British Overseas Airways flight 712 was scheduled to leave London's Heathrow airport bound for Sydney at 3:15pm on April 8, 1968. On the flight deck was Captain C W R Taylor, First Officer F B Kirkland, Second Officer J C Hutchinson,and Engineer T C Hicks as well as Check Captain G C Moss. Along with a cabin crew of six, there were 116 passengers on board the Boeing 707 that afternoon. 712 departed Heathrow at 3:27pm and just after the landing gear was retracted, there was a shudder throughout the airframe and a loud bang from the port side.

 


712's Engine Falls Away

The port inboard engine throttle lever moved back towards idle and the instruments indicated that the engine had failed. Taylor called for the engine failure checklist and Hicks began the drill. As he pulled the throttle to full idle, the landing gear warning horn sounded (it sounds when the landing gear is up and the throttle is retarded). Hicks and Moss both reached to switch off the warning bell, but Moss hit it first and Hicks, not realizing that Moss had done so, inadvertently shut off the engine fire alarm warning as well. No fire drill was started. A few moments later, Moss looked out the port side window and saw that the engine was indeed on fire and told Taylor that he should head back to the airport as soon as possible. Taylor then noticed that the engine fire warning light was illuminated and commanded the fire drill be initiated. Hicks began the engine fire drill as Kirkland called Heathrow to declare the emergency and Taylor began his turn back to the airport. The fire was so strong that, before Hicks could complete the engine fire drill, the fire burned through the mounting structure and fell away as it was designed to do. The fire still burned and the loss of the engine caused a loss of hydraulic power to the landing gear and flaps. Luckily, Taylor had extended the landing gear and the flaps stopped 3 degrees short of the fully extended position. Taylor managed to get the 707 back on the ground smoothly and used reverse thrust on the two outboard engines to slow the aircraft. Unfortunately, the reverse thrust also deflected the flames toward the fuselage. As soon as the aircraft stopped, Taylor ordered engine fire and shutdown drills on the remaining three engines, but an explosion on the port wing caused him to order the cockpit abandoned. Meanwhile, cabin crews had prepared for the emergency exit, but the explosion and resulting fire prevented them from using the port side and rear exit doors. Both Hicks and Taylor had exited the aircraft and were helping passengers on the ground. The rest of the flight crew, after being blocked from exiting out the front galley doors, left via the cockpit. Evacuation remained somewhat orderly and all but five people were able to exit the aircraft before it was overcome by fire and smoke and totally lost.


 712 Burns on the Ground

Clearly some sort of malfunction had sparked a massive fire within the port inboard engine. Puzzling to the investigators was the magnitude of the fire and the crew's inability to control or extinguish it. In retracing 712's flight path, investigators found fragments of the engine's compressor blades near the departure end of the runway. Further along, a piece of the engine cowling which had been blown off and portions of the number 5 compressor wheel rim. Examination of the engine after recovery showed that the number 5 compressor wheel had disintegrated due to fatigue, it's debris being blown through the engine and severing the fuel feed lines and allowing fuel to flow freely into the engine. Examination of the aircraft after the fire was extinguished showed that none of the fire shutoff handles had been pulled nor had the fuel boost pumps been turned off. Pulling the fire shutoff handles closes the fuel shutoff valve for that engine, shuts off the supply of hydraulic oil, and arms the fire extinguishers. The investigation then turned to why the crew had failed to complete the drill as required. The first clue came in Hick's accidental disarming of the engine fire alarm bell. Since the bell did not sound, it seems that the crew did not initially believe the emergency was a fire. When Moss pointed out the fire, it is thought that the crew had a miscommunication during the command to start the engine fire drill. Hicks had already started the engine shutdown drill and then simply continued with the drill as it was the same as the engine fire drill with the exception of pulling the handle, the first item. Since the checklist had already been started, it is thought that Taylor believed his crew had already pulled the handle. Though the fire light remained on, when the engine feel away from the aircraft, the light would have gone off and the crew's attention would be lost. Because of this, BOAC combined it's engine failure and fire drills into one checklist, all of which had to be confirmed instead of beginning with memory items.