Iced Out: The crash of UTair flight 120
On the 2nd of April 2012, a Russian airliner conducting a regional flight in Siberia ran into trouble immediately after taking off from the city of Tyumen. The plane swayed wildly from side to side as the pilots yelled over each other, seemingly unable to figure out what to do. Just one minute after takeoff, the ATR-72 plunged into a snow-covered field, cartwheeled, and burst into flames, killing 33 of the 43 people on board. As Russian investigators pored over the evidence, it became apparent that the pilots had neglected to de-ice the plane, causing them to take off with ice on the wings. But how could a pilot who flies in Siberia not understand the dangers of ice? As it turned out, quite easily: behind this seemingly inexplicable decision lay a series of miscommunications, regulatory loopholes, and misleading training that stemmed from Russia’s complicated decades-long transition to a Western-style aviation system.
UTair is one of the largest domestic airlines in Russia, with a fleet of 63 aircraft and over 70 destinations throughout the former Soviet Union and neighboring countries. Although UTair flies to cities all over Russia, its primary area of operations has always been western Siberia, where it originated in the 1960s as the Tyumen Directorate of the state airline, Aeroflot. Like many airlines in Russia, UTair got its start as an independent company following the breakup of Aeroflot after the collapse of the USSR. Based in the remote city of Khanty-Mansiysk with additional hubs in Surgut and Tyumen, UTair grew rapidly in the 2000s and into the early 2010s, purchasing dozens of new aircraft, hiring hundreds of new pilots, and introducing Western airplanes to replace its old Soviet models.
Among the new aircraft types introduced to UTair’s fleet in the 2000s was the ATR-72, a large twin turboprop produced by joint French-Italian company Avions de Transport Regional. The ATR-72 is a high-wing aircraft, with the wings attached to the roof rather than the chassis, which makes it ideal for operating in the tough conditions of Siberia where runways are often dirty or covered in slush. With a capacity of 74 passengers, the plane was also the perfect size to run one of UTair’s core routes: the constant back-and-forth trip between its two hubs in Surgut and Tyumen.
On the 1st of April 2012, 27-year-old Captain Sergey Antsin and 24-year-old First Officer Nikita Chekhlov flew UTair flight 119 from Surgut to Tyumen, the last flight of the day, arriving at Tyumen’s Roschino Airport shortly before midnight. As freezing rain mixed with snow fell over the city, they retired to an airport hotel, where they caught a few hours of sleep before reporting for duty at around 6:00 the next morning. As usual, their schedule that day was simple: they were to get back in the same airplane and carry out flight 120, the return trip to Surgut, at 7:30. After that, Antsin would go home: tomorrow was his 28th birthday, and he was looking forward to spending the day off with his family.
During the night, the intermittent rain and snow with temperatures fluctuating around freezing resulted in a significant buildup of ice on all the airplanes parked at Roschino Airport. Although ice is a fact of life when flying in cold climates, it presents a significant danger to aircraft. Even a thin layer of ice can change the shape of the wings, disrupting airflow patterns and reducing performance; on some aircraft types, just a couple millimeters are sufficient to prevent the plane from becoming airborne at all. In order to remove ice and snow before takeoff, Roschino Airport was well equipped with numerous ground crew personnel and de-icing vehicles armed with the latest in ice removal technology.
The first person to arrive at the ATR-72 that morning was an avionics technician, whose job was to inspect the plane for defects, including the presence of ice. He was soon joined by a mechanic, and they walked around the plane together, checking for anything out of the ordinary. They found nothing — neither mechanical problems, nor ice. The engines and other critical parts like the pitot tubes had been covered for the night to prevent ice buildup, and the covers had worked as intended. However, they didn’t check the top of the wings. Because the ATR-72 is a high-wing aircraft, it’s not possible to see the top of the wings from the ground without the use of a ladder, and for whatever reason, the avionics technician and the mechanic decided that they didn’t need to go find one. If the engines and the pitot tubes didn’t have ice, then surely the wings wouldn’t either, so what was the point?
