Flight 4590 - The Paris Crash

Accident Investigation

The official investigation was conducted by France’s accident investigation bureau, the BEA, and it was published on 14 December 2004. It concluded that the crash was caused by a titanium strip, part of a thrust reverser, that fell from a Continental Airlines DC-10 (Continental Flight 55) to Houston that had taken off about four minutes earlier. This metal fragment punctured the Concorde's tyres, which then disintegrated. A piece of rubber hit the fuel tank and broke an electrical cable. The impact caused a shock-wave that fractured the fuel tank some distance from the point of impact. This caused a major fuel leak from the tank, which then ignited. The crew shut down engine number two in response to a fire warning but were unable to retract the landing gear, which hampered the aircraft's ability to climb. With engine number one surging and producing little power, the aircraft was unable to gain height or speed, entering a rapid pitch-up then a violent descent, rolling left. The impact occurred with the stricken aircraft tail-low, crashing into the Hotelissimo Hotel in Gonesse. According to the report, the piece of titanium from the DC-10 had not been approved by the U.S. Federal Aviation Administration.

Conclusions

The investigators concluded that:

• After reaching take-off speed, the tyre of the number 2 wheel was cut by a metal strip lying on the runway, which came from the thrust reverser cowl door of the number 3 engine of a Continental Airlines DC-10 that had taken off from the runway several minutes before. This strip was installed in violation of the manufacturer's rules.
  
• The aircraft was slightly overloaded by about a ton.
  
• The aircraft was airworthy and the crew was qualified. The landing gear that later failed to retract had not shown serious problems in the past. Despite the crew being trained and certified, no plan existed for the simultaneous failure of two engines on the runway, as it was considered highly unlikely.
  
• Aborting the take-off would have led to a high-speed runway excursion and collapse of the landing gear, which also would have caused the aircraft to crash.
  
• While two of the engines had problems and one of them was shut down, the damage to the plane's structure was so severe that the crash would have been inevitable, even with the engines operating normally.

Alternative Theories

British investigators and former French Concorde pilots looked at several other possibilities that the report ignored, including an unbalanced weight distribution in the fuel tanks and loose landing gear. They came to the conclusion that the Concorde veered off course on the runway, which reduced take-off speed below the crucial minimum. The aircraft had passed close to a Boeing 747 carrying French President Jacques Chirac who was returning from the 26th G8 summit meeting in Okinawa, Japan, which was much further down the runway than the Concorde's usual take-off point; only then did it strike the metal strip from the DC-10.

The Concorde was overweight for the given conditions, with an excessively aft centre of gravity and taking off downwind. When it stood at the end of the runway, ready to roll, it was over its approved maximum take-off weight for the given conditions.

The Concorde was missing the crucial spacer from the left main landing-gear beam that would have made for a snug-fitting pivot. This compromised the alignment of the landing gear and the wobbling beam and gears allowing three degrees of movement possible in any direction. The uneven load on the left leg’s three remaining tyres skewed the landing gear, with the scuff marks of four tyres on the runway showing that the plane was veering to the left.

Finally, Brian Trubshaw and John Cochrane, the Concorde's two test pilots when the aircraft was being developed in the early 1970s, set the aft operating limit at 54 percent - beyond that, they found, it risked becoming uncontrollable, likely to rear up backwards and crash, exactly as Flight 4590 did in its final moments over Gonesse. However, Flight 4590's centre of gravity went beyond 54 percent, with the BEA stating a figure of 54.2 percent, while a senior industry source said that the true figure may have been worse: with the extra fuel and bags, it may have been up to 54.6 percent.