The Alpha Measurement

December 28, 2010 by Bruce Landsberg

Sometimes an accident hits so close to home it causes us to question the fundamentals. A friend lost some business acquaintances landing a Bonanza at his private strip when the 5,000 hour pilot inexplicably stalled and they spun in. He began to wonder if an angle of attack (AOA or Alpha) indicator would have helped and why they weren’t installed on many more aircraft. I’ve wondered myself.

Most of us were taught to use airspeed as a proxy for AOA. But it’s a derivative that measures indirectly and not always accurately. Instructors the world over have reminded pilots to watch airspeed but perhaps the warning should be to “Mind the Alpha.”  The FAA, through knowledge and practical tests, has attempted to ensure that we know that airplanes can be stalled at any airspeed or attitude. Yet every year about two dozen pilots, rookie and veteran alike, fatally misjudge that critical angle. Why?

My guess: distraction. The old bromide is to “Aviate, navigate, communicate.” But we get distracted by any number of shiny things or operational procedures that clamor for attention at the worst possible time during approach and landing. Typically, the aircraft is bleeding energy as the pilot reduces power, sets flaps, negotiates with ATC, follows traffic, etc. Alpha increases.  Turning and/or poor coordination often close out the scenario.

So why hasn’t the industry adopted Alpha and routinely given us a gauge to measure it? Good question. Are the current stall warning devices adequate on light aircraft? In today’s glass cockpits it would be relatively simple to add Alpha and appropriate warnings. The nice lady whose voice advises of 500 feet and IFR minimums might also let us know when Alpha was about to become critical:  “Alpha”, “Don’t stall”, “Lower the nose Dummy” could be spoken with increasing volume and stridency.  Some new light aircraft are developing a measure of automatic envelope protection through the autopilot system.  Is this what’s needed? Perhaps still more training is the ticket –  Air Safety Institute produced an award-winning online course, Essential Aerodynamics: Stalls, Spins, and Safety.

What about retrofit to the existing hardware? We did it to Air Safety Institute’s Piper Archer for about $4,000 installed. It allows for impressive short field performance but not many of the pilots have embraced it despite the fact that one can fly with precision and make impressive short field landings. I’m perplexed.

What do you think?

Bruce Landsberg
Senior Safety Advisor, Air Safety Institute

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53 Responses to “The Alpha Measurement”

  1. John Smith Says:

    Why is AOPA constant trying to get us poor GA pilots to spend money on issues easily resolved by proper training? A couple thousand here, a few thousand there. It would seem that AOPA think its membership has unlimited money. Who is AOPA catering to these days? It certainly isn’t it’s membership that’s for sure.

  2. Tony Says:

    Were I an owner, would I shell out $4,000 for an AoA indicator? Probably not. But tge reak question is why these aren’t already standard.

  3. David C. Says:

    Bruce, I think this is an excellent idea. While we may not be able to retool the existing fleet, there’s no good reason why not to employ this in the new glass cockpits that flights schools are rapidly shifting towards.

  4. Bruce Landsberg Says:


    Thanks for your note. Let me be clear – no one at AOPA is recommending that anyone be required to install anything. Part of Air Safety Institute’s mission is to research various technologies as they impact safety, training and pilot usability.

    There are some technologies that are highly cost effective and others that aren’t. Economics plays a large part in any owner’s decision. Risk tolerance by individuals also plays a part.

    We’re not selling anything – just asking questions. When more than two dozen people die annually – seems reasonable to at least ask why. You’ve given me some thoughts for a future blog.

  5. Marty Says:


    After two high profile military accidents that resulted in the loss of several lives and destruction of two very expensive airframes, I have been become very interested in the concept of alpha and wish the planes I flew were so equipped.

    Please keep bringing these ideas up. We all need to think about these topics to be the best we can be in the cockpit.

    Happy New Year!

  6. Brian Turrisi Says:

    You have touched on one of my modern questions about airplane technology. With all of the fancy glass cockpits appearing, I am amazed that no one is emphasizing or providing an easy path to include an AOA indicator in our planed. It clearly is the way to go from multiple standpoints including the ability to make better landings and safer ones. So what gives?

  7. Steve Ratkovich Says:

    Clearly, proper training and practice are the best defenses against unintended stalls. However, learning to use an AOA indicator from the beginnning might actually help the training equation. We are taught to use a combination of airspeed, attitude, control position and control feel to approximate our AOA and sense our nearness to the stall. Directly measuring alpha while learning to sense and react to all the other cues might help students better visualize AOA and cement their knowledge. Adding this technology to modern glass airplanes only makes sense. Retrofit to older airplanes should remain a matter of choice.

