1973 aviation accident
Aeroflot Flight 141 was an international flight from Moscow to Prague. On 19 February 1973, the Tupolev Tu-154 crashed short of runway 25 (now runway 24) of Prague Ruzyně Airport (now Václav Havel Airport Prague). Most of the passengers survived the crash, but many died in the fire that followed. Out of the 87 passengers and 13 crew members, 62 passengers and 4 crew members perished with 18 occupants having serious injuries and the remaining 16 with either minor or no injuries. The crash was the first loss of and first fatal accident involving the Tu-154.
The cause of the incident was not officially determined. The crew did not report any defects or troubles between the ATC frequencies. One theory stated wind shear, while another theory was that the pilots incorrectly set a horizontal stabilizer, yet another stated on unexpected atmospheric turbulence. The investigation of the accident also showed that controlling of the stabilizers was complicated. This was solved when the Tu-154 aircraft was being modernized to the Tu-154A.
Aircraft.
The aircraft involved was a Tupolev Tu-154, registered as CCCP-85023 was produced by the Kuibyshev Aviation Plant in September 1972. The airliner was then handed over to the customer - the USSR Ministry of Civil Aviation (operated under the Aeroflot brand ), to which it (according to some sources) arrived on 6 October.
It was operated in the 207th flying squadron as part of the Sheremetyevo Joint Air Squadron of the Central Directorate of International Air Communications (TsUMVS). For a short period of time, there were individual comments on the operation of the equipment and systems of the aircraft, but these comments were small and quickly eliminated, that is in general, the airliner was technically sound. Up until the day of the disaster, the aircraft had completed 261 take-off-landing cycles and flown 459.1 hours, including 4.1 hours from the last repair.
Crew.
The plane was flown by an experienced crew, the composition of which was as follows:
Chronology.
Flight to Prague.
The Tu-154 (i.e. CCCP-85023) performed Flight 141 on the Moscow-Prague route and at 06:50 UTC (09:50 MSK) on 19 February took off from Sheremetyevo Airport. In total, there were 87 passengers on board (85 adults, one 12-year-old child and one infant), 13 crew members, of luggage, of cargo and of mail. The amount of fuel in the tanks at departure was about , and the total take-off weight of the airliner was estimated at with a maximum allowable weight of . The plane alignment fluctuated within the range of 19,3-22,0% MAR when installed for the Tu-154 ranges from 16.5 to 28.0% MAC, i.e. also was normal.
Flight over the Soviet Union took place at FL330 (about ), then in the vicinity of Poland, the crew climbed to FL350 (about ). After the overflight of Warsaw, the air traffic controller (ATC) permission was given to descend to FL310 (about ) and on the approach to Czechoslovakia - FL290 (about ). The Polish-Czechoslovak border was completely crossed at FL220 (about ), and at 08:54 UTC from flight 141 they reported on the passage of Frýdlant (OKX) and the completion of the descent from . In response, the dispatch center in Prague instructed to continue the descent to an altitude of in the direction of Roudnice (RCE), and at 08:56 - maintain direction along the center line of the air corridor. At 09:00, the crew reported over Roudnice VOR, flying at an altitude of , to which it was instructed to switch the communication with the approach controller at a frequency of 121.4 MHz.  
Landing approach.
At that time there was an anti-cyclone over Czechoslovakia, accompanied by relatively good weather conditions without turbulence or icing. However, occasionally there were light snowfalls.
Having switched to the communication with the "Prague-approach", the crew immediately received instructions to follow through the EHO until the approach radio beacon was captured, and then to descend to with a report on the passage of an altitude of . At 09:02 UTC the plane reported on the passage of with a course of 135°, for which an order was given to switch to the communication with the "Prague-circle". After the transition to a new frequency, Flight 141 was instructed by the radar controller to continue to follow the approach radio beacon, information that they were the first in line to land on ILS on runway 25 (now runway 24), as well as permission to descend to by airfield pressure  - . Art. At 09:04 the crew received permission to descend to at the level of the airfield and were warned that the plane may have deviated a couple of kilometers from the route. After 40 seconds, the dispatcher transmitted that Flight 141 was from the airport and was following exactly the landing course, and at 09:05 he instructed to switch to the communication with the take-off and landing dispatcher (i.e. Prague – Tower).
Catastrophe.
Being from the airport, the crew switched to the communication with Prague-Tower and announced the approach to the airport with the intention of landing and visual observation of the runway. To this, the controller gave permission to Flight 141 to land on Runway 25, and also reported a ground wind of 250° at . At 09:06 UTC the crew requested and received information about the braking coefficient, which was "5", as well as a re-landing clearance. At 09:06:30 the crew confirmed receipt of the information, which was the last known message from Flight 141. The airliner was following exactly on the glide path, when in the area of the near-drive radio beacon Liboc (L), when they suddenly lowered their nose at an angle of 4.62°, to which the aircraft began descending rapidly. 
