Russian investigators have disclosed that the horizontal stabiliser of the crashed Flydubai Boeing 737-800 transitioned to nose-down pitch at a height of 900m (2,950ft) as the crew attempted a second go-around.
The aircraft, which had been climbing out of the approach to Rostov-on-Don, subsequently entered a dive from which it failed to recover.
Russia’s federal air transport regulator, Rosaviatsia, has outlined the sequence of the fatal 19 March accident in a 4 April safety bulletin.
While it has not disclosed conclusions about the crash, it says the commission of inquiry has recommended that 737 operators be urged to study go-around procedures and handling of aircraft, particularly in regard to longitudinal flight control.
Rosaviatsia is also recommending that carriers include simulator training for go-around and recovery in conditions of windshear and with failures relating to a jammed elevator.
The regulator has advised that the training includes studying the fatal loss-of-control accident involving a Tatarstan Airlines 737-500 which was attempting a night-time go-around at Kazan in November 2013.
Rosaviatsia says the Flydubai jet had informed air traffic control about the presence of windshear while conducting its initial approach to runway 22.
It climbed first to 5,000ft and then 8,000ft before entering a holding pattern. While holding, the crew reported a faint presence of icing and requested to climb to 15,000ft.
As the aircraft prepared to exit the hold the crew was given, at 03:20 local time, a weather update which stated that the visibility was 5km with a cloud base of 630m, plus winds from 230° of 25kt gusting to 35kt.
Two minutes later air traffic control told the pilots that it had no information regarding windshear. The crew subsequently requested permission to conduct the approach. Rosaviatsia indicates that the flight would have climbed to 8,000ft in the event of another go-around.
The crew opted to abort the approach again, at a height of 220m – at which point it would have been some 2.2nm from touchdown on a typical 3° glidepath. The inquiry has yet to disclose information about the autopilot status or the thrust settings used.
Rosaviatsia’s details on the meteorological conditions suggest that the aircraft, flying in darkness, would have penetrated the cloud base by the time the stabiliser moved to the nose-down position.
The aircraft came down in a steep dive and struck the runway about 120m beyond the threshold. None of the 55 passengers or seven crew members survived the high-energy impact.
Rosaviatsia says that initial analysis of the flight-data and cockpit-voice recorders shows no evidence of a powerplant or aircraft system failure.
The captain had just under 2,600h on type, including a little more than 1,000h in command, from a total of 5,965h.
Rosaviatsia says the inquiry is looking into the pitch control system of the aircraft and evaluating the crew’s operating procedures during the go-around.
It states that it plans to hold a conference on the safe operation of Boeing 737s, at a date yet to be fixed.