On 24 November 2014, a privately-operated Gulfstream III (N103CD) carrying 5 passengers left the paved surface whilst attempting to take off from runway 03 at Biggin Hill for a flight to Gander, Newfoundland at night and in low visibility caused by fog patches. The aircraft came to a stop on grass to one side of the runway and was evacuated. There were no injuries to the seven occupants but the extent of the structural damage sustained led to the aircraft being declared a hull loss.
The aircraft as it came to rest, showing area of skin crease and rupture (reproduced from the Official Report)
An Investigation was carried out by the UK AAIB. The aircraft was fitted with a 30 minute CVR and a 25-hour FDR but the tape based CVR was found to have an inoperative mechanism drive motor and yielded no data relevant to the accident. The FDR, which was not required to be fitted to the aircraft, was found to record only basic parameters and the data were not of sufficient quality to be useful to the investigation. It was noted that the only FDR-related scheduled maintenance was in respect of the ULB which was attached to it.
The built-in GPS receivers installed in two of the three iPads recovered from the aircraft facilitated a re-construction of the ground track of the aircraft during the attempted take-off using data from their NVM. Whilst the accuracy of the GPS position is "less effective when used within an aircraft" and the accuracy of the recorded tracks was not known, "the two recordings were largely consistent with each other". The recorded ground speed was found to have reached a maximum of about 70 knots during the take-off attempt and the ground track (see the illustration below) was found to be along the right-hand edge of the runway terminating at a position consistent with the final stopping position of the aircraft.
The recorded ground track of the aircraft. The field of view around the time of the accident of a CCTV installation from which recordings were examined to assess visibility is also shown. (Reproduced from the Official Report)
It was noted that the 36 year old aircraft commander had 4120 hours total flying experience of which 3650 hours were on the accident aircraft type. It was established that having been advised of the METAR issued 10 minutes prior to the attempted take-off which included wind calm, visibility in excess of 10 km with fog patches and a temperature/dew point split of 1º C, the crew had been cleared to taxi to holding point J1 for a runway 03 departure and had read it back correctly. The controller had then advised that "we are giving low level fog patches on the airfield, general visibility in excess of 10 km but visibility not measured in the fog patches; it seems to be very low, very thin fog from the zero three threshold to approximately half way down the runway then it looks completely clear" and this was also acknowledged.
Having reached the clearance limit and stopped, the aircraft was then cleared for take-off. On-site and recorded evidence showed that when the aircraft had then been taxied towards the runway from J1, it had failed to follow the taxiway centreline and its continuation as a lead-on line to the marked but unlit runway centreline. Instead, it had been lined up with the left main wheels in line with the runway edge lights (see the diagram below). These edge lights were positioned 3 metres to the right of the runway edge and located in a disused paved surface area and because this part of the runway was prior to the displaced landing threshold, they were red. In addition, with pavement to their right not available for aircraft use, they were embedded in the surface rather than mounted on short poles.
The area near the threshold of Runway 03 (reproduced from the Official Report)
The take-off run took the aircraft over this unmarked paved surface - which was at a 30º slant to the runway - for approximately 248 metres before it ran onto the grassed soft ground which lay beyond. Once he realised what had happened, the commander, who was PF rejected the take-off. Once the aircraft had stopped, the crew shut down the engines and all occupants evacuated the aircraft. There was no communication with ATC and the controller was initially unsure what had happened as "he could see only the top of the fuselage and tail above the layer of fog". However when he saw that all the aircraft lights had been extinguished, he had activated the crash alarm and two minutes later the airport emergency plan was activated when the AFS reached the aircraft and declared an aircraft accident.
It was found that on leaving the paved surface, all the aircraft wheels had immediately sunk approximately 0.25 metres into the ground and there were indications that the aircraft had begun to oscillate about the main landing gear. After travelling for 120 metres across the grass, the nose landing gear and the radome had detached and the aircraft had eventually come to a stop in line with the PAPI after a take-off run of slightly over 400 metres. After passing the displaced threshold lights, beyond which the white edge lights were on poles located in the grass, the left main wheels had damaged two of these lights. When the nose landing gear separated from the aircraft, it was found that it had struck the lower fuselage approximately 0.3 metres aft of its bay and torn a 6.5 metres long hole in the skin. A number of frames in this area were damaged, all aerials mounted on the forward lower fuselage were found to have been detached, and there was a crease and rupture in the skin over the top of the forward fuselage as annotated in the first illustration above.
It was discovered that neither the aerodrome chart published in the AIP nor the proprietary equivalent available to the crew on their iPads effectively depicted the detail of the area where taxiways, including the one used by the accident aircraft, intersected with the beginning of runway 03. The AIP was found to contain the following off-chart text caution but this information was not available to the crew:
The width at both ends of Runway 03/21, is twice that delineated by the associated edge lights due to extra pavement at one side. Since runway centre-line lighting is not installed, pilots should ensure that they are correctly lined up, especially if take-off is at night or when the runway is contaminated or in low visibility.
