On 28 July 2018, an ATR72-500 (YJ-AV71) being operated by Air Vanuatu on a domestic passenger flight from Tanna to Port Vila. during which type conversion line training for the First Officer was being performed, suffered a sudden failure of the right engine that reportedly led to significant smoke appearing in the passenger cabin. A MAYDAY was declared on that account but an apparently unrelated landing accident subsequently occurred when the aircraft veered off the destination landing runway soon after touchdown and collided with two unoccupied parked aircraft. All three aircraft were damaged, but no occupants on the in-service aircraft were injured.
An Investigation was commenced by the Papua New Guinea Accident Investigation Commission (AIC) the day after the accident following delegation of the whole Investigation to the AIC by the Vanuatu CAA, who then supported it as necessary with guidance on applicable Republic of Vanuatu Civil Legislation. The aircraft 2 hour SSCVR, FDR and QAR PCMCIA card were all recovered from the aircraft and their data downloaded. It was found that the Digital Flight Data Acquisition Unit (DFDAU) feeding the FDR was programmed with an ATR Data Frame Version which did not comply with FAA requirements for transport category aircraft and also noted that the data recording system of the aircraft was not capable of recording some parameters of interest specified in the FAR including hydraulic pressure, brake pedal activation, trim commands and brake pressure.
It was noted that the 34 year-old Training Captain, who was a French national, was both a Training Captain and ATR Fleet Manager. He had a total of 7,205 hours flying experience including 3,870 hours on type having gained his ATR 72 type rating in 2014. The 27 year-old trainee First Officer, a Vanuatu national who had been under supervision as PF for the flight, had a total of 1,629 hours flying experience including 55 hours on type, had recently gained an ATR 72 type rating and was undergoing line training to complete the type conversion process. He had previous experience on the DHC6 Twin Otter.
Whilst en-route at FL160 and about 60 nm from destination, both crew and passengers reported having heard ‘loud bangs’ from the right hand side of the aircraft which the Captain had concluded were attributable to disrupted airflow in the right engine due to a compressor stall. The ITT indication for that engine was seen to rise rapidly and, on exceeding its limit, a corresponding alert was triggered. The Captain immediately took over as PF, retarded the (corresponding) power lever and instructed the First Officer to find the ‘ABNORMAL ENG PARAMETERS IN FLIGHT’ Checklist. He subsequently called the Senior Cabin Crew Member (SCCM) to acknowledge the occurrence and was told that “smoke was entering the cabin from the right side of the aircraft”. On hearing this, the Captain was recorded as exclaiming “Smoke!” and immediately making a ‘MAYDAY’ call to Villa ATC advising “we got cabin smoke” which when queried was followed by a repeat of the ‘MAYDAY’ and “engine smoke and we got an engine problem, we might have to shut it down”. He then notified that they were commencing descent.
One minute later, both pilots donned their oxygen masks and recommenced the ‘ABNORMAL ENG PARAMETERS’ Checklist. They had only completed the first item on it when the Captain interrupted the First Officer by calling the SCCM for an update on the reported cabin smoke and was told that “smoke was still entering the cabin” upon which he instructed her to don her Protective Breathing Equipment (PBE) and carry out the required cabin smoke procedures. He then made a PA asking all passengers to remain seated and await further instructions. Whilst he was doing this, an ‘ELEC SMK’ Warning was annunciated and although the previous Checklist had not been completed, he immediately instructed the First Officer to find the ‘ELECTRICAL SMOKE’ Checklist. He then requested Vila ATC to arrange for the RFFS to be on Standby for their arrival “as the smoke situation would require them to stop on the runway to evacuate passengers”.
