CRITICAL LESSONS PILOTS SHOULD LEARN FROM THE APRIL 1968, BOEING 707 – 465 BRITISH AIRWAYS CRASH
55 years ago and to be precise, the 8th of April 1968 in the United Kingdom, British Overseas Airways Corporation Flight 712, an international scheduled passenger flight from London-Heathrow Airport (LHR/EGLL), United Kingdom, to Zürich-Kloten Airport (ZRH/LSZH), Switzerland, operated with a Boeing 707-465, registration G-ARWE, experienced an uncontained engine failure and a subsequent emergency landing at London-Heathrow Airport (LHR/EGLL), United Kingdom.The airplane was destroyed by the ensuing post crash fire. A flight attendant and four passengers died in the accident. The remaining ten crew members and 112 passengers survived. (122 survivors, 5 fatalities)
LOOKING INTO THE DETAILS:
The aircraft was operating Flight BA 712 from London-Heathrow Airport to Zürich and Sydney. A check pilot was on the aircraft for the purpose of carrying out a route check on the pilot-in-command. The aircraft became airborne from runway 28L at 15:27 and 20 seconds later, just before the time for the noise abatement power reduction, the flight crew felt and heard a combined shock and bang. The thrust lever for the No. 2 engine “kicked” towards the closed position and at the same time the instruments showed that the engine was running down. The captain ordered the engine failure drill. Because the undercarriage was retracted, the warning horn sounded when the flight engineer fully retarded the thrust lever; the check pilot and flight-engineer simultaneously went for and pulled the horn cancel switch on the pedestal whilst the co-pilot instinctively but in error pressed the fire bell cancel button. In front of him the flight-engineer went for the engine fire shut-off handle but he did not pull it. The check pilot then reported seeing a serious fire in the No. 2 engine. Having initially started an engine failure drill, the flight engineer changed directly to the engine fire drill. ATC originally offered the pilot-in-command a landing back on runway 28L and alerted the fire services but after a “Mayday” call Flight 712 was offered runway 05R which was accepted as it would result in a shorter flight path. About 1,5 minutes after the start of the fire,
No. 2 engine, together with part of its pylon, became detached and fell into a waterfilled gravel pit. At about the time the engine fell away the undercarriage was lowered and full flap selected. The undercarriage locked down normally but the hydraulic pressure and contents were seen to fall and the flaps stopped extending at 47deg, that is 3deg short of their full range. The approach to runway 05R was made from a difficult position, the aircraft being close to the runway and having reached a height of about 3000 feet and a speed of 225 kt. There is no glide slope guidance to this runway but the approach was well judged and touchdown was achieved approximately 400 yards beyond the threshold. The aircraft came to a stop just to the left of the runway centre line, about 1800 yards from the threshold.
After the aircraft came to rest the flight engineer commenced the engine shut-down drill and closed the start levers. Almost simultaneously the pilot-in-command ordered fire drill on the remaining engines. Before this could be carried out there was an explosion from the port wing which increased the intensity of the fire and blew fragments of the wing over to the starboard side of the aircraft. The pilot-in-command then ordered immediate evacuation of the flight deck. The engine fire shut-off handles were not pulled and the fuel booster pumps and main electrical supply were not switched off. There were more explosions and fuel, which was released from the port tanks, spread underneath the aircraft and greatly enlarged the area of the fire.
The cabin crew had made preparations for an emergency landing and as the aircraft came to a stop opened the emergency exits and started rigging the escape chutes. The passengers commenced evacuation from the two starboard overwing exits and shortly afterwards, when the escape chutes had been inflated, from the rear starboard galley door and then the forward starboard galley door. However, because of the spread of the fire under the rear of the fuselage the escape chute at the rear galley door soon burst and, following the first explosion, the overwing escape route also became unusable. The great majority of the survivors left the aircraft via the forward galley door escape chute.
“The accident resulted from an omission to close the fuel shut-off valve when No. 2 engine caught fire following the failure of its No. 5 low pressure compressor wheel. The failure of the wheel was due to fatigue. The following findings were reported:
i) The number 2 engine fifth stage low pressure compressor wheel failed due to fatigue. The reason for this has not been established,
ii) The failure of the No. 2 engine compressor wheel caused damage to the starboard side of the engine and to its cowling. This resulted in a fuel leak from the engine fuel supply line and a fire,
iii) After starting and before completing an engine overheat or failure drill, it became necessary for the crew to carry out a fire drill,
iv) The co-pilot cancellation of the fire bell instead of the undercarriage warning horn prevented the fire bell from ringing,
v) The closure of the fuel shut-off valve by pulling the fire handle was inadvertently omitted by the flight engineer when he carried out the fire drill. The omission was not noticed by the pilot-in-command, the co-pilot or the Check pilot. The Second Officer was in no position to observe the situation,
vi) The failure to close the fuel shut-off valve permitted the fire to continue,
vii) The BOAC fire and engine overheat or failure drills in force at the time were capable of misapplication under stress,
viii) The overall efficiency of the airport fire service was seriously reduced by some appliance deployment and equipment failures. However, they were successful in preventing the spread of the fire to 3 000 gallons of fuel in the starboard wing of the aircraft.”