Two comments:

1. In agreement with your points, awareness is not synonymous with safety.

2. If the FAA is going to get on the AoA bandwagon, they should man up and create some standards for the displays. Nice thing about a good old-fashioned steam-dial airspeed indicator is that everybody can read one at a glance. We lost a lot when glass navigators replaced VOR/LOC navigators that included simple CDI displays, because insufficient effort was devoted to standardizing the presentation and input of information in the new devices. Let's not go down the same rocky road with AoA displays. There's plenty of room for innovation under the umbrella of properly-written regulations. Really. The goal should be: any pilot; any airplane; any AoA display - same level of conveyance of information, with absolutely no type training required.

If we put the proposed effort into pilot training (and I support that notion), we would achieve the desired safety statistic without the gadget itself.

A few years ago, a magazine interviewed me about " glass panel" flight training. During the interview my remarks included that flying Technically Advanced Avionics required additional hours of ground and flight training to the existing popular curricula. As I believed that "glass deck" technology was complex and extensive regardless of the OEM. Specific platform training will help and this takes more time and money.

I believed then, as I do now, that the FAA needed to include minimum training standards and endorsements.

The article was submitted only to be return with an alternate write up on how wonderful I was as a CFI and as a TAA instructor. The choice given was the new write up or none. No need to bite the hand that feeds them they said. So, who am I to argue - I wanted to be famous.

The suggestion that an AoA systems be added to the FAA knowledge tests is opening a can of worms and perhaps open a path to formal TAA training under the FAA Practical Test Standards or ACS. I wonder what the AoA and TAA manufacturers would have to say about this.

It isn't clear to me what the AOA is going to do that the stall warning device, which has been incorporated into small airplanes for a long time now, didn't do.

"It isn't clear to me what the AOA is going to do that the stall warning device, which has been incorporated into small airplanes for a long time now, didn't do."

A stall-warning horn sits mute until AoA exceeds a "trip point" value, regardless of the rate-of-change of AoA. Well-designed AoA displays provide both the absolute instantaneous value of AoA and rate-of-change information. Presuming that the pilot is paying attention, this can be the wake-up call-to-action that needs to be initiated before the AoA attains a critical value.

It's all about the display of the information. Human factors studies show that traditional dial indications impart information better and more quickly than moving-tape indicators, because the needle's angle gives instantaneous value AND rate-of-change information - even when no numbers are painted on the dial. Compare a traditional two-hand clock presentation with a digital display of the time-of-day. The first works immediately, even without a display of the numbers; the latter requires the viewer to read the display, then associate the numbers with an abstraction of time.

Everyone is missing the point. It's not about avoiding stalls, or even safety, but a more precise way to fly. AOA is constant, and the best AOA for some desired climb performance for example doesn't change under different conditions, though the airspeed to attain that AOA can vary quite a bit.

In an ideal world, you would rarely use your airspeed indicator. You'd have an AOA indicator with several marks on it, one for best climb, one for normal climb, maybe several for various landing types, one for stall, etc.

Yes, most all GA airplanes have had an AOA indicator for decades...the stall warning indicator is an AOA indicator, and it can be used for flying an AOA. In fact, the Cessna 195 manual (I think...maybe it was the Cessna 180 manual) says for a short field takeoff, fly an angle of attack that keeps the stall horn just teetering on and off. The engineers knew the best angle of climb in that airplane is at an AOA just below the critical angle of attack, on any day, at any altitude, and any weight. Airspeed will vary significantly across the range of possible air temps, altitudes, and airplane weights, but the AOA for the best angle of climb is constant.

Flying AOA is just a more precise way to fly. The Navy flies AOA, not airspeed, and I think they know what they are doing.

There are fatal accidents due to approach to landing stalls where proper training would have prevented them. About 20 US fatalities annually. AoA instrument sales bank on increasing safety and on the reduction of fatalities attributed to flying at or over the critical angle of attack zone. The Alpha instrument will give you precision flying if properly calibrated but without proper training or understanding of the AoA the fatality toll will remain as is, much like the Cirrus BRS "new" deal. Thomas Yardley explains his caption well. On the other hand I look at what sells and its added expense to an already expensive and complex flying world. Precision flying at $3500+ is a hard sell.

Given that stall-spin accidents overwhelmingly occur during low-altitude maneuvering in the landing phase where the pilot's attention is almost exclusively focused on the external environment, one cannot help but wonder if another indicating device is really going to help.

Given that stall-spin accidents overwhelmingly occur during low-altitude maneuvering in the landing phase where the pilot's attention is almost exclusively focused on the external environment, one cannot help but wonder if another indicating device is really going to help.

One problem with the aircraft parachute is the tendency to regard it as a primary method of "saving" a flight. It should be used only as a last resort and thought of that way. Do car drivers regard the air bags as primary for any "jam" they might drive into. I hope not. They are there is things really get out of hand and not before.

