CONC, vicinity Paris Charles de Gaulle France, 2000
CONC, vicinity Paris Charles de Gaulle France, 2000
On 25th July 2000, an Air France Concorde crashed shortly after take-off from Paris CDG following loss of control after debris from an explosive tyre failure between V1 and VR attributed to runway FOD ruptured a fuel tank and led to a fuel-fed fire which quickly resulted in loss of engine thrust and structural damage which made the aircraft impossible to fly. It was found that nothing the crew failed to do, including rejecting the take off after V1 could have prevented the loss of the aircraft and that they had been faced with entirely unforeseen circumstances.
On 25th July 2000, a Concorde being operated by Air France on a passenger charter flight from Paris CDG to New York JFK caught fire as it rotated for take off from runway 26R in normal daylight visibility and subsequently failed to maintain altitude as the fire continued. The aircraft soon lost height and was destroyed by impact with a hotel situated just over 3 nm from the upwind end of the runway. All 109 occupants and four other persons on the ground were killed and 6 other people on the ground were injured.
An Investigation was carried out by the French Bureau d'Enquêtes et d'Analyses (BEA) with specific assistance from the UK AAIB because of the unusual shared responsibility for the aircraft type certificate between the UK and France. A preliminary report was published on 31 August 2000 followed by Interim Reports on 15 December 2000 and 10 July 2001.
In addition to the BEA "Technical Investigation" on July 26 2000, the French Government established a special “Commission of Inquiry” which “assisted the BEA in its work”. It was noted that eleven meetings had been held at which the Commission was informed of the progress of the BEA Investigation and, following discussion, it had then “approved the reports”. Also, in accordance with French law, a Judicial Inquiry in respect of the Accident took precedence over the BEA investigation and so all BEA activity at the accident site and examination of the various parts of the aircraft “were performed in coordination with those responsible for the judicial inquiry, strictly adhering to the procedures of that inquiry”. In this connection, “the accident site and the various parts of the aircraft (had remained) constantly under the control of the judicial authorities”.
The BEA investigation established that about 1700 metres along the runway, shortly after the aircraft had passed V1, and whilst accelerating through 175 KCAS, the front right tyre of the left main landing gear had run over a strip of metal which had fallen from another aircraft five minutes earlier. The explosive failure of this tyre had thrown tyre debris against the wing structure causing a rupture of fuel tank 5. Fire, fuelled by the leak, broke out almost immediately under the left wing. As rotation was begun at a speed of 183 KCAS some 15 kt before VR, marks on the runway showed that the aircraft was deviating to the left of the runway centreline. The crew were advised by the ATC that there were "large flames behind them". Almost simultaneously, thrust was suddenly lost from engine 2 as a consequence of debris ingestion and/or disruption of the intake airflow. The aircraft became airborne 2900 metres along the runway some ten seconds after rotation had begun, but the crew then found that, in addition to asymmetric thrust, they were unable to retract the landing gear. The aircraft flew for around a minute at a speed of 200 kt and at a radio altitude of 200 feet but, with only intermittent thrust from Engine 1, was unable to gain height or speed. When Engine 1 suffered a final loss of thrust, the aircraft "adopted a very pronounced angle of attack and roll attitude". Loss of thrust on engines 3 and 4 then followed as "a combination of deliberate selection of idle and by a surge due to excessive airflow distortion". Control was not regained.
The Investigation noted that:
" The crew had no way of grasping the overall reality of the situation. They reacted instinctively when they perceived an extremely serious but unknown situation, which they were evaluating by way of their sensory perceptions. Each time the situation allowed, they applied the established procedure in a professional way."
" (A) simulation (during the investigation) showed that a rejected take off would have led to a high-speed runway excursion. Under these conditions, the landing gear would have collapsed and with the fire that was raging under the left wing, the aircraft would probably have burst into flames immediately."
" Many pieces of the aircraft found along the track indicate that severe damage to the aircraft’s structure was caused in flight by the fire. Even with the engines operating normally, the significant damage caused to the aircraft’s structure would have led to the loss of the aircraft."
On the subject of the cause and effects on aircraft structure of tyre failure - in this case just a single tyre failure being the direct cause of a level of structural damage which resulted in a major fuel leak near a ready source of ignition - the investigation noted that:
"On Concorde, nineteen of the fifty-seven known cases of bursts/punctures were caused by foreign objects. All of this clearly shows that in addition to increased surveillance of runways and taxiways, it is becoming necessary to improve the resistance of tyres to damage. It is useful to note that certification imposes no dynamic destructive tests on tyres, which means that there is no indication of burst modes, the weight and size of debris. Nevertheless, with these factors, it would be possible to evaluate the energies released and to deduce the possible consequences on the aircraft’s structure."
