ASW #3: Accident Review: FOD Brings Down the Concorde
The third day of Airport Safety Week sees one of the annual event’s most enduring activities - the FOD walk. As I am not currently working on an airport or in Australia, I am going to miss taking part this year. Instead, I thought I would offer an analysis of the 2000 Concorde disaster as it would have to be the most significant FOD-related accident in history.
The following analysis is very limited. I just want to focus on the presence of the FOD on the runway, its immediate impact on the aircraft and factors associated with FOD detection and prevention.
Like all aviation disasters, this accident was the culmination of a complex set of variables interacting in a multitude of ways with identifiable and hidden feedback loops over short and long periods of time. The aftermath of this accident raises plenty of additional issues surrounding the criminalisation of accidents and just culture. But I will try to stay on point…
I’ll try.
À Paris, en Julliet
At approximately 4:40 pm, on the 25th July 2000, one of Air France’s Concordes (registration F-BTSC) lined up on runway 26 right at Roissy Charles de Gaulle airport (IATA: CDG) for its last flight. Operating as AFR 4590, the flight was a charter flight to New York where the 100 passengers were meant to meet up with a cruise destined for Ecuador. The flight was being operated with nine crew members on board.
After a short wait on the runway, AFR 4590 was cleared for take-off. The pilot flying advanced the throttles and a little over 30 seconds later, the aircraft passed its decision speed (otherwise known as V1). Very quickly after this, a tyre on the left main landing gear burst.
This triggered a complex chain reaction that resulted in the rupture of a left wing fuel tank, the ignition of the escaping fuel, the partial and complete loss of power from the left engines, damage to the landing gear retraction mechanism and the deterioration of the wing and control surface structures.
The result of this was an aircraft designed for speed not being able to accelerate or climb. The aircraft lumbered on for a short time, lost height and crashed into the La Patte d’Oie hotel a little less than eight kilometres from the airport.
Everyone on the aircraft died and four people on the ground died as well. There was an additional six people on the ground injured.
Le Coupable
The painstaking investigation followed the clues from the wreckage site back to the burst tyre on take-off and then to the discovery of a strip of titanium alloy found on the runway. The strip was found to be from an aircraft other than the Concorde but laboratory analysis found evidence of black marks and black elastomer deposits of a similar signature to the material found in the Concorde’s tyres.
This metallic strip was and has become the prime example of runway FOD - Foreign Object Debris.
Investigators set about finding the aircraft from which this metallic strip fell. They focussed on the aircraft that had departed the runway in the two hours prior to the ill-fated take-off. With the list of potential aircraft narrowed, the investigators determined that the strip was most likely a wear strip from a CF6-50 type engine with a Continental Airlines DC-10 having that type of engine departed CDG five minutes before AFR 4590.
The wear strip found on the runway
Technical and laboratory analyses showed that the part had come from this aircraft. Records also showed that another aircraft, an Air France B747, had departed the runway between the DC-10 and the Concorde.
Inspections de Piste
While FOD Radars are gaining traction around the world, in 2000, nearly all airports relied on, and most still rely on, runway inspections to ensure that FOD is not present on the runway. I think it is important to note, before discussing the investigations findings, that inspections cannot guarantee a FOD-free runway as there will like have been multiple aircraft movements between inspections. As noted above, the metallic strip sat on the runway for only five minutes before it triggered this disaster.
However, the investigation report notes the following:
There were no national standards for runway inspections at the time.
The Annex 14 standards and recommended practices, current at the time, called for a minimum of two inspections per day.
The aerodrome operator’s procedures called for three inspections per day with the first before 7:00 am, the second around 2:00 pm and the third around 9:00 pm.
The afternoon inspection on the day of the accident had only been partially completed due to other activities on the runway.
Further analysis by the BEA led to a couple of further observations and conclusions:
Runway inspection regimes lacked a certain standing in the minds of the aerodrome industry. As noted above, no national requirements existed and aerodrome operators were left to their own initiative. While CDG stated in its procedures that it would conduct three daily inspections, it averaged closer to two a day meaning that these inspections were often de-prioritised when faced with constraints.
The handling of the discovery of FOD on the runway was also called into question. There was no systemic approach to determining the origin of found FOD nor were robust statistics or monitoring systems maintained.
In conclusion, the investigators did acknowledge that the reliance on inspections alone to prevent FOD-related risk was “inconceivable.” They noted that increasing inspections would have limited impact and be available only to aerodromes with light traffic. They mentioned the benefit of a “permanent automatic detection system” but this type of system did not make it into the recommendations.
Tout Pour Rien?
So, if there was nothing that an inspection could do, why did I just write up this post?
Risk. I recommend taking a risk-based approach to runway inspections. Actually, take a risk-based approach to FOD in general. In fact, I wrote about this concept just over nine years ago.
In my risk model for FOD incidents, I noted that a “susceptible aircraft” might demand a higher level of intervention and even noted the Concorde as such an aircraft worthy of a dedicated pre-flight inspection.
A nine-year-old diagram (recycling, yay!)
Of course, hindsight is 20/20 and I can’t claim that I would have been able to avoid this disaster. But that is not why we share these stories and thoughts and ideas. We hope to avoid the next disaster.
Tomorrow is Safety Management Systems and as a Thursday, it might have to be a cheat day ;).
Images: Header : (cc) Daniel Mennerich, Metal Strip: (c) AP File & Diagram: Dan Parsons