On completion of this exchange, the First Officer began reading the ‘ELECTRICAL SMOKE’ Checklist. The first item referred the crew to the (general) ‘SMOKE’ Checklist which was then started. Half way through the Memory Items of that Checklist, the Captain interrupted and instructed the First Officer to go back to the ‘ELECTRICAL SMOKE’ Checklist and complete that first, but then quickly corrected himself and asked the First Officer to continue with the ‘SMOKE’ Checklist. The crew then “hastily completed the memory items and returned to continue with the ‘ELECTRICAL SMOKE’ Checklist and actioned the first 9 items but did not then refer as directed by that item to the ‘ACW GEN 1+2 LOSS’ Checklist. Five minutes after her original report of smoke in the passenger cabin, the SCCM called to say that “smoke was still present in the cabin and was intensifying” to which the Captain replied that “they would need to be ready for an evacuation of the passengers on the runway”.
With the aircraft now about 33 nm from Port Via, a Warning of Engine 2 Low Oil Pressure was annunciated and the Captain instructed the First Officer to find the ‘ENG 1(2) OIL LO PR’ Checklist. This had several (conditional) sub-checklists but when the First Officer was unable to determine which option was appropriate, the Captain temporarily returned control of the aircraft to the First Officer in order to run the Checklist himself before taking it back upon completion, which had required (eight minutes after the initial signs of engine distress) that the right engine be shut down. Completion of this Checklist then directed crews to move to the ‘SINGLE ENG OPERATION’ Checklist but this was not immediately run as the Captain then instructed the First Officer to check and confirm if they had completed the ‘ELECTRICAL SMOKE’ Checklist. The First Officer did so and advised that the next item on that Checklist required them to refer to the ‘ACW GEN 1+2 LOSS’ Checklist which the crew then commenced. After the first 10 items, this Checklist then consisted of two successive sub sections, the first headed ‘Before Landing’ and the second ‘After Touchdown’ and was completed by a reference list of ‘Lost Items’. The Captain intervened and instructed the First Officer to “reserve” the first sub section and continue with the rest of the Checklist but before he could finish it, the Captain “told him to start again from the top”. The First Officer did so “but before he could finish reading the first item, the Captain interrupted again by saying that they needed to complete the ‘SINGLE ENGINE OPERATION’ Checklist.
Once the First Officer located this, he began to readout the title but progress was briefly interrupted when the Captain called the SCCM to advise that he would be making a ‘brace’ call shortly before touchdown. This Checklist was then completed. By now, the aircraft was within 5 nm of the airport and the Captain instructed the First Officer to refer back to the ‘ACW GEN 1+2 LOSS’ Checklist and continue with its ‘Before Landing’ section.
No significant weather conditions existed at Port Vila and descending through about 1,900 feet for a visual approach, the landing gear lever was selected down and the flaps selected first to 15° and then 30°. To achieve the required manual landing gear extension process, the Captain again briefly handed control to the First Officer and successfully extended the landing gear from memory before resuming control. Of note was that the normal ‘Before Landing’ Checklist was not run which resulted in the rudder Travel Limitation Unit (TLU) remaining locked in its high-speed mode where it was when the engine was shut down and not then being checked and manually operated prior to landing, which had the effect of significantly limiting rudder authority at low speeds.
A left turn onto finals for runway 29 was initiated and as the aircraft subsequently turned finals 1 nm from the threshold at a height of 330 feet, the Captain made a ‘Brace’ call on the PA. Touch down within the TDZ followed with immediate but brief selection of maximum reverse pitch which after a slight deviation left of the runway centreline was followed by a return of the power levers ground idle as the speed continued to decrease. About 200 metres further on, at a speed of 65 knots, the power levers were reselected into reverse setting and the aircraft immediately veered left and departed the side of the runway. It travelled for 320 metres over grass and across a taxiway before colliding, at a speed of about 45 knots, with two parked, unoccupied, BN-2 Islander aircraft, damaging all three aircraft and coming to an abrupt stop. As soon as the aircraft stopped, the Captain ordered an emergency evacuation which the cabin crew then conducted in an orderly and expedited manner with no consequent occupant injuries.
An annotated approach and landing flight path. [Reproduced from the Official Report]
Damage to the two parked aircraft (see the illustrations below) was considerable with the forward fuselage of one being completely destroyed and the vertical stabiliser and rudder being sheared off the other. The right hand side of the ATR72 sustained significant damage which included to the fuselage, engine, propeller assembly and main landing gear nacelle.