The Causes of the Accident determined by the Investigation were as follows:
- High-speed passage of a tyre over a part lost by an aircraft that had taken off five minutes earlier and the destruction of the tyre.
- The ripping out of a large piece of tank in a complex process of transmission of the energy produced by the impact of a piece of tyre at another point on the tank, this transmission associating deformation of the tank skin and the movement of the fuel, with perhaps the contributory effect of other more minor shocks and /or a hydrodynamic pressure surge.
- Ignition of the leaking fuel by an electric arc in the landing gear bay or through contact with the hot parts of the engine with forward propagation of the flame causing a very large fire under the aircraft’s wing and severe loss of thrust on engine 2 then engine 1.
In addition, it was noted that “the impossibility of retracting the landing gear probably contributed to the retention and stabilisation of the flame throughout the flight.”
Following an initial assessment of the circumstances of the accident, the BEA and the UK AAIB issued the following Safety Recommendation on 16 August 2000:
- that the Certificates of Airworthiness for Concorde be suspended until appropriate measures have been taken to guarantee a satisfactory level of safety with regard to the risks associated with the destruction of tyres.”
This Interim Recommendation was subsequently rendered no longer applicable as a result of further progress in the Investigation about which full details were provided to the two manufacturers, the two operators and the jointly responsible airworthiness authorities, the UK CAA and DGAC. The latter two agencies then defined a list of requirements for a return of the aircraft type to service as follows:
- Installation of flexible linings in fuel tanks 1,4,5,6,7 and 8.
- Reinforcement of the electrical harnesses in the main landing gear bays.
- Modification of Aircraft Flight Manual (AFM) procedures so as to inhibit power supply to the brake ventilators during critical phases of flight and revision of the MEL to ensure that technical operational limitations cannot be applied for the tyre under-pressure detection system.
- Installation of Michelin NZG tyres and modification of the anti-skid computer.
- Modification of the shape of the water deflector and removal of the retaining cable.
- A ban on the use of volatile fuels and an increase in the minimum quantity of fuel required for a go-around.
Four further Safety Recommendations “specific to Concorde” were subsequently published having been brought directly to the attention of the airworthiness authorities and these were taken into account in the context of the aircraft’s return to service. One of these was applicable to both operators of the type (British Airways and Air France) as follows:
- that the airworthiness authorities, the manufacturers and the operators of Concorde reinforce the means available for the analysis of the functioning of aircraft systems and in-service events and for the rapid definition of corrective actions.
The other three were specific to the operation of the type by Air France:
- that Air France ensure that the emergency procedures in the section on Concorde utilisation in its Operations Manual be coherent with the Flight Manual.
- that Air France equip its Concorde aircraft with recorders capable of sampling at least once a second the parameters that allow engine speed to be determined on all of the engines.
- that the DGAC undertake an audit of Concorde operational and maintenance conditions within Air France.
Ten other Safety Recommendations described as ‘general’ were also made as a result of the investigation as follows:
- that the DGAC, in liaison with the appropriate regulatory bodies, study the reinforcement of the regulatory requirements and demonstrations of conformity with regard to aviation tyres.
- that the DGAC, in liaison with the appropriate regulatory bodies, modify the regulatory certification requirements so as to take into account the risks of tank damage and the risk of ignition of fuel leaks.
- that the DGAC ensure the rapid implementation of programmes for the prevention of debris on aerodromes. These programmes should involve all organisations and personnel operating on the movement area.
- that the ICAO study the technical feasibility of an automatic detection system for foreign objects on runways.
- that the FAA carry out an audit of Continental Airlines maintenance both in the United States and at its foreign sub-contractors.
- that the ICAO fix a precise timetable for the FLIREC group to establish propositions on the conditions for the installation of video recorders on board aircraft undertaking public transport flights.
- that the ICAO study the procedures for recording specific exchanges between cabin crew members and exchanges between the cockpit and the cabin.
- that the DGAC, in liaison with the appropriate regulatory bodies, study the possibility of installing devices to visualise parts of the structure hidden from the crew’s view or devices to detect damage to those parts of the aircraft.
- that the DGAC, in liaison with the appropriate regulatory bodies, study the possibility of modifying the regulatory requirements relating to new flight simulators so that they accurately reproduce the accelerations really experienced in the cockpit.
- that the ICAO put recommendation 8/1 of the AIG 99 meeting into practice in the shortest possible time and, while waiting for the results of this work, that the primary certification authorities ask manufacturers to immediately identify all potentially dangerous substances in case of an accident which are used in the manufacture of aircraft under their responsibility and to mention them in an explicit manner in documentation.
The Final Report of the Investigation was made public on 16 January 2002.
Editor's Note: This report is quite large (16Mb) and may therefore take some time to download depending on the speed of your internet connection.