The requirements for reporting visibility and related phenomena in UK METARS were reviewed. It was noted they required that 'fog patches' should be reported when "fog, 2 metres or more deep, is present on the aerodrome in irregularly distributed patches" and that if visibility in any direction other than that on which the overall meteorological visibility report is based is less than 50% of that visibility, then this reduced visibility must also be reported.
The regulatory context for the accident flight was examined and FAR Part 91 was found to have been applicable to the operation of the aircraft. This requires that when such an aircraft is operated outside the USA, such operations "must comply with the regulations relating to the flight and maneuver of aircraft there in force". The applicable UK regulations were found to state that an aircraft "must not take off when the relevant runway visual range is less than 150 metres otherwise than under and in accordance with the terms of an approval to do so granted in accordance with the law of the country in which it is registered". Additional UK regulations (UK CAP 168 Chapter 6) were also noted to prohibit any take-off from a runway without centreline lights when the RVR is below 400 metres. It was noted that there were no procedures for the measurement of RVR in respect of the departure end of runway 03 at Biggin Hill.
UK requirements for taxiway edge marking, (UK CAP 168 Chapter 7) where a contiguous paved surface not available for use was present, were found to require a specified marking (see the diagram below) which was not present at either of the locations where it should have been - the eastern side of the ORP at the beginning of Runway 03 where part of it is used as taxiway 'C', and the boundary between the southern end of the same ORP and taxiway 'J'.
The Investigation considered the issues surrounding the perception of runway lighting in conditions of poor visibility at some length and noted that "lighting standards are largely based on the tungsten light bulb technology that was prevalent at the time the standards were promulgated", whereas "LED lighting technology has since improved the capability of lights to hold colour over varying power ranges and over time and has (also) improved directional control of lighting”.
An extract from UK CAP 168 showing the required edge markings for taxiways designated within more extensive paved areas (reproduced from the Official Report)
A number of previous similar events which had been independently investigated was noted including:
The content of the 2010 Australian Transportation Safety Board (ATSB) Report 'Factors influencing misaligned take-off occurrences at night' was noted by the Investigation as applicable to many of the issues in the investigated event and other similar ones - in particular the identification in this report of issues related to lighting, surface marking and the presence of areas of additional but unavailable pavement peripheral to runway and taxiway lateral limits. It was noted that five of the factors identified in the ATSB Report as being present in misaligned take-offs were applicable in the investigated event:
- It was dark.
- It was potentially a confusing taxiway environment given that the aerodrome chart did not reflect the actual layout of the taxiways. Pilots had previously reported difficulty near the runway 03 threshold because of a lack of taxiway lighting.
- There was an additional paved area adjacent to the runway.
- There was no runway centreline lighting and the runway edge lights before the displaced threshold were recessed.
- Reduced visibility had prevailed.
The Conclusion of the Investigation was that:
"It appeared that the information available to the crew caused them to develop an incorrect expectation of their route to the runway. Both crew members believed that the runway had centreline lighting and, when the first right turn almost lined the aircraft up with some lights, their incorrect expectation was reinforced and they believed that the aircraft was lined up correctly. Cues to the contrary, such as runway edge lights on the other side of the runway, or the fact that the first three lights ahead of the aircraft were red (indicating that they were edge lights before the displaced threshold), did not appear to have been strong enough to make the crew realise that they had lost situational awareness."
It was also concluded in the particular respect of runway lighting that:
“The dominant common factor between this accident and other misaligned takeoffs is that a visually compelling line of edge lights was visible to the crew and was assumed to be centreline lighting. There is nothing inherent in an individual edge light that distinguishes it from a centreline light when viewed along the axis of the bi-directional element. It is the pattern of edge lights, and the relationship of this pattern to the pattern of other lights and to other visual cues, which identifies them as edge lights. If this complex relationship becomes disrupted or misinterpreted, perhaps for the reasons highlighted in the ATSB report, pilots can lose situational awareness. If individual edge lights could be identified as such directly, rather than through a process of interpretation, a crew would notice their error more easily should they line up for takeoff incorrectly."
Safety Action taken as a result of the investigated accident was noted as having included the following:
- Biggin Hill Airport installed reflective studs to delineate the taxiways and runway access points around the Runway 03 threshold as a temporary measure ahead of more permanent improvements to taxiway lighting. This action was intended to reduce the risk that crews following the taxiway around the first right turn after J1 would proceed straight ahead, as the aircraft in this accident did.
- The Chart Supplier involved added the cautionary information noted during the Investigation to the Biggin Hill AIP entry in its UK Chart Change Notices, pending a corresponding revision of its Biggin Hill Airport Diagram Chart.
One Safety Recommendation was made as a result of the Investigation as follows:
- that the International Civil Aviation Organisation initiate the process to develop within Annex 14 Volume 1, ‘Aerodrome Design and Operations’, a standard for runway edge lights that would allow pilots to identify them specifically, without reference to other lights or other airfield features. (2015-038)
The Final Report of the Investigation was published on 10 December 2015.