Contribution of Unstabilised Approaches to Aircraft Accidents and Incidents

Contribution of Unstabilised Approaches to Aircraft Accidents and Incidents

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

On 29 November 2017, a Boeing 737-900 on an ILS approach at Atlanta became unstable after the autothrottle and autopilot were both disconnected and was erroneously aligned with an occupied taxiway parallel to the intended landing runway. A go-around was not commenced until the aircraft was 50 feet above the ground after which it passed low over another aircraft on the taxiway. The Investigation found that the Captain had not called for a go around until well below the Decision Altitude and had then failed to promptly take control when the First Officer was slow to begin climbing the aircraft.

On 1 January 2020, an Airbus A350-900 made an unstabilised night ILS approach to Frankfurt in good visual conditions, descending prematurely and coming within 668 feet of terrain when 6nm from the intended landing runway before climbing to position for another approach. A complete loss of situational awareness was attributed to a combination of waypoint input errors, inappropriate autoflight management and communication and cooperation deficiencies amongst the operating and augmenting flight crew on the flight deck who were all type-rated holders of Thai-issued ATPLs. Neither of the observing pilots detected anything abnormal with the way the approach was being flown.

On 13 November 2020, a Boeing 727-100 configured for cargo operations veered partially off the landing runway at Kigali after a late touchdown on a wet runway before regaining it approximately 1,000 metres later. The Investigation concluded that viscous hydroplaning after touchdown which occurred a significant distance left of the runway centreline had been contributory but absence of a prior go-around was causal. It was also found that the flight crew licences were invalid and that there were significant discrepancies in respect of the aircraft registration, the status of the operator and the validity of the Air Operator Certificate. 

On 12 September 2020, an Airbus A318 was seriously mismanaged during a largely autopilot-controlled ILS glideslope capture from above and despite being unstabilised after the crew had intentionally ignored required approach management procedures, the flight was continued without hesitation to a landing. The Investigation found that the operator’s oversight of operating standards relating to unstabilised approaches was systemically flawed and also insufficiently supportive of their ‘Evidence Based Training’ method used for pilot training. It was also noted that the Captain involved had stated to the Investigation that “he considered this flight as a non event”.

On 16 May 2013, a DHC6-300 on a domestic passenger flight made a tailwind touchdown at excessive speed in the opposite direction of the of 740 metre-long runway to the notified direction in use and, after departing the runway to one side during deceleration, re-entered the runway and attempted to take off. This failed and the aircraft breached the perimeter fence and fell into a river. The Investigation identified inappropriate actions of the aircraft commander in respect of both the initial landing and his response to the subsequent runway excursion and also cited the absence of effective CRM.

On 8 February 2019, a Piper PA46-350P overran the landing runway at Courchevel and collided with a mound of snow which caused significant damage to the aircraft but only one minor injury to a passenger. The Investigation noted the Captain's low level of experience but the investigation effort was primarily focused on the risk which had resulted from a commercial air transport flight being conducted without complying with the appropriate regulatory requirements for such flights and without either the passengers involved or the State Safety Regulator being aware of this.

On 2 May 2016, a Boeing 737-800 veered off the 2,500 metre-long landing runway near its end at speed following a night non-precision approach flown by the Captain. It then stopped on grass having sustained damage to both the left engine and landing gear. The Investigation noted that a significant but allowable tailwind component had been present at touchdown and found that the approach had been unstable, the approach and touchdown speeds excessive and that touchdown had occurred beyond the touchdown zone after applicable operating procedures had been comprehensively ignored in the presence of a steep authority and experience gradient.

On 7 August 2020, a Boeing 737-800 making its second attempt to land at Calicut off a night ILS approach with a significant tailwind component became unstabilised and touched down approximately half way down the 2,700 metre-long wet table top runway and departed the end of it at 85 knots before continuing through the RESA and a fence and then dropping sharply onto a road. This caused the fuselage to separate into three pieces with 97 of the 190 occupants including both pilots being fatally or seriously injured and 34 others sustaining minor injuries. Significant fuel spillage occurred but there was no fire.

On 28 January 2019, an Airbus A320 became unstabilised below 1000 feet when continuation of an ILS approach at Muscat with insufficient thrust resulted in increasing pitch which eventually triggered an automatic thrust intervention which facilitated completion of a normal landing. The Investigation found that having temporarily taken control from the First Officer due to failure to follow radar vectors to the ILS, the Captain had then handed control back with the First Officer unaware that the autothrust had been disconnected. The context for this was identified as a comprehensive failure to follow multiple operational procedures and practice meaningful CRM.

On 19 October 2015, an ATR 72-600 crew mishandled a landing at Ende, Indonesia, and a minor runway excursion occurred and pitch control authority was split due to simultaneous contrary inputs by both pilots. A go around and diversion direct to the next scheduled stop at Komodo was made without further event. The Investigation noted that the necessarily visual approach at Ende had been unstable with a nosewheel-first bounced touchdown followed by another bounced touchdown partially off-runway. The First Officer was found to have provided unannounced assistance to the Captain when a high rate of descent developed just prior to the flare. 

 

Stabilised Approach Awareness Toolkit for ATC

Further Reading

CANSO

Part of the Stabilised Approach Awareness Toolkit for ATC

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