Damage to one of the parked BN2 aircraft. [Reproduced from the Official Report]
Damage to the other parked BN2 aircraft. [Reproduced from the Official Report]
Damage to the right side of the ATR72. [Reproduced from the Official Report]
The Captain subsequently stated that he had “no directional control or brakes and could not stop the runway excursion or the subsequent collision”.
Flight Crew Performance Issues
The investigation determined that despite the large difference in experience between the two pilots, neither of them had “adequate aircraft systems knowledge, particularly with regard to a smoke emergency” or “skill level” which contributed to a misdiagnosis of the smoke source and to the subsequent failure to select and action the right checklists in an orderly manner. It was noted that the Air Vanuatu SOPs included an explicit requirement to action checklists in such a way that “if a checklist is interrupted, reading must be resumed one step before the last read item” which was comprehensively ignored. However, it was ultimately of great significance that Normal Checklists were not completed once the in flight emergency had occurred since it was the failure to reset the rudder limiter manually to its low speed mode (giving +/- 27°of control instead of +/- 4°) which led directly to the loss of directional control when the Captain decided to use reverse pitch during the single engine landing on finding that, as alerted in one of the checklists which had been run in flight, normal braking (and in this case specifically differential braking) was not available.
Overall, “it was evident that aspects such as cognitive saturation, lack of situational awareness, time pressures, inadequate systems knowledge, checklist ambiguity, and confirmation bias influenced the crew’s decision making, which led to incorrect checklist selection, prioritisation and action” which contributed to a general lack of situational awareness.
Cabin Crew Performance Issues
The smoke event affecting the passenger cabin lasted almost 20 minutes but despite the Captain’s instruction to do so, the cabin crew did not don their PBE or provide wet towels to the passengers to help ease inhalation of the smoke. Once the Captain had declared a planned emergency landing, the cabin crew did not execute the required cabin preparation procedure. In general, the actions and inactions of the cabin crew during the emergency phase of the flight were not in accordance with either the applicable Cabin Crew Operations or Cabin Crew Training Manuals and specifically, they had not been aware of the smoke emergency procedure contained in them and had not been trained to execute all the actions required by this procedure.
Aircraft Operator Issues
The Investigation found that Air Vanuatu did not comply with its approved Pilot Check and Training Manual in respect of recurrent training. In particular given the incorrect use of smoke checklists during the investigated event, it was found that the Captain had not completed smoke training since May 2015. It was also found that this Manual “did not provide adequate guidance and emphasis on smoke emergencies”. Many other training areas that were reviewed were found non-compliant with the approved Air Vanuatu OM and it was concluded that “the lack of appropriate and regulated training” had contributed to the Captain’s poor tactical decision-making. The Investigation also noted that cabin crew emergency training had been inadequate.
The Right Engine Malfunction
The right engine compressor stall was found to have been caused by number 3 bearing distress. The root cause of this distress was relative rotation between the number 3 bearing inner race thrust side and the number 3 bearing rear spacer. This relative rotation was believed to have been caused by a problem with the stack-up of the various components around the No. 3 bearing during the last engine overhaul.
The smoke reported in the passenger cabin was attributed to the vibration-induced fracture of the low-pressure diffuser case in the right engine in association with the number 3 bearing distress which allowed oil from the No. 3 bearing cavity into the air conditioning system.
Other Airworthiness Issues
Examination of the Rudder Travel Limitation Unit (TLU) found that rudder travel authority neutral position in the high speed mode had been incorrectly calibrated so that it was operative between -1° and +7° instead of in accordance with the AFM requirement for authority between +/-4°.
The Causes (Contributing Factors) of the accident were formally documented as follows:
- The engine malfunction, although not directly causal to the accident, caused the generation of smoke, which prompted the declaration of a ‘MAYDAY’ and an immediate descent.
