I've been thinking about AOA's. A buddy has one with an audio input and it seems to be fairly beneficial, especially in a canyon turn or similar circumstance. My thinking has led to this question, and I pose it here for debate, could separate AOA's on each wing help avoid a spin? It seems like the intuitive answer is no, but a spin is one wing stalled more than the other. Given that, it seems like there would be different AOA indications in an uncoordinated stall or any uncoordinated turn. Thoughts?

It's an interesting idea, but stalls and spins are not the same thing. What avoids a spin is knowing how to use your feet when you stall the wing, coordinated or not. The ragged edge of a stall is not a good time or place to be staring at gages to figure out what's happening.

So you have one on each wing, so 2 AoA indicators in the cockpit.
Prior to a spin one indicator will show lift and the other will show no lift.

But in reality will be useless in a real life scenario, because you already are in a spin or prior to a spin and dont need to look at any indicators to feel and see what is going on, and actually would be a distraction trying to look 2 indicators and compare them.

I have an AoA indicator and use it a lot and like it, I highly recommend it, Vx, Vy,Vg, and for backcountry it tells you how much lift you have available , even the stall warning is going off, the indicator lets you know the available lift, in short means more information.
Go for it.

I agree that 2 AOA indicators would be unnecessary. The difference in lift (and there's still some lift in a stall) is not all that significant, and looking at gauges isn't something you need or want to do while in a spin. After some 500 hours using mine, I like having an AOA indicator, and it's a very useful instrument. But having 2 of them would be mostly redundant.

I suggest that if spins are bothering you, you might get some good spin training from an instructor who is good at upset recovery or aerobatic training. You'll find that spins are mostly handled by feel and procedure and counting rotations by looking out the windshield, not by looking at the panel. The only time I looked at the panel was learning how to stop the spin within 10 degrees of the heading I wanted, because that was something I expected to do on my CFI checkride, and the Inspector did indeed require that. It's also necessary to look at the airspeed indicator after stopping the rotation and doing the recovery, so that the airplane isn't allowed to fly faster than its redline airspeed. I suspect that the recovery pull out is one place that a single AOA might prove useful, because it's possible to do an accelerated stall while pulling out, if the yoke/stick is pulled back too hard and too soon. My aerobatics instructor had me do that, to emphasize that pitch angle relative to the horizon is irrelevant; it's the angle of attack being excessive that causes a stall, no matter where the nose is pointing.

Cary

For a mild, steeply pitched spin like most of us have experienced or practiced, the difference in angle of attack is quite small. In a 150, 172 or a Citabria, the difference appears to be somewhere between no more than a degree and perhaps two to three degrees (measured at the wingtips). The split increases slightly as it develops.

If a flat spin is induced (Citabria) the split can become pretty dramatic. The outside wing will be under the normal stall AOA while the inside wing can approach 45 degrees!

I have read that in spin tests of a 1970's biz jet, only the outboard portion of the outside wing was below the stall AOA, with AOA measured at some point on the inboard wing exceeding 60 degrees. The jet recovered only with a drogue and was henceforth fitted with dorsal stabilizers.

I doubt the input from devices at both wingtips would be as useful as simply operating with a usable AOA margin.

I agree that an audio-based AOA is a great asset, to any pilot - new or experienced.

You only need one AOA to avoid a spin, for conventional backcountry flight operations. Generally speaking, if you don't stall then you aren't going to enter a spin...

So, as is often the case lately, I'm a little unclear on this topic.

I can usually tell when I'm about to stall, but that is probably because I've never stalled unintentionally. Pitch up, controls get heavy and unresponsive, plane shudders, nose drops.... push forward, level wings, add power, recover.

Is the AoA device meant to show an impending stall that is not intentional? Like in a climbing or descending turn? Or on short final?

I'm still on wheels, but I have a set of amphib floats standing by. I have been entertaining the idea of an AoA indicator to digitize the angle of attack on the step and, separately, the angle of final approach but I'm not sure an instrument would be any better than a few hours of memorizing the sight picture out the window.

They aren't cheap, so I'm struggling to understand the cost/benefit.

