Etihad Flight EY9878

A cargo arrival from Beijing

Etihad Airways flight EY9878 left Beijing Capital International Airport at 0219 UTC on 6 June 2020 for Abu Dhabi. The Boeing B787-10, registered A6-BMD, carried cargo and three pilots. A copilot flew the aircraft, the captain monitored, and a second copilot occupied the jump seat. The climb and cruise passed uneventfully. The aircraft spent about two hours forty minutes at FL360 before climbing to FL380 for the later part of the flight.

Before descent, the crew prepared the arrival and briefed the approach. An Abu Dhabi ATIS message uplinked at 0902 gave a local pressure setting, or QNH, of 999 hPa and an expected RNAV Yankee approach to runway 31L. The descent procedure required the crew to preselect the destination pressure after receiving ATIS. Both operating pilots overlooked that step. The stored value remained 1009 hPa, the QNH used at Beijing. Descent from cruise began at 0937.

High on the arrival

The aircraft followed the EMERU 2D arrival. Abu Dhabi Approach could not clear it below FL160 earlier because of the transfer agreement between Dubai and Abu Dhabi air traffic control. EY9878 leveled at FL160 at 0949:19. The crew became concerned about the height still to lose before the approach, and concentrated on managing the aircraft's energy.

At 0951:19, about three nautical miles before EMERU, Approach cleared the flight down to 7,000 feet and for the RNAV Y approach from TUGVA. The controller gave no QNH with either clearance, although the operating manual and an existing supplementary instruction required it. The controller had relied on the crew's earlier confirmation that they had received ATIS India.

At 0952:36, descending through approximately FL146, the captain changed his altimeter from standard pressure to the stored 1009 hPa. The copilot changed his setting one second later. All three pilots remained unaware that the value was wrong. The AAIS found that fixation on energy management had degraded monitoring around the change from flight levels to local altitude. The report estimated that the incorrect setting made the aircraft's true altitude about 300 feet lower than the indicated altitude.

Recovering the descent profile

The copilot changed from vertical navigation to flight level change mode, or FLCH, at about 13,130 feet indicated altitude. The crew deployed speedbrakes and reduced the target speed. At TUGVA, the initial approach fix, the aircraft indicated 10,920 feet against a maximum altitude of 10,000 feet. The captain and copilot continued to focus on losing height. When the controller asked whether they could lose the altitude with 23 nautical miles remaining, the crew answered that they could.

The crew returned to vertical navigation at 9,835 feet and set 470 feet, the decision altitude, much earlier than the procedure specified. They selected FLCH again near 6,570 feet. With the decision altitude selected, that mode allowed descent toward 470 feet while bypassing the altitude constraints in the flight management system. The AAIS found that the prescribed procedure for intercepting the vertical path from above required VNAV mode, which protected those constraints. The captain did not detect or challenge the combination of FLCH and the low selected altitude.

At about 2,150 feet indicated altitude, roughly 1.2 nautical miles before KUSOK, VNAV PTH became active again. This brought the aircraft onto a path calculated with the incorrect pressure setting. At KUSOK the aircraft was about 110 feet below the indicated profile; adding the pressure error placed it approximately 410 feet below the nominal profile.

Investigators compared the descent gradients achieved in the different modes. The interval in VNAV with speedbrakes deployed produced a steeper average gradient than the first interval in FLCH with speedbrakes. They concluded that changing to FLCH had been ineffective. They believed that applying full speedbrakes from EMERU while remaining in VNAV SPD would have allowed the aircraft to reach the TUGVA altitude restriction. The report also found that the arrival design met the applicable criteria in the hot atmospheric conditions of the incident flight.

Ground alerts and missed checks

The ground radar system generated a minimum safe altitude warning at 0958:27, about 8.7 nautical miles from the runway threshold. It lasted ten seconds and reflected a prediction that the high descent rate could take the aircraft below a configured minimum altitude. The Approach controller associated it with the aircraft's proximity to an area of minimum vectoring altitude and did not advise the crew to check QNH and altitude, as the procedure required.

The flight then transferred to Tower. At 1000:16, an approach path monitoring warning activated about 3.5 nautical miles from the threshold and lasted 45 seconds. The system displayed this warning as an MS label, like the earlier altitude warning. Approach did not react because the aircraft was on Tower frequency. The procedures then in force provided no instructions for Approach to notify Tower of that alert, or for Tower to advise the pilots. The Tower controller was unaware of the warning.

