View Full Version : Conditions in de-pressurized zone

20th Jul 2011, 10:48
To what conditions is equipment exposted to (regarding presseure and temprature), which is installed in tail area of an airplane (non-pressurized Zone)?

Old Fella
20th Jul 2011, 12:15
Before you get "bashed" for asking the question, those areas which are not pressurised will be exposed to the range of temperatures felt between ground temperature to whatever temperature is encountered at cruising level. The pressure variation will be ambient pressure anywhere between that at ground level and that at cruising level.

20th Jul 2011, 13:05
Check out ISA that will be pretty close

20th Jul 2011, 22:11
Having to work in those unpressurized zones on a hot ramp, it can be just as hot if not hotter than your car can get on the same day. At altitude I would assume over time it gets close to OAT, a tad bit warmer due to shelter and warming operating components.

21st Jul 2011, 04:16
a tad bit warmer due to shelter and warming operating components

This could include hot bleed ducts, air cycle machines (packs), hot wheels and brakes, etc.

Someone once told me that if stowaways in the wheel wells don't get crushed or fall out on takeoff, their next worry is extremes of heat from wheels and brakes. Then, of course, hypoxia and cold.

Old Fella
21st Jul 2011, 04:43
Shahone. I presume you are not a pilot. What Felixthecat is referring to is International Standard Atmosphere (ISA) which you can find, among other places, on Wikipedia. ISA is 1013.25 hPa pressure and 15 degrees C at Sea Level. As altitude is increased the temperature will usually decrease by approximately 2 degrees C per 1000 feet (up to about 36000 feet) and pressure decreases by roughly 1 hPa per 30 feet. Hope this is helpful.

21st Jul 2011, 06:18
Thank you guys for your helpful input. So one could safly assume that the cabin temprature at altitude drops roughly to the same level as the outside temprature (suppose -50C)? How long does it take for the temprature to fall to this extent. And is this area accessable during flight?
Is the cargo area pressurized?

@Old Fella
your assumption is correct. I thank you for your explination, it is very helpful indeed :)

Old Fella
21st Jul 2011, 08:27
Cabin temperature and pressure are governed and regulated by controlling the rate at which conditioned air is allowed to be exhausted from the pressure hull. On most aircraft which are pressurised, the cargo hold is also pressurised. The temperature is maintained in the cabin to keep passengers comfortable and some cargo compartments, as well as being pressurised, are also kept warm.

CJ Driver
21st Jul 2011, 21:59
Many aircraft have unpressurised equipment bays with avionics gear - it doesn't mind being in a cool place.

If you have an unpressurised and unheated baggage area, it's a good place to keep the beers for when you land. :}

Old Fella
22nd Jul 2011, 02:15
CJ Driver. The C130 rear cargo door was a great place to keep the "refreshments" cold. Many a carton of beer and slab of frozen prawns travelled there over the years. In fact, on the C130A which had no 'underfloor heating' system, any fluid spilled on the floor in the area of the ramp hinge would freeze on longer flights at higher levels.