Jim.
I think you missed my original post.
I am not advocating sealing off the engine compartment full time. As you say
there is quite a bit of heat given off by the exhaust and engine block that
has to be taken away.

What I am advocating is that you design the cowl so that the air supply to
the engine is CONTROLLED by a inlet flap that would normally be locked open,
but could be closed in the event of a fire under the cowl. I agree you would
never get a 100% air seal, but (second point) combined with a halon fire
suppression system one could control a fire fairly quickly.
It's got to be a better system than diving towards the ground at 200mph.
Michael Burke.

<... isolate the engine compartment from sources of fresh air ...>
Don't know how you'd do that. Radiators exhaust into the engine compartment.
If there was no air circulation in the engine compartment you'd have VERY
hot exhaust parts heating all that stagnant air and radiating to wherever
(fuel rail? Belts & electrics? Coolant lines?) and roasting everything. Any
plastic airplane (or cowl) would melt forthwith. The air leaking past even
good baffling would support one hell of a fire.

If there was an easy answer, it would be implemented by now ... Jim S.



Dale Rogers wrote:


Hans,

  I think you missed Michael's point.

  It isn't the volume of air that's at issue, but rather where that air has
to go. A direct-air cooled engine needs the air to travel in intimate
contact with the cylinder fins - filling the entire engine compartment. An
indirect-
air cooled system allows the airstream to be confined to a ductwork where
there are no flamable liquids or gasses, making it far easier to isolate the
engine compartment from sources of fresh air.

Regards,
Dale R.




From: Hans Conser <conserreceipts@earthlink.net>
Date: 2005/08/26 Fri AM 10:29:50 EDT
To: "Rotary motors in aircraft" <flyrotary@lancaironline.net>
Subject: [FlyRotary] Re: Fire extinguishers


On Aug 26, 2005, at 12:55 AM, Michael Burke wrote:




...
   The point I'm making is this. The rotary is NOT air cooled, (directly
anyway)therefore we can take a different approach in designing the cowl. We
do not need a large volume of air blasting into the cowl, because the the
radiators can be set up so that they are ducted from the outside seperately.
...




Actually liquid cooled engines need a great volume of air than air cooled
engines. This is because the temperature differential (Delta T) of the
aircooled engine is much greater. In other words it takes less air to cool
400 degree cooling fins vs 220 degree coolant.

Hans Conser