I have been flying Piper Cheyenne II's for over 30 years. They have an AOA installed from the factory that "controls" the SAS system. Neither Piper nor any training facility has ever emphasized this instrument and indeed I know it is there but do not use it as a pilot flying aid.

BZ

These pressure differential "lift reserve" devices do not indicate AoA! Look at the original testing results. At higher speeds the stall point is NOT at the same indicated point. In other words, an accelerated stall in a steep bank will not be indicated at the same point as a normal landing configuration stall. So you may be lulled into a false sense of safety in steep banks near stall. This needs thorough testing and examination in order to prevent accidents. They are great for normal approaches and getting your energy right, thus preventing floating or landing short, but don't use them in a bank.

When airbags first became mainstream (circa 1992) it was observed that drivers with airbags tended to take more risks in driving maneuvers compared to those without airbags. The knowledge that something is there to "save you" caused them to rachet up the risk to the same point as it was before the airbag. Human nature is hard to overcome sometimes.

I have used an Alpha Systems AOA in my aircraft for 9 years. First with the multi-segment light bar and then later with the more traditional chevron light bar and later added the audio option.

Some general comments: 1. The AOA indicator on the glare shield is the best location for seeing where AOA is at any given moment of flight. Burying the display in the instrument panel is not good.

2. Stall Warning devices are calibrated to sound at 5-8 knots above stall. AOA on target is generally at 1.3 Vso, which is close the the recommended approach speed for most GA singles. So, assuming a 50 knot stall speed then you will have 2-3x more margin when going below AOA target speed than with the aircraft stall warning annunciation.

3. Kelley, I am not sure what point you are trying to make. As the bank or wing loading increases then the accelerated stall speed will increase above the normal stall speed. The differential pressure sensor replicates this process and will show increased AOA at a higher IAS in a steep bank.

4. I agree without training then AOA is just another toy. With proper training you will have more consistent landings for touch down points and warning for abnormal situations.

As a aviation writer for another publication I endorse these units and find AOA a plus to safe flying through 9 years experience in my own aircraft and 20 years experience in many model Citations.

Fly Safe Everyone

Kelley is right, these differential lift reserve don't measure aoa and at least back when it was originally patented (4,559,822) they didn't try to pretend it did.

It doesn't actually measure flow angle accurately, the inventors equations are wrong. There was a wind tnnel test online that showed that, but I can find it anymore.

Even if it did accurately measure flow angle, the flow angle under the wing is not the AoA because the wing turns the air. That's its job after all.

The bally shannon tests show a ranges 5-7 mph for the on speed light at the same config, weight, g. That's less accurate than flying airspeed.

These things seem to rely on the combination of imprecise readings combined with subjective feelings...I don't think they would look good under any kind of objective test of what they claim to measure - AoA.

A final thought is, if you had fdrs and could posthumously interview pilots that spun in, would you find the problem that they didn't know what speed (or aoa) they were flying, or that they didn't know what speed (or aoa) stall was. Different issues with different solutions.

If Air France 447 had been equipped with an AoA indicator when they lost reliable airspeed readings, would the right-seat pilot have continued applying nose-up stick pressure until the crash? I'm just sayin'...

I think what it comes down to is setting expectations. When Cirrus came out, everyone talked about the BRS and the design of the plane and how safe it is. I think they did a dis-service to the plane and the BRS by not talking realistically and stating plainly that you still have to know what you are doing and make wise decisions. So, Joe pilot goes out and buys a Cirrus and suddenly he's invincible. It has all the latest avionics, it looks like a spaceship in there, it has the BRS, the wing is unstallable, and I AM INVINCIBLE!!!! The reality, as we all know, is that you still have to be a capable pilot and make good decisions.

So, as far as AOA goes, if you know how to use it, and use it wisely, I should think it will help those pilots. Although I am not convinced that it is any better than the stall indicator on my Mooney. Because when I hear that indicator going off, I don't really want to push it any farther to see how close I can get.

This homo sap has been flying for years without a stall warning horn or AoA indicator. Evidently, I'm blithely unaware of precision flying.

For me, when it comes to stalls, power lines, mountains, other aircraft - I simply am trained to keep a determined distance from each, and just don't care to split 2 seconds or 2 miles into scaled micro-measurements to allow me to fly 'more precisely' toward those things. I'd rather use the space, time and power precisely in the air to allow me a greater, not reduced cushion to fly woolly and imprecise if I wish to. I like it both ways.:)

On another note this AoA push appears, once again, to be a manufacturer's drive to promote the groupthink Paul mentioned to sell their gadget - like so many pilots with 30k glass panels in homebuilts on clear days flying to breakfast - so I'll wait to see if more '..distracting flashing lights and blaring horns' will change the GA accident rate any.

