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Date: Mon, 11 Jan 2010 19:41:18 -0500
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From: Hamid Wasti <hwasti@lm50.com>
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Subject: Re: [LML] Do-it-yourself AOA Project
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It is an interesting product with some clever ideas, but a very poor 
implementation. It is unlikely that it will keep working reliably for 
long in the real-world/real-aircraft environment.

The system does not take into account flap deployment.  Anyone here use 
flaps?

The "normal" position of the probe is with the Hall sensor at the zero 
point of the magnet. Anyone concerned about the fact that the system 
could report "normal" output if the probe or the magnet falls off?

Even the most rudimentary analysis of the Hall sensor's output as its 
temperature varies from -20C to +50C would reveal a potential for some 
worrisome inaccuracies. You could stall several LEDs before you expect 
to, or you could be several LEDs away from a stall when the system says 
you should be stalling. Would you be more or less likely to actually 
stall in these situations?

The design does not take into account the fact that each LED that is on 
will cause the main IC's temperature to rise by about 15C. A little slow 
flight practice with a 6 LEDs on and the IC is well past its 100C limit, 
generating a burning smell and possibly smoke. Same would happen after 
an engine out as you glide down at best glide speed. Can you think of a 
worse time to find smoke in the cockpit?

This is just a partial list of issues, but I think it gets the picture 
across.  The only thing worse than not having something is having 
something that is not reliable.

Regards,

Hamid

Gary Fitzgerald wrote:
> He has an article on this project in the Dec. 2008 edition of Sport
> Aviation.  Interesting use of a Hall Effect sensor.
>
> Gary Fitzgerald
> LNC2 extra-slow build ~70%
> engine: TBD
> St. Charles, MO
>
>
> ----- Original Message ----- 
> From: "billhogarty" <billhogarty@hughes.net>
> To: <lml@lancaironline.net>
> Sent: Sunday, January 03, 2010 3:08 PM
> Subject: [LML] Do-it-yourself AOA Project
>
>
>   
>> For those folks that liked the do-it-yourself Automatic Engine Dryer
>> Project article written by David Barker in the October issue of the EAA
>> Sport Aviation magazine,  there is another do-it-yourself project on the
>> web for a $ 50 Angle of Attack indicator that mounts on the pitot tube.
>> Check out "barkeraircraft.com".
>>
>> Happy New Year,  Bill Hogarty
>>
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