running with scissors wrote in
message om...
"John Gilmer" wrote in message
...
"Bob Gardner" wrote in message
news:QODIb.85072$VB2.187788@attbi_s51...
No way. You start off at sea level, of course, and they pump the
chamber
pressure down to 25000 feet with masks on...then they do some
experiments
with a few of the pilots taking their masks off, just to show how
severely
their abilities are affected. Then comes the explosive decompression,
which
takes the chamber from 25K back down to sea level in a second or two.

SIlly question but ...

Why would "they" pressurize the aircraft to sea level? Why not some
compromise "pressure" like that equivalent to, say, 6,000 or 8,000 feet?


EMWTK

"they" dont. cabin pressurization is normally at 8000ft though crew
may elect to use different cabin pressures under certain circumstances
(eg medevac operations where pressurization is a factor)

Sec. 25.1 Applicability.

(a) This part prescribes airworthiness standards for the issue of type
certificates, and changes to those certificates, for transport category
airplanes.
http://www.astech-engineering.com/sy...apart25d.html#
Pressurization

Sec. 25.841 Pressurized cabins.

"(a) Pressurized cabins and compartments to be occupied must be equipped to
provide a cabin pressure altitude of not more than 8,000 feet at the maximum
operating altitude of the airplane under normal operating conditions."

Transport category:

* All jets with 10 or more seats or greater than 12,500lb Maximum
Takeoff Weight.
* All propeller driven airplanes with greater than 19 seats or greater
than 19,000lb Maximum Takeoff Weight.


Obviously the rule would not normlly apply to Medivac operations.

HTH,

Paul Nixon