Emirates EK521

Case Studies

Eddie sez:

This was a surprising accident on many fronts. First, Emirates has a sterling safety record; they were perfect with the Boeing 777. Second, from the what I've seen of Boeing manuals they take all of this very seriously. And finally, the incident itself seemed at first to be one of those cases of a perfectly good airplane destroyed for reasons unknown.

Here is what we knew right off the bat: The Boeing 777 appeared to be coming off a stable approach into gusty winds and a hot runway with thermals. Everything appeared normal into the flare. While the touchdown was a little late, it wasn't too bad. The airplane appeared to go around, climb briefly, and then fall to the runway. Passengers evacuated (some with their carry ons in hand) and the airplane was engulfed in flames. What?

The accident report came out three and a half years later. It is a very well written report. In a nutshell:

  • The crew did everything right all the way to the flare. Briefs, call outs, crew coordination. Very good.
  • The captain initiated the flare 15 feet earlier than he should have. (As someone I used to fly the Boeing 707 with used to say, "I've done worse and bragged about it.")
  • The combination of shifting winds (headwinds to tailwinds) and hot runway thermals made it difficult to touch down in the touchdown zone, so the captain elected to go around.
  • The captain wasn't aware that the aft set of wheels on the trucks of his main landing gear were going in and out of ground mode, which made the airplane think it was on the ground for a second. When the captain pressed the Takeoff / Go-Around (TO/GA) button, the go-around thrust mode of the auto throttles were disabled because they were "on the ground."
  • The captain did not realize he was at idle thrust as he pitched up for the go around.
  • The airplane ran out of speed. As the airplane began to sink, the captain realized his power state and manually advanced the power, but it was too late.

Let's go through the accident report and then we can take away a few lessons.

Everything here is from the references shown below, with a few comments in an alternate color.

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Photo: Emirates EK521 wreckage, from Reuters
Click photo for a larger image

Last revision:

20200206

Accident Report

  • Date: 3 August 2016
  • Time: 08:37 UTC
  • Type: Boeing 777-31H
  • Operator: Emirates
  • Registration: A6-EMW
  • Fatalities: 0 of 18 crew, 0 of 282 passenger, 1 ground casualty
  • Aircraft Fate: Destroyed
  • Phase: Landing Go-Around
  • Airport: Dubai International Airport (OMDB), the United Arab Emirates

Narrative

[AAIS, §1.1] History of the Flight

  • Approximately 60 minutes prior to landing, the Commander and the Copilot completed the approach briefings for OMBD runways 12L and 30L. The Commander briefed the Copilot that in case of a go-around, flaps 20 was to be selected and climb to 3,000 ft. This was in accordance with the missed approach LIDO plate 7-50.
  • At 0735, the United Arab Emirates National Center of Meteorology and Seismology (NCMS) issued a moderate windshear warning affecting all OMDB runways, with a validity from 0740 to 0900. The OMDB Arrival automatic terminal information service (ATIS) commenced broadcasting the windshear warning at 0800 with information ZULU.
  • At 0806, as recorded in the cockpit voice recorder (CVR), the Commander briefed for the possibility of windshear and stated to the Copilot that “in case of a windshear, windshear TOGA, no configuration change”. They then discussed their previous go-around experiences. The Copilot stated that he experienced a windshear during descent “like three months ago”. The Commander stated that “I had one into Dubai but it was more like wind shift. The speed went ten knots more so we went around”.
  • At 0829, and at 0831, two preceding aircraft performed go-arounds. The go-arounds were followed by two Emirates B777 aircraft that landed on runway 12L at 0833 and 0835. The UAE521 flight crew were not informed by ATC of the two go-arounds.
  • The approach was stabilized before 1,000 ft radio altitude. As the Aircraft descended through 930 ft radio altitude at 0836:10, the Commander disengaged the autopilot and continued the approach, with the autothrottle (A/T) engaged, in accordance with the Operator’s policy. The A/T was in ‘SPEED’ mode. The flight directors remained in the ‘on’ position.
  • At 0836:22, as the Aircraft passed 750 ft radio altitude, at 153 kt indicated airspeed (IAS) the flight data recorder (FDR) recorded that the wind direction changed from a headwind to a tailwind component.
  • At 0836:40, at 450 ft radio altitude, and 156 kt IAS, an automated ‘minimums’ callout was annunciated, and the Commander announced “Landing”. The Copilot provided feedback indicating that he had heard and understood the Commander’s decision. The wind speed component was now 10 kt from 317 degrees.
  • So far everything is just about perfect.

  • At 0836:56, passing 190 ft radio altitude at 152 kt IAS, the Copilot announced “Sixteen knots tailwind”, which was acknowledged by the Commander. During this time, the Commander was maintaining the Aircraft on the nominal glidepath, at an average pitch of 0.7 degrees.
  • Winds, especially in a very hot climate, are bound to gust and even if your SOP says 10 knots is your maximum tailwind, if the winds were okay at 200 feet and you decide to land, is another 6 knots at this point useful information?

