REFLECTOR: A/C (was Re: GRT Displays overheating - Anyone elseseethis?)

[Brian Michalk]

It was almost certainly bleed air.  For military purposes, it's light 
and simple.

One of my previous jobs, we built electronics to fly in externally 
mounted pods.  Heat rejection was our biggest enemy.  Keep power 
consumption low, and it gets easier.  There's some crazy stuff out there 
with the extreme being water cooled blade mounted VME or PCI cpu 
boards.  That stuff is insanely expensive because the military is the 
only customer, and most things are in quantity 1 to 10.  How about a 3" 
muffin fan that costs $400?  I thought we were getting ripped off, but 
after seeing the testing that goes into it, and the performance 
parameters it makes more sense.  Most times we had no choice either.  
The customer states the requirements and we had to engineer to them.

On 07/11/2012 09:42 AM, Mark Magee wrote:
> Funny the cabin A/C issue just won't die in the midst of this La Nina heatwave. I was discussing the glass cockpit in an AH 64 Apache Longbow last summer with the pilot displaying his bird at a local festival. The nacelles on the port and starboard are all electronics for fire control, targeting etc. etc. He allowed that one turbine was started and the A/C(s) were started before the the other engine was started or the rotors clutched in. This was purely to cool the cabins holding the electronics, and that on a hot day it could take a few minutes before the electronics cabins were cool enough for the electronics suites to begin powering up. All the while he and the gunner would wait to engage the rotors because they weren't going anywhere until all the electronics reported OPS NORMAL. At the core of it all was multiple A/C units: I didn't cover with him if it was bleed air A/C or what.
> I think cabin A/C is a good idea for many reasons, but as we are beginning to see the old steam gauges could handle high cabin temps better than current glass.
>