Into the Wind: The crash of Flydubai flight 981

Wreckage of flight 981 littered the runway after the crash. Image source: RT

On the 19th of March 2016, an Emirati Boeing 737 struggled to land in the Russian city of Rostov-on-Don. After abandoning their first approach, the crew circled the airport for two hours, waiting for conditions to improve before trying again. In the dead of night, well past 3 a.m., the pilots finally made the fateful decision to begin a second approach. Coming in against a near hurricane-force headwind, the pilots were unable to stabilize the approach, forcing them to go around again. But this time, something went terribly wrong: just seconds into the climb, the plane pitched steeply downward and nosedived into the runway, obliterating the aircraft and killing all 62 people on board. Over the course of a grueling investigation that lasted nearly four years, Russian investigators slowly revealed the story of a captain who was mentally unprepared for the maneuver he was about to attempt. He fell behind his aircraft, unable to predict its next move, and struggled to understand how his control inputs were affecting its motion. It was in this environment that he inexplicably put the plane into a fatal dive, even as his first officer screamed at him to pull up. How could he have made such an incomprehensible error? Answering this vexing question would prove to be one of the most challenging parts of the entire investigation.

The Flydubai Boeing 737–800 involved in the accidents. Image source: Mohammedreza Farhadi Aref

Flydubai is a state-run carrier based in the United Arab Emirates, founded in 2008 as a budget alternative to the country’s flag carrier, Emirates. At the time, Flydubai operated a fleet consisting entirely of Boeing 737–800s . On the 18th of March 2016, one of these 737–800s was scheduled to operate Flydubai flight 981, a regular passenger flight from Dubai to the city of Rostov-on-Don in southern Russia. Today, the plane was lightly loaded: only 55 passengers boarded the red-eye flight, well under one third of its total capacity. Seven crew members joined them, including the two pilots. Like many pilots in the UAE, they were not from the region: in command was Captain Aristos Sokratous, who was from Cyprus; his first officer was Alejandro Cruz Álava, from Spain. The flight attendants came from five different countries, including Colombia, Kyrgyzstan, and the Seychelles. In contrast to the diversity among the crew, almost all of the passengers were Russians and Ukrainians taking a cheap flight home.

The route of Flydubai flight 981. Map source: Google

Flydubai flight 981 left Dubai International Airport at 9:37 p.m. local time, more than half an hour behind schedule. En route, the pilots received weather reports from their destination. A storm was rolling across Russia’s Don region, bringing high winds, rain, and turbulence to the entire area. Air traffic authorities had issued several SIGMETs (short for Significant Meteorological Information) warning of severe turbulence, and gusts of up to 72kph had been recorded in the Rostov area. But the pilots had come prepared: due to the higher fuel costs in Rostov-on-Don, they had taken on extra fuel in Dubai, giving them an abnormally large cushion in case they had to hold or attempt multiple approaches. Although neither pilot had flown to Rostov before, they were well aware of all the procedures they would need to land there.

At 1:17 a.m. local time, flight 981 began its descent toward the airport. Weather on the ground was bad: the controller informed them that they would be landing into a 40kph headwind, gusting as high as 54kph. Weather reports also indicated the presence of wind shear. Wind shear, a rapid change in wind speed and direction over a short distance, can be extremely hazardous to aircraft. The pilots discussed the possibility of encountering wind shear and established that, should the wind shear alarm activate, they would perform an immediate go-around using the wind shear avoidance maneuver. A regular go-around — in which a flight aborts its approach, climbs out, and rejoins the holding pattern — calls for the pilots to raise the landing gear, retract the flaps to 15 degrees, and accelerate the engines to climb thrust. In contrast, the wind shear avoidance maneuver is meant to be performed as quickly as possible, allowing the pilots to keep the gear down and the flaps extended while using maximum engine power to compensate for the resulting drag.

One example of wind shear is a large change in wind speed by altitude. Image source: Cliff Mass

At 1:42, as flight 981 descended through an altitude of 1,100 feet above ground level, on board equipment detected the presence of wind shear between the plane and the runway. A predictive wind shear warning sounded: “GO AROUND, WIND SHEAR AHEAD!”

The crew were ready for just such a situation. Within one second of the alarm, Captain Sokratous initiated the wind shear avoidance maneuver and announced, “Wind shear, go around!” Flight 981 entered a rapid climb, briefly exceeding the maximum allowable airspeed with the flaps extended. However, the go-around was otherwise normal, and the pilots leveled off at 8,000 feet, well above the wind shear. Captain Sokratous and First Officer Álava carefully debriefed their performance during the maneuver, noting that they momentarily oversped during the climb. Sokratous remarked to a flight attendant that regulations required the plane to undergo extra inspections after landing as a result of the overspeed incident.

