Sender: <marv@lancaironline.net>
To:  lml@lancaironline.net
Date: Tue, 03 Nov 2009 16:56:41 -0500
Message-ID: <redirect-3915042@logan.com>
Received-SPF: none
 receiver=logan.com; client-ip=206.210.66.135; envelope-from=rpastusek@htii.com
From: "Robert Pastusek" <rpastusek@htii.com>
References: <list-3914569@logan.com>
In-Reply-To: <list-3914569@logan.com>
Subject: RE: [LML] AOA installation question
MIME-Version: 1.0
Content-Type: text/plain;
	charset="us-ascii"
Content-Transfer-Encoding: 7bit
Thread-Index: AcpcmeCEg+FUszX1TmWryRyVebm75gAFCYog
Content-Language: en-us

Ralf,

First of all, I think you are making a very good decision to install an AOA.
The AOA Pro you are apparently planning to install has other good
functions...such as warning of gear not extended in landing
configuration...if you chose to hook them up. I have an AOA Pro in my IV-P
and really like it/find it useful.

Your idea on sensor port installation below is close, and probably good
enough--I don't think the upper and lower wing locations are super critical,
as you'll calibrate it in flight to the pressures actually observed, and
this should offset any installation error. For the "technically correct"
answer, read on.

The "equal chord" point on a Lancair wing (not symmetrical) will be slightly
closer to the leading edge on the bottom than the top. As I said before, I
don't think the location is that critical, but you might check with Advanced
Flight Systems (new owners) just to confirm. They've always been most
helpful and courteous when I called: Rob Hickman, (503) 263-0037. Second,
you'll want to mount the upper and lower sensor ports approximately the same
distance from the wingtip (span-wise). This is more significant if  you're
mounting the ports near the wingtip where the flow is not completely
longitudinal. Lastly, the tubes provided in my kit for moisture trap, etc,
are porous. They need to be sealed inside and out with epoxy or
similar...ask me how I discovered this... :-(

Bob Pastusek


Ralf wrote:

Based on the discussions on this list I am putting an AOA indicator in.
I am putting it in the right wing outside of the fuel tank.

The unit calculates the angle of attack taking the pressure from the top of
the wing, the bottom of the wing, the static pressure and ram air pressure.

You are required to make a hole in the top and bottom of the wing. The holes
are supposed to have the same % of cord dimension from the leading edge (see
attached sketch).

Question: is someone able to provide a procedure to determine these two
points? How accurate does that have to be?

My idea was: guess and mark the leading edge, take the half dimension of the
thickness of the tailing side. Roll the wing that I get a horizontal plane
through these two points by using a water level. Take a led on a string and
mark top and bottom surface of the wing (see sketch).

Thanks for your help