  • At 115 ft radio altitude and 157 kt IAS, the Copilot announced “Reducing to thirteen knots”, with reference to the tailwind. This was acknowledged by the Commander who replied “Checked”. The rate of descent was decreasing from 800 to 700 ft per minute, with an average pitch angle of 0.5 degrees. This was followed by a cockpit automated callout of “One hundred”. The wind speed was now 13.5 kt from 308 degrees. Because of the reduction in the tailwind component, the airspeed started to increase which resulted in the A/T retarding both thrust levers.
  • At 0837:05, the Aircraft passed over the threshold of runway 12L (figure 1) at about 54 ft radio altitude and 159 kt IAS. Over the next four seconds automated callouts of ‘fifty’, ‘forty’, ‘thirty’, ‘twenty’ and ‘ten’ were annunciated.
  • At 0837:06, after the Aircraft had flown approximately 100 m beyond the threshold, as recorded by the FDR, the Commander initiated the flare at approximately 40 ft radio altitude with a pull on the control column.
  • Their manual called for flare initiation at between 20 and 30 feet. In the 747 we used to teach: "At 50 feet, do nothing. At 40 feet, think about it but don't do it. At 30 feet, do it." If you initiate the flare the same, every time, you will train yourself to hit the touchdown zone more consistently.

  • At the start of the flare, the pitch angle changed from 0.0 to 0.4 degrees. Over the next 5 seconds, until the Aircraft reached 7 ft radio altitude, there was a steady increase in the Aircraft pitch angle from 0.4 to 2.6 degrees, with a corresponding decrease in the sink rate from 692 towards 350 ft per minute.
  • At 0837:08, as the Aircraft passed 25 ft radio altitude, 158 kt IAS, approximately 300 m beyond the threshold, the A/T mode changed on the cockpit primary flight display (PFD) flight mode annunciations (FMA) from ‘SPEED’ to ‘IDLE’. As designed, from 25 ft radio altitude, the A/T transitioned both thrust levers towards the idle position, and the engine pressure ratio (EPR) steadily decreased from 1.074 to 0.98.
  • Approximately two seconds later, the airspeed decreased to 153 kt as the Aircraft descended below 13 ft radio altitude.
  • From 0837:12 at 5 ft radio altitude several pulls and pushes on the control column along with control wheel roll and rudder inputs were recorded by the Aircraft FDR. The Commander made a left roll input to the control wheel, and at about this time, the Commander said “Oops”. The IAS had increased to 160 kt, and the ground speed was 176 kt and decreasing.
  • Two seconds later, with the Aircraft at 2 ft radio altitude, the IAS had increased to 165 kt, the ground speed had reduced to 172 kt, and the sink rate had reduced to 80 ft per minute. The Commander uttered an exclamation and stated “Thermals”, and the Copilot replied with “Check”. Neither flight crewmember was aware of the increase in airspeed because their focus was on external scanning of the runway.
  • The Commander stated that in an attempt to have the Aircraft touch down, he had momentarily pushed the control column three times to lower the nose. This action was confirmed by the data recorded on the FDR.
  • I think the go-around culture at Emirates is admirable in that they, like most of us, preach that if you are unstable or will no be landing in the touchdown zone, go around. I think the problem with that is that a low altitude go-around can be a risky event and it may be safer to accept a longer landing if you know you have the performance. Looking at a B-777 landing I think it should be able to tolerate landing a bit hot. I tended to fly the Boeing 747 onto the runway and, to be honest, I do that with the Gulfstream too.

  • At 0837:16, the Aircraft rolled 3 degrees to the left due to the wind effect and the Commander corrected with right control wheel input of 30 degrees. In response to this input, the resulting right bank of 7.4 degrees caused the right main landing gear to contact the runway approximately 1,090 m beyond the threshold.
  • The right main gear contact with the runway caused it to ‘untilt’ as indicated by the main landing gear ‘tilt’ and ‘untilt’ switch position recorded by the Aircraft FDR. Runway contact was made at an airspeed of 161 kt IAS, 14 kt above the landing reference speed of 147 kt.
  • I am told the airplane lands so softly that often the first indication in the cockpit of the main gear untilting is movement of the speedbrake handle. In the older Boeing 747s your first clue was a mechanical click from a solenoid in the gear handle, preventing gear handle movement because you were on the ground. We often did what we called "landing attitude demonstrations" to teach the airplane's attitude during landing. We would put the airplane inches above the runway for half the runway's length while pointing out visual cues. If well done, that aft-most set of trucks would roll along the runway without an untilt. You just couldn't tell from the cockpit that you had an untilt otherwise.