It was really a rhetorical question looking for some debate on the concept. I'm not worried about spins in the Skywagon. There's just been a lot of buzz about LOC and spins and I was wondering if there might be some potential for creating a spin prevention indicator using two AOA's.
Personally, I definitely want an AOA with audible feedback. I was very impressed by my buddie's King unit. I might need to put one on my Xmas list. Hopefully my wife is reading this thread...
Chris

Hi all,

I'd like to deviate this thread a bit and solicit comments on an AoA for pilots who use Contact's Brisk Walk Rate of Closure approach to landings and his energy management turns. It seems to me that a pilot practiced in these techniques might not require or get as much advantage out of the device? I was just at Oshkosh and lots of vendors selling these. Just wondering what the experts think? Thanks in advance.

I am thinking of getting iLevil's BOM which has an AoA.....

http://tinyurl.com/yahhws3k

Blue skies,

Tom
KCMA

albravo wrote:Is the AoA device meant to show an impending stall that is not intentional? Like in a climbing or descending turn? Or on short final?

I'm still on wheels, but I have a set of amphib floats standing by. I have been entertaining the idea of an AoA indicator to digitize the angle of attack on the step and, separately, the angle of final approach but I'm not sure an instrument would be any better than a few hours of memorizing the sight picture out the window.

They aren't cheap, so I'm struggling to understand the cost/benefit.

Yes, an angle of attack indicator is intended to inform you of an impending stall, intentional or not. But, if you can feel the approach of an intentional stall, you should also be able to feel the impending unintentional stall.

As to seaplane ops, I seriously doubt an AOA device would help you on the step to find the "sweet spot". That is indicated by acceleration, which you can feel, but which an AOA device can't measure.

There MAY be some benefit to an AOA device in glassy water landings, but I would still trust my own senses far more than the AOA devices being sold for GA airplanes.

MTV

I vote with Hammer and MTV

Spent close to 60 yrs flying with no AOA other than my internal organs.
Learning to ride the burble early stages of the burbble should be enougn.

The more you stick INSIDE the cockpit the LESS time you spend
looking out for what really matters.

The only additional "approach" instrument I put in was a slow speed ASI.
I mounted it 90* CCW so the 40 was at the top.
Amazing what ones peripheral vision can catch when that big white needle
stands erect. Others who initially laughed- learned to love it.

Nuff for now

Chhris C

I agree with those who would like an audible AOA. Mine is visual only (it uses a needle over a face that is green to the right, yellow in the middle, and red to the left), and although it's mounted on the top of the panel where I can see it without taking my eyes away from what's in front of the airplane, there have been plenty of times in the last 500 some hours that I've had it in the airplane in which I didn't see what it was doing because I was looking elsewhere (like you're supposed to do in the pattern!). So if I had my druthers, an AOA would be both visual and audible, and it would be lit for night use (mine's not lit). Mark Korin, the owner of Alpha Systems, offered last year at OSH that he'd give me a pretty fair discount if I wanted to upgrade, but I haven't taken him up on it--lots of other things to spend airplane money on, right?

My seaplane flying skills, such as they are, make me agree with Mike that the AOA indicator wouldn't help on take off. That really is a "feel the sweet spot" sort of thing, from my limited SES training experience. My glassy water training didn't give me enough experience to comment on whether an AOA indicator would be helpful there.

My take on having an AOA indicator is such that if I were to buy another airplane, it would be fitted with an AOA indicator very soon after purchase. Although I have enough time in the saddle over the last 4 1/2 decades that I can feel a lot of what the airplane is telling me, the AOA indicator gives me a lot of confidence that what I'm feeling is correct. It is most useful while maneuvering at slow airspeeds--the trend that is obvious during slow speed turns can be a bit eye-opening at first. There are those who suggest that an airspeed indicator is all that is necessary in the small airplanes that we fly, but even with relatively limited differences between lightly loaded and heavily loaded and with forward CG vs. aft CG, I can say for certain that the AOA indicator serves its purpose well.

Cary

Thanks for all the comments; good to see the Board so alive. But no responses to my primary question:

Re: AoA for pilots who use Contact's Brisk Walk Rate of Closure approach to landings and his energy management turns. It seems to me that a pilot practiced in these techniques might not require or get as much advantage out of the device?