About 30 minutes before the scheduled departure time, Captain Antsin and First Officer Chekhlov arrived at the plane to prepare for the flight. Antsin conducted a quick walk-around check, but he didn’t have a ladder either, so the wing surfaces remained unexamined. After Antsin returned to the cockpit, the avionics tech boarded the plane to brief the crew about the results of his pre-flight inspection, noting that there were no mechanical defects and no ice. He didn’t mention that he hadn’t checked the top of the wings. Pleased to hear that the airplane was clean, Antsin replied, “We are not going to be treated, we will take off as is.”
There were plenty of signs that there should be ice on the plane (which there was). Every other airplane at Roschino Airport that morning (except two that were only making a brief stopover) had requested de-icing, the weather conditions were conducive for ice formation, and there was fresh snow all around the airport, including on top of parked aircraft. But Antsin relied on (and was entitled to rely on) the word of the ground handler, which he failed to question. After boarding 39 passengers and two flight attendants, UTair flight 120 to Surgut pushed back from parking spot number three without having de-iced. Little did the pilots know that the surfaces of the wings and horizontal stabilizer were covered in at least four millimeters of ice.
As the pilots taxied the plane to the runway, Captain Antsin switched on the plane’s on-board de-icing systems. Although the de-icing systems were designed to be used in flight, not on the ground, there was technically no prohibition against this, and many pilots at UTair made a habit of turning the system on during taxi to check that it was functioning properly. The on-board de-icing system inflates rubber “boots” inside the leading edges of the wings and stabilizers to remove ice which accumulates there while in flight. But while the plane is parked, ice can build up across the entire upper wing surface, rather than just along the leading edge. The de-icing boots can’t remove ice that has formed behind the leading edges.
As the de-icing boots inflated, the pilots looked back to check that they were working. “It doesn’t want to inflate on the ground for some reason,” said Captain Antsin.
“Yes,” said First Officer Checkhlov.
“No — ah, it’s peeling off normally, it is inflating,” Antsin said, watching as the de-icing boots cracked a layer of ice and snow off the leading edges. But despite seeing ice fall off the plane when he activated the de-icing boots, he apparently didn’t understand that there was likely to be additional ice out of reach of the boots, or assumed that if there was, it wasn’t a problem. Having concluded that the system was working normally, he switched it off and lined up for departure.
At 7:33 a.m., flight 120 lifted off the runway and began to climb away from the airport. Initially, nothing seemed to be wrong. But behind the scenes, the layer of ice on the wings and stabilizers was already causing performance problems. The extra drag from the ice on the wings forced the plane to adopt a higher-than-normal angle of attack in order to achieve the normal climb rate. At the same time, the uneven ice layer on the horizontal stabilizers created an aerodynamic disturbance which pulled the elevators slightly toward the nose up position without any input from the pilots. Noticing that the plane was trying to pitch up too steeply, Antsin muttered a curse, “Oi, blyad’,” and set the stabilizer trim to its maximum nose down position. By moving the entire stabilizer toward nose down, he was able to counteract the unexpected behavior of the elevators and keep the plane at the correct pitch angle.
So far, this was the only indication of a problem. But the pilots had not made the connection between the unusual elevator movements and the presence of ice, and they continued the takeoff as though nothing was wrong. The plane continued to accelerate toward its target climb speed of 170 knots, apparently without difficulty.
Up until this point they had been flying with the flaps extended to 15 degrees in order to increase lift for the initial climb. But at higher speeds the flaps must be retracted; under normal conditions, the minimum speed for flap retraction is 132 knots. As flight 120 accelerated through this speed, Captain Antsin called out, “Flaps up.”
“Speed check, flaps up,” said First Officer Checkhlov, pulling the flap lever back to the retracted position.
Neither pilot knew that they had just made a colossal mistake. The math is complex, but the principle is fairly simple: given a particular wing shape, there is a specific angle of attack — the angle of the plane relative to the airstream — where the wings cannot produce enough lift to overcome drag, and the airplane stalls. Ice on the wings fundamentally changes the parameters of this equation. By detrimentally changing the shape of the wings, ice increases drag and reduces lifting capability, causing the plane to stall at a lower angle of attack.
On flight 120, the increased wing camber from the extended flaps served to counteract the negative impact of the ice. With this wing shape, the stall angle of attack was fairly normal, and the plane was able to climb without any problems. But when First Officer Chekhlov retracted the flaps, the flaps stopped compensating for the detrimental lift effects of the ice, which caused the stall angle of attack to instantly drop to a value approximately equal to the actual angle of attack of the aircraft at that very moment.