  • From 0837:16 to 0837:22, as recorded by the Aircraft FDR, both main landing gear experienced a series of ‘tilt/untilt’ cycles. During this six-second period, there were two automatic partial movements of the speedbrake lever recorded by the FDR.
  • The Commander stated during his interview “Below 2,000 ft started having tailwind and getting close to the runway, like 50 feet flare height, we had thermals updraft coming from the ground because of the heat so it was pushing the aircraft up so it caused a long flare. It [the Aircraft] was going towards the end of the touchdown zone, so after that we decided to go around.”
  • The Copilot stated during his interview “The flare felt like it just wouldn’t land it was bumpy.” The Copilot also stated, “I would say we were definitely less than 50 feet at the initiation of the go around.”
  • The Commander stated that he pushed the left takeoff/go-around (TO/GA) switch and then called “Go-around”. The push on the TO/GA switch did not have any effect on the A/T and the thrust levers remained at the idle position.
  • The Commanders’ declaration of a go-around was immediately followed by a ‘long landing’ automated cockpit annunciation. The Commander pulled the control column back and the Aircraft pitch-up angle started to increase. One second after the Commander’s ‘go-around’ declaration the Copilot responded by saying “Okay”. This was followed by a second ‘long landing’ cockpit annunciation.
  • During his interview, the Commander stated he had his right hand on the thrust levers when he pushed the TO/GA switch. He stated that the initiation of the go-around was before touchdown. He could not remember any changes in the flight director and the FMA after pushing the TO/GA switch. He also stated that during the go around, he pitched the Aircraft to an approximate pitch attitude of 7.5 degrees and had positive climb.
  • Analysis showed he may have nudged the thrust levers forward as he was hitting to TO/GA switch, but not forward enough to increase the thrust.

  • The FDR indicated that the Aircraft had touched down for a duration of six seconds. During this time, both main landing gear were simultaneously in ‘ground’ mode for a period of less than two seconds. The nose landing gear remained in the air throughout this time. At 0837:22 the Commander called “flaps 20”.
  • Just before 0837:23, the main landing gear transitioned back to ‘air’ mode, and the Aircraft became airborne at 153 kt IAS (VREF + 6.5 kt), with the flaps in the 30 position (landing configuration). As the Aircraft climbed, the wind direction was from 102 degrees at 8 kt. The Copilot moved the flap lever to the flaps 20 position and verbally confirmed this action. The Aircraft continued gaining height and when it reached approximately 47 ft radio altitude, the Copilot announced “Positive climb.” In his interview, the Copilot stated that he could not recall information in changes in the FMA and had referred to the PFD vertical speed indicator to confirm that the Aircraft was in a positive climb.
  • Are you really going to divert your attention at this point to read the FMA? I can't fault the copilot for this, but he should have checked that the thrust levers had been advanced, that thrust came up, and that they were accelerating.

  • The Commander called “Gear-up” as the Aircraft was passing 58 ft radio altitude, at a rate of climb of 608 ft per minute, and 145 kt IAS. Thereafter, the rate of climb started to decrease. Shortly after the “Gear-up” call by the Commander, the Tower transmitted a modified missed approach instruction to UAE521 to continue straight ahead and climb to 4,000 ft.
  • We are used to watching airspeed like a hawk with an engine failed but we should have that same caution with all engines operating.

