Re: Explosive decompression - how fast?

On May 8, 5:51 am, Brian Davis <brda...@[EMAIL PROTECTED]
> wrote:
> SNIP:
> The difficulty in transfering this case to one of large-area explosive
> decompression is one of timing (how long does the pressure difference
> last) and distance (it's easy if you are in the breach and the breach
> is small... but a very short distance away from the hole, the wind and
> pressure forces drop sharply.
>
>Just hope the hole is a dozen feet away and you have your safety belt
faste=
ned. Agreed, the outrush certainly will not scour the corners of the
cabin. =
OTH Richard Whatshisface (Reed?) the shoe bomber probably would have gone
ou=
t the blast hole if his shoe had detonated. Not that he would have cared.
>One factor in an explosive decompression with the engines running is that
t=
he pressurization (engine bleed) air continues to be directed into the
cabin=
 at full flow. Of course, there is a limit to the size of the hole the
syste=
m can cope with. I worked out the equivalent horse power used to operate
one=
 air cycle machine (the heat/cool machine) - about 400 (air) horsepower.
Its=
 efflux is the source of pressurization air. Jet transports have usually
hav=
e 2 or 3 of these air machines. When they are saving fuel they turn one
off.=
 The pressurization system is normally 'on' all the time with the cabin
outf=
low valve(s) regulating the cabin pressure. The crew can vary the cabin
pres=
sure in flight but normally only does this if the automatic mode has
failed.=
 Operating the manual mode is part of the crew's practical check - and
chang=
ing power settings requires resetting the outflow valve position to avert
pa=
ssenger ear complaints ad to match the landing field atmospheric pressure.
F=
orex, La Paz is up about 13,000 feet..
The main problem with a rapid decompression is time of useful
consciousness. That's why the FAs instruct parents to don their own
mask and insure they are getting oxygen and only then see to the
children. TUC at 45000 is nominally about 9 seconds . . . how long its
takes deoxygenated blood to travel from the lungs to the brain.
Walt BJ