While applauding the general sentiment; I would caution against cluttering up the Written Test Question pool with any more superfluous chaffe. It is already filled with kerflapsnaffle mnemonics and ADF nav techniques and Remote indicating compasses directions of rotation and questions about nonexistent weather charts that it is no longer a useful metric for performance but rather an exercise in endurance.it would make as much sense as having questions about operating the BRS handle in the SR22 or the canopy latch on my AA5b or the 13 sump drains on certain C-types. .

I'm going to second the note on Air France 447 and add a personal note of a guy I worked with who killed himself on takeoff trying to get over trees. He was on a personal strip, very narrow, and while he mowed the grass he didn't mow the the grassy overgrowth along the narrow runway, at least not below the level of the wings. In a takeoff into the sun, the airplane drifted a few feet and the left wingtip struck the grass, slowing the airplane down in the takeoff roll. He got over the first set of trees but not the next and did a full stall into them and burned in the airplane after it hit.

Of course, this was the guy who had crashed a Cessna into a ball, he got out and said "Wow, I can crash in a Cessna and everything will be all right!"

Until the gas catches fire, I suppose.

Anyway, he may have been able to save his butt with an AOA indicator, maybe not, but there's always the possibility it could have. Then again, if he had just trimmed the overgrowth along the runway then all this would have been moot. Still, I'd think taking off in front of trees may be a good time to have AOA . . .

David, sorry to hear about your friend. I agree the AoA may have prevented the stall (in the Cessna T/O example) IF the pilot could keep his wits about him, follow the AoA, and intentionally fly into the treeline instead. That is a tough thing to do. For a view of what that's like, search for that youtube video from the past year of the Stinson 108 that hit trees while departing a backcountry airstrip at high DA while fully loaded.

Bottom line is sometimes it's too late to do anything about it once you have passed the abort point (if you bothered to have one). That's why you need to be fanatical about your DA calcs and leave yourself generous margin. I flew off a really short strip for many years and looking back I'm actually glad that part of my life is behind me.

Hello Paul,

This issue is not what its seems. Years ago I stopped trying to convince pilots regarding the benefits that a AOA gauge could provide. Most just listened politely and kept on with their business and continued to fly in the manner they had become accustomed. However things have now changed.

Insurance companies are tired of paying out the same money for the same accidents that occur at the same rate year after year. Wouldn't you want your insurance premiums reduced? Why should I have to pay a higher insurance premium for an accident that was preventable? Better yet, the training takes so little time, the equipment is available, and how do you explain to the family that he or she didn't need to die. As a group, pilots, and the companies that insure them have accepted this accident rate for stall/spin events for decades.

I imagine that very soon if you equip your plane with a AOA gauge your insurance will cost less. If you don't you'll be charged a bit more to cover the planned for accident rate. After all, if I went to the trouble to equip my plane, (which I have) and gone thru the training to know how to use it, (I'm Navy trained), why should I pay more for aviation insurance than another pilot who doesn't?

The insurance companies will finally lead the change, talking about its benefits is not enough incentive to switch over. In the end, if you were the one to have to break the news to a family that lost its father in a stall spin accident, the cost of the equipment and training would be inconsequential.

Finally, to the fellow that wrote the following I did not understand some of the terms you used. Flow Angle? I'm not sure what that is.

Even if it did accurately measure flow angle, the flow angle under the wing is not the AoA because the wing turns the air. That's its job after all.

Hello Paul,

This issue is not what its seems. Years ago I stopped trying to convince pilots regarding the benefits that a AOA gauge could provide. Most just listened politely and kept on with their business and continued to fly in the manner they had become accustomed. However things have now changed.

Insurance companies are tired of paying out the same money for the same accidents that occur at the same rate year after year. Wouldn't you want your insurance premiums reduced? Why should I have to pay a higher insurance premium for an accident that was preventable? Better yet, the training takes so little time, the equipment is available, and how do you explain to the family that he or she didn't need to die. As a group, pilots, and the companies that insure them have accepted this accident rate for stall/spin events for decades.

I imagine that very soon if you equip your plane with a AOA gauge your insurance will cost less. If you don't you'll be charged a bit more to cover the planned for accident rate. After all, if I went to the trouble to equip my plane, (which I have) and gone thru the training to know how to use it, (I'm Navy trained), why should I pay more for aviation insurance than another pilot who doesn't?

The insurance companies will finally lead the change, talking about its benefits is not enough incentive to switch over. In the end, if you were the one to have to break the news to a family that lost its father in a stall spin accident, the cost of the equipment and training would be inconsequential.

Finally, to the fellow that wrote the following I did not understand some of the terms you used. Flow Angle? I'm not sure what that is.

Even if it did accurately measure flow angle, the flow angle under the wing is not the AoA because the wing turns the air. That's its job after all.

