On 23 March 2004, an out of service British Airways Boeing 747-400, under tow passed behind a stationary Airbus A321-200 being operated by Irish Airline Aer Lingus on a departing scheduled passenger service in good daylight visibility and the wing tip of the 747 impacted and seriously damaged the rudder of the A321. The aircraft under tow was cleared for the towing movement and the A321 was holding position in accordance with clearance. The towing team were not aware of the collision and initially, there was some doubt in the A321 flight deck about the cause of a ‘shudder’ felt when the impact occurred but the cabin crew of the A321 had felt the impact shudder and upon noticing the nose of the 747 appearing concluded that it had struck their aircraft. Then the First Officer saw the damaged wing tip of the 747 and informed ATC about the possible impact. Later another aircraft, positioned behind the A321, confirmed the rudder damage. At the time of the collision, the two aircraft involved were on different ATC frequencies.
An investigation was carried out by the UK AAIB and found that the wing tip of the 747 would have been overhanging the paved extent of the taxiway being used even if on the taxiway centerline. This is shown on the diagram below, Figure 3 taken from the AAIB Report.
Collision geometry EICPE and GBNLK
It was established that the three-man towing crew had assumed that as they had been cleared to tow along the route used and were on the centreline, they would be clear of all obstacles. The investigation found that “this assumption of obstacle clearance was compounded by the lack of guidance information in the practices and procedures manuals for the towing crew. Nowhere in these manuals was there information on the responsibilities of the towing crew during towing operations, including information on obstacle clearance.”
The Investigation also found that the State Regulations governing the ground movement of aircraft not under the command of flight crew were not appropriately specified and that the content of the primary UK CAA generic guidance document was not sufficiently clear on towing responsibilities.
It was considered that “Like the towing crew, it might be expected that ATC should have predicted the collision and provided forewarning to the crew towing G-BNLK. However, the vantage point provided to the ground controller only enables the identification of obvious potential collisions and therefore the onus for obstacle clearance must rest with the person responsible for the aircraft, be it the towing crew or flight crew.” It was noted that this limit of responsibility was envisaged in generic UK ATC procedures contained in UK CAP 493 Manual of Air Traffic Services which states that an ATC service is provided to assist in preventing collision between aircraft on the manoeuvring area.
The Full Report of the Investigation may be seen at /bookshelf/books/1207.pdf. It contains three Safety Recommendations:
Safety Recommendation 2004-72
“The Civil Aviation Authority should consider amending Rule 37(2) of the Air Navigation Order (CAP363) to specifically make it the duty of those persons responsible for the towing of aircraft on manoeuvre areas of aerodromes to take all possible means to ensure that the aircraft under tow does not collide with another aircraft, or other obstacle, regardless of any Air Traffic Control or Ground Movement Control clearance.
CAA document CAP 642 Airside Safety Management provides guidance on safe operating practices at airports and includes various sections on the towing of 'dead' and 'live' aircraft. It also includes a large section on the use of vehicles on the airside part of an airport and the recommended training syllabus for the drivers. Nowhere does it mention that the towing crew of an aircraft under tow is responsible for obstacle and wingtip clearance, indeed some of the guidance puts the onus back onto ATC for the provision of this clearance. Although, Chapter 2 'Managing the Risks', Section 5 'Moving Aircraft' states:
'The movement of aircraft on the ground, either under their own power or towed, creates a number of hazards that are unique to the aviation industry. In particular operating jet or propeller engines can cause fatal or serious injuries and extensive damage to equipment or other aircraft.',
This document neither expands the information above for the towing of aircraft in airport manoeuvring areas, nor does it specifically identify the hazards, such as wingtip clearance, nor does it provide guidance on how to avoid them. Also omitted from these documents is any guidance to the towing crews on what action should be taken, if there is need to obtain clarification or assistance should a potential hazard present itself. It is therefore recommended that:”
Safety Recommendation 2004-73
“The Civil Aviation Authority should enhance CAP 642 Airside Safety Management to include guidance on the responsibilities of towing crews of aircraft under tow, especially with regard to obstacle and wingtip clearance in aircraft manoeuvring areas so that such clearance is not inferred from ATC clearances to tow an aircraft.
The operator, who had in turn been trained by the airport authority, provided the training for the towing crew. Nowhere in this training had there been any emphasis on the responsibilities of the crew whilst the aircraft is under tow, for maintaining a look out and ensuring obstacle and wing tip clearance. It is therefore recommended:”
Safety Recommendation 2004-74
“British Airports Authority plc should ensure that training of individuals for the issue of 'C' manoeuvring area licences, includes the responsibilities of drivers for obstacle clearance and that ATC clearance instructions does not infer obstacle or wingtip clearance.”