Singapore B773 at Shanghai on Sep 2nd 2019, "Don't sink" and "Terrain, pull up" after takeoff

Last Update: April 20, 2021 / 17:07:26 GMT/Zulu time

Bookmark this article

Photo of Singapore Airlines 9V-SWD, Boeing 777-300 — Singapore Airlines 9V-SWD, Boeing 777-300 (Photo credit: InSapphoWeTrust / Flickr / License: CC by-sa)

Incident Facts

Date of incident
Sep 2, 2019

Classification
Incident

Airline
Singapore Airlines

Flight number
SQ-825

Departure
Shanghai Pudong, China

Destination
Singapore, Singapore

Aircraft Registration
9V-SWD

Aircraft Type
Boeing 777-300

ICAO Type Designator
B773

Airport
Shanghai Pudong International Airport, Shanghai

Airport ICAO Code
ZSPD

A Singapore Boeing 777-300, registration 9V-SWD performing flight SQ-825 from Shanghai Pudong (China) to Singapore (Singapore) with 120 people on board, departed Pudong's runway 35R at 00:35L (17:35Z Sep 1st), after takeoff the autopilot was engaged. Climbing through about 360 feet AGL the GPWS sounded "DON'T SINK!" three times. The crew performed throubleshooting and changed the pitch mode, however another "DON'T SINK" follwed by a "TERRAIN! TERRAIN! PULL UP!" GPWS alert occurred. The crew disengaged the autopilot, increased thrust and pitch, the warnings ceased and the aircraft climbed to safety and continued to destination for a safe landing.

On Sep 5th 2020 Singapore's Transportation Safety Investigation Board (TSIB) reported the occurrence was rated an incident and is being investigated by the TSIB. The final investigation report is already being drafted.

On Apr 20th 2021 the TSIB released their final report concluding the probable causes of the incident were:

- The EGPWS “DON’T SINK” events encountered by the flight crew were the result of the FMC having registered a speed/altitude constraint of “250/500” for the waypoint PD062. The PIC had inadvertently keyed in “250/0500” instead of the intended “250/0500A”.

- As to the activation of the EGPWS “PULL UP” warning alert, the investigation team was unable to determine the reason of the activation. However, the aircraft manufacturer suspected that the warning could be as a result of the combination of the low radio altitude, descent rate and flight path angle required to capture the 500 feet altitude constraint that had been entered into the FMC. The PIC did not identify that there was an abnormal condition with the auto-flight system despite the series of “DON’T SINK” alerts over a period of relatively short time.

- This occurrence also revealed many instances where the flight crew did not comply with the operator’s standard operating procedures, where the flight crew lost situational and flight mode awareness, and where the flight crew’s crew resource management performance in terms of communication had not been optimal.

- The PIC had to deal with a number of issues prior to the departure. Each of these issues, by itself, would have been just a minor issue for the PIC. However, together, these out-of-the-normal pre-flight circumstances might have perturbed the PIC. The extent of any perturbation could not be ascertained, and the investigation team could only suspect that they could have added up to some significant stress on the PIC and contributed to his lapses in FMC programming and decision-making during the flight.

- Notwithstanding that the PIC’s training and assessment record did not indicate any issues in the area of auto-flight management, there might be room for improvement on the part of the operator to ensure that its auto-flight management assessment programme is robust.

The TSIB reported the captain (55, ATPL, 18,370 hours total, 11,085 hours on type) was pilot flying, the first officer (29, CPL, 1,744 hours total, 1,744 hours on type) was pilot monitoring.

The TSIB reported that prior to departure the crew had to go through a number of issues, which were related to weather as well as to five MEL items, one of which reference the right hand engine's inoperative pneumatic manifold temperature sensor, which caused the high pressure shut off valve to be locked into the closed position and was particularly difficult as it required reference to five more MEL items. The crew subsequently experienced difficulties with their CPDLC communication which worked only intermittent. After receiving their operational flight plan indicating departure from runway 34L and SID HSN 22X the captain tried to download the route into the FMC but had trouble to do so, hence decided to manually input the route into the RTE1. He noticed that the first waypoint of the route was "HSH 250/1970A" with a constraint of not more than 250 KIAS and 1970A feet (at or alove 1970 feet indicated by the trailing A). The first officer returned from his walk around, the crew engaged in a detailed briefing of the MEL items.

The first officer finally managed to download the pre-departure clearance via CPDLC, the crew noticed that instead of runway 34L they were now assigned runway 35R with the SID HSN 12X. Thus the captain needed to amend his former inputs and chose to use the FMC's ROUTE COPY function to copy the former RTE1 route into RTE2 and amended RTE2 to HSN 12X. The crew then briefed the departure, the captain noticed that the FMS was showing waypoint PD062 as first waypoint without any constraints (PD062 ---/----). Although the captain was aware that this was not abnormal, he preferred to have the speed contraint in place. Hence he keyed the speed and altitude constraint in as "250/0500" (erroneously omitting the trailing A indicating at or above 500 feet). After verifying the route the captain was satisfied with the route and activated the route.