  • At 0837:29, the Copilot stated “Gear-up” while the Aircraft was climbing pass 77 ft radio altitude and 135 kt IAS. The Copilot then read back the Tower instructions and changed the preselected missed approach altitude from 3,000 ft to 4,000 ft in the MCP.
  • Two seconds later, at 0837:31, the Aircraft started to lose height after reaching a maximum of 85 ft radio altitude at 131 kt IAS.
  • Three seconds after the Aircraft started to lose height, the Commander called “Windshear TOGA” as the Aircraft was sinking below 67 ft radio altitude. The A/T mode on the FMA changed from ‘IDLE’ to ‘THR’ (‘thrust’ mode).
  • One second later (0837:35), the Commander advanced both thrust levers manually to maximum at the same time as an automated ‘don’t sink’ cockpit aural warning was annunciated. The Copilot called out “Check speed” followed by a cockpit AIRSPEED LOW caution at 128 kt IAS, and a ‘don’t sink’ cockpit aural warning annunciation for the second time. Following these warnings, the Aircraft was losing height at a rate of 800 ft per minute. The Commander increased the Aircraft pitch to 9.2 degrees in an unsuccessful attempt to regain height.
  • At 0837:38, the Aircraft aft fuselage impacted the runway, at a speed of 124 kt IAS, which was above the Aircraft stall speed. The impact with the runway occurred 18 seconds after the initiation of the go-around, and 7 seconds after the Aircraft started to sink from 85 ft radio altitude.
  • The FDR data indicated that the EPR for both engines had started to respond to the manual thrust lever movement, but the height remaining did not provide enough time for the engine thrust to increase sufficiently to prevent the Aircraft from sinking onto the runway.
  • The Commander stated during his interview “we noticed the aircraft speed dropping so I applied maximum power because TO/GA power sometimes limits the thrust so I pushed the thrust lever forward. However, the aircraft continued to lose airspeed because of the shifting wind and windshear. At that time, I called windshear TOGA”. The Commander stated that after gear up “the speed started reducing until the aircraft lost speed and then it started going down”. He further clarified that “It didn’t climb much just a few feet once we started positive climb and then I felt the aircraft just sinking”.
  • The initial impact point of the Aircraft on runway 12L was abeam the intersection with taxiway November 7, with the landing gear in transition to the ‘up’ position. The right (No.2) engine contacted the runway and the engine/pylon assembly separated from the wing as the Aircraft slid along the runway.
  • Fire was observed on the right engine and pylon and another fire started to emanate from the bottom of the left (No.1) engine. After the Aircraft came to rest adjacent to taxiway Mike 13, on a magnetic heading of approximately 250 degrees, and 70 m to the right of the runway centerline, dense grey smoke was observed coming from the right side of the fuselage in the vicinity of the right main landing gear bay.
  • At 0839:04, the Commander transmitted a ‘mayday’ call and informed ATC that the Aircraft was being evacuated. The flight crew completed the evacuation checklist in about one minute from the time that the distress call was transmitted and instructed the cabin crew to commence the evacuation.

Analysis

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Photo: UAE 521 flightpath and impact along Runway 12L, AAIS, Figure 1
Click photo for a larger image

The Aircraft, General

This airplane had all the necessary "bells and whistles" to fly its assigned task.

[AAIS, §3.2.1]

  • The Aircraft was certified, equipped, and maintained in accordance with the Civil Aviation Regulations of the United Arab Emirates.
  • The Aircraft was airworthy when dispatched for the flight, and there was no evidence of any defect or malfunction that could have contributed to the Accident.
  • The Aircraft was structurally intact prior to impact, and mostly remained intact after the impact.
  • The post-Accident examination reports did not find any evidence of any Aircraft component or system malfunctions.
  • The Aircraft was equipped with a long landing alerting system that annunciated a ‘long landing’ alert at a distance of 1,280 m beyond the runway 12L threshold, some 92 m further along the runway than the programmed alert distance.

Auto Throttles

[AAIS, §1.6.2.3]

  • The A/T provides thrust control from takeoff to landing. The selective positions of the A/T are: ‘off’ and ‘arm’. When the A/T is armed and activated (by the pushbutton switch), it will move the thrust levers to achieve either ‘speed’ or ‘thrust’ control, depending on the selected mode.
  • Either pilot can move the thrust levers manually at any time to override the A/T. After manual positioning, the A/T will return the thrust levers to the position corresponding to the previously active mode. With the A/T active, during landing and below 25 ft radio altitude, the thrust levers will move towards the idle position and the A/T mode on the FMA will change to ‘IDLE’.
  • After touchdown, in manual or automatic flight, until the thrust reversers are selected, the A/T mode stays at ‘IDLE’. By design, because the TO/GA switches are now inhibited, either because the weight-on-wheels is valid, or the aircraft radio altitude is less than two feet for more than three seconds, pushing the TO/GA switch does not affect the mode and the A/T will stay at ‘IDLE’.
  • In order to activate the A/T for a go-around, all of the following conditions must be fulfilled: A/T arm switch is in the ‘arm’ position; aircraft is in ‘air’ mode; glideslope is engaged or the flap lever is not in the ‘up’ position; thrust limit mode is not at ‘takeoff’; and either TO/GA switch is pushed.
  • Pushing either TO/GA switch when the A/T is enabled will automatically advance the thrust levers to the go-around thrust setting. If the TO/GA switch is pushed during the inhibited period, the A/T will not automatically advance the thrust levers to the go-around thrust setting.
  • The flight director does not provide go-around guidance when the aircraft is on the ground. The flight director is enabled when the aircraft is in ‘air’ mode and upon pushing a TO/GA switch when glideslope mode is engaged or when the flaps are out of the ‘UP’ position.

Main landing gear truck tilt/untilt

[AAIS, §1.6.2.4]

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Photo: Main landing gear tilt position, AAIS, figure 7.
Click photo for a larger image

  • Each main landing gear consists of a six-wheel truck with a truck position actuator that tilts the truck up 13 degrees in preparation for landing and down 5 degrees for gear retraction.
  • When the main gear is extended for landing, the ‘tilt’ position of the truck allows the aft wheels to contact the runway first. The truck will then ‘untilt’ allowing the center and forward wheels to contact the runway surface.
  • Truck tilt sensors are installed to sense the tilt position of the truck. From 13 to 10 degrees, the sensor transitions from the ‘tilt’ to the ‘untilt’ position.

