The accident happened whilst the Boeing 747 cargo aircraft was being landed on runway 23 at London Heathrow Airport (LHR). At touchdown the number 4 pylon forward bulkhead, which supports the front of the engine, began to break free of the pylon because of weakening by fatigue and other pre-existing damage. The resulting downward movement of the engine during the landing roll ruptured the engine fuel feed pipe and several other connections with the engine including engine monitoring and fire warning circuitry. The high volume of fuel issuing from the ruptured fuel pipe caused a severe fire to develop under the number 4 pylon. The fire continued until the crew physically observed the fire as the aircraft was being turned off the runway at block 77(0), at which point the fire drill was carried out. This resulted in the closure of the fuel shut-off valve in the wing. The aircraft was brought to a halt and the airport fire service quickly brought the residual fire under control. CAUSE: “The accident was caused by the failure of the forward bulkhead of the No 4 pylon when it was subjected to landing loads after it had been weakened by pre-existing fatigue. A major contributory factor was the absence of any routine check item which might otherwise have detected the onset of failure at an early stage.”