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Let's say when flying, I encounter smoke and the smell of something burnt in the cockpit. Should I open the door or a window to clear the smoke?

My thoughts: the smoke may be toxic; opening the door brings in fresh air and avoid incapacitation. But, if something is burning, opening the door also brings in plenty of oxygen, and the fire will spread very rapidly.

I'm asking about GA planes.

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  • $\begingroup$ You should focus the question on GA because the airline answer is uniformly "don oxygen mask, and smoke goggles, land at nearest suitable airport" and then follow the QRH to start pulling main bus breakers to isolate the electrical fault. $\endgroup$ – casey Nov 14 '15 at 16:36
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    $\begingroup$ What does the P.O.H. for the aircraft you're flying have to say about this? $\endgroup$ – Ralph J Nov 14 '15 at 16:42
  • $\begingroup$ During a fire on board SAA flight 295, a 747 Combi, the procedures called for them to ascend to a low altitude and open two of the cabin doors to evacuate the smoke. $\endgroup$ – TomMcW Nov 14 '15 at 20:26
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If possible, you should do whatever the operating handbook for your aircraft says but don't hesitate to do something different if you think it's necessary (more on that below).

I checked a couple of POHs that I have to hand and they don't mention the doors specifically, but there is a slight difference in what they say about cabin ventilation.

The C172S checklist emphasizes avoiding drafts, including shutting air vents and ventilating only after fighting the fire:

ELECTRICAL FIRE IN FLIGHT

  1. Master Switch -- OFF.
  2. Vents, Cabin Air, Heat -- CLOSED.
  3. Fire Extinguisher -- ACTIVATE.
  4. Avionics Master Switch -- OFF.
  5. All Other Switches (except ignition switch) -- OFF.

WARNING

AFTER DISCHARGING FIRE EXTINGUISHER AND ASCERTAINING THAT FIRE HAS BEEN EXTINGUISHED, VENTILATE THE CABIN.

  1. Vents/Cabin Air/Heat -- OPEN when it is ascertained that fire is completely extinguished.
    [...]

The PA28 checklist on the other hand says that the vents should be open:

FIRE IN FLIGHT

Electrical fire (smoke in cabin):
Master switch....OFF
Vents....open
Cabin heat....OFF
Land as soon as practicable

But practically speaking, fire in the cabin is a really extreme situation and it's hard to say that you should always follow the checklist (if you even physically can). For example, if the cabin fills with smoke and you can't see anything at all you might have to try to clear the smoke somehow just to keep control of the aircraft, even at the risk of feeding the fire. The Piper POH acknowledges that the pilot is the best person to decide what to do:

The procedure given is general and pilot judgement should be the determining factor for action in such an emergency

For a real-life account of a cabin fire in a C172RG, see this AOPA Real Pilot Story. They had to open the door to be able to see and land, which reinforces the point about doing whatever you have to do in an extreme scenario.

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  • $\begingroup$ Clearly the difference between the checklists is that the first assumes availability of fire extinguisher (the word “activate” suggests there might even be a built-in extinguisher for the electronics bay) and the later does not. Presumably the extinguisher is a halon one designed for use in closed spaces (some halon agents are effective at 7-9% concentration, leaving enough oxygen for humans to breathe) and having vents open while using the extinguisher would just blow out the extinguishing agent. While when not extinguishing, the smoke has to be vented so the crew can still see and breathe. $\endgroup$ – Jan Hudec Nov 16 '15 at 14:06
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Burning smells in an aircraft always need to be taken seriously, not least because it could be a sign that you're breathing in carbon monoxide, which could effectively incapacitate you without you even realising.

In an unpressurised aircraft you wouldn't exactly be bringing in more oxygen, so to speak, as the cabin altitude is already the same as outside. But yes you would be adding wind to a flame which could spread it instead of extinguishing it, but IMO this risk is worth taking compared to the alternative.

I'm not sure if there's a formal recommended procedure for all aircraft, but it would be prudent to initially look around and see if there is a visible flame. If not, you must close all air conditioning vents and open the windows. If you see smoke you should land immediately in a field. If not, divert to the nearest airfield, ensuring the fresh wind is blowing in your face.

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  • $\begingroup$ You'd be bringing in fresh oxygen if some inside the aircraft is being used up by a fire, though... $\endgroup$ – Jon Story Nov 14 '15 at 21:19

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