Smoke, fire, door-open

Fire is the one emergency where the airplane is actively trying to finish the flight for you. Everything about the response is built around speed: cut the fuel to it, get the smoke out, and put the airplane on the ground before the situation gets a vote.

Fire: engine, electrical, cabin

The three in-flight fires have different sources but a common spine — starve the fire, then land now. The opening steps are memory items, done from recall, not read off a card.

• Engine fire in flight. Cut its fuel: mixture to idle cut-off, fuel selector OFF, and per the C172S checklist the master OFF as well; turn cabin heat and air OFF so you aren't ducting smoke into the cabin. Then fly a descent toward a forced landing — do not attempt a restart. With the engine shut down, increasing airspeed in the descent can deprive the fire of oxygen and may extinguish it; the exact speed is type-specific, so take it from your POH §3 rather than a memorized number. The procedure is the constant across airplanes — shut down the fire's fuel source, increase airspeed, land as soon as possible — and the POH supplies the value for your trainer. You are now flying a power-off arrival (IX.B), and that's the right trade.
• Electrical fire (acrid smell, smoke from the panel). The source is electrical power, so master OFF removes it. If you genuinely need power back, restore buses and avionics one item at a time so the faulted circuit reveals itself. Use the Halon extinguisher at the base of the flames.
• Cabin fire (upholstery, a dropped cigarette, baggage). Attack it with the extinguisher, then ventilate and land as soon as practical.

Smoke is the real killer

Flames get the attention, but smoke and toxic fumes incapacitate the pilot first — and an unconscious pilot doesn't land an airplane. That reframes the priority: after the fire drill, getting breathable air and getting on the ground beat everything else. Ventilate (the calculus flips only briefly during an electrical fire, where you may want vents closed to deny it air before knockdown, then open them after). When in doubt with smoke in the cabin, the answer is a precautionary or emergency landing at the nearest suitable spot — sooner than feels necessary.

The door that won't kill you

A door or window popping open in flight is almost pure startle and distraction — and that, not aerodynamics, is the hazard. The C172 flies normally with a door ajar; it's loud and alarming, but the airplane is fine. The accidents come from a pilot who fixates on the door, stops flying, and loses control while reaching for it.

So the response is the discipline that runs through this whole area (and IX.B, and VI.D): fly the airplane first. Accept the noise, maintain attitude and altitude to the ACS tolerance, and either secure the door in a stable phase of flight or simply land and close it — most doors won't latch in flight against the airflow anyway. The right mindset is "annoying, not urgent."

<CFR id="91.3" /> is the authority behind the aggressive moves these call for. In an in-flight emergency the PIC may deviate from any rule to the extent required — descend through airspace you'd normally clear, land off-airport, declare and go. Fire is exactly the situation §91.3(b) was written for: act first, explain later.