Bird strikes on the starboard engines of a Russian-operated Antonov An-12 freighter caused the aircraft to lose control and crash just seconds after it took off from Moscow Domodedovo Airport earlier this year.
Russia’s Interstate Aviation Committee (MAK) says the bird impact took place at a height of 70-75m (230-245ft), while the aircraft was travelling at 160kt, and caused the virtually simultaneous shut-down of both engines on the right wing.
Investigators are recommending improvement of information transfer between air traffic control and the airport division responsible for monitoring bird activity.
The aircraft, operated by Moscow-based Atran, was conducting flight 9655 from Moscow to Komsomolsk-on-Amur via Omsk and Bratsk with a shipment of aviation fittings bound for the KnAAPO aircraft production plant.
Owing to the destruction of the flight-data recorder by fire, MAK has derived its conclusions largely from the cockpit-voice recorder, radar information and the testimony of witnesses to the 29 July accident.
Although the An-12 was departing in early-morning darkness, Domodedovo’s automatic terminal information service included a cautionary statement regarding birds – albeit for runway 32R rather than the An-12’s departure runway 32C. Such bird warnings were usually included in the ATIS information as a matter of course, says MAK, adding that the reports “did not reflect the reality” of the ornithological situation.
It states that visual monitoring of birds, given the time of night, would have been “almost impossible”. However the cockpit-voice recorder indicates that the crew commented on the presence of birds.
The crew started the four Ivchenko AI-20 engines at 04:01 and made no comments about the functioning of the An-12’s systems. MAK says the aircraft was within weight and balance limits.
Controllers cleared the aircraft to take off and, after rotating, the aircraft climbed normally for a few seconds. But about 15s after lift-off, with the An-12 just 300m past the end of the runway, the CVR recorded a sound similar to a compressor stall. One of the crew members stated that the outboard starboard engine had failed before a second engine, the starboard inboard, also stopped operating.
MAK investigators discovered “small parts of organic origin” as well as feathers in the exhaust ducts of the two starboard engines.
It says the engines were hit by at least two birds large enough to stop the powerplants operating. The flight operations manual of the An-12, it adds, does not contain recommendations to the crew for controlling the aircraft after simultaneous loss of both engines on the same side during take-off.
The pilots battled to keep the aircraft airborne as it lost height but about a minute after the engine loss, with the An-12 in a right bank of more than 100°, the aircraft struck trees and disintegrated killing all seven occupants.
MAK highlights three other instances in which An-12s have crash-landed after encountering birds immediately after take-off.
In August 1993 an An-12 departing Slavgorod in Russia came down when a bird strike caused two engines, one on each side, to fail, while in June 2004 a Sudanese Sarit Airlines An-12 lost both starboard engines on departure from Wau in southern Sudan. In March last year an Armenian Phoenix Avia An-12 lost three engines at Payam in Iran.
MAK says these aircraft were able to retain a degree of control long enough to attempt a landing because they were flying at a lower height and in conditions of better visibility. But the Atran crew had “little opportunity” to do the same owing to the darkness and the onset of fog.
Investigators are also recommending that Antonov and associated institutes consider developing a procedure for crews in the event of simultaneous shut-down of two same-side engines on the An-12.
* Source: flightglobal.com's sister premium news service Air Transport Intelligence news