Colyn,

I installed my sensing switch (per Jim Frantz) so it activates the “Flaps” annunciation, and goes to the “flaps down” AOA configuration as soon as the flaps start moving from the full up position.  These functions are both controlled by the flap sensing switch and can’t be triggered independently as far as I know.

I believe that at a given weight and airspeed, the wing generates more lift but the same angle of attack indication on the AOA (pressure differential between upper and lower wing sensing ports) with the flaps down. If you calibrate the AOA system to “flaps down” stall speed, it will be at a lower indicated airspeed than when the flaps are up.

This means that when the AOA system goes into “flaps down” indicating mode, it will be showing “on speed” and “stall” at a lower indicated airspeed than that at which the airplane will actually stall with partial flaps. It would indicate the correct stall AOA only at the position it was calibrated (flaps full down).

I therefore think the most conservative installation would be to switch the system to “flaps down mode” when the flaps are fully down. As a practical matter, if I were doing mine again, I’d set the switch to change when the flaps go past 20 degrees…or more specifically, when they change from moving aft to rotating down.

There is another way to do this. You can calibrate the AOA at any airspeed (within reason) and configuration (flaps up, flaps partial, or flaps down) you chose. The machine simply displays AOA measurements that you’ve previously told it were stall AOA’s in various configurations, so you can make it repeat these back to you at the speed/configuration you chose. I am not advocating creative installation/calibration here, just understanding what you are actually calibrating this very good system to show…

My two cents…

Bob

Posted for Colyn Case <colyncase@earthlink.net>:

 while we're on this, I'm interested where others, especially IVP owners, put 
their flap switch for the AOA, and what the AOA really does with that 
information.   Roughly speaking, it's going to store separate pressure curves 
for flaps on and flaps off.   but which would be most conservative:
 a) put the switch so that it detects ANY flaps
 b) 10 degrees
 c) 20 degrees
 d) full
 
 My thought was to put it at 12 degrees or so.
 
 Colyn

[Having worked many airshows with Jim Frantz, the developer of the AOA Pro, the standard answer to your question was to install the flap switch so it actuates with any flap actuation.  It simplifies the installation and is the most conservative setting.  FWIW.... <Marv>   ]


 
 On Oct 3, 2010, at 7:46 PM, Bill Bradburry wrote:
 
> John,
> There is a microswitch on the flap torque shaft that tells the AOA Pro that
> you have lowered flaps.  It dutifully tells you that it knows that by
> announcing "Flaps!".  It that is happening over and over, you have a loose
> connection or short or bad switch.
> 
> It is located somewhere under the seats.
> 
> Let us know what you find.
> 
> Bill B
> 
> -----Original Message-----
> From: Lancair Mailing List [mailto:lml@lancaironline.net] On Behalf Of John
> Hafen
> Sent: Saturday, October 02, 2010 1:05 PM
> To: lml@lancaironline.net
> Subject: [LML] "FLAPS" Warning Voice
> 
> Gents,
> 
> I have a IVP with duel Cheltons and an AOA Pro.  Taxiing out, after lowering
> my flaps to 10 degrees for takeoff, I get a random "FLAPS" voice warning in
> the headset.  
> 
> After takeoff and raising the flaps, the voice mercifully goes away.
> 
> Back in the pattern, with the flaps down, the voice warning starts up again.
> It squawks if I have one, two, or three notches of flaps down.
> 
> On roll-out, after the flaps are retracted, the warnings cease.
> 
> Question for the group:  How do I make the voice warning go away?
> 
> My AOA is calibrated, and I've been all through the Chelton setup screens to
> no avail.
> 
> Please let me know what I'm missing.
> 
> Thanks in advance.
> 
> John Hafen
> IVP 413AJ
> 275 hours
> 
> 
> 
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