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I found this on the Boeing 777 and it was on the Captain's side behind the speaker.


1 Answer 1


That is the sensor for the “cockpit door decompression-sensing latching system”. Most pilots I know are not aware of this system as it is not usually covered during training.

I have seen this system tested by using your mouth to blow a stream of air over the sensor. This creates a brief pressure differential which automatically unlocks the flight deck door.

  • $\begingroup$ Very interesting! Does it actually open the entire flight deck door? My FCOM says something about "two hinged decompression panels". It sounds like only these would open. $\endgroup$
    – Bianfable
    Jun 19, 2022 at 17:56
  • $\begingroup$ Yes, it unlocks the door. The decompression panels are separate items. $\endgroup$ Jun 19, 2022 at 19:02

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