The fact is, whether these were the good fixes to the potential risks
Is that all risks have been taken into account to determine the solutions to bring ?
Or is that some risks have been set aside by the use of comforting statistics ?
With hindsight we know that the fixes applied were not enough to protect against fuel tank failure arising from a hydraulic shock inside the tank. But bearing in mind that this failure mechanism was completely unknown at that time (at least in the civil side of the industry) we can judge whether the fixes applied were consistent with giving adequate protection
against the 1979 state of the art from section1.16.4.2 of the BEA report.
The relevant parts of that section state:
Risk of fire. Based on the data about the leak in the accident, the study concluded that the risk of fire was limited, considering:
o that the size of the penetrations and the rate of flow of the leak are sufficiently low;
o that ignition cannot be caused by rubber or metal debris penetrating the tank;
o that the fuel leaks from tanks 6 and 7 follow the flow under the wing and remain generally parallel to the aircraft axis without meeting areas of separation and thus dissipate via the wing trailing edge .The secondary nozzle’s temperature is too low to ignite the fuel;
o that fuel from leaks in tanks 5 and 8 may accumulate in the landing gear well. Only the electrical circuits in this compartment constitute a possible source of ignition;
o that ignition of the fuel on contact with hot brakes would not definitely occur, bearing in mind the average temperature reached by the brakes;
o that in case of penetration of the tanks forward of the air intakes, leaks would be limited (due to the limited size of the debris taken into consideration) and could only enter the engine at a very low speed (after landing) and at a high thrust level
Most of the solutions then proposed were in fact put into effect and were the subject of Airworthiness Directives:
• AD of 14/01/8, applied from 21/01/81, calling for the installation of a system for detection of main landing gear tyre under-inflation. An improved version of this system was then applied by AD on May 15 1982,
• AD of 14/01/81, applied on 21/01/81, calling for improvements in protection in the normal braking hydraulic system,
• AD of 5/05/82, applied on 15/05/82, defining an inspection procedure for the main landing gear tyres and wheels before each takeoff,
• AD of 5/05/82, applied on 15/05/82, calling for the installation of new reinforced wheels in order to limit damage in case of contact with the ground and for new reinforced tyres capable of bearing twice the normal load (the regulations require one and a half times).
As a result of studies carried out on the risks of damage from pieces of tyre and on trials performed at the CEAT in 1980 to justify the integrity of the structure in case of direct penetration, it was concluded that it was not necessary to install protection for the underside of the wings.
1.16.4.2.2 Other Events
All of the tank penetrations that occurred after the Washington event involved aircraft operated by British Airways. It should be noted that after the modifications carried out after this event, tank penetrations following a tyre burst were caused only by secondary debris.
In most cases, this debris came from the destruction of equipment located in the landing gear area, probably dislodged by pieces of damaged tyre. The parts in question include the water deflector and the gear door latch.
Everyone will have their own view on this I'm sure - I'm staying out of it !