraft sank in 90 ft of water to the Chuuk Lagoon seabed.
2.3 Flight crew actions
During the flight, before the TOD briefing, the oral communications between the PIC, the copilot, and air traffic control were in a normal tones and in an orderly manner. However, during the approach below 10,000 feet, communication between the pilots was minimal and not in accordance with SOPs, and they were not using standard phraseology.
From the time the auto-pilot was disconnected at 625 ft (677 ft), the aircraft was never in a stabilised approach and so a go-around should have been conducted immediately.
2.3.1 Human Factors and medical
The AIC obtained the services of an aviation investigation medical practitioner who has specialised in aircraft accident and serious incident medical and psychological investigations for more than 20 years. Under the provisions of the Civil Aviation Act 2000 (as amended) and the Commissions of Inquiry Act, this expert examined ALL relevant evidence and provided the AIC with assessment and findings. No evidence of fatigue was presented.
2.4 Enhanced Ground Proximity Warning System (EGPWS)
The investigation found that the crew did not take any remedial action in response to the Glideslope and Sink Rate Caution64 alerts (aural alerts). The EGPWS additionally issued the red PULL UP visual alert on the PFD at 307 ft (364 ft) when the aircraft penetrated the Sink Rate Envelope of the Honeywell EGPWS MK V Mode 1 Graph. (See Figure 32). During the approach the crew lost situational awareness, with their attention channelised, and the aircraft entered the storm cell with heavy rain after passing the MAP. The PIC did not arrest the excessive rate of descent, and flew the aircraft increasingly below the Glideslope. The crew of P2-PXE were fixated on the task of landing the aircraft and did not notice the visual PULL UP caution alert at the bottom of their PFD. Therefore, they (crew) did not take any positive action to arrest the high rate of descent and avoid landing in the lagoon. In fact, neither of the pilots were aware of the rapidly unfolding unsafe situation. The investigation found that the crew had received similar aural alerts on previous approaches in visual conditions where the aircraft was safely landed. This would have contributed to the perception that the alerts during the accident approach were nuisance alerts, and therefore disregarded them. A visual display of the steady red PULL UP on the PFD, was not noticed by either of the pilots, and therefore was not sufficient to alert them to the imminent danger. A steady message surrounded by lights during a critical phase of flight where the PIC is fixated on other displays may not be an effective means of alerting the crew that the unsafe situation has developed to the next level. The investigation determined that the light blended in with the displays and was not noticed by both pilots when it illuminated, nor did it have any features to effectively draw the attention of the crew after its illumination. The AIC Human Factors investigation determined that it is likely that a hard aural ‘WARNING’ alert or a flashing visual PULL UP would have more effectively drawn the attention of the pilots during this critical phase of flight where workload was higher and attention fixated. It could be the last line of defence for any crew who may unknowingly or inadvertently get in a similar fixated situation. The investigation found that it is important for aircraft alerting systems to be able to effectively draw attention and provide information to flight crew, to allow them (the crew), to distinguish between levels of unsafe situations as they develop. If an alert signifying an elevation of an unsafe condition is missed by crews, they may not be able to recognise that the unsafe condition has developed to the next level and requires urgent corrective action. In January 2019, the AIC recommended to Honeywell that a continuous “WHOOP WHOOP PULL UP” hard aural warning, simultaneously with the visual display of PULL UP on the Primary Flight Display, should replace the Sink Rate Caution alerts (aural alerts) to alert a crew of imminent danger when the aircraft continues to descend below 500 ft Radio Altitude and below the glideslope. However, during subsequent discussions with Honeywell and Boeing, the AIC was informed that such hard-aural warning might not be an option for older generation EGPWS. From a Human Factors perspective, in the absence of a continuous “WHOOP WHOOP PULL UP” hard aural warning, changing the steady PULL UP visual display to a flashing visual display PULL UP on the PFD is desirable. That could be more effective than a steady PULL UP visual display to alert flight crews to imminent danger when the aircraft continues to descend below 500 ft Radio Altitude and below the glideslope. A hard-aural warning alert or flashing visual warning, demanding an immediate flight crew response would clearly be desirable in the interest of safety enhancement. The AIC issued recommendations to Ho n Administration in relation to EGPWS alerts and warnings.
US NTSB STATE OF MANUFACTURE CONCLUSIONS
The US National Transportation Safety Board’s Accredited Representative and Technical Advisers representing the State of Manufacture, had full access to the evidence, including all recorded data and the cockpit imagery (video), in accordance with Annex 13 international obligations. The NTSB team provided their conclusions, which have been duly considered during the drafting of the Final Report.
With respect to cause #7 above, the NTSB Team requested that the substance of their comments be appended to the Final Report, in accordance with Paragraph 6.3 of Annex 13, Standard.
The AIC agreed to publish the NTSB Team’s findings and conclusion, which states:
NTSB staff disagrees that an additional warning would have been effective in alerting the crew. The conclusions and the supporting information in the draft report effectively demonstrate that the pilots:
• Lost situational awareness. • Disregarded 16 EGPWS alerts that had occurred in the 19 seconds preceding impact with the water. • Disregarded vertical guidance being displayed on the Primary Flight Display (PFD). • Did not comply with the Air Niugini go-around policy after the first and subsequent EGPWS alerts. • Did not comply with the Air Niugini go-around policy after the approach had become unstable with the descent rate exceeding 1000 feet per minute.
NTSB staff believes that the actions of the pilots to disregard the 16 EGPWS alerts and to not comply with Air Niugini policy clearly demonstrate that the crew was unresponsive to guidance that should have prompted a clear and decisive action to initiate a missed approach.
NTSB staff believes the disregard of the alerts, disregard of the PFD display guidance, and the continuation of an unstable approach demonstrate that any additional guidance, alert, or warning would be similarly disregarded by the flight crew and ineffective in preventing the accident.