Accident of IL-18 near Kalyazin

IL-18V with tail number 75840 (serial number 182005301, serial number 053-01) was manufactured by the MMZ Znamya Truda plant approximately in September 1962 . On September 29, he was transferred to the Main Directorate of the Civil Air Fleet , which initially sent the airliner to the Vnukovo squadron of the Moscow Territorial Administration. On February 10, 1965, the aircraft was converted into a modification of the IL-18 RT (an aircraft measuring station, used to communicate with spacecraft) and sent to the aircraft of the USSR Navy . In 1988, the board 75840 again converted into a model of the IL-18 V. February 8, 1999 he switched to the airline IRS Aero . In total, at the time of the crash, the 39-year-old airliner had 11 617 flight hours and 5582 landings, the resource of most components and assemblies was almost completely exhausted ^[1] .

The aircraft performed that day the charter passenger flight LDF-9601/02 on the route Moscow ( Domodedovo ) - Khatanga - Krasnoyarsk - Khatanga - Novosibirsk - Khatanga - Moscow (Domodedovo). Its crew was piloted, consisting of commander A. N. Sominsky, co-pilot V. V. Mikhailov, navigator V. F. Fedorishin, flight mechanic A. P. Kozhevin, as well as flight attendants O. A. Yakovleva and L. A. Solovchuk. At 20:53 (17:53 UTC), when the aircraft completed the last leg of the route (Khatanga - Moscow), the crew contacted the radar control manager and reported on the estimated time of flight of the next mandatory reporting point. IL-18 RA-75840 at that time flew at a magnetic course of 200 ° at the echelon of 7800 meters at a speed of 410 km / h. On board were 18 passengers ^[2] .

The flight was normal, when at 21:17 (18:17 UTC) when the autopilot was working, the elevator unexpectedly dived, thereby directing the plane down. The plane bent to the ground at an angle of 40–42 °, and overload for a short time became negative 0.5 g , which prevented the pilots from fully realizing their physical abilities to hold the helm. When the overload became normal (1), the pilots finally applied a total effort to the helms of about 120-160 kilograms, starting to pull them “towards themselves” in order to try to straighten the airliner. IL-18 at that moment was already racing at a speed of 580 km / h. Trying to pull the helms on himself, one of the pilots probably accidentally ran into the left pedal (controls the rudder ), because of which the left roll began to develop. At an altitude of 6300 meters, the airliner rushed to the ground with a vertical speed of 120 m / s with a left roll of 19 °, and its translational speed had already exceeded the maximum permissible and reached 610 km / h. The efforts of the pilots were not enough to withdraw the aircraft from the dive at a speed of 850 km / h. At 21:19, at an angle of about 12 ° and with a left roll of 43 °, the Il-18 flying at a 150 ° course crashed into the ground and completely collapsed. All 27 people on board died. The place of fall was found 15 kilometers southeast of Kalyazin ( Tver region ) ^[2] .

Investigation

During inspections, the commission found a number of violations on the technical condition of the aircraft ^[2] :

1. All four engines had expired storage periods.
2. Duplicates of the forms of the two engines were opened at 123 ARZ of the Ministry of Defense of Russia with violations and deviations from the established requirements. For example, in one of them the repair date was not indicated, and on the inserts for the duplicate of the signature form of the workshop head and senior OTK master were falsified. The duplicate of another form did not contain the date of its establishment, and the engine release date did not correspond to the actual one, the operating time from the beginning of operation did not correspond to the actual one, the number of repairs and the date of the last repair were not indicated, there was no record of the engine conservation time after repair, inserts with a list of replaced when repair of parts, parameters of control tests of the engine, a list of units installed during repair of the engine were not attached.
3. The APU TG-16M form no. AM 041050 was missing.
4. The installation date of one of the propellers on the plane did not correspond to reality, and the installation of this propeller was not included in the airplane form.
5. Forms of aircraft, engines, passports of units and products at IRS Aero Airlines were filled out irregularly and untimely.
6. The accounting of the monthly norms of independent flight of command and flight personnel and the implementation of independent approaches and landings by co-pilots was not conducted.
7. Monitoring and analysis of the quality of flight operations according to flight information was carried out in violation of the standards, and applications from the flight service for complex decryption of flight information were not submitted. The flight performance index was not kept in the flight service.
8. The flight schedule of the RA-75840 during the flight LDF-9601/02 was developed by the airline’s management in excess of the working hours, since at a rate of 11 hours 30 minutes the crew’s working time lasted 14 hours 45 minutes.

Conclusions

The commission was unable to pinpoint the cause of the disaster. It is most likely that a combination of several factors led to the disaster ^[2] :

• the AT-2 trimming machine failed, due to which the elevator trimmer spontaneously deviated from the balancing position to the extreme dive position during electric control, which caused the formation of an articulated moment on the elevator that led to the rotation of the cable drum of the RM-913 steering machine of the autopilot longitudinal control channel AP-6EM-311 and elevator deflection to dive when autopilot is on;
• the protection system of the AT-2 trimmer from spontaneous deviation of the elevator trimmer, which, when certain (threshold) forces appeared in the elevator control wiring generated by the deviating trimmer, should disconnect the UT-2 trimmer deflector even before the elevator deviates for a dive, in this case did not work;
• there was an uncompensated hinge moment of the elevator due to the trimmer being in the position −4 ... -4.5 ° at the time the autopilot was turned off, which led to a sharp movement of the elevator to dive, which in turn led to an intensive transition of the aircraft to decline with rapid growth vertical and translational speeds;
• due to the intensive transition of the aircraft to a dive, a negative vertical overload occurred, lasting up to 6 seconds, and for only 12 seconds the vertical overload was less than 1, which led to the fact that the pilots could not make sufficient efforts to timely bring the airliner to a horizontal position ;
• the plane entered very quickly at a peak and accelerated to unbelievable speeds, which required excessive effort from the pilots to take them out to horizontal flight;
• in this situation, the crew did not resort to the manual control of the elevator trimmer indicated in the RLE, which could significantly reduce the efforts at the helm when the aircraft was brought out to horizontal flight.

The most likely reason for the spontaneous deviation of the elevator trimmer to dive and the AT-2 protection system to fail from a dangerous level of spontaneous deviation of the trimmer could be failures in the RMU-5066D relay magnetic amplifier and the FD-2007 phase discriminator. However, due to the complete destruction of the aircraft, it was impossible to establish unequivocally where and why the failure occurred ^[2] .

After the disaster, serious restrictions were imposed on the airline "IRS Avia". As for the Il-18 aircraft, it was taken into account that over the many years of history of their operation there have already been cases where refusals in longitudinal control have occurred, and they could not establish the exact cause anywhere. In 2001, 18 Il-18s continued to operate in the Civil Aviation of Russia, with 14 in the passenger service. After this catastrophe, it was decided to stop commercial passenger transportation on IL-18 aircraft ^[2] .

A. V. Elistratov, the head of the DHW airworthiness and technical development department of the Civil Aviation Administration, V. P. Tarshin, the head of the Flight Standards Department, and V. A. Rudakov, the head of the Department of State Flight Safety Oversight, given that it is unambiguous to determine the cause of the accident with an airplane Il -18 RA-75840 was not possible, as well as the presence of other cases of longitudinal control failures on IL-18 aircraft, ... to amend the certificate of serviceability of the IL-18 aircraft for operation, providing yuschee prohibition of passenger transport. Until October 21, 2002, make the appropriate changes to the certificates of state registration and operational documentation of IL-18 aircraft.

- First Deputy Minister A. V. Neradko ^[3]

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