Captain Sokratous decided to hold off on making any more landing attempts until another incoming plane, an Aeroflot Sukhoi Superjet 100, had made its approach. This would give them more information about the conditions along the approach path. First Officer Álava requested that they be put into a holding pattern near the airport until the SSJ-100 had either landed or elected to divert.

At 1:53, the Aeroflot SSJ-100 reported that it had encountered wind shear on final approach and was going around. No flights had managed to land in Rostov-on-Don for quite some time, and Álava was getting worried. While Captain Sokratous was out of the cockpit, he conversed with a flight attendant in Spanish. “All the aircraft have left,” he said, “We’re the only ones here doing this nonsense.”

“Where did they go?”

“I don’t know. Because there was an Aeroflot and… I don’t know about the other… they left. They went to other destinations. We have fuel enough,” he added, noting that holding was technically possible. “But I don’t think that… with such weather, if it keeps being bad, it’s not worth it. Actually, I don’t understand why they plan these types of flights to this Russian place at night, when they already know there’s shit weather during the daytime — and they plan it at night!?” But despite his venting to the flight attendant, he made no explicit mention of his concerns to Captain Sokratous when he returned from the bathroom.

Path of flight 981 after the go-around, with ATC and CVR transcript excerpts. Image sources: Google and the IAC

As bands of the storm raced across the Don steppe, Sokratous adjusted their holding pattern several times to avoid the worst of the weather. At 2:06, the Aeroflot SSJ-100 attempted another approach, but was once again forced to abandon it due to wind shear. Although First Officer Álava privately wanted to divert, Captain Sokratous was adamant that they wait until conditions improved.

At 2:16, the Aeroflot SSJ-100 aborted a third approach, again due to wind shear. Its pilots gave up on landing at Rostov-on-Don and diverted the flight to Krasnodar. In light of the situation, Captain Sokratous came up with a new plan: flight 981 would hold either until conditions improved, or for two hours, whichever was sooner; then they would make one more approach, and if they had to go around, they would divert to their alternate airport in Volgograd, where the weather was much better.

Several factors went into this decision. If flight 981 diverted to Volgograd, they would have to sort out lodging for the passengers (at great expense to the airline), and it would throw off Flydubai’s flight schedules much more than would a two-hour hold followed by a successful landing in Rostov. They would also be able to perform the return flight to Dubai without exceeding their duty time limits — which wouldn’t be possible if they diverted. He was also confident that their earlier approach was entirely stable except for the wind shear warning, and that in its absence, they would be fine. Considering the circumstances, it was a perfectly acceptable decision.

Path of flight 981 after the go-around, with ATC and CVR transcript excerpts. Image sources: Google and the IAC

Captain Sokratous carried out a long conversation with a flight attendant, then called the airline dispatcher and began another equally long conversation, during which the dispatcher suggested that they change their alternate destination from Volgograd to the Caucasus tourist town of Mineralnye Vody. The dispatcher encouraged them to hold as long as they needed and recommended that they try their hardest to land in Rostov. After a lengthy discussion of approach plans and weather conditions, both pilots agreed to select Mineralnye Vody as their new backup airport. They also briefed how they would go around if they encountered wind shear on approach again — using the same “wind shear avoidance” procedure they used the first time.

Concerned about duty time limits, Captain Sokratous said, “I don’t know man, if we divert there, we are gonna be out a lot of hours, we are late for five hours, man.”

First Officer Álava joked, “I see my future is sleeping in the aircraft!”

By now, it was after 3:00 a.m. local time, deep into both pilots’ circadian low — the period during the night where they are normally asleep, and bodily functions slow. This is the time when pilots are most likely to make mistakes, as fatigue limits their perceptiveness and increases their reaction times.

Path of flight 981 after the go-around, with ATC and CVR transcript excerpts. Image sources: Google and the IAC

At 3:20 a.m., the pilots elected to begin their second and final approach attempt, despite sustained winds at ground level in excess of 50kph. Factoring into their decision was the controller’s report that there was no wind shear on the runway — although what she actually meant was that no one had reported wind shear on the runway. This was, of course, because nobody had landed or taken off from Rostov-on-Don in several hours. In hindsight, this error — likely a result of the controller’s substandard English proficiency — could have misled the pilots into believing that conditions were better than they were.

As flight 981 descended through turbulence and icing conditions, the controller reported a low altitude headwind of nearly 100kph. Fearing severe wind shear, the pilots carefully laid out for each other and for the controller exactly what they would do if they encountered it.

