Do Not Open Door
by Chris MacDonald
As an airline passenger, I found this one generated more questions than it answered. It’s on the door of a large Air Canada jet (a 767, I think, but I could be wrong).
Just who is this aimed at? Under what conditions would I (or anyone) be reading this sign, from outside, while the red light is flashing? Is there some chance that someone qualified to be standing outside this door, while the light is flashing, someone with an understanding of how to open the door, wouldn’t also know when not to do so?
I’m sure there are perfectly reasonable answers to those questions. But as someone boarding a plane about to soar above the Pacific ocean, I gotta say I found them somewhat unsettling.
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As an airline pilot, I’m reasonably well-qualified to answer this question.
If the aircraft is pressurized, opening the door can prove seriously hazardous for the person underneath it. This is actually a fairly common way for ground crew or flight crew to get injured.
Aircraft can become pressurized on the ground either on purpose (in order to test or repair leaks), or accidentally. The accidentally pressurized aircraft is fairly easy to do: Simply connect a pressurized air cart to the aircraft with a door closed. The air carts are designed to move high volumes of climate controlled air through the aircraft while it’s on the ground in order to make the cabin comfortable for passengers as they board. It’s designed to work with the door open.
It’s unfortunately easy to forget to check that the door is open before connecting an air cart. Perhaps the aircraft has been left unattended for some time in which case the door must be closed, and in order to cool/heat the cabin an air cart is attached before the crew remembers to open the door…. Opening the door at that point could cause serious injury. Thus the light.
Thanks very much for taking the time to explain that!
I guess this illustrates an interesting (and I suspect, common) problem: this is obviously an incredibly important sign for a handful of professionals to see and to obey, but a few hundred other people are passing by it every day wondering what the heck it is, whether it applies to them, and whether it should worry them!