Air/ground system (AGS)

[AAIS, §1.6.2.5]

  • The AGS transmits an ‘air’ or ‘ground’ mode signal to aircraft systems including the A/T, auto speedbrake, and autobrake systems.
  • Two variable reluctance strain load sensors are installed on each wing side landing gear beam. In ‘ground’ mode, the aircraft weight-on-wheels (WOW) will load the landing gear beam causing it to elastically bend.

Aircraft touchdown

[AAIS, §1.11.2.1] The FDR recorded parameter for the main gear truck position of TILT / UNTILT is the truck tilt sensor. The main gear WOW sensor state is not a recorded FDR parameter. For a period of six seconds, from 0837:16 to 0837:22, the main landing gear entered a series of ‘tilt’ (‘air’ mode) and ‘untilt’ (‘ground’ [GND] mode) cycles. Some cycles were in phase, or partially in phase, for both main gear, while for other cycles the main gear attitude changed for a single gear only.

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Photo: Calculated go-around after TO/GA switch push, AAIS, figure 21.
Click photo for a larger image

[AAIS, §1.16.2.2]

  • The evaluation showed that maintaining the same pitch attitude as the Accident flight, eight seconds after the Commander called for a ‘go-around’, pushing the TO/GA switch at 13,385 seconds FDR time, which corresponds to the time that the landing gear lever was moved to ’up’, the Aircraft could have achieved a positive rate of climb as the engine thrust increased. After the TO/GA switch push, the A/T would have moved the thrust levers with a maximum rate of 10.5 degrees per second, to achieve an EPR of 1.414 in approximately eight seconds. During this time, the Aircraft would have descended and the minimum radio altitude reached by the Aircraft to safely fly away in the hypothetical scenario was 17 ft. Figure 21 illustrates the calculated simulation.
  • For UAE521, the actual thrust lever increase, which was a manual advancement by the Commander at 13,392 seconds FDR time, was performed fifteen seconds after the Commander called for a ‘go-around’.

[AAIS, §1.17.1.6

  • During the manual landing, the FCTM ̶ Flare and Touchdown, states that after the aircraft nose passes the threshold, the pilot is recommended to change his visual sighting point to the far end of the runway in order to control the pitch attitude during the flare. The FCTM recommends initiation of the flare when the main gear is approximately 20 to 30 ft above the runway by increasing the pitch angle approximately 2 to 3 degrees in order to slow the rate of descent.
  • For airspeed control, the FCTM states that when the A/T is engaged and active, the thrust levers are automatically retarded to idle at 25 ft radio altitude and the 5 kt addition to VREF will be bled off and the engine thrust will reach idle power at touchdown.
  • The FCTM stated that small pitch adjustments will be required in order to maintain the desired descent rate after flare initiation and to hold sufficient back pressure on the control column to keep the pitch attitude constant.
  • I used to preach this in the Boeing 747 and continue to do so in every Gulfstreams I've ever flown: you need to keep a descent all the way to touchdown, I shoot for 100 to 200 fpm. The ground effect off the wings and compression of the struts takes care of softness of the touchdown. This from someone with a lot of hours in the Boeing 777:

    The most common way to lose a smooth touchdown (not that smooth touchdowns mean its a good landing) is that the aircraft is ‘held-off’ just as it touches down. By that, I mean not letting the aircraft weight settle into the oleos. If you hold it off, just as the wheels touch the runway, the trucks will go off tilt (13-14 degrees) and the spoilers will deploy and the weight will come down rapidly onto the oleos with a tiny little ‘bump’ (most pax would think this is a very good landing).

  • Pilots are trained that, ideally, and at an airspeed of approximately VREF, the main landing gear will touch down simultaneously with the thrust levers reach idle.
  • The FCTM stated that “If the flare is too abrupt and thrust is excessive near touchdown, the airplane tends to float in ground effect. Do not allow the airplane to float or attempt to hold it off. Fly the airplane onto the runway at the desired touchdown point and at the desired airspeed.