Then, at an altitude of 1,100 feet, a powerful wind gust hit the plane head on, causing their indicated airspeed to increase far past the maximum allowable on a stabilized approach, according to standard operating procedures.

Noticing the deviation, First Officer Álava exclaimed, “Check the speed!”

Recognizing that the approach had become unstable, Captain Sokratous called out, “Okay, go around!”

This was a critical moment — the pilots were now forced to go around not due to wind shear, as they had expected, but due to a simple case of an unstabilized approach. This distinction would prove to be the initiating factor in the catastrophe that followed.

The unexpected initiation of a go-around due to a reason other than wind shear took Captain Sokratous by surprise. He was mentally prepared to perform a wind shear avoidance maneuver, but was now being asked to perform a regular go-around instead. As a result, he accelerated to maximum thrust as though he were performing the wind shear avoidance maneuver. At the same time, First Officer Álava configured the plane for a normal go-around, retracting the flaps to fifteen degrees and raising the landing gear. Without the flaps and gear inducing drag, using maximum thrust is overkill — especially on a half empty plane near the end of its fuel load. As a result, the plane began to climb more steeply and rapidly than expected. To try to reach the target pitch angle of 15 degrees nose up, Sokratous pushed his control column forward with considerable force.

A basic explanation of how a stabilizer trim system works. Image source: the FAA

This created a so-called “out of trim” situation. The 737’s horizontal stabilizer can be adjusted up or down to “trim” the aircraft, adjusting its neutral pitch angle toward either nose up or nose down. During the go-around, the stabilizer trim was automatically adjusted to nose up to help maintain a stable climb. When Captain Sokratous pushed the nose down with his control column, he moved the elevators in the direction opposite that of the stabilizer, a conflict that is said to put the aircraft “out of trim.” He found it difficult under such circumstances to maintain 15 degrees nose up, and the plane’s pitch began to fluctuate wildly.

First Officer Álava warned him, “Keep it to fifteen degrees, nose up!” But when Sokratous momentarily let off pressure on the yoke, the pitch jumped to 18.5 degrees, which was much too high.

Suddenly and without explanation, Captain Sokratous flipped the two “trim switches” on his yoke to move the stabilizer trim toward nose down. He held the switches down for twelve seconds, pushing the stabilizer back through neutral and into an extreme nose down position. The plane pitched down violently, throwing unsecured objects and people into the ceiling.

“Be careful!” Álava screamed. “Be careful! Be careful!”

“Oh, shit!” Sokratous muttered.

Álava continued to shout at his captain, “No, no, no, no, no, no, no! Don’t! Don’t do that!”

By the time Sokratous let off the trim switches, the 737 had pitched to 40 degrees nose down and entered a high-speed dive. The plane accelerated straight toward the ground at maximum thrust, but for some reason, Captain Sokratous continued to push his control column forward.

“No! Pull it! Pull it!” Álava yelled. “Pull it! My god!”

Only now did Álava finally grab his own control column, hauling back as hard as he could to try to pull out of the dive. But instead of pulling back, Sokratous rolled the plane sixty degrees to the left, even as the ground proximity warning system began to blare, “PULL UP! PULL UP!”

Security camera footage shows the final seconds of Flydubai flight 981. Video source: Commercial Plane Lovers on YouTube

By that point, it was too late. The last sounds heard on the cockpit voice recorder were the pilots’ terrified screams as the plane ran out of altitude. Flydubai flight 981 plowed nose first into the runway in a steep left bank at over 600kph, utterly obliterating the aircraft. A massive fireball erupted over Rostov-on-Don as the atomized fuel ignited. The plane punched a meter-deep hole through the pavement, jamming much of the wreckage like an accordion into the crater before it was blasted back out again under its own momentum. Ragged pieces of the airplane rained down across the surrounding area, leaving the rain-slicked runway strewn with thousands of unidentifiable fragments of the 737 and its unfortunate occupants. Upon seeing the explosion, fire crews rushed to the scene to help, but they could barely find anything recognizable as having been part of an airplane. It was clear that none of the 62 people on board had survived.

An aerial view of the crash site later that morning revealed that little remained of the Boeing 737. Image source: TASS

Investigators from the Interstate Aviation Committee (IAC), a joint investigative body representing much of the former Soviet Union, arrived on the scene later that morning. Most of the wreckage was far too badly mangled to draw any conclusions — this investigation would have to rely on the black boxes alone.

Investigators were astonished to discover that Captain Sokratous had simply nosedived his plane into the runway for no apparent reason. This suggested that he had suffered from some kind of spatial disorientation. One of the most common types of spatial disorientation is a somatogravic illusion. In the absence of visual cues, acceleration can be mistaken for a nose high pitch, prompting a pilot to put the plane into a dive to prevent a non-existent stall. But a closer examination of the sequence of events showed that Sokratous didn’t start the dive until well after the window of opportunity for a somatogravic illusion had already passed.

