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There are accidents where the pilots couldn't see the instruments and literally flew the aircraft blindly due to the excessive smoke in the cockpit, ranging from UPS Flight 6 to other accidents.

How come no company has made an airtight cockpit to prevent smoke from entering the cockpit? Even though it can be said it is complex I think it doesn't make an multimillion airliner a lot more expensive?

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    $\begingroup$ What happens when the smoke originates in the cabin? $\endgroup$ – Ron Beyer Nov 24 '18 at 15:44
  • $\begingroup$ @RonBeyer a system that vacuums the air? Or better an system that vacuums the smoke to an airlock? $\endgroup$ – Jonathan Irons Nov 24 '18 at 15:45
  • $\begingroup$ Ok, so what happens when there is smoke on the other side of the vacuum system and it blows smoke into the cockpit? Are we just abandoning the passengers at this point? How do we design for failure modes for all the wires, control cables, tubes, etc that need to go into and out of the cockpit? There is an easier solution that exists... Smoke hoods. $\endgroup$ – Ron Beyer Nov 24 '18 at 16:43
  • $\begingroup$ @RonBeyer the problem 1 doesn't apply to cargo craft and that's all I can say. Thanks for the answer $\endgroup$ – Jonathan Irons Nov 24 '18 at 16:50
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    $\begingroup$ See How to land the aircraft when the flight deck is full of smoke? for equipment to use in case of smoke in the cockpit. $\endgroup$ – mins Nov 24 '18 at 23:12
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Cockpit smoke will come from either of two sources:

  1. The air conditioning pack supplying it, such as the air cycle machine gone bad (more or less a turbo charger like device) with bearings and seals failed. This usually results in smells more than smoke. Another one is smoke from the engine compressor - unusual because are aren't really major sources upstream of the bleed ports unless something is introduced from outside. Cooked deicing fluid is the biggest source. Fluid gets in the compressor, and the temperature at the bleed discharge ports can be 500-800F at takeoff thrust. If the bleeds are started right after deicing without a clean-out engine run first to purge the compressor, you'll get stinky haze in the cabin/cockpit from cooked fluid. This has caused many a turn-back. Another one would be smoke from an APU that blows up while supplying bleed.
  2. You can also get smoke from burning out fan motors in supply ducting, but cockpit smoke so intense that it causes a control crisis is almost always from burning wiring in the cockpit itself, such as behind control panels or interior panels (see Swissair flight 111).

So the main thing is, smoke coming from the air conditioning system can be reduced by turning the system off, but that isn't the problem. It's smoke originating from within the cockpit itself, mostly from wiring. Considering how rare those events are, it's not really practical to create a hermetic seal between the space behind interior panels and the interior space and still have a maintainable and reasonably light airplane.

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  • $\begingroup$ Which Swiss Air accident? $\endgroup$ – Jonathan Irons Nov 24 '18 at 17:52
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    $\begingroup$ The one that burned up and crashed off the east coast of Canada from a wiring fire in the roof from, I believe, the cabin entertainment system. $\endgroup$ – John K Nov 24 '18 at 17:54
  • $\begingroup$ OH I remember Mayday Fire On Board $\endgroup$ – Jonathan Irons Nov 24 '18 at 17:58
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    $\begingroup$ A smoke-tight seal is not all that heavy or a maintenance nightmare. But there's too much to potentially seal. The killer is the need for a separate ventilation system for the cockpit. Generally systems are designed to keep smoke from getting into the cockpit, but that design often doesn't stand up to real-life fires. $\endgroup$ – Therac Nov 25 '18 at 5:59

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