As has been mentioned by several posters, simple differential pressure is not AOA. Think of mounting the probe to the wall of a wind tunnel (the angle (AOA) is now fixed). As the wind tunnel changes airspeed, the cockpit indicator will also change ... but the actual AOA is not changing.

On the flow angle comment, the poster is referring to AOA. Putting the probe below the wing (like replacing an inspection panel) is a poor location to measure AOA as the airflow parallels the airfoil. This is why pitot tubes are placed there, minimizing angle changes into the pitot tube.

On the AF447 accident, the crew did have AOA ... in 4 forms: on the airspeed indicator, on the attitude indicator (pitch reserve indicator), as the stick shakers and as the stick pusher. Part of the problem is that when the flight control system is operating normally, the stall recovery technique is full power and full aft stick ... the problem was the flight control system computer was not in normal mode.

Paul's point is quite valid, and calibration of an AoA is not straightforward in dynamic turning conditions. I once was on short final in my Apache Geronimo when the controller asked for a 360 (the Geronimo was a familiar sight to the tower guys), so I applied full-throttle on both engines and did a 30-35 degree banked turn. I throttled back when I was aligned back with the runway, and landed normally in 1/3 of the field length. No Problem! But as I was doing the max throttle turn, I was quite aware that I had no idea how close to a dynamic stall I really was. Now add an AoA, and I could have monitored my margin against loss-of-lift and protected against a fatal stall. However, AoA calibration is straight-and-level at 4,000 feet or above (the FAA altitude limit for screwing around in a twin). The dynamic loading of the wing by engines should make that calibration conservative, regardless of bank angle. So has that been tested in a light twin? Probably not. Just one instructor did have a student enter a stall and the beginnings of a spin during 5 years my twin was used for training and his words and expression as he described the experience suggests that a test pilot might want an ejection seat before doing AoA calibration checks in a max performance turn. And why else would I want an AoA? I don't stall in straight-and-level and am quite aware of the dangers of the turn to final and keep my rudder straight then. No question, an AoA is valuable and I have considered installing one under the "situational awareness" clause. Note - the 1956 PA-23 does not have a stall warning indicator or an AoA.

Alan, you fly well ... and correctly. If your PA-23 has a stall warning system (probably a little vane on the leading edge), this device is AOA-based. It will protect you whether the airplane is turning or in level flight, at sea level or 15,000 feet, at light or heavy weight, at 1G or 3Gs and at -20 or +95 degrees temperature. The problem is that it only works at one point and won't protect you if you change the stall speed very rapidly (roll into a turn and pull abruptly ... i.e. overshot the runway centerline when turning base to final). The big plus of continuous AOA is that you know how far away you are all the time ... not just the one point that says, "You've gone too far!" Keep up the great flying!

(PS. 25+ years of Flight Test certification experience ... and AOA is a passion)

Alan, you fly well ... and correctly. If your PA-23 has a stall warning system (probably a little vane on the leading edge), this device is AOA-based. It will protect you whether the airplane is turning or in level flight, at sea level or 15,000 feet, at light or heavy weight, at 1G or 3Gs and at -20 or +95 degrees temperature. The problem is that it only works at one point and won't protect you if you change the stall speed very rapidly (roll into a turn and pull abruptly ... i.e. overshot the runway centerline when turning base to final). The big plus of continuous AOA is that you know how far away you are all the time ... not just the one point that says, "You've gone too far!" Keep up the great flying!

(PS. 25+ years of Flight Test certification experience ... and AOA is a passion)

Agree 100

I don't see the point in incorporating an AoA meter in a light airplane. As already stated,we have Stall Warnings, admittedly with their limitations. And I also ask; what about 'stick position'? What real additional safety benefit is to be derived? Also, how effective will an AoA meter be at low speed (on approach) in a lightly wing loaded airplane in gusty conditions?

First and foremost, I agree that an AOA meter in any VFR airplane is not a good solution to the stall/spin problem. Good pilots have their eyes looking outside when they are in the pattern (during both takeoff and landing).

The type of airplane is not relevant except that airliners don't stall/spin in the pattern as often as GA aircraft. Without getting into a lot of detail like Reynolds number, etc., the wing stalls at set angle of attack (per flap, spoiler, landing gear, etc. configuration). The current stall warning systems give an ~5 knot warning prior to stall. If the wind gust component is 10 knots, how long does it take to pass through that 5 knot warning? Light airplanes have less gust margin than larger airplanes due lower stall speeds (typical approach speeds being 1.3 Vstall.

GA airplanes also maneuver much more in the pattern, and stall speeds change a lot (and rapidly) with load factor. Situational awareness (continually knowing how far from stalling you are) would be very effective in saving lives.

I doubt that anyone is still looking at these posts, but I invite anyone that is to contact me personally at fly-in-home@att.net if you are. I'd love to discuss this topic with any and all.