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10-18-2009, 07:29 PM
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Join Date: Aug 2005
Location: Estacada, OR
Posts: 787
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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.
__________________
Richard Scott
RV-9A Fuselage
1941 Interstate Cadet
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10-19-2009, 03:36 AM
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Join Date: Jul 2007
Location: Indian Harbour Beach
Posts: 87
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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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10-19-2009, 07:39 AM
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Join Date: May 2005
Location: Savannah, GA
Posts: 1,301
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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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10-19-2009, 10:13 AM
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Join Date: Jan 2005
Location: Powder Springs, Ga
Posts: 309
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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!
__________________
Kurt Lohmueller A&P, DAR
Powder Springs, Ga
RV6A "Kurt's Toy" - Flying
RV12 - Flying - Sold
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10-19-2009, 10:32 AM
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Join Date: May 2005
Location: Savannah, GA
Posts: 1,301
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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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10-19-2009, 02:28 PM
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Join Date: Dec 2007
Location: Flagstaff, AZ
Posts: 2,653
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Quote:
Originally Posted by doctornigel
Is there a reason you HAVE to install the stall warning vane? Any FAR's or such? Thanks.
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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.
__________________
Patrick Kelley - Flagstaff, AZ
RV-6A N156PK - Flying too much to paint
RV-10 14MX(reserved) - Fuselage on gear
http://www.mykitlog.com/flion/
EAA Technical Counselor #5357
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10-20-2009, 12:58 PM
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Join Date: Feb 2005
Location: Apollo Beach, FL
Posts: 10
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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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10-20-2009, 01:09 PM
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Senior Curmudgeon
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Join Date: Sep 2005
Location: Dayton Airpark, NV A34
Posts: 15,420
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Pitot backup?????
Quote:
Originally Posted by B. Hoover
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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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.
__________________
Mike Starkey
VAF 909
Rv-10, N210LM.
Flying as of 12/4/2010
Phase 1 done, 2/4/2011 
Sold after 240+ wonderful hours of flight.
"Flying the airplane is more important than radioing your plight to a person on the ground incapable of understanding or doing anything about it."
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10-20-2009, 02:59 PM
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Join Date: Feb 2005
Location: Apollo Beach, FL
Posts: 10
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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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10-21-2009, 06:57 AM
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Join Date: Feb 2006
Location: Peachtree City, Georgia
Posts: 440
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Quote:
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There are no ugly probes to slow you down or collect ice and no moving parts to break.
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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)
__________________
John Goodman - 40572
First flight was 25 June, 2011
N711JG
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