The result was that the ATR-72 went from a mostly normal climb to a nearly stalled state with no change in the position of the aircraft in space. The plane suddenly began to buffet violently as the airflow separated from the wing surfaces, prompting Chekhlov to exclaim, “Whoa!”
“What the hell is this?” said Antsin.
“What the hell is this buffeting?” said Chekhlov.
“Autopilot disengage,” Antsin announced, taking manual control of the airplane.
Fourteen seconds after retracting the flaps, the stall warning activated, shaking the pilots’ control columns to warn them of the impending stall. The right wing, which had been facing into the wind and had accumulated a thicker layer of ice, began to lose lift, causing the plane to roll forty degrees to the right.
The sudden activation of the stick shaker combined with the uncontrolled roll seemed to catch the pilots totally by surprise. Antsin grabbed the yoke and turned it hard to the left, but he didn’t appear to react to the stall itself. “What the hell is this!?” Chekhlov said again.
“Report it!” said Antsin.
“Report what, blyad’!” Chekhlov shouted. “What’s the failure!?”
“I don’t understand!” Antsin shouted back. As he pushed the controls all the way to the left, the plane stalled completely and the left wing dropped; the plane rapidly rolled sixty degrees to the left and began to fall from the sky.
As the plane dropped toward the ground, Captain Antsin frantically pulled back on the controls to try to pull up, but this made the stall even worse. An automatic system called the stick pusher intervened to try to push the nose down and decrease the angle of attack, but it wasn’t strong enough to overcome Antsin’s desperate inputs.
“Yob tvoyu mat’!” Chekhlov cursed as a snow-covered field rose up to meet them.
Antsin keyed his mike and stammered into the radio, “UTR 120, going down!”
Three seconds later, there was a scream, and the cockpit voice recording came to an abrupt end. After just 64 seconds in the air, UTair flight 120 slammed into a field a short distance past the end of the runway in a nose down position with a steep left bank. The plane cartwheeled on impact, sending pieces of the aircraft tumbling through the snow while a massive fireball erupted from the severed fuel tanks. Large chunks of the ATR-72 skidded to a halt in the snow, surrounded by flames.
Remarkably, some passengers managed to survive the crash and the fire, possibly because they were thrown from the plane and into the deep snow that blanketed the impact zone. Most of the passengers were seated level with or behind the wings, an area which was totally destroyed in the crash; despite the fact that the nose and the tail were the only large sections to remain intact, the survivors were generally seated elsewhere. As firefighters rushed to the scene of the crash, they found 13 people, all seriously injured, clinging to life in the vast debris field. Helicopters and ambulances rushed them to local hospitals, where two died in transit and one died on the operating table hours later. In the end, ten passengers survived, while 33 people, including all four crewmembers, perished in the crash.
Investigators with the Interstate Aviation Committee (MAK), an international agency which investigates air crashes across the former Soviet Union, were able to determine the basic sequence of events within days. Despite weather conditions which were conducive to ice formation, the pilots elected not to de-ice because the ground handler, who hadn’t checked the wings for ice, told them there wasn’t any. After takeoff, the ice on the wings caused a reduction in performance and reduced the critical angle of attack, leading to a stall when the pilots retracted the flaps. The pilots then failed to recognize the stall and carry out the stall recovery procedure, which called for them to extend the flaps to 15 degrees and pitch the nose down. Engineering simulations showed that simply extending the flaps back to 15 degrees would have been sufficient by itself to prevent the stall and save the plane. But this sequence of events left two key questions: why didn’t the ground crew or the pilots anticipate the presence of ice on the wings? And why didn’t the pilots react correctly to the stall warnings?
The MAK found that neither pilot was particularly experienced. Captain Antsin had 2,600 flying hours, nearly all of it on the ATR-72, but had only recently upgraded to captain. His young first officer had just 1,800 hours. Both received good marks in training, but it was the content of the training that stood out: it included barely anything about the dangers of ground icing (that is, ice which forms while the airplane is parked). Everything focused on in-flight icing, and for good reason: multiple ATR-72s had crashed in the past due to ice formation in flight. Furthermore, the pilots’ training records contained so few details that it was not possible for investigators to establish the extent to which they understood the importance of de-icing the plane on the ground. Both pilots’ lack of knowledge about aircraft icing was put on display when they activated the on-board de-icing equipment while taxiing. Despite seeing ice and snow fall off the wings after turning on the de-icing boots, they either did not understand that this meant there was ice on all areas of the wing surface, or they didn’t understand that the de-icing boots wouldn’t remove it if there was. In flight, droplets impact the plane horizontally, adhering to the wing and stabilizer leading edges, and the pilots had been thoroughly drilled to expect ice specifically in these areas. The lack of training on ground icing and insufficient critical thinking in the moment led the crew to miss this obvious sign that there was a problem.
