Mailing List lml@lancaironline.net Message #68891
From: Colyn Case <colyncase@earthlink.net>
Subject: Re: [LML] Re: AoA flap position switch
Date: Mon, 6 Jan 2014 10:29:04 -0500
To: Lancair Mailing List <lml@lancaironline.net>
Marv,

I asked that question to current owners of aoa pro and couldn't get a straight answer.  What I would really like to understand is what does the AOA "see" as the flaps change position, ignoring the effect of the flap switch for a minute.

Colyn

On Jan 6, 2014, at 10:13 AM, <marv@lancair.net> <marv@lancair.net> wrote:

I don't know if it was mentioned in the installation instructions but the AOA flap switch should be setup to signal flaps down at about 1/3 of their down travel.  While there are an infinite number of flap positions the AOA only tracks 2 of them, flaps up and flaps down.  The logic of setting the switch to trigger flaps down when they're only 1/3 of the way down is that's the approximate location when the flaps' position impact drag more than lift.  The critical AOA from 1/3 to full flaps is very similar and is the reason that Jim Frantz always suggested that switch position as the most appropriate compromise to not having multiple flap position data available for the instrument.  I hope this helps. 

            <Marv>   


John Cooper <snopercod@comporium.net> wrote:

> On my L-235 I couldn't figure out a good way to mount a microswitch for the
>AoA system which would engage in the "flaps down" position, so I used a
>U-shaped magnetic reed switch instead. The NO contacts close when a ferrous
>object passes between the two arms of the switch and my flap actuator arm
>serves that function. I glued a couple phenolic "guides" onto the switch in
>case the flap actuator and switch became mis-aligned for any reason. This
>scheme seems to work, but I'm fiddling with the adjustment at the moment.
>This photo (looking aft) shows the flaps in the "UP" position and the
>microswitch not engaged.
>



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