On 3/10/02 11:35 AM, "Fred Fillinger" <fillinger@ameritech.net> wrote:
> Ira Rampil wrote:
>>
>> Greetings all,
>>
>> Having recently watched with interest the traffic on AOA I thought I would
>> mention another choice, the DIY choice which I selected.
>>
>> A prominent commercial AOA device uses a probe made of a small block of
>> metal providing a known leading edge geometry which can me positioned in
>> angle to match the wing to which it is attached. Plans for a "quite"
>> similar device can be found at:
>>
>> www.snyder.on.ca/pages/angle%20of%20attack.jpg
>
> I just now noticed in this .jpg that the 2 ports are drilled parallel,
> and how that best reads AOA is escaping me. There may be differential
> pressure as relative wind varies, but perhaps too small for a reliable
> instrument. It may _appear_ to work, if it's basically an ASI - which
> reads out a stall speed, but not true AOA.
>
> One of the AOA makers uses similar design, but ports are angled to
> each other. There, as rel. wind varies, the differential pressure
> changes a lot.
>
> I'd prefer electronic transducers to read the diff., to add an aural
> alarm. But I've wondered whether you could use like a 2-1/4" UMA ASI,
> and plug the lines into the pitot and static ports. Play with the
> angle on the ports with first some kind of mockup on the wing.
> Repaint the face for AOA indication.
>
> How do you drill a 5-7/8" long hole in 1/2" thick ali. stock? I'd
> just pot some flox around tubing and fittings, in an aerodynamic
> shape, before going through 10 feet of 'lumnum stock trying!
>
> Regards,
> Fred F.
>
Hi Fred,
Note down at the bottom of the aluminum bar there are two holes one on
either side of the leading edge corner and each forming the port to the long
channel. The shape of the sensor end of the bar is important, thus making
it out of the bar stock is actually easier.
As for technique, actually I cheated and had my friend Steve Jasik (Mr.
MacNosy) use his CNC mill with an extended end-mill.
The Vendor of the differential pressure gauge actually already makes a
electronic reading version. I was considering running the two pressure
lines into 2 unused pressure ports on the EFIS/one so that the miniheliac is
just a power off backup.
Your Mileage May Vary!
Ira
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