After the FMC had been prepared the first officer had further questions regarding the MEL items and the captain spent some more time to explain his plan and the action needed to be taken. Ground staff, concerned the flight could be further delayed, came on board querying when they could close the aircraft doors, the captain sent them off the aircraft advising the crew would tell them when the doors could be closed. The crew needed to convert China's metric altitudes into feet using the tables. The captain intended to engage the autopilot early in order to reduce workload, however, the first officer later stated he did not recall the captain communicating this plan.

During taxi the crew again reviewed the MEL items, lined up runway 35R. During acceleration for takeoff the needed MEL actions were smoothly taken, the aircraft became airborne, the gear was retracted and the captain called for A/P engagement while the aircraft was climbing through 360 feet AGL. The first officer activated the autopilot. Climbing through 400 feet the AP announciators changed to SPEED/LNAV/VNAV PTH, the first officer called the announciators out twice with no response from the captain, the captain later stated he did not recall hearing the call outs.

The aircraft climbed past 500 feet AGL, the speed trend indicated increasing speed, believing the aircraft had already climbed above 1000 feet AGL the captain called for the flaps to be retracted. However, according to the QAR the aircraft did not reach 1000 feet AGL, it climbed to a maximum of 750 feet AGL, then descended back to 500 feet AGL consistent with the altitude constraint for waypoint PD062 the captain had keyed into the FMC. The captain did not recognize the aircraft had stopped climbing and was descending towards 500 feet AGL.

During the initial stages of the flap retraction the EGPWS issued a "DON'T SINK!" caution startling both captain and first officer who did not expect such a caution in this stage of the flight. The captain intended to not rush and first complete the flaps retraction as he deemed the flight stable. 9 seconds after the first call the EGPWS again issued a "DON'T SINK" caution, the flaps were still retracting, and another 9 seconds later the EGPWS issued a third "DON'T SINK". Only at this point the crew recognized the aircraft had levelled off and they needed to re-initiate a climb. The captain engaged Flight Level Change on the Mode Control Panel, however, returned to VNAV 2 seconds later. The aircraft thus continued to remain at 500 feet AGL. A fourth "DON'T SINK" caution was issued by the EGPWS followed shortly by a "PULL UP" warning. In response the captain disengaged the autopilot, pushed the thrust levers forward and manually pitched the aircraft up, the warning ceased.

Climbing through 1600 feet AGL the captain re-engaged the autopilot, the MCP had not been reset and VNAV PTH was still active, the aircraft pitched down to descend to 500 feet again. The TSIB wrote: "At this time the FO noticed on his ND that there was a “250/0500” speed/altitude constraint set for the waypoint PD062. He realised that it was this altitude constraint that had been causing the aircraft to attempt to maintain 500 feet when VNAV was engaged. The FO alerted the PIC that they needed to cancel the speed/altitude constraint and the FO pushed the altitude selector button on the MCP to delete the programmed speed/altitude constraint. After doing so, there was no more issue with the aircraft climbing to the intended altitude and the flight proceeded to Singapore without further incident."

The TSIB analysed:

It was clear that the events encountered by the flight crew were the result of the FMC having registered a speed/altitude constraint of “250/0500” for the waypoint PD062. The PIC had inadvertently keyed in “250/0500” instead of the intended “250/0500A”. This meant that, when the armed VNAV mode became active at 400 feet AGL, it would provide guidance commands to the A/P to maintain the programmed altitude of 500 feet. Given the high rate of climb and aircraft inertia, it was not possible for the auto-flight system to immediately capture 500 feet. Hence the aircraft climbed through this altitude before commencing a descent in an attempt to maintain the programmed altitude until PD062.

...

There were a number of instances in this occurrence where the flight crew did not comply with the operator’s SOPs:

- Before the departure runway was assigned and while the FO was not in the flight deck, the PIC manually set up RTE 1 on LEGS page in the FMC based on the hardcopy of OFP they received. This practice was not in accordance with the operator’s SOP whereby manual OFP entries into the FMC were to be made by both the flight crew together as cross-checking was required.

- After ascertaining the departure runway from the PDC, the PIC copied RTE 1 to RTE 2 and then changed the runway and SID to Runway 35R and SID HSN 12X respectively, but he did not select ACTIVATE after doing so and started briefing the FO on the flight route. During the briefing, he noticed that the speed/altitude constraint for waypoint PD062 displayed only as “---/-----" and proceeded to manually enter the constraints. After briefing the FO regarding the flight route, the PIC then pressed ACTIVATE and executed RTE 2 into the FMC. This was not in accordance with the procedure where the route should have been activated prior to selecting the SID (see Footnote 7). Had RTE 2 been activated prior to selecting the SID, the FMC would have automatically displayed the predicted speed and altitude of all the waypoints when the SID was selected. When the PIC did not follow the steps in the procedure, the PD062 waypoint was presented as “---/-----”, which led the PIC to manually enter the speed/altitude constraints for PD062. The manual entry would take precedence over FMC’s predicted speed and altitude.

