GL6T, Prestwick UK, 2014
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|On 6 March 2014, a Bombardier Global 6000 being landed by a pilot using a HUD at night was mishandled to the extent that one wing was damaged by ground contact due to excessive pitch just before touchdown. During the Investigation, a Global 6000 operated by a different operator was similarly damaged during a night landing. The Investigation discovered that relevant operational documentation was inconsistent and pilot training had (in both cases) been inappropriate. These issues were resolved by a combination of aircraft manufacturer and aircraft operator action|
|Actual or Potential
|Human Factors, Loss of Control|
|Aircraft||BOMBARDIER Global 6000|
|Operator||TAG Aviation Espana|
|Type of Flight||Public Transport (Passenger)|
|Intended Destination||Glasgow Prestwick Airport|
|Take off Commenced||Yes|
|Location - Airport|
|Airport||Glasgow Prestwick Airport|
|Tag(s)||Extra flight crew (no training),|
Inadequate Aircraft Operator Procedures,
HUD used by PF
Ineffective Monitoring - PIC as PF,
Unintended transitory terrain contact,
Aircraft Flight Path Control Error
|Tag(s)||Strong Surface Winds|
|Damage or injury||Yes|
|Causal Factor Group(s)|
On 6 March 2014, a Bombardier Global 6000 (EC-LTF) being operated by TAG Aviation España on a passenger flight from Madrid to Prestwick made abnormal contact with the runway during touchdown at destination and, after a normal taxi in, was found to have been damaged as a result. The flight involved was serving as a Line Check for the aircraft commander which was being conducted from the supernumerary crew seat.
The event was investigated by the UK Aircraft Accident Investigation Branch (UK) (AAIB). Flight Data Recorder (FDR) and Cockpit Voice Recorder (CVR) data were available and used to assist the Investigation.
It was established that the routine revenue flight was being used as part of an annual line check on the operating aircraft commander conducted from the supernumerary crew seat. The flight was uneventful until the commander began the night ILS approach to runway 12 at Prestwick. The A/T and AP were engaged for the approach, the former throughout, the latter until it was disengaged at 400 ft agl. The HUD fitted above the left glareshield was in use during the approach in accordance Operator SOPs for all approaches.
The Reference Speed (Vref) for the planned flap 30 landing was 112 KIAS and with no gusts reported (the wind velocity passed with the landing clearance was 190º/12 knots - a crosswind component of 11 knots) this was used as the target speed for the approach. Once the AP had been disengaged, the commander continued to compensate for the crosswind by pointing the aircraft nose to the right of the runway centreline. At approximately 100 ft agl, "a nose-down control column input caused the rate of descent to increase and the aircraft deviated below the ILS GS". A right wing down attitude began to develop and, at 85 feet agl, with about 330 metres to go to the displaced threshold, left rudder was applied and the aircraft began to align towards the runway centreline as a rapid roll to the left occurred. In response to what he subsequently states he believed to be a gust of wind, he made a control wheel input to the right and after briefly centring the rudder then applied left rudder and, passing 50 feet agl, commenced a flare by pitching to about 7.5º nose-up. The wings were then held in a near level attitude "which required an average control wheel input of 35º to the right but with the rudder pedals almost neutral". After this attitude had been maintained for approximately four seconds, a yaw to the right began. At a recorded 6 feet agl, the airspeed had decayed to Vref - 6 knots and the flare was increased by pitching up quickly to "about 11.7º". In response to a concurrent rapid roll to the right, the control wheel was moved about 50º to the left but the roll continued, reaching nearly 12º before reversing. In this nose-high attitude, the right wing contacted the runway and shortly afterwards the right MLG compressed with the right wing still 7º down at Vref - 13 knots. A roll left then again right followed and the aircraft landed left of the centreline with about 3.5º right wing down. Neither of the operating crew or the Check Captain were aware that there had been a wing strike.
The aircraft was taxied to the terminal where the passengers disembarked and the Check Captain then sat in the cabin while the aircraft was taxied to an overnight parking position. There, a tug driver working on another aircraft reported that he had seen sparks from the vicinity of the aircraft when it landed. The runway was inspected and marks indicative of a wing strike were found to the right of the centreline between the displaced threshold and the usual touchdown point. A subsequent inspection of the aircraft then revealed corresponding damage to the right wing.
