Summary: AAR 1/2009, 29 December 2006

139 © Crown copyright 2009 AAIB Bulletin: 2/2009 G-XLAC, G-BWDA and G-EMBO Air Accident Report 1/2009 AIRCRAFT ACCIDENT REPORT No 1/2009 This report was published on 9 January 2009 and is avaiable on the AAIB Website www.aaib.gov.uk REPORT ON THE SERIOUS INCIDENTS TO BOEING 737-81Q, G-XLAC, ON 29 DECEMBER 2006; AVIONS DE TRANSPORT REGIONAL ATR-72-202, G-BWDA ON 29 DECEMBER 2006 EMBRAER EMB-145EU, G-EMBO ON 29 DECEMBER 2006 AND BOEING 737-81Q, G-XLAC ON 3 JANUARY 2007 AT RUNWAY 27, BRISTOL INTERNATIONAL AIRPORT Three aircraft were involved in the principal events described in this report: (i) Aircraft No 1 (This aircraft was involved in two events) Registered Owner and Operator: XL Airways UK Ltd Aircraft Type and Model: Boeing 737-81Q Registration: G-XLAC Place of Incident: Runway 27, Bristol International Airport Latitude: 51º 22' N Longitude: 002º43' W Date and Time: (i) 29 December 2006 at 1150 hrs (ii) 3 January 2007 at 1832 hrs (ii) Aircraft No 2 Registered Owner and Operator: Aurigny Air Services Ltd Aircraft Type and Model: Avions de Transport Regional ATR-72-202 Registration: G-BWDA Place of Incident: Runway 27, Bristol International Airport Date and Time: 29 December 2006 at 1215 hrs (iii) Aircraft No 3 Registered Owner and Operator: British Airways CitiExpress PLC Aircraft Type and Model: Embraer EMB-145EU Registration: G-EMBO Place of Incident: Runway 27, Bristol International Airport Date and Time: 29 December 2006 at 2133 hrs All times in this report are UTC unless otherwise stated. 140 © Crown copyright 2009 AAIB Bulletin: 2/2009 G-XLAC, G-BWDA and G-EMBO Air Accident Report 1/2009 Synopsis The serious incidents involving G-BWDA and G-EMBO were notified to the Air Accidents Investigation Branch (AAIB) on 29 December 2006. An investigation into the two serious incidents began on 2 January 2007. During this investigation, the events involving G-XLAC, and others, were identified. All events took place during landings at Bristol International Airport, hereafter referred to as BIA. The AAIB investigation team comprised: Mr K Conradi (Investigator-in-Charge) Mr T J Atkinson (Operations) Mr S J Hawkins (Engineering) Mr C J Scott (Flight Recorders) Resurfacing and re-profiling work was taking place on parts of the runway at BIA as part of a major project to resurface the manoeuvring area pavements, and sections of the runway surface were ungrooved ‘base course’ asphalt. From 14 November 2006, there were reports from flight crew of a variety of problems related to the friction characteristics of the temporary runway surface, though no serious incidents occurred until 29 December 2006. On that day, the flight crew of G-XLAC experienced poor stopping performance during landing. Later that day, the flight crew of G-BWDA experienced stopping and lateral control difficulties during landing, and the aircraft departed the runway surface and came to rest on the grass area at the side of the runway. Later still, the flight crew of G-EMBO experienced lateral control difficulties during landing, and the aircraft partially left and then regained the runway. On 3 January 2007, another flight crew, also operating G-XLAC, experienced poor stopping performance. The airport was subsequently closed whilst grooves were cut in the base course. After it re-opened there were no further incidents. The investigation identified the following causal factors: 1. Reduced friction on the wet ungrooved base course sections of the runway caused flight crews to experience reduced braking action and reduced lateral controllability on landing in strong crosswinds. 2. The Flight Operations Department Communication (FODCOM) advice published by the CAA regarding operations on runways notified ‘slippery when wet’, in wet conditions, was not communicated by operators to flight crews. 3. The passing, by ATC, of braking action reports based on Mu-meter friction assessments, gave flight crews a false confidence in the braking action available on the wet runway. The investigation identified the following contributory factor: 1. G-BWDA landed in a crosswind outside the operator’s published limits and the subsequent use of reverse thrust was contrary to the advice contained in the company’s Operations Manual. The AAIB has made five Safety Recommendations. Findings The aircraft 1. There was no evidence of the aircraft involved in the incidents having experienced a technical fault. 2. The only damage was to G-BWDA, which suffered damage to its left propeller. 141 © Crown copyright 2009 AAIB Bulletin: 2/2009 G-XLAC, G-BWDA and G-EMBO Air Accident Report 1/2009 3. The tread depths and pressures of the tyres on the incident aircraft were, as far as could be determined, within allowable limits. The runway 4. The runway resurfacing work at Bristol Airport was complex because it involved an attempt to reshape parts of the runway prior to resurfacing. 5. Several separate areas of the runway had a temporary ungrooved base course Marshall Asphalt surface. 6. The runway resurfacing work was undertaken at night and during the winter to avoid disrupting flight schedules. 7. The longest stretch of ungrooved base course was the central runway portion and was 295 m long and covered the full width. 8. Marshall asphalt is not porous and, when used as a surface course, is usually grooved to allow water to drain to the side of the runway. 9. The surface friction of the ungrooved base course had not been assessed using a Mu‑meter with self-wetting in dry conditions predominantly due to the prevailing weather. There was a dry period on 8 December 2006 but no staff were available to conduct the runs. 10. Mu-meter runs carried out in wet conditions revealed that the ungrooved base course had significantly less friction than the grooved runway sections. 11. Mu-meter runs of the central ungrooved section, undertaken in natural wet and damp conditions, indicated that the friction of the ungrooved base course was probably below the Minimum Friction Level (MFL) of 0.50. 12. The airport operator’s risk assessment plan had not adequately addressed the hazards presented to aircraft operating on the temporary surfaces in wet and windy weather. 13. Runway surface contractors believed that temporary ungrooved base course did not represent a significant risk and were more concerned about limiting the length of ungrooved surface course to 100 m; no length limitation was specified for the ungrooved base course. 14. The information promulgated by NOTAM, that braking action information would be available during wet conditions, was incorrect. 15. Following the incidents investigated in this report, the airport operator closed the runway on 7 January 2007 and cut temporary grooves in the ungrooved base course. 16. The runway was re-opened on 8 January 2007; no further runway excursion or braking difficulty reports were received after this date. 17. The instruction in CAP 683 concerning friction assessment for resurfaced runways did not clearly include portions of runways which have been resurfaced. 142 © Crown copyright 2009 AAIB Bulletin: 2/2009 G-XLAC, G-BWDA and G-EMBO Air Accident Report 1/2009 18. The 295-metre full width section of runway surface covered with ungrooved base course asphalt did not provide adequate friction for safe operations when the runway surface was wet. 19. The airport authority was aware of the poor braking action provided by the ungrooved base course asphalt but did not take steps to increase the braking action available until 3 January 2007. Flight operations 20. A significant number of flight crews experienced difficulties decelerating the aircraft after landing. 21. The flight crews of two aircraft were unable to prevent their aircraft leaving the paved surface while landing in strong

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Summary: AAR 1/2009, 29 December 2006

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Summary AAR 1/2009. Boeing 737-81Q, G-XLAC; Avions de Transport Regional ATR-72-202, G-BWDA and Embraer EMB-145EU, G-EMBO

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