Where is Contact when you need him? Probably up flying! LOL

Blue skies,

Tom

Tom,

As others have pointed out, what is outside the cockpit is more important. The extra help to slow down as we approach the numbers, rather than go too fast or drag it in, is visual reference to the apparent rate of closure with the numbers or anything in the beginning of the landing zone. Looking at the airspeed indicator is of no help. It would be dangerous to just arbitrarily decrease airspeed. I have never used one but arbitrarily increasing the angle of attack would be similar, I expect. It is perhaps strange, but the rate of closure does appear to speed up on an airspeed stabilized approach arriving at short final. And we certainly wouldn't use a stabilized ground speed approach to a stop sign with our automobile. This optical illusion, apparent rate of closure, really works well with either auto or aircraft.

Thanks Contact. Your response about what I expected. Fly to avoid high AoA unless you are in ground effect and about to land.
Best,
Tom

I missed your question on the energy management turn. I expect the AOA indicator might help us get maximum zoom up without stalling in the initial part of the energy management turn. Probably more accurate than airspeed indicator. Like everything in contact flying, however, I trust my senses of sound, sight, kinetic feel, etc more than any instrument.

We lost some old pilots in the transition to trusting instruments in IMC. Now we are losing young pilots in the transition back to contact flying, which has become a lost art. Integration of contact and instrument flying has benefited those who stay high but has hurt the art of maneuvering flight. And we all are in the maneuvering flight realm on every takeoff and landing.

I'm very much an advocate of keeping the eyes outside the airplane - especially when flying close to terrain. I am, however, sold on the benefits of the AOA instrument.

Specifically, I really like the ones that mount above the glare shield (like the Bendix-King KLR-10) and the Alpha Systems AOA with their "heads-up" display. Both allow you to clearly see the AOA indication while keeping your eyes totally outside the cockpit. I got to fly with the Alpha Systems AOA in a friend's airplane a year or so ago, and thought "I should put one in the experimental Bearhawk Patrol I'm building," instead of using the "built-in" AOA in the EFIS system I expect to use. Although if the EFIS-based AOA had a voice annunciation feature, it might be a decent alternative.

It is apparent that the folks who are advocating the glareshield mounted AOA devices because they are in your line of vision do little if any low level maneuvering flight.

When you are maneuvering at low level (including that potentially problematic base to final turn), most of us are NOT staring out the front of the airplane. We're either looking at something on the ground (critters, pipeline, final approach course, approach end of runway, etc) or looking for traffic. None of that involves looking straight ahead. At least only occasionally.

I've spent several thousand hours looking at stuff on the ground. That can be dangerous work if you're not really in tune with your airplane....the feel of it, the sound of the airflow over the airframe, the sensation you perceive in your after section......etc.

Maybe an AOA with audible indication would work for some applications, but in my case at least, it wouldn't, because much of what I did was radio telemetry, where listening carefully to often very faint signals is the task.

Granted, not many folks are doing that. But, sticking an indicator up on the glareshield is only marginally more useful than mounting it in the panel.

Opinion only.

MTV

flyingzebra wrote:[snip]
and I was wondering if there might be some potential for creating a spin prevention indicator using two AOA's.

"the ball" and a single AOA should suffice, no?

My AOA indicator is both audio and visual. In practice, I never look at the indicator, I just listen to it. Regarding energy management turns, like Contact said, perhaps in theory you can make a more efficient pitch up, but once the turn starts it is useless if you are doing the maneuver correctly since the whole point is to unload the wing. An unloaded wing doesn't stall.

Regarding spin prevention, AOA gauges are only accurate in the flight conditions they were calibrated in, which is coordinated flight. Slips/skids, intentional or not, produce error in the sensing of AOA. Finally, the conventional stall horn on Cessnas are telling you AOA information, they jut don't have the scale that an AOA gauge has. They can still be used for some AOA differentiation: off, occasionally chirping, on contiously... now if they come on continuously too far above the break, then they are of little value.

This video has been posted before (https://m.youtube.com/watch?v=CrPJac80W9Y), but in it they talk about the pitch reference between the wing and the horizon, which assuming a normalized approach path (brisk walk) equates nicely to AOA, and your eye will pick up deviations looking at the horizon much faster and with better fidelity than trying to glean that info from a 1" display in the cockpit