"John R Weiss" wrote:

"Gord Beaman" wrote...

Dunno about smart but yes the 'hole' is indeed 3 or 4 inches wide
(and there's two usually) but they're not wide open all the time
(only when 'dump' is selected). They have another valve portion
which mates with them and regulates the 'outflow' to regulate the
cabin pressure which controls the 'cabin altitude'.

On the 747 the outflow valves that regulate cabin pressure are about 1 x 3 feet,
and there are 2 of them. Normal opening is in the range of 12-19%, or about
103-164 square inches. A .40 cal bullet has a cross-sectional area of about
0.126 square inches, or about 1/1000 of the normal outflow area.

Even a full pax window, at about 6x8 inches, has less area. Though it would be
noisy and breezy if a window disintegrated (until a serving tray or something
got stuck in it), rapid depressurization would not occur, as the outflow valves
would adjust over the course of about 2 seconds.

Of course, the size of the outflow valves in smaller airplanes would be somewhat
smaller, but the net result would be similar.

I agree...the size of valves that I quoted belong to a Convair
580...VERY much smaller than a 747, but I'm still surprised by
how large the 747 ones are. Anyhow, I agree with you about the
outflow valve compensating for a blown out window. Pretty well a
'nonevent' as far as disaster is concerned.
--

-Gord.