Firefighters and officials examined the widely scattered wreckage. Image source: Reuters

Sokratous was actually afflicted by a more subtle type of incapacitation. The unexpected circumstances of the go-around threw him off track, taking him down a path that he hadn’t plotted out in advance. He quickly fell behind his aircraft, unable to predict its next move. A pilot should always be mentally ahead of their aircraft so that they’re ready to respond to its motion. However, Sokratous became so focused on trying to achieve the right pitch angle that he lost his mental picture of how his inputs were actually affecting the aircraft. All he needed to do was relax the control column and apply a small amount of nose down trim to stabilize the aircraft in a 15-degree climb. Instead he kept pushing his control column forward, creating an out of trim situation that made the plane more difficult to fly. It was actually this difficulty that may have prompted him to put the plane into its fatal dive.

When a pilot makes an input using the control column, he or she receives a feedback force that increases proportionally with the size of the input. When Sokratous held the control column forward to try to keep the pitch at 15 degrees, he had to apply 23kg (50lbs) of continuous pressure to maintain that input. Investigators believe that he wanted to relieve that feedback pressure so that he could stabilize the plane’s pitch more easily.

On light aircraft like the ones on which Sokratous first learned to fly, the feedback on the yoke is transmitted directly from aerodynamic forces acting on the flight control surfaces. These aircraft have trim tabs instead of stabilizer trim. While stabilizer trim moves the whole horizontal stabilizer, a trim tab is attached to the trailing edge of the elevator, and can be adjusted to help hold the elevators in a particular position. This reduces the control column force needed to maintain that elevator input. When the trim tab position corresponds to the elevator position, the natural feedback force on the control column is reduced to zero. Therefore, a pilot can hold the yoke in the desired position and adjust the trim tab until extra force is no longer required to keep it there (see diagram below).

How control column feedback works on light single engine or twin aircraft. (Own work)

In contrast, feedback on the Boeing 737 is generated by the Feel and Centering Unit, a device that artificially creates feedback force directly on the control column. The Feel and Centering Unit can only react to elevator inputs made using the yoke. Moving the stabilizer trim does not change the feedback force because, unlike a trim tab, it does not affect the position of the elevators. Therefore, to maintain a pitch angle while relieving the required control column force, a Boeing 737 pilot must slowly relax the control column to neutral as they adjust the trim to the desired setting. Otherwise they will just compound their input without reducing the feedback force.

How control column feedback is generated on a Boeing 737. (Own work)

In all likelihood, when Captain Sokratous wanted to reduce the feedback pressure on his control column, he reverted to what he remembered from his days flying light aircraft. Believing that he could relieve this pressure by bringing the trim in line with his elevator input, he started adding nose down stabilizer using the trim switches, but this made no difference because the trim was not linked to control column feedback force. This may be the reason he held the trim switches down for 12 seconds, causing the plane to enter a deadly nosedive — he expected to stop when the feedback pressure went away, but this cue never came.

As it turned out, Captain Sokratous might not have appreciated this nuanced difference between the feedback mechanisms on light aircraft and on the Boeing 737. The details of the feedback system aren’t included in training, and investigators could not positively conclude that he knew about them. Had he taken a moment to think carefully about the effect of his trim input, he probably would have realized that it was dangerous. But his state of mind did not allow him to do this.

Some of the wreckage was jammed into a crater in the runway. Image source: Vasily Maximov

Even after the plane entered the dive, the pilots could have recovered if they had pulled up in a timely manner. But Captain Sokratous barely reacted to his aircraft’s extreme maneuvers. In the face of a rapidly escalating situation, he simply froze up, unable to move mentally past whatever task he was focused on. Contributing to this “freeze” was the fact that the plane momentarily entered a zero-gravity state during the beginning of the dive. A sudden transition to zero-G has been shown to cause serious disorientation among pilots who haven’t experienced it before. To make matters worse, zero-G conditions cause dirt and dust to rise off the floor into the air, potentially creating difficulty seeing and breathing. These factors probably caused Sokratous to become subtly incapacitated — that is, he was conscious and aware, but unable to think logically or take action.

Wreckage of flight 981 litters the runway after the crash. Image source: RT

However, it was clear from the cockpit voice recording that First Officer Álava knew exactly what was happening. He yelled at Sokratous to stop trimming down and start pulling up, but by the time he grabbed the controls himself, it was much too late to save the plane. Had he done so just a few seconds earlier, flight 981 might not have crashed. So why didn’t he?

