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  #11  
Old 10-18-2009, 07:29 PM
RScott RScott is offline
 
Join Date: Aug 2005
Location: Estacada, OR
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It doesn't matter very much where you install the AFS AOA--it has an audio warning so you don't need to look at it. OTOH, it does make sense to put it where it is close to your line of sight.
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  #12  
Old 10-19-2009, 03:36 AM
doctornigel doctornigel is offline
 
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Location: Indian Harbour Beach
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Is there a reason you HAVE to install the stall warning vane? Any FAR's or such? Thanks.
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  #13  
Old 10-19-2009, 07:39 AM
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Ed_Wischmeyer Ed_Wischmeyer is offline
 
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Location: Savannah, GA
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Default Some theoretical thoughts

Here's a bunch of thoughts in no particular order:
* AOA is a great concept when maneuvering near the ground at low speeds. The real question is whether a visual display is appropriate when you're mostly looking outside, i.e., when you need it most. My opinion is that an aural stall warning with multiple sounds, sort of like a Cessna reed-style system, has the most potential, especially if it is calibrated to give warning of a too-slow approach that can lead to a hard landing.
* AOA can be great for maintaining optimum AOA for long range cruise or for Vy.
* I've read what I consider a lot of hype about AOA. I think that the concept has merit for some things, but , for example, AOA won't tell you when to rotate on takeoff.
* I've not read anything about how you use AOA to reduce your susceptibility to gusts on short final. There are plenty of formulae for airspeed, by comparison. Having a device with no procedures for using it and just saying "it's wonderful" is nonsense at best....
* At Boeing, many customers were excessively on the AOA bandwagon. Boeing eventually had several of its most senior and most respected engineers write an article to bring sanity to the discussion.
* Over the years, I've tried several times to write an article on AOA, but when I started asking the hard questions, vendors had trouble finding me an airplane to fly.

My opinion? I think that most of the value of AOA is hooked up to a variable sound aural alert. I like having it as a secondary indicator for Vy and optimum AOA. But, having flown a number of aircraft with no stall warning system at all, I can (and do) get by without it. And it's not clear how much operational advantage there is to holding precise AOA for Vy and long range cruise for the operations I do.

Ed Wischmeyer
(lotsa good letters go here)
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  #14  
Old 10-19-2009, 10:13 AM
664781 664781 is offline
 
Join Date: Jan 2005
Location: Powder Springs, Ga
Posts: 309
Default AOA Warning

My AOA has got my attention twice in the last year. (got Angle, Angle push in the headset). Once turning crosswind on climb out and another turning base to finial. First time had 90 indicated with a good VSI, don't know what happened but I droped the nose anyway. 2nd time was indicated at 105 in a steep bank, just unloaded it a little and it went back to in the green on the indicator. You may want to wire the audio in both headsets, mine is just in the pilots side. My son was flying from the right the first time and he did not know why I took it away from him!
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  #15  
Old 10-19-2009, 10:32 AM
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Ed_Wischmeyer Ed_Wischmeyer is offline
 
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Default Thoughts on voice alerts

When I was at Boeing, I did research on appropriateness of voice alerts for different situations (including manned simulator trials), and based on that and other thoughts, I'd prefer a series of sounds to voice alerts for high AOA:
* The first part of a sound often is just an attention getter, and if it's a word, chances are it will get lost and will need to be repeated if it's important
* Voices can be too compelling and block more important aural information sources. (That may not be the case for a stall warning).
* You can't tell if the silence between words is a deliberate pause between words or if the causal situation has been resolved
* I've not thought of any words I'd like to hear during a stall or high AOA situation. And it's not clear to me that having "push" given as an instruction is always going to be what I want.

And it's interesting that I never heard any discussions while I was at Boeing about wanting to make stall warning be a voice alert....

Multi-tone AOA for eyes-out flying at low speeds and low altitudes? Cool! Eyes-in AOA for optimizing climb and cruise? Maybe, but don't know how much difference it would really make for my operations. Voice alerts? NO.

Ed Wischmeyer
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  #16  
Old 10-19-2009, 02:28 PM
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flion flion is offline
 
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Quote:
Originally Posted by doctornigel View Post
Is there a reason you HAVE to install the stall warning vane? Any FAR's or such? Thanks.
No. I'd venture to say that almost no RVs have a stall warning vane, with the exception of the -10. There is no FAR requiring it.

Regarding Ed's first comment in the first set, not all 'low-and-slow' is visual. And I can glance at an AOA as easily as I can do my regular scan while landing. Not disagreeing with the idea that an aural alert is a good idea, though.
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  #17  
Old 10-20-2009, 12:58 PM
B. Hoover B. Hoover is offline
 
Join Date: Feb 2005
Location: Apollo Beach, FL
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I'm still dreaming about my RV, but the reason I plan on installing an AOA system is for a back up to the Pitot/Static system. If icing (or bugs) blocks my pitot tube then I still have an excellent way to gauge airspeed during approach and landing. On planes with large gross wt. changes the approach speed is calculated for each landing. However, the AOA will always be the same (assuming the same amount of flaps are used).
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  #18  
Old 10-20-2009, 01:09 PM
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Mike S Mike S is offline
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Location: Dayton Airpark, NV A34
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Default Pitot backup?????

Quote:
Originally Posted by B. Hoover View Post
I'm still dreaming about my RV, but the reason I plan on installing an AOA system is for a back up to the Pitot/Static system. If icing (or bugs) blocks my pitot tube then I still have an excellent way to gauge airspeed during approach and landing. On planes with large gross wt. changes the approach speed is calculated for each landing. However, the AOA will always be the same (assuming the same amount of flaps are used).
Dynon uses extra holes in the pitot for the AOA function, if the pitot freezes up, I suspect the AOA will already be blocked too.

AFS uses a couple of very tiny holes on the wing, one top, one bottom. I expect they will also be subject to the same freezing problem as a pitot.

Bugs, who knows what they will plug up.

All that said, my buddy with an AFS 3500 absolutely loves his internal AOA,
uses it faithfully.
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  #19  
Old 10-20-2009, 02:59 PM
B. Hoover B. Hoover is offline
 
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Location: Apollo Beach, FL
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Default Pitot backup?????

Well, I?m a fan of some type of redundancy? I don?t like singe point failures. (see I even said that twice ) The planes I fly all have redundant pitot/static systems and airspeed indicators. Knowing how fast you?re going, especially slow/close to the ground, is important. I was just reading about somebody flying a RV who had a cracked pitot line going into an instrument and it was throwing off his indicated airspeed. You can?t cross check it against GPS, but AOA would give you an accurate indication of how you?re doing at approach speeds. I will have to do a lot more research, but the Advanced Systems one says ?The AOA Pro and Sport are lightweight and easy to install. There are no ugly probes to slow you down or collect ice and no moving parts to break.?
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  #20  
Old 10-21-2009, 06:57 AM
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johngoodman johngoodman is offline
 
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Location: Peachtree City, Georgia
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Quote:
There are no ugly probes to slow you down or collect ice and no moving parts to break.
I wouldn't say airspeed probes are ugly - form follows function. The Dynon heated pitot/AOA is identical to most other probes in appearance and shouldn't "collect ice". It doesn't have moving parts, so why the resistance to Angle Of Attack?
It works in all phases of flight, will show you best climb, maneuvering, approach, etc. with just a glance. And yes, it will show you rotation speed in a way - it will show your wing flying when you should have already rotated. (g)

John
(yup, I'm Navy)
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