Fire and Smoke — Page 160, Lesson 254

I want to walk you through the fire and smoke procedures for aircraft engines, starting with turbo-jet engines. This is a critical emergency sequence you need to know step by step. First, you close the engine thrust lever — that's the power control you normally push forward for takeoff and climb. Then you move the engine HP cock to off. "HP cock" stands for high-pressure cock, which is the valve that controls fuel flow to the engine's high-pressure fuel system. After that, you pull the appropriate engine fire warning switch — and I want to stress "confirmed" here, meaning you must be certain that the warning is genuine before you pull it. What does pulling that switch do? It isolates the fuel supply from the engine, usually both the high-pressure and low-pressure fuel supplies. That removes the obvious source of fuel feeding the fire. So the first action is fuel shutoff. Now, if the fire warning persists after you've done that, you rotate the engine fire warning switch — either left or right — and hold it in that position for one second. That operates one of the two fire extinguisher systems for that engine. You then wait 30 seconds. If the warning still persists after that wait, you rotate the switch to the other system — against the stop — and hold for one second. That operates the remaining extinguisher system for that engine. If the fire warning remains illuminated even after both extinguisher systems have been discharged, the Boeing checklist, for instance, advises landing at the nearest suitable airport. So the sequence is: fuel shutoff, first extinguisher, wait 30 seconds, second extinguisher, then land as soon as possible if it's still showing a fire. Now let's move to turboprop engines. The procedure is inherently the same as for a turbojet engine, with one addition: at some stage during the procedure, there will be a requirement to feather the propeller. Feathering means turning the propeller blades edge-on to the airflow to minimize drag and stop the windmilling effect, which is important because a windmilling propeller can continue to drive the engine even after fuel is shut off. Let's talk about fire in the aeroplane more broadly. Engine fires are a rare event, and the extinguishant — the fire-extinguishing agent — used to combat such fires is predetermined. That means the type of extinguishing agent for engine fires is already specified and installed in the aircraft's built-in fire suppression system. However, the most likely scenario for a fire in an aeroplane is either a fire caused by electrical arcing or overheating of electronic equipment, or a fire generated in the galley, or careless or deliberate extinguishing of smoking material where smoking is allowed. Illegal smoking is also a serious fire risk — that means passengers smoking in lavatories or other non-smoking areas. For combating fire in the cabin and on the flight deck, hand-held extinguishers are used. This is different from the built-in engine fire extinguisher systems I just described. It is therefore necessary for cabin crew and flight deck crew to know which type of fire extinguisher should be used on what type of fire, and to be aware of the hazards associated with the use of extinguishers in the closed environment of the aircraft cabin or flight deck. Different extinguishing agents can be toxic or cause suffocation in a confined space, so crew need to understand those risks.