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In a message dated 98-11-30 02:17:06 EST, Michael D Smith writes:

<< I just don't like the thought of porting overboard turbo
 boost when at flight levels, as the current seems to do. >>

The hot/cold valve should be configured to as an either/or valve. Either you
take air off the discharge of the turbos or after the third heat exchanger.
Since you need the air for pressurization anyway, there is no performance
penalty and very little weight penalty for this "Heater".

Electric heaters are a bad idea. Two 600-watt heaters would draw about 100
amps requiring a second alternator plus posing a significant fire hazard.

Heat muffs are also problematic, as they would need to be pressurized,
virtually leakproof and require lots of pressurized plumbing and valving.
There is also the matter of CO2 poisoning.

The only other way I can think of would be to put a small engine oil cooler in
the cabin with a fan to circulate air through it. A leak would put hot oil in
the cabin. Oops.

Stick with the standard setup. It works well, it is light and simple plus
there is a certain Zen in getting something (heat) by not doing something
(cooling). I have found that there is PLENTY of heat even at FL290 and rarely
have the control more than 1/2 out.

Compliments of the season.
Brent