Moscow oblast

It appears that a technical problem occurred with the slats which deployed in an inappropriate angle after rotation. Nevertheless, the cause of the power loss on two engine remains unknown.

The commission considered that the most probable cause of the accident was an adverse combination of the following factors:
- Icing of the stabilizer (probably due to lack of heating in the leading edge),
- A pitch manoeuvre executed to correct a deviation from the glide path which resulted in a g-loading of 0,6 - 0,5,
- Extension of the flaps to the full landing setting, which had the effect of degrading the airflow over the lower surface of the stabilizer and, consequently, of producing loads on the control column which promoted a further increase in the negative g-loading and prevented recovery of the aircraft from the developing nosedive.
Owing the destruction of the aircraft it was not possible to check the actual functioning of the stabilizer deicing system.

The cause of the disaster to aircraft DC-8-62 JA-8040 resided in the fact that during take-off and following attainment of the safety speed V2, the crew put the aircraft into a supercritical angle of attack which resulted in loss of speed and altitude. The aircraft's assumption of supercritical angles of attack was the consequence of one of the following circumstances:
- Inadvertent extension of the spoilers in flight, leading to a fall in the maximum value of the lift ratio and an increase in drag;
- Loss of control of the aircraft by the crew in conditions associated with malfunctioning of the No. 1 or No. 2 engine consequent upon possible ice formation on the engine intake at a time when the de-icing system was switched off.
The anomalies in the functioning of the engines observed by the crew and other witnesses may have arisen after the aircraft had assumed a supercritical angle of attack with the spoilers extended.

The exact cause of the accident could not be determined with certainty. However, the assumption that the loss of control was the consequence of a technical problem with the elevator control system or the longitudinal control system wass not ruled out.

Loss of control after the crew suffered a spatial disorientation in reduced visibility.

It was determined that both engines failed because during the test, all electrical systems were out of order. The crew forgot that the fuel transfer system was unserviceable as well and that the fuel should be transferred manually. Such situation forced the crew to ditch the aircraft.

It was determined that an explosive device composed by 400 to 800 grams of trinitrotoluene (TNT) exploded approximately 7 to 15 seconds after rotation. The bomb was apparently placed in a hand baggage placed on the cabin floor, maybe under the seat number 45. The detonation ruptured the cabin floor, the left root and the control cables were cut and inoperative. The airplane entered an uncontrolled descent and lost several pieces at an altitude of 200 meters before striking the ground. Despite extensive investigations that will end in 1973, the Soviet authorities wont be able to identify the author of this act of sabotage.

The accident was the consequence of the combination of the following factors:
- Poor flight preparation,
- Lack of crew coordination,
- Lack of interaction between the instructor and the rest of the crew,
- Irresponsible actions on part of the flight engineer.

It was determined that the crew failed to follow the approach checklist and forgot to lower the undercarriage. The following factors were considered as contributing:
- Several propeller blades detached while contacting the runway surface, causing severe damage to the fuselage,
- A fire erupted following an electrical short-circuit in the cargo hold combined with a hydraulic leak,
- Lack of coordination on part of the cabin crew who failed to follow the safety and evacuation procedures,
- Lack of efficiency and assistance on part of the ground firefighters who arrived on the scene 15-20 minutes after the accident.