Go-Around

[AAIS, §1.17.1.7

  • According to the FCOM ̶ Go-Around and Missed Approach Procedure (Appendix B to this Report), a normal go-around is initiated by the pilot flying pushing the TO/GA switch. The pilot flying then calls for ‘flaps 20’, and the pilot monitoring positions the flap selector lever to ‘20’. Both pilots then verify rotation to go-around attitude and that engine thrust increases. The pilot monitoring will verify that the thrust is sufficient for go-around and will adjust as necessary. After a positive rate of climb is verified on the altimeter, the pilot monitoring calls ‘positive climb’. The pilot flying will verify the positive rate of climb on the altimeter and call for ‘gear-up’. The pilot monitoring selects the gear-up and confirms that the flight directors are ‘on’. The pilot flying will limit the bank angle to 15 degrees if the airspeed is below the minimum maneuvering speed. When the aircraft is above 400 ft radio altitude, the pilot flying selects or verifies a roll mode. The pilot monitoring will verify that the missed approach altitude is set, after which further procedures follow for the climb and navigation until the after takeoff checklist is completed.
  • This procedure is almost identical to the flow we used to call "To L and Back" in older Gulfstreams. See Lessons, below. Our newer airplanes are so automatic that we sometimes forget to do these steps because they always seem to get done. Until they don't.

  • It is stated in the FCOM – Autopilot Flight Director System (AFDS) Procedures that the pilots must always monitor airplane course, vertical path and speed. Additionally, the AFDS procedures state that pilots must verify manually selected or automatic AFDS changes; use the FMA to verify mode changes for autopilot, flight director and autothrottle; and should announce changes on the FMA and verify changes to the thrust mode display when they occur.
  • The General Information section of the FCTM states that when the term “Set thrust” or “Verify that thrust is set” is used in various places in the FCTM and FCOM, pilots are required to verify the EPR indication.

The Crew

I am impressed with how much this crew did right that was cancelled out by the few things they did wrong. It is an object lesson in how much the details count in aviation.

[AAIS, §1.5.1.1] The Commander

  • After completing a total of 6,283 flying hours, and satisfying the Operator’s selection process, he began his two-month upgrade training to become a commander on the B777 in March 2015. At the time of the Accident, he had flown 1,173 hours as a commander on the B777 and his total flying time was 7,457 hours.
  • The Commander performed 54 go-around maneuvers in the simulator with no adverse comments relating to his handling.
  • In March 2015 during his upgrade to commander training, the Commander practiced rejected landings from heights below 50 ft, but before the aircraft had touched down. His most recent bounced landing recovery training, and his last windshear recovery training were carried out in March 2015. The Commander stated that he had never practiced normal goarounds after touchdown with the autothrottle armed and active.
  • During two of the Commander’s upgrade training sessions, between March and May of 2015, the evaluator had commented on landing technique related to flare and that the landing was towards the end of the touchdown zone. The Operator stated that provided a pilot lands within the touchdown zone, it is considered safe and satisfactory.
  • Flight data monitoring (FDM) data records for the Commander indicated that all landings were performed within the requirements of the Operator and within the runway touchdown zone.
  • The Operator’s FDM data recorded that, on 13 April 2016 at OMDB, the Commander as the pilot flying had performed a normal procedural go-around following an approach that became unstable due to wind shift resulting in a rapid speed increase.
  • After the Aircraft passed the runway threshold, the Commander stated that his attention was outside the cockpit, focused on the far end of the runway. He stated that his practise, in accordance with his training, was not to look at the cockpit instrumentation after the flare was started. In addition, he stated that during the attempted go-around, he was focused on the Aircraft attitude during the rotation and described his state of mind at that stage of the go-around as being “tunnel visioned”. He could not recall if there was movement of the thrust levers from idle position after initiating the go around when he pushed the left thrust lever TO/GA switch.
  • During his interview, the Commander stated that his seat was in the optimum position and he had his right hand on the thrust levers during the entire landing phase including the attempted go-around.

[AAIS, §3.2.1]

  • The Commander started to flare the Aircraft at approximately 40 ft radio altitude, approximately 100 m beyond the threshold. The FCTM recommends initiation of the flare when the main gear is approximately 20 to 30 ft above the runway surface.
  • Passing 7 ft radio altitude, the Aircraft floated over the runway and at 2 ft radio altitude, the IAS reached 165 kt. There was a 12 kt airspeed increase in approximately four seconds, during which time the descent rate decreased.
  • The flight crew did not observe that the speedbrake lever had partially deployed twice during the six seconds the Aircraft main landing gear had cycled between ‘tilt’ and ‘untilt’.
  • The Commander had stated that his right hand remained on the thrust levers during the attempted go-around. After pushing the left TO/GA switch, the Commander did not recognise that there was no tactile feedback of thrust lever movement.
  • The flight crew did not observe that the FMA modes did not change and that the flight director was not giving pitch guidance. They were not aware that the A/T mode had remained at ‘IDLE’.
  • Contrary to the FCOM ̶ Go-around and Missed Approach Procedure, after ‘flaps 20’, the Commander and the Copilot omitted the steps of engine thrust verification and continued to action the procedure from the ‘positive climb’ item.

