REFLECTOR: Duct ventillation

[Rene Dugas]

Carbon Monoxide tester would be appropriate.  I have one of the little card
type to be sure but a battery operated type would be good during testing.
Your mileage may vary.  At altitude the outcome can be more insidious and
dangerous.
Rene' Dugas, MD

-----Original Message-----
From: reflector-bounces at tvbf.org [mailto:reflector-bounces at tvbf.org] On
Behalf Of Terry Miles
Sent: Thursday, October 22, 2009 3:36 PM
To: 'Velocity Aircraft Owners and Builders list'
Subject: Re: REFLECTOR: Duct ventillation

Scott,
That could have been me about being able to smell what's going on in the
engine compartment, and a vote for not sealing off the engine compartment
from the utility ducts.  For my 2 cents the high pressure in the engine
compartment is enough so as to travel up the utility ducts all the way to
nose wheel well and from from there into the cockpit.  I don't think the
potential for smoke and fumes in the cockpit is the greater risk of not
being able to sniff the engine compartment.  My guess is if you opened all
your cockpit ram air inlets, that any acrid smoke from the nose area would
be diluted enuf.  Obviously that is personal opinion.  I had a fuel injector
vibrate loose enough to smell.  That's why I opened the cowl (fuel smell)
and that is how I discovered it, and that's why I think the way to do today.
Terry

-----Original Message-----
From: reflector-bounces at tvbf.org [mailto:reflector-bounces at tvbf.org] On
Behalf Of scott at tnstaafl.net
Sent: Thursday, October 22, 2009 13:35
To: Velocity Aircraft Owners and Builders list
Subject: Re: REFLECTOR: Duct ventillation

> At, say, an airspeed of 150 kts the dynamic pressure available is 
> about 14"
> H2O.

If you mean the differential pressure between entry and exit, that's
excellent!  Most of the cooling experts say that no matter everything else
if the differential pressure isn't high enough you won't cool the engine.

> Block the wiring ducts at the firewall to prevent the flow of air forward.
> This is a good idea anyway, because if ever there is an event of fire 
> in the cowl, you don't want it going up the ducts.

I've always thought that too but, somebody on the list did mention some
incident where he smelled something and put down to investigate. It would
have been a serious problem but the slight airflow carrying the smell
through the duct alerted him to it in time.

Scott

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