Cockpit checks also failed to expose the pressure error. The automatic 2,500-foot radio-altitude callout occurred when the barometric altitude indicated approximately 2,670 feet. The normal difference at Abu Dhabi with the correct QNH was less than 100 feet. For the rest of the approach, the difference ranged from about 150 to 380 feet. The AAIS found that the captain did not notice the unusual discrepancy, most probably because cockpit scanning or awareness of the difference was inadequate.

At the 1,000 feet radio-altitude callout, the barometric altitude indicated about 1,350 feet and the runway was approximately four nautical miles away. The AAIS found that the response to that callout did not effectively include the required distance-to-touchdown crosscheck. The vertical situation display offered flight path and runway cues, but the crew did not use them to assess their vertical position. Etihad's procedures lacked detailed guidance for that display crosscheck.

Four red lights and a go-around

The aircraft was fully configured for landing as it passed KUSOK. The crew reduced speed and retracted the speedbrakes. With VNAV PTH active and the speed settling, they perceived that they had recovered the correct profile. At 1000:04 the aircraft crossed KATIG, the final approach fix, at 1,300 feet indicated altitude and about 950 feet radio altitude. Its indicated altitude matched the chart, while the incorrect pressure setting put the aircraft about 300 feet below the nominal vertical path.

Haze obscured the colours of the PAPI lights after KATIG. The reported weather indicated visibility of at least ten kilometres, but the AAIS found that forward visibility at higher altitudes was lower in both approaches. As the lights became distinct, the captain saw four reds and ordered a go-around. The copilot pressed the TO/GA switches at 1001:06, approximately 1.3 nautical miles from the threshold, at about 210 feet radio altitude. The lowest recorded radio altitude was 202 feet, when the aircraft began to climb.

The crew retracted the landing gear before moving the flaps from 25 to 20. This differed from the prescribed go-around sequence. The AAIS found no consequent risk during the remaining go-around. A later ground inspection found the PAPI system functioning correctly. The flight crew learned during investigation interviews that the go-around had begun only about 200 feet above the ground.

The pressure error exposed

During the climb, Approach supplied QNH 998 hPa and asked when the crew would be ready for an ILS approach to runway 31L. The captain answered that they were ready, but did not read back the QNH. The crew left their altimeters at 1009 hPa. The aircraft leveled at an indicated 4,000 feet, while the controller's display showed approximately 3,700 feet.

The controller queried the pressure setting and altitude. At 1004:27 the crew began correcting the setting, exposing the 300-foot altitude shortfall. They climbed to the cleared 4,000 feet and leveled there at 1005:10. Approach continued with vectors for the ILS, including descent to 2,000 feet. EY9878 landed at 1017:32. During the landing roll the captain confirmed that the PAPI lights had appeared to function correctly on short final. All three pilots were uninjured, and the aircraft sustained no damage.

Investigation findings and lost recording

The AAIS determined that the incorrect QNH setting caused the aircraft to fly below the vertical profile. It identified omitted QNH preselection, fixation on energy management, omitted QNH information from Approach, ineffective use of the vertical situation display, missing instructions to the crew following ground altitude warnings, and reduced forward visibility as contributing factors. Aircraft defects, crew qualifications and fatigue were excluded as factors by the investigation.

The occurrence was reported to the AAIS about 23 hours later. The crew had not appreciated its severity, and the aircraft operated its next scheduled service. Its two-hour cockpit voice recording was overwritten. The flight data recorder held 72 hours and preserved the incident data. Investigators synchronized those data with recorded air traffic communications and used crew interviews. They could not determine why destination QNH preselection had been overlooked, or whether the required altimeter and 1,000-foot callouts had been made.

Changes and six recommendations

Etihad added a requirement to confirm QNH before the initial approach fix for RNP AR approaches. It issued separate Boeing and Airbus approach guides, mandatory questionnaires and training on incorrect pressure settings, monitoring, distraction and workload. The airline refined VNAV altitude-setting techniques with Boeing and incorporated the event into its October 2020 to March 2021 proficiency-check syllabus.

GAL ANS reinforced QNH issuance, reviewed controller communications and issued instructions covering MS alerts for both Approach and Tower. The final report, issued on 28 September 2021, made six recommendations. Four addressed Etihad: QNH preselection, checking the effectiveness of safety actions, detailed vertical situation display guidance and monitoring by additional pilots. One asked GAL ANS to consider incorporating its alert instructions into the operating manual. The sixth asked the GCAA to consider 25-hour cockpit voice recording for qualifying new aircraft and a programme to upgrade older aircraft.