Flight Sequence

[AAIS, §2.2]

  • After the A/T had changed from ‘SPEED’ to ‘IDLE’ mode at 25 ft radio altitude, the airspeed decreased by 6 kt and was 153 kt at 10 ft radio altitude. As the Aircraft passed the runway aiming point and approximately 480 m beyond the threshold, the airspeed started increasing and at 2 ft radio altitude, it reached 165 kt IAS with the Aircraft approximately 840 m beyond the threshold. There was a 12 kt airspeed increase over approximately four seconds, during which time the groundspeed decreased by 5 kt, and the descent rate decreased from 432 ft per minute to 80 ft per minute. The airspeed increase was 18 kt above the landing reference speed of 147 kt VREF.
  • The Investigation concludes that the 12 kt airspeed increase was due to a horizontal windshear as the wind shifted from a tail wind to a head wind component. The wind shift most likely occurred as the Aircraft was descending below 7 ft radio altitude as this was when the Commander first felt the Aircraft being affected by the environmental conditions of hot air raising from the runway surface and the wind shift. During this period, the Commander first exclaimed “Oops” followed by “Thermals”. The Commander made several inputs on the control column, control wheel and rudder in order to maintain wings level and keep the aircraft aligned with the runway centerline.
  • The additional lift created because of the increasing performance of the Aircraft contributed to the prolonged floating of the Aircraft over the runway. Even though the Commander was not aware of the increasing airspeed, he had responded to the increasing performance and in an attempt to land, three times made small pitch attitude corrections to lower the nose of the Aircraft. During this time, the Aircraft pitch angle decreased from 2.6 degrees to an average of 1.2 degrees between 5 ft and just prior to the touchdown. The action taken by the Commander was in line with the recommendation of the FCTM ̶ Landing Flare Profile as it was stated that the touchdown body attitude (pitch angle), should be reduced by 1 degree for each 5 kt above the touchdown speed. For UAE521, the touchdown speed was calculated by the flight crew to be 147 kt (VREF30 + 0).
  • With the TO/GA switches inhibited because of the right main gear weight-on-wheels (WOW) [‘ground’ mode], pushing the TO/GA switch had no effect on the A/T mode. As designed, when the Commander pushed the left TO/GA switch, the FMA A/T mode remained at ‘IDLE’. As neither pilot had observed the FMA, they were not aware that the A/T mode had not changed to ‘THR’.
  • When the Commander called for ‘flaps 20’, 2.5 seconds after the go-around command, both main landing gear were in ‘ground’ mode, with the Aircraft pitch angle increasing towards 7.4 degrees. Although the flight crew stated that they were not aware that the Aircraft had touched down, the Commander was aware that the Aircraft was close to the runway and therefore he limited the pitch angle in order to avoid a tail strike.
  • The Operator’s Go-around and Missed Approach Procedure required both pilots to verify rotation to go-around attitude and that engine thrust was increasing, after the pilot monitoring selected flaps 20. The pilot monitoring was then required to verify that thrust was sufficient for the go-around and adjust as necessary.
  • The Copilot called “Positive climb” 1.5 seconds after confirming flaps 20, when the Aircraft vertical speed was approximately 592 ft per minute, and the airspeed was decreasing towards 147 kt IAS. The Copilot’s call was followed by the Commander’s call for ‘gear-up’, four seconds after the Aircraft became airborne. The airspeed continued to decrease and was 145 kt IAS at 58 ft radio altitude with the pitch angle increasing towards 8.4 degrees.
  • Less than 12.5 seconds from the time that the TO/GA switch was pushed, the Aircraft had insufficient energy remaining to gain further height. The energy loss was aggravated by the landing gear doors opening.
  • The Aircraft loss of airspeed was perceived by the Commander as a windshear effect, which prompted him to call “Windshear TOGA”. The sink rate was increasing towards 500 ft per minute as the Aircraft sank below 67 ft radio altitude with the airspeed decreasing below 130 kt IAS. Soon after, the Commander pushed the TO/GA switch and manually advanced both thrust levers fully forward, as per the Operator’s windshear escape maneuver procedure. Only at this time did the Commander realize that the engines were not producing sufficient thrust.
  • Eighteen seconds after the initiation of the go-around the Aircraft impacted runway 12L approximately 2,530 m beyond the runway threshold. The Aircraft was controllable until impact, but the height available was insufficient to prevent impact with the runway.
  • The Aircraft manufacturer’s post-Accident Performance Evaluation calculated that, as the Aircraft gained height, at approximately 58 ft radio altitude when the landing gear lever was selected to the ‘up’ position, a successful go-around could have been flown had the thrust levers been advanced to go-around thrust by the A/T, or immediately by manual advancement of the thrust levers, and had the pitch been maintained at go-around pitch. The performance analysis indicated that as the engines accelerated, the Aircraft would lose some height but would clear the runway at a minimum height of 17 ft radio altitude before safely climbing away. This hypothetical recovery scenario was possible, had the UAE521 flight crew been [aware] of the Aircraft state, which was not the case.
  • The Investigation concludes that the Commander maintained the stabilized approach criteria established by the Operator during the attempted tailwind landing. However, the landing distance was increased due to the early flare, the updraft created by the thermals rising from the runway surface and flight in ground effect which caused the Aircraft to remain airborne beyond the FCTM recommended touchdown of between 305 m to 610 m. Beyond this point, the Aircraft entered a performance increasing windshear as the wind shifted to a headwind.
  • Because the Commander was not aware that the Aircraft had touched down and that the TO/GA switches were inhibited, he relied on the Aircraft automation when he pushed the TO/GA switch based on his training for the initiation of a normal go-around. His perception, as well as that of the Copilot, was that the Aircraft was airborne when he pushed the TO/GA switch. However, neither pilot had monitored the engine thrust and Aircraft performance as required by the Go-Around and Missed Approach Procedure. By the time the loss of airspeed was recognized, the actions taken in executing the windshear escape maneuver were too late to avoid impact with the runway.

