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Contribution of Unstabilised Approaches to Aircraft Accidents and Incidents

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Article Information
Category: Toolkit for ATC - Stabilised Approach Stabilised Approach Awareness Toolkit for ATC
Content source: EUROCONTROL EUROCONTROL
Content control: EUROCONTROL EUROCONTROL

Description

The Flight Safety Foundation (FSF) established that unstabilised approaches were a causal factor in 66 % of 76 approach and landing accidents and incidents worldwide between 1984 and 1997.

It was found that many low and slow (low energy) approaches have resulted in controlled flight into terrain (Controlled Flight Into Terrain (CFIT)) because of inadequate vertical position awareness. Low energy approaches may also result in "loss-of-control" or "land-short" events.

High energy approaches have resulted in runway excursions and also have contributed to inadequate situational awareness in some of CFIT accidents.

It was found that a crew’s inability to control the aircraft to the desired flight parameters (airspeed, altitude, rate of descent) was a major factor in 45 % of 76 approach-and-landing accidents and serious incidents.

Flight-handling difficulties have occurred in situations which included rushing approaches, attempts to comply with demanding ATC clearances, adverse weather conditions and improper use of automation.

Consequences

Unstabilised approaches can be followed by:

  1. Runway excursions
  2. Landing short
  3. Controlled flight into terrain
  4. Hard landings
  5. Tail Strike

Contributory factors

Weather conditions or approach types which can increase the chances of an unstabilised approach are:

  1. wake turbulence
  2. strong winds
  3. low visibility
  4. heavy precipitation
  5. an approach with no visual references (e.g. night or Instrument Meteorological Conditions (IMC))
  6. visual approach
  7. circling approach

Aircraft Accidents and Incidents Related to Unstabilised Approach Listed on SKYbrary

  • B738, Mangalore India, 2010 (On 22 May 2010, an Air India Express Boeing 737-800 overran the landing runway at Mangalore when attempting a go around after thrust reverser deployment following a fast and late touchdown off an unstable approach. Almost all of the 166 occupants were killed when control was lost and the aircraft crashed into a ravine off the end of the runway. It was noted a relevant factor in respect of the approach, landing and failed go around attempt was probably the effect of ‘sleep inertia’ on the Captain’s performance and judgement after a prolonged sleep en-route)
  • L410, vicinity Lukla Nepal, 2017 (On 27 May 2017, a Let 410 attempting to complete a visual approach to Lukla in rapidly deteriorating visibility descended below threshold altitude and impacted terrain close to the runway after stalling when attempting to climb in landing configuration. The aircraft was destroyed by the impact and two of the three occupants fatally injured. The Investigation concluded that the Captain had lost situational awareness at a critical time and had been slow to respond to the First Officer’s alert that the aircraft was too low. Safety Recommendations included the establishment of an independent and permanent Air Accident Investigation Agency.)
  • B738/B738, vicinity Oslo Norway, 2012 (On 31 October 2012, a Boeing 737-800 on go around after delaying the breaking off of a fast and high unstable ILS approach at Oslo lost separation in IMC against another aircraft of the same type and Operator which had just taken off from the same runway as the landing was intended to be made on. The situation was aggravated by both aircraft responding to a de-confliction turn given to the aircraft on go around. Minimum separation was 0.2nm horizontally when 500 feet apart vertically, both climbing. Standard missed approach and departure tracks were the same.)
  • B744, vicinity Bishkek Kyrgyzstan, 2017 (On 16 January 2017, a Boeing 747-400F failed to successfully complete a night auto-ILS Cat 2 approach at Bishkek and the aircraft crashed and caught fire killing its occupants and 35 people on the ground and seriously injuring 36 others. The Investigation found that the flight crew had comprehensively failed to monitor the achieved approach flight path and, after capturing and flying down the false upper ILS GS lobe, had then failed to promptly initiate a go around at the applicable decision altitude. The fact that an automatic ILS approach could continue even on a false glideslope was noted.)
  • B738, vicinity Memmingen Germany, 2012 (On 23 September 2012 a Boeing 737-800 made a premature descent to 450 feet agl in day VMC whilst turning onto visual finals at Memmingen after the FMS selected altitude had been set to a figure only 44 feet above runway threshold elevation of 2052 feet amsl. EGPWS Alerts of ‘Sink Rate’ and ‘Caution Terrain’ prompted initiation of a go around which, as it was initiated, was accompanied by a an EGPWS ‘TERRAIN PULL UP’ warning. The go around and a second successful approach to runway 24 were uneventful. A Final Investigation Report has not been published (June 2021).)

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Stabilised Approach Awareness Toolkit for ATC

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Part of the Stabilised Approach Awareness Toolkit for ATC