Criminal Negligence

On June 28, 1982, an Aeroflot Yak-42 was operating a passenger flight from Leningrad to Kyiv. There were 132 people on board - 124 passengers and 8 crew members.

While approaching Kyiv, the crew was instructed to descend to 7,800 meters. The descent was being carried out under autopilot control. Suddenly, the rate of descent increased sharply. The stabilizer did not respond to nose-up commands, causing the autopilot to disconnect. The Yak-42 entered an increasingly steep dive. The pilots pulled back on the control columns, but then the aircraft rolled to the left, reaching 35 degrees within seconds. Spinning, the airliner plunged toward the ground at a speed of 600 km/h. Under enormous aerodynamic loads, the fuselage structure began to break up, and at an altitude of 5,700 meters the aircraft tore apart into several pieces.

The wreckage was found scattered over an area of 23 square kilometers near the western outskirts of the village of Verbovichi, not far from the Belarusian town of Narovlya. All 132 people on board were killed. It remains the deadliest aviation disaster on the territory of Belarus, as well as the worst accident in the history of the Yak-42 and of all aircraft designed by the Yakovlev Design Bureau.

The investigation into the crash involved Alexander Sergeyevich Yakovlev himself, the General Designer of the Yakovlev Design Bureau. The commission determined that the cause of the sudden dive was a catastrophic failure of the stabilizer repositioning mechanism (MPS), a screw-jack actuator. Because of a design flaw, the screw pair was subject to constant excessive wear. The wear was further aggravated by an unsuitable choice of lubricant. The inspection schedule for this mechanism was such that, during routine checks every 300 flight hours, it was impossible to detect signs of excessive wear in the screw pair.

As a result, the threads became so badly worn that the nut and screw separated in flight. Since this mechanism also served as the stabilizer’s forward support, the stabilizer was quickly forced by the oncoming airflow to its maximum angle, sending the aircraft into a dive. As the speed increased, aerodynamic forces tore off the stabilizer, which then caused the left roll.

After the crash, Yak-42 operations and production were suspended for two years. Detailed inspections of aircraft already in service revealed excessive wear in the stabilizer actuator threads on many of them.

For approving the defective design of the mechanism for serial production, the officials who had approved the MPS drawings and signed and stamped them were convicted by a verdict of the Supreme Court on October 20, 1983. They were sentenced to two years’ imprisonment under Article 172 of the RSFSR Criminal Code for negligence, with a one-year deferment of the sentence under Article 46-1 of the Criminal Code.