The MAK noted that while the ATR-72 flight manual — which all pilots are required to read — did explain the dangers of ground icing, this manual was in English, not in Russian, and it was written at a high level with complex language used throughout. A review of the English language program in which both pilots participated showed that it was woefully inadequate to prepare them to read the manual. The course barely got beyond rote phrases that could be used when communicating on the radio, and recordings of the pilots’ oral exams showed that they struggled to form basic sentences without memorizing them beforehand. Nevertheless, both pilots passed the course and began flying the ATR-72. Russian regulations required that pilots flying planes with English-language technical documents have an understanding of English which is “sufficient” to read and comprehend the manual, but the regulation provides no criteria that can be used to determine what level of English proficiency is “sufficient.” After a previous accident in 2008 the MAK had recommended that Russian authorities clarify this, but no action was taken. As a result, the pilots were allowed to fly the ATR-72 despite being unable to read key documents that explained safety-critical aspects of the aircraft operations, including ground icing.
But how was it possible that a captain who had flown his entire career in Siberia could fail to gain at least some knowledge of ground icing through direct experience? The answer was actually quite simple: during the Siberian winter, it’s almost always too cold for ice to stick to a parked airplane. Ice forms when the temperature is between -3˚C and +5˚C; any colder than this and droplets are already frozen when they strike the plane, causing a buildup of snow, not ice. Because pure powder snow sloughs off easily during takeoff, no de-icing is necessary. The accident flight was actually the first flight all winter where Captain Antsin would have needed to de-ice the plane.
Attention now turned to the ground crew. Ground handlers who serviced other planes that morning reported that they found ice on almost all of them. So why didn’t the ground handlers working on flight 120 check the wings for ice, and why did they tell the captain that there was no ice if they hadn’t actually checked?
Ground handling services at Roschino Airport in Tyumen were run by a company called UTair Technic, which was owned by the same parent company as UTair Aviation, for which it provided ground handling and maintenance services on a contractual basis. It turned out that UTair Technic had been hiring its ground handlers practically right off the street, putting them through a short on-the-job training course, and releasing them for duty. This included the avionics technicians and mechanics who serviced the planes on the ramp and were responsible for de-icing. Prior to July 2012, Russian regulations did not require ground handlers to have any special certification, so UTair Technic’s bare-bones training regime was in fact legal. However, Russian regulations did require a maintenance certification in order to make decisions related to the airworthiness of an aircraft, including whether or not there was ice on the wings. This resulted in a confounding situation where ground handlers didn’t require any certification to get the job, but a key part of the job — de-icing planes — required a special certificate. Furthermore, UTair company rules stipulated that ground handlers must be trained in an approved training facility, which UTair Technic was not. Despite the fact that UTair ran an accredited training facility right there in Tyumen, UTair Technic ground handlers at Roschino Airport weren’t sent to this facility, and UTair had failed to catch on to the fact that UTair Technic was violating the terms of the contract by conducting unregulated in-house training for ground handlers.
Investigators compared the training received by uncertified versus certified ground handlers and found that the difference was stark. At an approved training facility, ground handlers could expect to receive 16 hours of theoretical and practical training related to aircraft icing. But at UTair Technic, they received just 30 minutes! The ground handlers trained by UTair Technic couldn’t possibly have understood the danger of aircraft icing or the nuances of detecting it on various types of airplanes. They knew how to apply de-icing fluid, and that was about it. The avionics technician who inspected flight 120 for ice was in no way qualified to do so, and he didn’t understand that it was important to check the tops of the wings on an ATR-72, or what the consequences could be if he didn’t. Despite this lack of knowledge, he told the captain that he hadn’t found any ice, and thus made a decision about the airworthiness of the plane, which should have required a certification.
