Initial investigations into the fatal loss of an Azerbaijan Airlines Antonov An-140-100 turboprop have discovered that three independent gyroscopes were not providing stabilised heading and attitude performance information to the crew early in the flight.
The findings have been released by Ukraine’s Kharkov State Aircraft Manufacturing Company (KSAMC), which builds the An-140. The company says there is no evidence of failures in the aircraft’s engines, control systems or power supply.
Flight AHY217 had been operating from the Azeri capital Baku to the Kazakh city of Aktau on 23 December.
Preliminary information from air traffic control and flight-recorder data shows that, after climbing to an altitude of 6,900ft (2,100m), the aircraft entered a descending spiral, the radius of which tightened from 500m to just 100m in the space of four and a half orbits.
“In the climb stage the aircraft deviated from the established flight trajectory,” says KSAMC. “Then the crew reported to [air traffic control] about a technical problem on board the aircraft.”
The company says that the flight-data recorder registered a “simultaneous absence” of information from all three gyroscopes during the climb. “At the present time the reason for the absence of gyro-horizon indications has not been established.” The gyros provide pitch, roll and heading peformance information to the relevant flight displays.
Azeri state aviation company AZAL director general Jakhangir Askerov says: “This situation is not normal and is unique – it is the consequence of certain events, which will be studied.”
All 23 occupants of the aircraft – comprising 18 passengers and five crew members – were killed after it crashed on the Caspian Sea coast. Rescue work at the crash scene was hampered by poor weather, including low cloud, winds and rain.
The aircraft, which KSAMC confirms was registered 4K-AZ48, was completely destroyed. It was the ninth of the type to be constructed by KSAMC and the first to be delivered to Azerbaijan Airlines in late 2004.
Loss of the An-140 has prompted the Azeri government to temporarily ground Azerbaijan Airlines’ An-140s. The airline was taking delivery of a batch of four of the type.
KSAMC says that its agreement to supply the type to the carrier “remains valid”, but adds: “The period of its fulfilment will be adjusted, to take into account the final findings of the investigating commission.”
Designed to replace ageing Soviet types such as the Antonov An-24 and Yakovlev Yak-40, the An-140 began rolling off the production lines in 2002. The -100 model is a longer range variant of the baseline model.
Only around a dozen aircraft, of which a third are An-140-100s, are in service with airlines in Azerbaijan, Iran and Ukraine. But the Azeri accident marks the second fatal loss of the type following the crash of an Aeromost-Kharkov An-140 in Iran in December 2002.