New style emergency exits

Robert M. Gary wrote:
I have to admit I would feel a bit more uneasy sitting next to an
outword opening door. Are you sure the door doesn't pull in and then
open out like the main door? Doors that open straight out require more
complex locking mechanisms because they naturally always want to open
in flight. The inward opening doors are referred to as "plug" doors
because you cannot physically open them when the aicraft is under
pressure, the air pressure holds the door firmly closed. Normally, you
only see outward opening doors for cargo where getting the door to
swing in might be difficult. In those cases there is a very complex
mechanism of cams and locks to hold the door closed against the
pressure. They are also notorious for having small leaks (not a safety
issue, just irritating).

-Robert

Robert,
The pictures clearly indicate: pull the handle and the door swings out
and up.
Michelle

Regardless of the motion of the door in opening, you can count in there
being pressure sensors that block the locking mechanism from actuating
when the pressure in the cabin is higher than external pressure...
They don't all have to be electrical to still be safe in case of total
electrical failure... A simple bellows mechanism, no different from
your altimeter, can push a locking pin into the doors hardware anytime
the inside pressure exceeds the external pressure...

denny

Denny wrote:
Regardless of the motion of the door in opening, you can count in there
being pressure sensors that block the locking mechanism from actuating
when the pressure in the cabin is higher than external pressure...
They don't all have to be electrical to still be safe in case of total
electrical failure... A simple bellows mechanism, no different from
your altimeter, can push a locking pin into the doors hardware anytime
the inside pressure exceeds the external pressure...

There must be some kind of override to this. Imagine the situation of
a plane sitting on the ground with a fire in the cabin. I would
imagine that would make the inside pressure higher than the outside
pressure, but clearly not a case where you want to prevent the doors
from opening.

Roy Smith wrote:
Denny wrote:

Regardless of the motion of the door in opening, you can count in there
being pressure sensors that block the locking mechanism from actuating
when the pressure in the cabin is higher than external pressure...
They don't all have to be electrical to still be safe in case of total
electrical failure... A simple bellows mechanism, no different from
your altimeter, can push a locking pin into the doors hardware anytime
the inside pressure exceeds the external pressure...


There must be some kind of override to this. Imagine the situation of
a plane sitting on the ground with a fire in the cabin. I would
imagine that would make the inside pressure higher than the outside
pressure, but clearly not a case where you want to prevent the doors
from opening.

I know that our airline evac checklist includes the pushing of the
emergency depress. Otherwise the main door will not open. Had to test it
a few times and it is kinda fun....
The more I thought about it a simple differential pressure switch that
dis-engages the handle would work nicely.

Michelle

"Roy Smith" wrote in message ...

... Imagine the situation of
a plane sitting on the ground with a fire in the cabin. I would
imagine that would make the inside pressure higher than the outside
pressure, ....


Have you ever seen the trick to get a hard boiled egg into a pop bottle. Put a smoldering piece of paper in there then
put the (shelled) egg over the bottle opening. The burning paper consumes the O² in the bottle and the egg gets pulled
inside....