Captain Antsin in turn had no reason not to take the technician’s report at face value. He too had little understanding of the dangers of ground icing. He also did not know, and was not required to know, the full range of weather conditions which had occurred during the seven hours that the aircraft was parked. And finally, he was eager to get home to celebrate his birthday. In fact, his desire to go home as soon as possible may have led him to subconsciously discount clues that there could be ice on the plane (such as the presence of fresh snow and the fact that other planes were de-icing), while favoring clues which supported his desired outcome (that is, an absence of ice, and an on-time departure).
Just a few minutes later, one last opportunity to prevent the departure of flight 120 was tragically missed. The ground handling shift supervisor was working on a plane in parking spot number two, adjacent to the accident airplane; unlike most of his subordinates, he was fully certified to make airworthiness decisions. While he was working on this other airplane, the mechanic who inspected flight 120 told him that Captain Antsin had elected not to de-ice his plane. Under company rules, the supervisor was required to call dispatch and stop the release of any aircraft on which there was evidence of ground ice and the pilot had refused de-icing services. Having been trained in a proper facility with the full 16-hour de-icing course, he should have recognized the likelihood that there was ice on the ATR-72, but he figured the pilots knew more about this than him, so he declined to take any action.
But even after the plane departed, a crash was not inevitable. The pilots could have regained control with a loss of just 300 feet by doing nothing more than following existing stall recovery procedures. So why didn’t they take these basic steps to save their airplane?
The key factor was the stall’s sudden onset. Prior to the pre-stall buffeting, the only sign that anything was wrong was the unusual elevator behavior, which caused Captain Antsin to apply full nose down trim to maintain the proper climb angle. The manufacturer was well aware that this could be a symptom of ice on the horizontal stabilizer, and in fact a scenario based on this exact phenomenon was programmed into the Finnair flight simulators used by both pilots during training — but the scenario was not used. Therefore, the elevator behavior might have seemed like evidence of a mechanical problem rather than an ice problem.
Once the stall actually occurred, the symptoms didn’t correspond to the stalls the pilots had experienced in training. In the training simulations, the stalls had always developed slowly, with airspeed progressively dropping and angle of attack increasing until it reached the critical point. But in this case, the speed and angle of attack didn’t change: instead, a change in aircraft configuration caused the critical angle of attack to suddenly decrease toward the actual angle of the plane. Colloquially known as a “change of configuration stall,” this type of incident has taken pilots by surprise before: in 1972, 118 people died when British European Airways flight 548 experienced a change of configuration stall after the captain retracted the droops at too low an airspeed. In both cases, the near-instant onset of a stall without any preceding warning signs resulted in the failure of the crew to recognize that a stall was occurring.
In fact, the evidence suggests that the pilots’ first reaction to this sudden upset was not to engage the stall recovery procedure, but to search for a mechanical failure. The unusual elevator behavior had already put them on the lookout for a mechanical problem, and the instantaneous loss of control seemed to confirm this suspicion. Adding weight to this theory was Chekhlov’s response to Antsin’s order to report a problem: “Report what? What’s the failure?”
Recovery from a stall relies on the pilots pushing the nose down to reduce the angle of attack. But in addition to their failure to recognize the cause of the problem, neither pilot had been trained on reacting to stalls at very low altitudes, a procedure which requires suppressing the deeply rooted instinctual urge not to pitch down while near the ground. When the plane began to lose altitude, Captain Antsin began to pull up with all his might because the proximity of the ground triggered a fight-or-flight response that overrode all logical thinking. His actions also overrode the stick pusher that was trying to automatically pitch the nose down, although this system could not have saved the plane by itself even if it was allowed to operate.
Throughout the brief flight and while on the ground, the pilots made several poor decisions that contributed to the tragic outcome. While part of this was due to a lack of knowledge, the MAK also thought some of it could be put down to fatigue. Neither pilot could have gotten more than four and a half hours of sleep the night before the flight, based on when they checked into and out of the airport hotel. Such a short rest break was allowed under Russian regulations because the pilots had only carried out one flight the previous day (the flight into Tyumen just before midnight), effectively making this a split shift rather than two separate shifts with a full rest break between them. Nevertheless, this disruption to their natural sleep cycle would have reduced their mental performance for the rest of the day. The MAK also found that they had probably developed long-term fatigue due to an overly demanding work schedule. UTair had been expanding so rapidly that the only way to keep the schedules was to force pilots to fly as close to the maximum number of permitted monthly hours as possible. One way it accomplished this was by pressuring pilots not to spend their vacation days — in fact, at the time of the crash, both pilots had built up over 100 unused vacation days, some of which normally would have been used to relax and recharge. The result was that the pilots were always overworked and never operated at peak performance.