  8. John P Says:

    I believe this is an extremely important issue. With as many fatalaties as we have each year because of excedding AOA, it would make sense to me to have an “AOA” gauge to provide a timely warning and perhaps save some liives. I think whether a pilot could have been better trained or not is a separate issue with many variables and not really a valid criteria for whether an “AOA” gauge or some type of warning system should be installed. One of my airplanes is flown by several different people, including students. It is a glass cockpit G-1000. Personally, I would opt for a retrofit even at $4000. and even though we have never had a problem. I think they should be optional.
    Happy New Year Bruce, Keep up the good work.

  9. Jim Shawley Says:

    If I’m not mistaken, approaches to the flight deck on carriers is based on Alpha more than anything else (some of you Naval Aviators can correct me). Also, an alpha meter could prove useful in turbulence, especially if it’s a “voice” so that one could slow down to a Va that allows for the occasional “beep” or whatever.

    At any rate, I’m just a little ambivalent about this. Might be good for training, so one could visually see on a meter what one is feeling in the controls and hearing; same with, for example, a G-meter….

  10. Brian Knoblauch Says:

    I’d love to have AOA on the airplanes, but $4,000 is way out of reach. If they were around $1,000 it might be doable…

  11. Russ Says:


    There is no good reason something as simple as this should cost that much money.

    If the AOPA wants stuff like this adopted they need to be pushing for more reasonable FAA approval processes and liability limitations to encourage manufacturers to introduce new technology at competitive prices. Encourage competition, open up the market.

    Why does a $30 voltage regulator from NAPA cost $120 if it’s FAA approved? The answer to that is the same problem that prevents good technology like this from being added to aircraft.

    Until then I’m stuck with keeping old airplanes flying with technology limited to a whistle stuck in the wing.

    I’m not sitting on a pile of cash that I dont know what to do with, and neither are most pilots I know.

  12. Joseph W. Szarmach Jr. Says:

    We do have an alpha gauge of sorts: the stall horn. It has a direct correlation to the AOA – and though it does not show it in analogue form, it still sounds when the airfoil nears the critical AOA.

  13. Ken Malandro Says:

    Though I’m only a student of flight, I’ve been successful in business, and know that only through self-analysis and improvement can any industry continually be successful. I think your points on improving tools (alpha AOA gauges & aircraft auto-assists) in GA aircraft are right on, and I’d venture that we all should consider leaps rather than smaller steps in advancing safety in the aircraft. However, preserving a purists approach to flying may still be important to many, so i’d suggest that life-saving equipment be considered mandatory, but that cutting edge safety advancements like auto-assisted angle of attack control, or VMC-to-IMC control assistance, have override switches allowing the purist to handle flight the way he/she finds most fulfilling (and in case of failure). Lives are paramount to cost (which will level off over time), certainly those of our passengers.

  14. Bob Newton Says:

    Glad you brought this to the forefront and I hope the skeptics try to keep an open mind on AOA. There is an ever expanding group of advocates that will be able to personalize its value while a number of us are trying to develop core training and broad understanding that ensures the AOA gage is properly used and crosschecked for optimum flight performance.

  15. Will Moore Says:

    Thanks for the great article, Bruce. I fly a Pilatus PC-12, the only single engine aircraft I know of with an AOA indicator installed as standard equipment. It’s well worth it. At final approach speeds, the AOA indicator becomes a primary instrument, with the airspeed indicator used for secondary reference. The Pilatus enjoys an excellent safety record, due I believe in part to this installed equipment. I’ve also had the opportunity to try out the brand of AOA indicator you mentioned in your blog. It offers the same safety benefits, and if it can be had, as you say, for $4000 installed, it’s still cheaper than most things in aviation.

  16. Fred Scott Says:

    Bruce, you ask why haven’t we installed AOA in the light aircraft fleet. It’s partly because most pilots seem to believe that it’s very costly. That used to be true, but no longer.

    AOA is affordable! A reliable AOA system that will give us an EARLY warning of impending stall only $550 – $1,600 (plus a few hours of easy installation)

    EXCEPT FOR the most highly skilled pilots among us, who ALL AGREE that AOA is the way to go…there is also a widespread ignorance among us of WHAT an AOA indicator can do. Why would anyone know? After all, very few light aircraft pilots have ever flown an AOA system.

