Angle of Attack indicator

[Sweetnam]

At AOPA Hartford I spoke with the designer of Alpha Systems' angle of attack indicator [www.alphasystemsaoa.com]. It looks simple and well-made. They're available as a simplel mechanical version. As an aerial photographer I spend alot of time maneuvering at 1-2,000 feet and operating out of short runways. I'd feel safer having the AOA information. I have never heard the stall horn through my David Clark's.

Has anyone installed one of these? Is there an STC or is the dreaded Field Authorization the only way to put one on a 170?

Happy landings, Leslie

[GAHorn]

Leslie, you're going to have to discuss with them their suggested basis-of-approval for installation of their product.

The problem with some products (even those with apparent merit) is their failure to obtain and provide a basis of approval for the necessary alterations of certificated aircraft to provide for continued airworthiness. In the "old days" this was not viewed as such a big deal... but these litigious days, it's a dereliction-of-duty and the hope-to-find-a-gullible-customer that some mfr's offer products for sale.

I wouldn't want to be the one to tell you it's no big deal... and then be held accountable by you for having mislead you... when in fact it is the mfr's responsibility to provide the legal basis for the use of their product on a certificated airplane. (But I also didn't see anywhere on their website that they recommended it for certificated airplanes, either.... Perhaps their position is that it's intended only for experimental types...and letting the owner of the certificated aircraft be his own fool?)

If their installation requires significant alteration of the airplane (such as that described in FAR 43, Appx A, Major Alterations) then you will need a basis of approval for the installation. Their website didn't work or download very well for me, despite several attempts, but it does not appear to offer installation details that I could determine any useful info from. It appears some alteration of the wing will be required to accomodate their transmitter/detector, so I'd guess it is going to be a major alteration requiring either STC or field approval. I'd get their opinion in writing before I gave them any money.

(To be truthful, I can't see how such a device is much more than a digitized/illustrated stall warning device. Even flying aerial photography and low-level manuevering, both of which I've done quite a bit,... I wouldn't consider spending money on that item. When manuevering an airplane while focusing on outside references, there's little to be gained by constant reference to anything but trend-instruments anyway. The airspeed indicator is much better at trends than an AOA, in my opinion.)

HTH

[paulm60]

Hi Leslie,

I found your post after searching for AOA indicators; did you install one of Alpha System's kits?


Thanks,

Paul

[ronjenx]

At AOPA Hartford I spoke with the designer of Alpha Systems' angle of attack indicator [www.alphasystemsaoa.com]. It looks simple and well-made. They're available as a simplel mechanical version. As an aerial photographer I spend alot of time maneuvering at 1-2,000 feet and operating out of short runways. I'd feel safer having the AOA information. I have never heard the stall horn through my David Clark's.

Has anyone installed one of these? Is there an STC or is the dreaded Field Authorization the only way to put one on a 170?
Happy landings, Leslie

Go here http://www.alphasystemsaoa.com/?q=frequ ... _questions

About a third of the way down, they talk about 337/major/minor alteration. Could be either one.
Print off their brochure and take it to an IA, and see what he says.

[Brad Brady]

Brent and I installed one in the mid '80's for Marvin Nicoles, In his 170 A .......I still haven't seen a need for one........Brad

[KS170A]

I think if properly installed, it would give you a good sense of your true best glide speed, which some day may help make a better glide should a glide be required. I like the benefit of knowing what the optimal angle of attack is regardless of weight, but I find it more beneficial in higher-performance aircraft. I do not think I would put this at the top of my modifications list for a 170. My hangar-mate has one in his 182...looks more of a gimmick than anything. Handy in the jets, but seat-of-the-pants says about the same in our 170s.

[learaviator]

I have one of the Alpha Systems AOA mechanical kit and am considering putting it on my 170A. I am wanting to evaluate it because we are considering putting them on our 802 Air tractors if it seems to be useful. Does anyone have one of them on a 170 or know of someone that does?

[boydkl]

I thought it would be a useful "safety" addition to our 170A. My wife bought one and surprised me with it as a Christmas present.
Unfortunately, it will require a 337. When I talked with them (manufacturer) they were encouraging and sent me a note about an approval (337) obtained by an owner of a C172 out in Lubbock a few years back.
In my opinion it will be a "minor alteration" since I plan to reinforce the inspection plate hole in front of the right wing strut (if required) and mount the sensor through the inspection plate. I hoppe to get it done later this year or next year.
The 337 will be a great way to meet my local FSDO troops...

[blueldr]

According to the letter from the FAA shown by "ronjenx" above, it appears to me that a log book entry would be sufficient.

[GAHorn]

I thought it would be a useful "safety" addition to our 170A. My wife bought one and surprised me with it as a Christmas present.
Unfortunately, it will require a 337. When I talked with them (manufacturer) they were encouraging and sent me a note about an approval (337) obtained by an owner of a C172 out in Lubbock a few years back.
In my opinion it will be a "minor alteration" since I plan to reinforce the inspection plate hole in front of the right wing strut (if required) and mount the sensor through the inspection plate. I hoppe to get it done later this year or next year.
The 337 will be a great way to meet my local FSDO troops...

The location you are considering does not meet the installation requirements. IN their FAQs section, they specify "3.) 6” back from the leading edge..."

The leading edge of the wing, and the area forward of the strut is a "disturbed" area. The installation requires undisturbed air.

This is nothing more than a pitot/static type of instrument and subject to the same issues. It is not a mechanical AOA in the traditional sense and is subject to ice, bugs, and airflow problems ...same as your original pitot tube.

[boydkl]

I would not want to go the log book entry solution unless I had a letter from the local FSDO stating that "they" did not need a 337 for this installation.
RATS! I did not think about the area in front of the strut being "disturbed". The manufacturer would likely have warned me when I got back with them. I may have to go for a "new inspection port/sensor mounting" location outboard of the strut for the 337.

[Brad Brady]

As I posted earlier...I feel that the AOA instrument is no more than a toy to double check the airspeed indicator. If your Butt and the air speed indicator is telling you, you are in trouble, you have already exceeded what ever the AOA will tell you. (when your butt starts pulling foam from the seat.....your not going to make the end of the canyon) Oh! by the way.. it is a major repair and does need a 337....

[johneeb]

As I posted earlier...I feel that the AOA instrument is no more than a toy to double check the airspeed indicator. If your Butt and the air speed indicator is telling you, you are in trouble, you have already exceeded what ever the AOA will tell you. (when your butt starts pulling foam from the seat.....your not going to make the end of the canyon)

Then it's time to do a canyon approach! (I have no idea what the value was in practicing those in a 4 engine jet)

[Brad Brady]

sorry John, I just re posted....you will need to re read my last post.

[GAHorn]

Boyd...it's not just in front of the strut... It's anywhere within 6" of the leading edge according to their installation instructions, and they do not define that point but the leading edge skin goes all the way back to the front spar. I suspect you'll have to find a place farther aft.

On top of all that.... the device MUST indicate a stall SIMULTANEOUSLY with the factory audible stall warning. If it doesn't ..it must be recalibrated to do so. With that in mind....why bother with the thing? What will it accomplish other than to require you to divert your attention/visually from outside to inside the airplane...adding to the hazards of your intended purpose of manuevering?