FAR 23.2440 — Powerplant Fire Protection
FAR 23.2440 sets Part 23 powerplant fire protection rules: designated fire zones, shutoff means, fire detection, and extinguishing requirements.
In Plain English
FAR 23.2440 is a Part 23 airworthiness standard that tells designers how to protect small airplanes from powerplant fires. Any powerplant, APU, or combustion heater that combines flammable fluid with an ignition source must live inside a designated fire zone — a区 area engineered to contain and mitigate a fire.
Key requirements:
- Components, lines, fittings, and controls exposed to fire must be located to prevent fire hazards, be fire-resistant if they carry flammable fluid/gas/air or must keep working during a fire, and be fireproof (or shielded) if they store concentrated flammable fluids.
- A shutoff means must stop hazardous flammable fluid from entering the zone, without limiting safe operation of remaining engines or critical equipment, and it must guard against inadvertent operation.
- Fire detection is required for multiengine airplanes (where it helps) and any zone with an extinguisher.
- Fire extinguishing is required for zones out of pilot view, zones embedded in the fuselage (with redundancy), and any zone on a level 4 airplane.
Why it matters: pilots rely on these certification features — firewalls, fuel shutoffs, fire-warning lights, and bottles — every time they run an engine-fire checklist.
Regulation Text
14 CFR § 23.2440§ 23.2440 Powerplant fire protection.
(a) A powerplant, auxiliary power unit, or combustion heater that includes a flammable fluid and an ignition source for that fluid must be installed in a designated fire zone.
(b) Each designated fire zone must provide a means to isolate and mitigate hazards to the airplane in the event of fire or overheat within the zone.
(c) Each component, line, fitting, and control subject to fire conditions must—
(1) Be designed and located to prevent hazards resulting from a fire, including any located adjacent to a designated fire zone that may be affected by fire within that zone;
(2) Be fire-resistant if carrying flammable fluid, gas or air, or is required to operate in the event of a fire; and
(3) Be fireproof or enclosed by a fire proof shield if storing concentrated flammable fluids.
(d) The applicant must provide a means to prevent hazardous quantities of flammable fluids from flowing into, within or through each designated fire zone. This means must—
(1) Not restrict flow or limit operation of any remaining powerplant or auxiliary power unit, or equipment necessary for safety;
(2) Prevent inadvertent operation; and
(3) Be located outside the fire zone unless an equal degree of safety is provided with a means inside the fire zone.
(e) A means to ensure the prompt detection of fire must be provided for each designated fire zone—
(1) On a multiengine airplane where detection will mitigate likely hazards to the airplane; or
(2) That contains a fire extinguisher.
(f) A means to extinguish fire within a fire zone, except a combustion heater fire zone, must be provided for—
(1) Any fire zone located outside the pilot's view;
(2) Any fire zone embedded within the fuselage, which must also include a redundant means to extinguish fire; and
(3) Any fire zone on a level 4 airplane.
[Doc. No. FAA-2015-1621, Amdt. 23-64, 81 FR 96689, Dec. 30, 2016, as amended by Doc. No. FAA-2022-1355, Amdt. 23-65, 87 FR 75710, Dec. 9, 2022]
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Oral Exam Questions a DPE Might Ask
Q1Under Part 23, what defines a designated fire zone and what must be installed in one?
Per FAR 23.2440(a), any powerplant, APU, or combustion heater that contains a flammable fluid together with an ignition source for that fluid must be installed in a designated fire zone, which must provide means to isolate and mitigate fire or overheat hazards.
Q2What does FAR 23.2440 require for components and lines exposed to fire conditions?
FAR 23.2440(c) requires those components, lines, fittings, and controls to be located to prevent fire hazards, be fire-resistant if they carry flammable fluid/gas/air or must operate during a fire, and be fireproof (or enclosed in a fireproof shield) if they store concentrated flammable fluids.
Q3When is a fire extinguishing system required in a Part 23 fire zone?
FAR 23.2440(f) requires a means to extinguish fire (except in a combustion heater zone) for any fire zone outside the pilot's view, any fire zone embedded in the fuselage (with a redundant means), and any fire zone on a level 4 airplane.
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