    As you know, I am the person who lost the two friends at my private runway. TWA Captain Tom Rosen lost two more, last summer. That’s when Tom and I said “Enough! Let’s stop the stall/spins”. An AOA is the ONLY tool that can make that happen. (None of us have ANY financial interest.)

    Here’s the research we undertook on AOA:

    We sincerely hope that our work will build on the earlier research of the AOPA Air Safety Institute (formerly “Foundation”)

    Fred Scott

  17. Craig Says:

    Hi Bruce,

    While I’m not a pilot yet (though I soloed in gliders in the 90’s in which I had spin training) I’ve been an avid student of aviation safety for *many* years, having read thousands of articles and accident reports. Based on all my reading, as part of my plan to learn this year, will be to buy a used taildragger to learn in and the first two things I will to add to the plane, before my very first lesson, will be an engine monitor and AOA indicator. I want to monitor my engine like it’s in intensive care full time and I don’t want to stall at low altitude. I know these won’t be cheap, but it’s worth it to me.

    In regards to cost, it’s not surprising that more and more people are deciding to build a plane when they see that everything is less than 1/3 the cost of certified. After I get my certificate I plan to build a plane for just that reason (Bearhawk).

    Cost to add AOA to an experimental? Well, see here:


  18. Craig Says:

    Actually I notice that those AOA indicators are good for certified too, so really the difference is that in the experimental you can install those yourself.


  19. C.K. Lee Says:

    Thanks for your attention to an important safety issue – the stall/spin accident – and the dead simple cure: the AOA indicator. I was able to recently fly behind one for the first time and found it to be a very intuitive way of knowing exactly what was happening out on the wing. It was much better than the airspeed indicator at providing a visual and aural presentation of the margin between current configuration and the buffet/stall. I came away impressed with how useful this would be in the wider GA fleet – most especially training aircraft. Building in a sensitivity to the margin for error from Day One might help our aspiring pilots avoid the all-too-common accidents in the pattern.

  20. John White Says:

    Every airfoil on an airplane works because of two things :relative wind (dynamic pressure) and the airfoils AOA to the RW. Simple. Yes but the average CFI only talks about it in class room and not in airplane. Unlearned Pilots and CFI’s refer to airspeed and never relate AOA yet the controller is in one or the others hand while they are flying. The elevator control! IT is a good AOA indicator. Works as a pitch controller up to Critical AOA then it is only an AOA controller. At Critical AOA you loose pitch but still have AOA control. Airplane will stall at same stick position for a given weight and CG regardless of airspeed positive or negitive.
    Having an AOA indicator would make it so much simpler to teach for those that so teach it. the system you are talking about is really a “Stall Margin Indicator” and not a true AOA but will serve the purpose just fine. I would like to see the people who fly airplanes demand it and the FAA get up to speed and endorse an AOA system instead of some of the other measures they have mandated to try to prevent the inadvertent Stall /Spin.

  21. Al Aitken Says:

    Wings produce lift based on a number of variables…the predominate two being Coefficient of Lift (CL) and Angle of Attack (AOA). For any given airfoil design, CL is directly proportional to AOA…and will reach a critical level (stall) at the same AOA regardless of airspeed, weight, bank angle or G-loading. An airspeed indicator is only an indirect illusion into those other parameter relationships…useful more for determining when you’ll reach your destination rather than “IF” you’ll reach it safely.

    General aviation pilots who balk at the usefulness of AOA indicating systems do so primarily because they have had little to no introduction to it during their training…and because until lately, AOA indicating systems have been expensive for the general aviation owner/pilot. That is changing…and long overdue.

    A stall warning vane/horn provides some protection from critical AOA/CL, but only about 7-10 KIAS above stall AOA, and provides no continuously progressive information from its onset to the actual stall. An AOA indicating system on the other hand provides earlier indication of approaching trouble and a continuous display of narrowing stall margin…regardless of airspeed, attitude or flight conditions. Airspeed will lie to you, AOA will not.

    Military pilots learned AOA from the beginning and use it not only to provide safe and manageable approach speeds to ships and other runways, but also to eke out the absolute best in maneuvering performance from their machines.

    AOA is the future. It will become standard on all airplanes as the understanding of and enthusiasm for it grows among our general aviation pilots.