Not knowing the cause of the situation, the pilots increased engine power and began to pull the controls towards themselves. Thus, trying to raise the nose and take the plane out of the descent, but these measures did not have a significant effect. Flight 141 managed to fly over the R7 expressway, after which about behind it and from the end of runway 25 with a slight right bank crashed and immediately the right main landing gear strut into the frozen ground. The contact was hard and the landing gear collapsed from the impact, after which, at a distance of from the runway end, the airliner crashed into the ground. At a distance of the airliner scattered parts across the runway and immediately then, the jet fuel leaking from the ruptured fuel tanks ignited, causing a fire, which immediately began to flare up. Finally, from the end of Runway 25 and to the right of the extension of its axis, Flight 141 finally came to a halt, after which the rapidly spreading fire completely destroyed the airliner.
According to the airport's meteorological service, at that time there was a light snowfall, partly cloudy with a lower boundary of and with gaps at an altitude of , wind 260° at , sometimes increasing to , stood over the airport, the air temperature , visibility .
Rescue work.
The disaster occurred at 09:07 UTC (10:07 local time), and just after, the fire service announced an alarm. Subsequently, the landing dispatcher also gave an alarm. The fire trucks were located from the crash site, to overcome which it took them 90 seconds, after which at 09:09 the Fire Trucks arrived at the crash site, when the fire had already covered the rear of the fuselage and in the center section area and the windows in the back began to burst due to the high temperature. However, Firefighters concentrated their efforts to rescue people in the front of the cabin, since there could still be survivors in it. Within three to four minutes, 34 people managed to escape, when by 09:14 a fire spreading on the left side engulfed the entire cabin, while the compressed air cylinders in the front part began to explode, so it was no longer possible to carry out rescue operations. At 09:17 the city fire brigades were called to help extinguish the fire, and at 09:20 the fire was subdued, although the fire in the cabin continued to be fueled by the jet fuel flowing from the destroyed tanks. At 09:45 the fire was completely brought under control.
As a result of the disaster, 62 passengers and 4 flight attendants were killed, that is, only 66 people, with 53 dead were found inside the plane, and 13 outside. According to the pathological examination, 51 people died from burns, and 15 from multiple injuries. The survivors of which 15 passengers and 3 crew members were injured. The remaining 16 occupants were relatively unharmed.
The crash of Flight 141 was the first accident in the history of the Tu-154. Also at the time of the events, in terms of the number of people who perished (66 dead), this disaster ranked second in Czechoslovakia (succeeded by the crash of TABSO Flight 101, 82 dead).
Investigation.
Conclusions of the Czechoslovakian Commission.
After analyzing the situation, the Czechoslovakian investigators made the following conclusions:
In connection with the complete destruction of the plane in a collision with the ground and the subsequent fire, a commission from the Ministry of Transport of Czechoslovakia came to the conclusion that it could not accurately determine the cause of the disaster. There is only a possibility that during the landing approach the Tu-154 encountered an unexpected turbulence and got under the influence of wind shear.
Conclusions of the Soviet Commission.
Soviet investigators criticized the work of the 207th flying squadron, whose leadership carried out the organization to prepare for the flight with serious violations, including: 
The possible reason for the disaster to occur is when the investigators called the error of the crew commander Chernetsov, who at low altitude shifted the stabilizer from the landing position to the flight position. Having deviated from the requirements of the Flight Operations Manual and did not ensure the landing configuration of his aircraft in time, the commander, by his actions, led to a lack of time, which in turn significantly contributed to further erroneous actions to control the stabilizer and create an emergency. The very design of the stabilizer control switch allows such a mistake, and therefore, imperceptibly for the crew, the stabilizer changed its angle from -5.5° to 0°. But in the landing position, the stabilizer created a pitching moment, trying to raise the nose of the aircraft, while compensating for a significant diving moment opposite in direction, which was created by the landing configuration of the wing and vice versa, tried to lower the nose. Shifting the stabilizer to the flight position led to the fact that the pitching moment was removed, after which the diving moment began to lower the nose. Attempts by the crew to correct the situation by deflecting the steering wheel turned out to be ineffective due to the small area elevators.
Effects.
For the period of the investigation, all Tu-154s were temporarily grounded. Soon the design of the aircraft was tweaked, including emergency exits, increased engine power, and also changed the control system. Subsequently, the Kuibyshev aircraft plant began to produce the Tu-154 model A, and shortly after the model B.
References.
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