Kazakh investigators have revealed that an Azerbaijan Airlines Embraer 190 experienced two explosions about 25s apart, and lost pressure in all three hydraulic systems, after aborting an attempt to land at Grozny.
The aircraft suffered serious flight-control damage and its crew, after considering a number of diversion options, chose to fly to Aktau in Kazakhstan where the jet crashed.
Preliminary findings from the Kazakh-led accident investigation commission state that the aircraft, arriving from Baku on 25 December last year, had sought vectoring for the approach to Grozny’s runway 26 after losing both GPS navigation systems.
But after two attempts to land in poor visibility, the crew informed the tower that the flight was returning to Baku.
The tower asked if they could head for the waypoint PINTA, to the northeast of Grozny, to which the crew replied that they still needed vectoring owing to the loss of GPS.
Some 50s later the jet was climbing through an altitude of 3,500ft, pitched 12.3° nose-up, with a right bank of 26° as it turned to the north. Neither GPS system was receiving satellite signals and a DME rangefinder was not receiving signals from the ground.
At this instant, the cockpit-voice recorder picked up a “sonic boom”, says the inquiry, and both the autopilot and autothrottle disconnected.
Over the next 3s the aircraft lost all pressure in one of its hydraulic systems, then suffered a failure in its pitch-trim system. The crew was also notified that an aft service door had opened.
The aircraft started to depressurise within 8s of the bang and, a few seconds later, a second hydraulic system entirely lost pressure, closely followed by a near-complete loss of pressure in the third.
Two seconds after this collapse of the hydraulic system – and 25s after the initial explosion – another similar bang was captured on the cockpit-voice recorder.
The crew told Grozny tower that the jet had suffered a bird-strike, requesting the nearest airport with good weather and asking for the conditions in Mineralnye Vody, and then Makhachkala, before being transferred to the Rostov control centre.
After requesting the weather in Makhachkala and Baku, and telling Rostov control that they would head for Baku, the crew then opted to divert to Aktau. The communications from the crew mentioned the possibility that an oxygen tank had exploded, with passengers being rendered unconscious.
The diversion to Aktau took the crippled jet across the Caspian Sea, and the crew contacted Aktau tower about 50min after the incident began, telling controllers that control surfaces had failed and the jet was being manoeuvred with the throttles.
While attempting to line up visually with runway 11, the crew deployed the landing-gear and extended flaps, while terrain warnings and ‘pull up’ commands sounded in the cockpit.
The aircraft was pitched 5.8° nose-down and banked 35° to the right, with the horizontal stabiliser 1.76 units up, when it struck the ground.
Although the destruction of the aircraft resulted in 38 fatalities, 27 passengers and two crew members survived the accident.
Examination of the wreckage resulted in the discovery of extensive damage to the tail surfaces, as well as the left wing and engine, from multiple penetrations from foreign objects. Forensic analysis is being carried out on these objects, which are also believed to have damaged internal systems including hydraulic lines and the pitch-trim system electrical wiring.
