PPRuNe Forums - How cold does it get when you depressurise during flight testing?

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RMC	9th May 2018 11:24

How cold does it get when you depressurise during flight testing?

I am really interested to know from a practical what kind of temperature drop you would get overall from the combination of loosing your warm air through the outflow valves coupled with the adiabatic heat loss. I guess it will vary with aircraft volume and OATs etc but any empirical experience would be much appreciated.
I have looked at the engineering responses to this question and calculating it mathematically seems to require computer simulations. Thanks in advance.

Avtrician

10th May 2018 10:12

At 10.000 ft it gets pretty cold, esperienced it in a Herc may years ago on a test flight. Not only de-pressurised, but opened the rear door as well. Interesting to watch bits of hay, string ond other loose stuff disappear out the back. :)

ICT_SLB

11th May 2018 03:30

We once had to depressurise our CRJ when around FL200 after hail cracked the Copilot's windshield over Oklahoma. Can't say I noticed any appreciable drop in temperature even though we only had the usual Flight Test interior with just the Insulation bags rather than a fully paneled one. IIRC the ECS was still providing warm air, it just was being dumped rather than being retained.

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