Causes

[AAIS, ¶3.3] The Air Accident Investigation Sector determines that the causes of the Accident are:

  • During the attempted go-around, except for the last three seconds prior to impact, both engine thrust levers, and therefore engine thrust, remained at idle. Consequently, the Aircraft’s energy state was insufficient to sustain flight.
  • The flight crew did not effectively scan and monitor the primary flight instrumentation parameters during the landing and the attempted go-around.
  • The flight crew were unaware that the autothrottle (A/T) had not responded to move the engine thrust levers to the TO/GA position after the Commander pushed the TO/GA switch at the initiation of the FCOM Go-around and Missed Approach Procedure.
  • The flight crew did not take corrective action to increase engine thrust because they omitted the engine thrust verification steps of the FCOM Go-around and Missed Approach Procedure.

Lessons

One of the reasons I feel the need to explicitly come up with a number of "lessons learned" here is that we who fly automated airplanes get into new habit patterns that override older habits. We don't always understand every detail about our automatic systems but since they "always" work, we stop worrying about it. So nothing that follows is new, but perhaps it is forgotten.

  • Fly the same approach angle and cross the threshold at the same height, unless the approach calls otherwise, so everything feels the same as often as possible.
  • Initiate the flare when called for. This changes with approach angle; if you are authorized to fly steep approaches, understand that that flare height will increase.
  • In the flare, with your right hand on the throttles, confirm they come to idle. With most airplanes (but not all), you or the autothrottles should hit idle the same time you touch down. Keep your right hand on the throttles during the final portion of the approach, through the flare, and the rollout. On most airplanes movement of the throttle is immediate tactile information that might be available elsewhere, but only at the expense of having to divert your eyes.
  • Fly the airplane onto the runway. There are only two exceptions to this, that I know of. First, if your position along the runway or any conditions exist that make stopping doubtful, go around. Second, if the speed is such that you cannot touch down with the mains first, go around.
  • If you decide to go around, keep your right hand on the throttles and confirm they go forward. There have been cases, such as this one, where the throttles didn't move. There have been other cases where one throttle did not come up and the asymmetric thrust went unnoticed until it was too late. I recommend you activate the automation (such as TO/GA) if your SOPs call for it, every time. Even if it is too much thrust, it gets you headed in the right direction. But don't trust that.
  • Get into a ritualized callout in the simulator so it transfers to the airplane about these first steps. For most of my airplanes this has been "Go around, flaps 20." For most airplane the first thing that happens on gear retraction is that the gear doors open and that increases drag. For most airplanes going from an approach setting of flaps to the go around setting reduces drag greatly while decreasing lift slightly.
  • As you pitch up the first officer announces that you have a positive rate of climb by checking the altimeter and vertical velocity are both going up. After calling "gear up" the pilot flying needs to focus first on aircraft pitch, then airspeed, and then navigation.
  • The first officer should ritualize the situation also. In older Gulfstreams there was a flow called "To L and Back" because it was shaped like an upside-down letter L that was traced up, left, right, down. The flow was basically: (up) flaps, gear, check throttles forward, heading, (left) LNAV, (right) reset altitude select window, (down) check thrust setting. The newer aircraft do much of this automatically, but it still makes for a good crosscheck.

See Also:

Air Accident Investigation Sector (AAIS) Accident Final Report, Case No: AIFN/0008/2016, Runway Impact During Attempted Go-Around, Emirates, Boeing 777-31H, A6-EMW, Dubai International Airport, The United Arab Emirates, 3 August 2016

Air Accident Investigation Sector (AAIS) Accident Preliminary Report, Case No: AIFN/0008/2016, Runway Impact During Attempted Go-Around, Emirates, Boeing 777-31H, A6-EMW, Dubai International Airport, The United Arab Emirates, 3 August 2016