Cheers,
I detect some missunderstanding in regard to pressure distribution
outside and inside - the source of air movement unless one puts in a fan.
Just like the wing, the cockpit roof produces low pressure where it
speeds up the air (top of windscreen), and high pressure where it slows the
outside air - bottom of windscreen middle. There are other sources of
course, but the former are fairly general. So we should take air from the
lower windshield area, and exhaust it from the roof - in general.
There is another caveat which has my belief: In order to provide
safe ventilation, the exhaust capability should equal the total of cold and
warm air volume. As well, the cockpit pressure should exceed the ambient
pressure (to prevent infusion of bad air and clearing capability if smoke
arises. Admittedly this does not seem to give the same characteristics, but
if the exhaust outlet is controlled, then both can be achieved. If you want
hot air, close off cold air and open warm, then adjust exhaust for positive
pressure. For cold air reverse the sources as before. If you want windshield
deforst/demist, blow clearing air up from bottom of windshield and exhaust
at roof nearby. If you want fresh air, close roof and open rear exhaust (I
will be using an aerodynamic form at back of fuselage)*.
If smoke threatens, open up all inputs, and adjust exhaust for best flow.
Anyway, that's my two cents worth....
Happy Landings
Ferg
* - the design is a highlift form with holes drilled at the lowpressure
point. The website seems to have disappeared but I can send copies of
original pages.
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