- When the aircraft was climbing past 400 feet AGL after take-off, the FO observed the VNAV engagement on the FMA and announced “SPEED / VNAV PTH” twice. However, the PIC did not acknowledge the FO’s callouts as he did not hear them. The FO did not challenge the PIC to acknowledge his callout as required by the procedure.

- In response to the EGPWS “PULL UP” warning alert, the PIC disconnected the A/P and manually increased the engine thrust and pitched the aircraft up into a climb at 15 degrees. While the PIC had carried out the recovery manoeuvre in a timely manner, he did not adhere fully to the EGPWS escape manoeuvre by disengaging the auto-throttle and pitching the aircraft to 20 degrees as required.

The investigation team was unable to determine the reason of the activation of the EGPWS “PULL UP” warning alert. However, the aircraft manufacturer suspected that the warning could be as a result of the combination of the low radio altitude, descent rate and flight path angle required to capture the 500 feet altitude constraint that had been entered into the FMC. The investigation team noted that that there was no maintenance record of any defect relating to the EGPWS before the incident and there had been no report of any problem with the EGPWS following the incident.

...

There were a number of instances in this occurrence where the flight crew’s performance in terms of CRM had not been optimal:

- The FO’s own experience was that it was not necessary for the PIC to input the speed constraint in respect of PD062 on SID HSN 12X when the FMC displayed a speed/altitude constraint of “---/-----”. However, he did not raise any query with the PIC on the need to do so. Also, while he observed the PIC’s input of the speed/altitude constraint, he did not notice that the PIC had keyed in “0500” instead of “0500A”.

- The PIC planned to engage the A/P early after take-off in order to use the auto-flight system to reduce the workload in managing the flight and had informed the FO. However, the FO did not recall that the PIC communicated his plan to engage the A/P early.

- With respect to the first “DON’T SINK” caution alert, the PIC thought that it could be due to a tailwind. The FO did not think so and was more inclined to believe that it had something to do with the VNAV PTH flight mode. However, the FO did not challenge the PIC.

- Following ATC’s clearance for the aircraft to climb to 6,000 metres AGL (19,700 feet), the FO called out “197” and saw the PIC set a different altitude figure on the MCP. The FO did not hear the PIC’s callout for the altitude that the PIC set although he heard the PIC mutter something unintelligible. The FO then repeated the callout two more times, but the PIC did not respond to him and the FO did not pursue the matter further with the PIC. (See paragraph 1.7.1 (a)) The PIC’s intention of starting the aircraft to climb by setting an intermediate altitude followed by the final setting of “197” was not communicated to the FO.

The investigation team opined that the FO was not assertive in eliciting the PIC’s response to his callouts or in questioning the PIC when he had doubts about the PIC’s actions. The investigation team felt that the FO should have applied the escalation technique taught in CRM training to alert the PIC of the FO’s concern regarding the lack of responses from the PIC. Good communication can serve to maintain a shared understanding and situation awareness.

...

This occurrence is an apt reminder of the guidance given in the Flight Crew Training Manual (FCTM) that, when automation does not perform as expected, the flight crew should reduce the level of auto-flight and identify and resolve the condition and that the original level of auto-flight should only be resumed after they have regained proper control of the flight path and performance level.

Notwithstanding that the PIC had achieved an above-average grade and been considered good in the area of auto-flight management during his line and base checks, the investigation team felt that it might be desirable for the operator to review its auto-flight management assessment programme to ensure that it is robust.

Metars:
ZSPD 021900Z VRB01MPS 9999 -SHRA BKN012 OVC040 24/23 Q1013 NOSIG=
ZSPD 021830Z 05002MPS 360V100 9999 -SHRA BKN012 OVC040 24/23 Q1013 NOSIG=
ZSPD 021800Z 06003MPS 350V090 9999 -SHRA BKN012 OVC040 24/23 Q1013 NOSIG=
ZSPD 021730Z 05004MPS 360V090 9999 BKN012 OVC040 24/23 Q1013 NOSIG=
ZSPD 021700Z 04004MPS 360V080 9999 BKN012 OVC040 24/23 Q1013 NOSIG=
ZSPD 021630Z 05003MPS 010V090 9999 -SHRA BKN012 OVC040 24/23 Q1013 NOSIG=
ZSPD 021600Z 08004MPS 010V120 9999 -SHRA SCT011 OVC040 24/23 Q1013 BECMG TL1630 BKN010 OVC040=
ZSPD 021530Z 08004MPS 040V100 9999 -SHRA SCT011 23/23 Q1013 NOSIG=
ZSPD 021500Z 09005MPS 050V110 9999 -SHRA SCT011 23/23 Q1014 NOSIG=