Ryanair has introduced a ‘discontinued approach’ procedure after a serious incident at London Stansted during which a Boeing 737 Max 8-200 breached its go-around altitude, leading the crew to push the jet into a steep descent.
The aircraft pitched to 17.7° nose-down in instrument conditions, reaching a descent rate of 8,880ft/min, triggering ‘sink rate’ and ‘pull up’ alerts from the ground-proximity warning system.
According to the UK Air Accidents Investigation Branch, the aircraft reached 295kt with ‘flap 5’ configuration – above the 250kt speed limit for this setting – and descended to 1,740ft above ground before recovering.
The crew had planned an ILS approach to Stansted’s runway 22 on 4 December last year.
As the pilots attempted to intercept the glideslope from above, however, the approach became unstable and the crew opted to execute a go-around 3.6nm from touchdown, at an altitude of 1,940ft.
The autopilot disengaged and the captain manually pitched the aircraft nose-up, following the flight directors, while the autothrottle increased thrust and the first officer cleaned the configuration.
But investigators found that the crew had not entered a missed-approach altitude into the aircraft’s mode control panel prior to the go-around.
This meant that, as the 737 climbed away, its flight directors did not indicate that the aircraft needed to level at 3,000ft. The captain was “fixated” on the flight directors, says the inquiry, and did not notice the failure to level off.
After breaching the go-around altitude the aircraft continued to climb, reaching just over 4,000ft before a descent was initiated.
With the autothrottle still engaged and go-around thrust still set, the aircraft accelerated as it descended, and the first officer cautioned over the airspeed.
Although the captain extended the speedbrakes and manually retarded the thrust levers, the autothrottle advanced them again to go-around power. The first officer then held the levers at ‘idle’ as the captain pitched the aircraft nose-up – generating a vertical acceleration of up to 1.89g.
Just after the recovery commenced, the ground-proximity warning system issued ‘sink rate’ and ‘pull up’ alerts to the crew.
The crew entered the correct missed-approach altitude on the mode control panel and disconnected the autothrottle, stabilising the aircraft and levelling it at 3,000ft. It was subsequently vectored for an ILS approach to runway 22 where it landed without further incident.
None of the 126 occupants was injured.
The inquiry points out that the entire incident took place in instrument conditions, with no external visual references, although it adds that the crew probably did not suffer from spatial disorientation.
Ryanair introduced a ‘discontinued approach’ procedure in June this year, the inquiry adds, for use when an approach is aborted prior to glideslope capture. It is intended to confirm flight-director selections and aircraft configuration prior to executing a go-around above the 500ft ‘stabilised approach’ call.
