THE UKRAINIAN-LED commission investigating the crash on 10 February of the Antonov An-70 four-prop-fan prototype has ruled that the main cause of the accident was "human error", despite continuing allegations of technical problems with the aircraft.
The commission says that the mid-air collision of the An-70 with an An-72 chase aircraft had occurred "due to a combination of non-standard circumstances, the major of them being the human factor".
Leonid Berestov, the official Russian representative on the investigation board and deputy director of the Gromov Flight Research Centre, says: "The careless actions of both crews in their formation flying led to a collision and crash."
Contrary to the official statements, reports on possible technical faults of the An-70 continue to emerge. Sources close to Antonov say that, during the first flight on 16 December 1994, the Zaporozhye Progress D-27 prop-fan gearboxes functioned unsatisfactorily. This, it is understood, led to an eight-week break in flight-testing.
After correcting that fault, the tests were resumed on 8 February: the third flight was made on 9 February and the fourth the following day.
Several faults with the flight-control system were reported, in the second and third flights including a flap failing to deploy after a control input claim sources.
In the mid-air collision, the left horizontal tail and half of the fin of the An-70 was smashed away by the An-72 fuselage. The An-72 lost a flap on its right wing.
Borestov says that the mutual aerodynamic interference played a role at the very close distance and as a result, the aircraft "...were sucked to each other".