A more detailed examination found abrasion of the composite wingtip in three positions, the heaviest having worn through the skin to expose the aluminium wing structure beneath. The damage to the rear of the wingtip extended onto the corner of the wing trailing edge and as the flaps and slats had been extended, the corner of the leading edge slat and the rear tip of the outboard flap track fairing had both been planed flat. Further damage was found to the outboard trailing edge of the aileron and the static wicks locates furthest outboard on the aileron were missing. It was noted that no pre-impact technical issues were identified that may have affected the handling of the aircraft during the accident landing.
The Check Captain stated that he felt that the commander used the correct crosswind technique and that the aircraft had been affected by a sudden gust prior to touchdown to which he took the commander's very quick control input in the last 10 feet to be a response to. All three pilots shared the same view on what the standard crosswind landing technique should be - crabbed towards the wind until just before touchdown with the rudder then used to align the aircraft with the runway using an aileron input to keep the wings level.
It was noted that the commander had made comments during the taxi from the terminal to the overnight parking position about the effect of the HUD (not fitted to the other pilot position) saying that "it produced a bright green glow which had disorientated him" and had "acted a bit like a mirror" and impeded his view of the runway. He followed this by stating that in future he would not use the HUD at night in windy conditions although later, he said that he was comfortable using the HUD but that "at night, in good weather conditions, it may become difficult to see some of the symbols on the HUD when there are bright lights in the vicinity of the runway" and that "if the HUD brightness is turned up to counteract this, the effect can be to flood the screen with green light from the symbology (so) that it may then be difficult to discern the runway and its immediate surroundings through the screen". The Investigation examined the AFM and other relevant Manuals and noted that the former gave the maximum demonstrated crosswind component for takeoff and landing as 29 knots with no additional crosswind limit relating to use of the HUD for a Category 1 ILS approach. It was noted that neither the AFM, the FCOM or the OM Part 'B' provided any guidance on crosswind landing technique. It was noted that an 'Operations Reference Manual' (ORM) and a 'Pilot Training Guide' which were not part of the Operator's approved documentation also existed and that the crew were "expected to refer to them" in relation to recurrent simulator training details. Overall, there was a degree of complexity and some inconsistency between the various sources of 'SOP'. The view of the three pilots on how a crosswind landing should be conducted was found to correspond to the introduction to the subject in the ORM but this material was not included in the FCOM.
In respect of HUD use Bombardier provided the Investigation with some comments from their senior engineering test pilot who said that pilots who were new to HUDs had to learn not to fixate on the screen but to “look through” it, otherwise their peripheral view of the outside world could be affected. He also said that each pilot needed to find the level of screen brightness which they were most comfortable with. He advised finding that new pilots initially tended to set the brightness level too high and this could cause the HUD symbology to become a distraction, particularly during a landing with a significant crosswind. He was of the view that to reduce the chances of fixation on the screen, pilots flying an aircraft fitted with a HUD should aim to use it all the time. Bombardier also shared with the Investigation the opinion on HUD use of one of its customers who said that his personal preference was to turn the HUD off for a crosswind landing because it "channelised" his visual cues and did not help him to de-crab the aircraft whilst keeping the wings level.
On 17 April 2014 whilst the Investigation was in progress, another Global 6000 (CS-GLB) suffered a similar wing tip strike during a night crosswind landing at Luton. Although the circumstances were slightly different, this crew were also unaware that a wing strike had occurred and the pilot involved, who had been using the HUD, believed that his technique had been in accordance with that included in his Company OM Part 'B'.
Safety Action taken by Bombardier as a result of both these accidents included an amendment to the Global 6000 FCOM to include the recommended technique for a crosswind landing which was already published in the same document for other Global variants and in the Global 6000 ORM. A number of improvements to training materials for wingtip strike avoidance and HUD use were also made. The operators of both aircraft involved in these accidents also undertook various actions including changes to make their FDM programmes more relevant to the management of the crosswind landing risk and the provision of additional pilot training on crosswind landing technique.
The Final Report was published on 14 August 2014. No Safety Recommendations were issued as a result of the Investigation and no concise summary of the findings or a formal conclusion was included.
- Cross Wind Landings
- Head Up Display
- Situational Awareness
- Error Management (OGHFA BN)
- Managing Interruptions and Distractions (OGHFA BN)
- Vision (OGHFA BN)
- Pilot Perception
- Crosswind Landings, Flight operations briefing notes, AIRBUS