The answer might lie in a single note left by an instructor during one of his recurrent training sessions. “[Álava] needs to be quite a bit more assertive in what is needed from the Captain,” the instructor wrote. “Tell him/her what you want done and do not wait for the Captain to enquire with you or direct you in this regard. Need to be more decisive in taking actions when needed.” It appears that in a situation that demanded decisive action and overruling the captain, his natural hesitancy to act might have doomed everyone on board. Further evidence for this interpretation came shortly after the first go-around, when Álava told a flight attendant that he thought holding at Rostov was “nonsense,” but never attempted to convince Captain Sokratous to divert the flight.

Another view of the crash site. Image source: Erik Romanenko

One of the most mystifying aspects of the crash of Flydubai flight 981 is that both pilots appeared competent and prepared throughout the flight up until the moment they lost control. They didn’t skip any procedures; they carefully weighed all their options; they openly discussed each other’s performance; they exercised caution and good judgment; and they prepared detailed contingency plans. This crash should therefore serve as a cautionary tale about latent risk. Although Sokratous and Álava were decent pilots, they were well into their window of circadian low, flying in an unfamiliar area amid volatile weather. The base level of risk on this flight was high. If they had factored this into their decision about whether or not to divert, the story might have had an entirely different outcome.

An example of an instantaneous reconstruction of the Heads Up Display indication as it might have appeared to Captain Sokratous during the dive. Image source: the IAC

The IAC finally published its report on the crash in November 2019, more than three and a half years after the accident. Over a year was spent trying an entirely new investigation technique: reconstructing what was shown on the Head Up Display, or HUD. The HUD projects an attitude indicator, airspeed indicator, and other instruments directly onto the windscreen so that pilots can refer to them while looking outside the plane. Captain Sokratous was using the HUD at the time of the crash, so investigators used flight data to painstakingly reproduce what he might have seen at various points in time. Investigators hoped that reconstructing the HUD would help them understand Sokratous’ actions. Although it’s unclear whether the analysis of the HUD added any meaningful insight into the crash, it did break new ground in the field of aircraft accident investigation, and could prove useful in the future.

People placed flowers by a temporary memorial at the airport in Rostov-on-Don. Image source: Donland.ru

In its final report, the IAC recommended that Flydubai give its pilots more detailed training on the manual operation of stabilizer trim, install HUDs for its first officers as well as its captains, consider training pilots in major upset scenarios involving zero- or negative-G, train pilots to recognize signs of subtle incapacitation, and create a standard procedure to call out the type of the next maneuver (for example, wind shear escape maneuver vs. go-around). It also recommended that Russia’s air transport agency enhance its scrutiny of English proficiency among aviation personnel, organize joint training for controllers and meteorologists to help them better transmit wind shear information to flight crews, and find aspects of Boeing 737 operation that might not be covered in training but could be significant to a pilot transitioning from light aircraft. Further recommendations included that Boeing revise its 737 operations manual to note changes in the plane’s behavior during a go-around when it has a high thrust to weight ratio; and that Boeing update its manual to give more detail about the relationship between stabilizer trim and feedback forces, among many other suggestions. One of these was that Boeing consider redesigning its stabilizer trim system to prevent pilots from making inputs that cause a severe out of trim situation. This recommendation resulted in a lengthy argument between the IAC and Boeing, which claimed that such a change was incompatible with its design philosophy that always gives flight crews full command over all the controls.

In 2013, Tatarstan Airlines flight 363 met a similar fate after its captain nosedived the plane during a go-around. Image source:

A go-around is one of the most difficult procedures that a pilot may be asked to perform during the course of normal flight. Flydubai flight 981 was not the first accident in Russia to occur as a result of a pilot putting the plane into a dive during a go-around. In 2013, Tatarstan Airlines flight 363, a Boeing 737, crashed during a go-around in Kazan after the captain pitched steeply down to counter an excessive nose-up attitude. All 50 people on board were killed. And in 2006, the pilots of Armavia flight 967 flew their aircraft into the Black Sea after the captain made nose down inputs during a go-around on approach to Sochi. All 113 people on board were killed. In the former case, the captain was found to be improperly qualified to fly the 737; in the latter, the pilots were in a state of extreme psychoemotional stress that robbed them of their ability to reason. Every pilot should keep accidents like these in the back of their mind while performing a go-around. When in doubt, take a step back, look at the big picture, and then fly the airplane.

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Analyzer of plane crashes and author of upcoming book (soon™). Contact me via @Admiral_Cloudberg on Reddit or by email at kylanddempsey@gmail.com.

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