Message-ID: <37C09AA9.CFC59EF5@calweb.com>
Date: Sun, 22 Aug 1999 17:49:45 -0700
From: "Hamid A. Wasti" <hwasti@calweb.com>
To: Lancair list <lancair.list@olsusa.com>
Subject: Re: ram air
References: <000001beecbc$b3d2dc60$0200000a@scottdah>
Mime-Version: 1.0

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Scott Dahlgren wrote:

> The Questair Venture group did quite a bit of work with ram air as they were
> trying to get more air into the engines of their high flying planes. They
> had some luck by actually mounting thin (.032" thick?)sheet aluminum plates
> onto their props, close to the spinner, about 2x the cord thickness (please
> note I am not recommending any of this...).

A few years back ('94-95 time frame) Roy Lopresti (sp?) did similar tests for
the Mooney.  He had one of the prop companies make a special prop that looked
very much like what you are describing here.  There were pictures in some of the
aviation magazines with lots of projections about what it would do for high
altitude cruise.  Since we have not heard a word about that project since then,
one can guess that the actual results were not as impressive as the
projections.  The article talked about synchronizing the prop so that the
pressure pulse arrived at the intake valve at just the right time.

> the dynamic pulse you receive putting the carb inlet close to the prop will
> do you little to no good at cruise speed on the Lancair as the ratio of prop
> wash velocity to ambient velocity is too close to unity to gain any
> sustained pressure increase at the manifold.

The IO-360 equipped  E and F model Mooney's have a "Ram Air" port just below the
cowl and above the air filter.  It allows ram air to bypass the filter box.  It
typically increases the MP by about 1".  I am not sure about the prop wash
velocity, but the airplane trues out at about 150KTS give or take 10 knots (most
of it take, very little give)

> You could get a lot of valuable information on these designs from the
> Venture group. They may have perfected the art at this point and have all
> the pros and cons for you and maybe have something for our group as well.

If you do not want to mess with the prop, a close look at any E or F model
Mooney at your local ramp will give you a few ideas as well.  Do remember that
by doing this you are bypassing the air filter and are risking ingesting stuff
which will cause engine failure.  For this reason, many Mooney pilots do not use
the ram air.  The Mooney POH prohibits the use of the ram air in precipitation,
clouds, below 5000 MSL and an AGL limit as well.

Hamid

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