This was a classic case of an airline that thought too much about whether it could and not enough about whether it should. Too many airlines have tried to expand too quickly in an effort to make money, without making sure that their safety nets are capable of keeping up. Between 2010 and 2011, UTair saw a 40% increase in passenger turnover, hired over 200 new pilots, and bought several dozen new airplanes. The airline didn’t have enough instructors to train all these new hires, and the pilots that were ready to fly found that the airline had resorted to violating their duty time limits. Despite this, UTair’s department of flight safety, which tracked compliance with safety procedures, reported a drop in procedural deviations in 2011 compared to 2010. UTair claimed to have analyzed over 21,000 flights and found only 26 deviations, an assertion that the MAK approached with skepticism. Investigators believed the real number was far higher, since they found six procedural violations merely by looking through previous flights that had been retained on the accident airplane’s flight data recorder. The MAK felt that UTair’s flight safety department was deliberately putting very little effort into collecting data, simply so the department managers could report a year-on-year decrease in violations, which would make them look good in the eyes of their superiors. This self-congratulatory reporting of meaningless “improvements” was a very useful way to get a job promotion during the time of the Soviet Union, but it also meant that the department had virtually no data with which to identify and correct unsafe trends in pilot behavior.
As a result of the findings of the investigation, the MAK issued several dozen recommendations intended to close regulatory loopholes, improve training about the dangers of ice, increase pilots’ English proficiency, improve pilots’ understanding of the aerodynamic behavior of their aircraft, increase regulatory and procedural compliance at UTair, improve UTair’s safety management system, strengthen the decision-making process around aircraft de-icing to make sure no one person can act as a single point of failure, and much more besides. As of July 1st 2012, ground handlers in Russia are now required to be certified, although this change had been scheduled well before the accident. Meanwhile, inspections of UTair Technic facilities resulted in the suspension of the company’s maintenance certifications issued by the European Union and Bermuda, preventing it from working on planes registered in those countries. (Most Western-built airliners in Russia, including the accident airplane, are registered in Bermuda in order to avoid import tariffs. Consequently, UTair Technic needed to be approved by Bermudan authorities in order to service those airplanes). And UTair itself soon collapsed under its own weight — in 2015 it nearly went bankrupt and was forced to sell off more than half its fleet. It nevertheless remains one of Russia’s largest domestic airlines, and it continues to uphold a substandard level of safety: in 2018, a UTair Boeing 737 slid off the runway in Sochi and caught fire; all the passengers lived, but an airport employee died of a heart attack and the plane was a write-off. And in 2020, another UTair 737 was substantially damaged after the pilots landed in snow short of the runway in Usinsk, causing the landing gear to collapse.
The crash of UTair flight 120 is a microcosm of several overlapping difficulties that Russia’s aviation industry has faced since the breakup of the Soviet Union in 1991. Prior to 1991, Russia had a completely separate safety environment and regulatory safety net; it used only Russian-built aircraft and the only airline was the state-owned carrier Aeroflot. In the early 1990s, however, everything changed virtually overnight: huge portions of Aeroflot’s fleet were sold off and became private companies, which began importing Western-built aircraft that were designed to a totally different set of criteria than the Soviet planes Russian pilots were used to. Many of these planes came with documentation written in English and required entirely new skillsets in order to fly them safely. Russia also tried to import a Western regulatory safety net, but numerous concepts (such as the position of “ground handler”) didn’t map 1:1 with the concepts which had been developed over 70 years of Soviet aviation. The result was widespread confusion and the adoption of sometimes dangerous coping techniques to comply with rules that few people really understood. The post-Soviet period in Russia is one of the only periods in history where a country’s standard of aviation safety actually got worse. Today, the reputation of Russian aviation is on the mend — but crashes like UTair flight 120 show that there remains plenty of work to be done.
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