Foam Supply vs. Turret Demand on a Runway Response
At 09:05, a Bombardier Challenger 350 reports a right engine fire during takeoff roll at Runway 27. The aircraft stops on the runway, 1,200 ft from the departure end. ARFF Truck 1 arrives alone; Truck 2 is staged at the south fire station, four minutes away. Truck 1 carries 1,500 gal water, 200 gal of 3% AFFF, and 500 lb dry chemical. Its bumper turret flows 1,000 gpm; the roof turret flows 1,500 gpm; the front handline flows 250 gpm at 100 psi. The foam tank gauge reads 160 gal, and the water gauge reads 1,400 gal. Wind is 10 kt from the left. Eight passengers and two crew are evacuating through the main cabin door, away from the engine. The engine fire is attached to the right nacelle and is impinging on the wing. There is a thin fuel film under the right wing but no running fuel fire. What is your plan?
1. Calculate foam and water duration for the bumper turret at 3% and recommend an attack tactic.
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At 1,000 gpm and 3%, foam concentrate flow is 1,000 × 0.03 = 30 gpm. With 160 gal of foam, duration is 160 ÷ 30 = 5.3 minutes. Water duration is 1,400 ÷ 1,000 = 1.4 minutes, so water is the limiting agent, not foam. A continuous bumper-turret attack would empty the water tank in about 84 seconds. Use the bumper turret in short, aimed bursts of 10–20 seconds to knock down flame and protect the evacuation path, then switch to the 250-gpm handline. At 250 gpm, foam flow is 7.5 gpm, so 160 gal lasts about 21 minutes; water lasts 1,400 ÷ 250 = 5.6 minutes. The handline gives a longer, controllable attack for wing cooling and foam blanket maintenance. Keep the dry chemical available for a nacelle fire, but do not rely on it alone because it will not cool the wing or prevent reflash. Request Truck 2 early.
2. How should the handline and dry chemical be used to control the engine fire and protect the evacuation?
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Position upwind/left of the aircraft, keep the apparatus off the fuel film, and advance the handline to the upwind side of the engine. Use a fog pattern to cool the nacelle and wing, and apply foam to the fuel film to suppress vapor. Do not open the nacelle unless necessary; if the fire is inside the engine cowling, a small amount of dry chemical through the access port can knock down flame, but continue cooling with water. Prioritize the evacuation path: keep the handline between the fire and the passengers if they are moving toward the left. Use the bumper turret only when the handline is insufficient and only in bursts. Preserve enough water for a retreat and for Truck 2's arrival. If the fuel film ignites and runs, use foam from the handline to build a blanket ahead of the fire, not a straight stream that spreads fuel.
3. If Truck 2 is delayed and the fire escalates to a running fuel fire, what changes in your plan?
Read the worked answer
Shift from rescue support to defensive fire control. Keep the handline on the wing and use foam to blanket the spill; do not chase the fire. If water is below 25% (about 350 gal), stop the bumper turret entirely and use only the handline in short pulses. Position the apparatus so it can retreat without crossing the fuel film. Request additional ARFF and mutual aid; notify incident command that the resource is insufficient for a sustained attack. Continue protecting the evacuation path and cooling the wing until relieved. Dry chemical is a last resort for the engine fire, not for the spill. The priority remains life safety: keep passengers moving upwind and away from the vapor zone.