- The smoke detection by the electrical smoke detector caused the ambiguous ‘ELEC SMK’ warning to activate in the cockpit causing the Captain’s confirmation bias and subsequent diversion of the attention away from the engine issue.
- The confirmation bias created by the ambiguous ‘ELEC SMK’ warning led to the selection and action of the ‘Electrical Smoke’ Checklist.
- The First Officer’s lack of aircraft systems knowledge and introverted behaviour increased the workload on the Captain and contributed to the steep flight deck authority gradient. This significantly contributed to the degraded CRM.
- The oversight of the ‘Note’ in the QRH ‘SMOKE’ Checklist and the absence of similar information in the QRH ‘ELECTRICAL SMOKE’ Checklist encouraged the crew to continue the checklist without other consideration.
- The Alternating Current Wild (ACW) generators were switched off and the DC Bus Tie Contactor (BTC) was isolated through compliance with the QRH ‘ELECTRICAL SMOKE’ Checklist by the flight crew resulting in the loss of hydraulic system pump power and the illumination of several fault lights.
- The crew were referred by the QRH ‘ELECTRICAL SMOKE’ checklist to action the QRH ‘ACW GEN 1+2 LOSS’ checklist and completed the ‘before landing’ section of this drill in place of the normal QRH ‘Before Landing’ checklist. This caused the crew not to check the (rudder) Travel imitation Unit (TLU) setting.
- With the DC BTC isolated, the shutdown of the No. 2 engine caused all DC bus 2 supplied systems to lose power. This resulted in a number of system faults, failures and cautions.
- The activation of numerous fault and failure messages as a result of the QRH ‘ELECTRICAL SMOKE’ checklist and the shutdown of the No. 2 engine significantly contributed to crew cognitive saturation and reduced situational awareness and crew vigilance.
- The lack of situational awareness caused the crew to select reverse thrust with ground control and braking systems unavailable.
- The selection of reverse thrust caused the aircraft to turn to the left and exit the runway.
- The absence of hydraulic control, brakes, and aerodynamic control prevented the crew from correcting the undesired course change, runway excursion, and subsequent collision with the parked aircraft.
The following 5 Safety Recommendations were made during the Investigation, the first four issued on 27 July 2019 and the fifth on 6 August 2019:
- that ATR should ensure that the word ‘Note’ on the QRH ‘SMOKE’ Checklist is reclassified to, and represented by, an amber ‘CAUTION’ that is ergonomically able to draw the attention of flight crews to the ambiguity presented by the electrical smoke warning. [19-R19/18-1002]
- that ATR should ensure that a ‘CAUTION’ statement with content similar to the content of the ‘Note’ in the QRH ‘SMOKE’ Checklist is included in the QRH ‘ELECTRICAL SMOKE’ Checklist. [19-R20/18-1002]
- that ATR should ensure that one of the following two actions is taken:
- The rudder Travel Limitation Unit (TLU) low speed check, along with other essential check and action items, is included in the ‘Before Landing’ section of the QRH ‘ACW GEN 1+2 LOSS’ Checklist and every other Abnormal and Emergency Checklist that has gear and flap extension procedures.
- The Quick Reference Handbook (QRH) (is amended so that it) contains appropriate information to inform crews that the ‘Before Landing’ sections of the ‘ACW GEN 1+2 LOSS’ Checklist and other Abnormal and Emergency Checklists is not a substitute for the normal ‘Before Landing’ checklist. [19-R04/18-1004]
- that Air Vanuatu should ensure that their Cabin Crew are adequately trained on cabin safety duties in relation to smoke emergency procedures. [19-R22/18-1002]
- that Air Vanuatu should ensure that its Flight Crew are adequately trained, current and competent in the execution of smoke emergency procedures. [19-R23/18-1002]
The Final Report of the Investigation was completed on 29 October 2019 and subsequently published. It was noted that at publication of this Final Report, neither ATR nor Air Vanuatu had informed the Papua New Guinea AIC of any Safety Action proposed or taken to address the safety concerns identified during the Investigation.