    Al Aitken
    Lt.Col. USMC (Ret.)
    AOPA #620626

  22. Josh-D. S. Davis Says:

    Looks like most FSDOs count this as a MINOR alteration since it replaces an inspection hatch, it’s not tied into existing vacuum/static/pitot lines, and doesn’t require cutting holes.

    Looks like the kits are $550 to $1500 and the labor is 6-8 hours ($360 to $680).

    In other words, the installed cost for a standalone AoA gauge would range from $910 to $2180.

  23. Jim Osborn Says:

    Bruce, let me add my voice to commend Air Safety Institute for doing immeasurable good by bringing AOA to the forefront as a safety device heretofore largely unknown to the G/A community. Particularly now; at a time when AOA systems have become remarkably affordable.

    For all its superb attributes exhibited in every phase of flight, I’m convinced the most compelling reason to embrace AOA as an essential aircraft accessory, is that AOA is the ONLY warning device available (visual, aural or tactile) that independently and continuously provides crucial slow-speed alerts – LONG BEFORE traditional stall warning devices can detect that airspeed and lift have decayed below safe flight conditions. In human terms, the value of that is PRICELESS, as is sadly evidenced by far too many NTSB reports of stall/spin tragedies that could have been avoided with AOA instrumentation displaying/voicing a timely warning to “straighten up and fly right”… as the old song goes.

    Life is much too precious to ignore the incalculable value of such a simple and affordable device as AOA; one that can literally stop the carnage typically brought on by “‘distraction” at critical moments while maneuvering low and slow.

    Key to widespread awareness rests in educating G/A pilots about AOA;…. we simply don’t know what we don’t know. Your contribution toward that end, Bruce, is to be applauded, .

    When retired TWA Captain Tom Rosen was explaining AOA to a non-pilot friend during a recent flight in Tom’s Bonanza, the friend asked… “why don’t all aircraft have AOA?” With continuing awareness being raised by Air Safety Institute and a host of others of like mind, hopefully at some time in the foreseeable future the answer will be… THEY DO!

  24. Doc Cottingham Says:

    I have always wondered why aoa instruments were not standard on ALL aircraft since the beginning of time. We have known their effectiveness. Why do manufacturers continue to ignore this simple device? This is one of those cases where the forced acceptance of a device makes sense; did you have a choice on a stall warning horn? How do we accept vortex generators on aircraft to assist in slower approaches, but do not have the aoa instrument to verify the affect? For all the money spent on non-essential devices, it makes sense that we should all have the benefit of aoa indicators. What could the price be if volume increased to match the numbers of all aircraft flying? Certainly would be lower, and more acceptable to the fleet.

  25. Wes Clarke Says:

    Angle of attack is significantly supeior to airspeed for low airspeed operations. I flew F8 fighers off aircraft carriers using AOA as the primary speed control reference and it allows very accurate approach speed control. I have wondered for years why it wasn’t available on civilian aircraft. It should be!

  26. grumpy Says:

    Don’t push the envelope so much and the stall warning horn should be all you need. If you hear it anywhere other than in the flare, lower the nose! Of course, noise cacelling headsets would be of no help in this situation since you wouldn’t hear the horn in the first place. An Angle-of-Attack indicator? Just one more gizmo to keep your eyes inside the cockpit. FLY THE AIRPLANE!!!!!!!!!

  27. lance fisher Says:

    I installed a similar AoA indicator in my Baron several years ago and it’s my primary instrument for “airspeed” when approaching to land. I’ve become so accustomed to this that I probably couldn’t say what my ASI was showing on final immediately after a landing. I have the gauge mounted in the glareshield so it’s easy to read when one’s attention is focused outside and I can refer to it whenever AoA is critical such as during any low speed maneuvers. FWIW, I suspect that one could even safely perform the “impossible turn” with this instrument without any risk of stalling.

    If the technology and knowledge that makes an AoA indicator feasible existed in the 20’s and 30’s It’s likely that we’d all be flying with AoA (or the “lift reserve” equivalent) instead of the dynamic pressure gauge mistakenly called an “airspeed” indicator (the only time the ASI indicates airspeed is when flying in standard sea level conditions). A dynamic pressure gauge (ASI) does have value but only for things like flap and gear speed limits and Vne/Vmo. There’s gotta be a reason that most military airplanes and many high end GA aircraft have AoA and with the affordable systems available today there’s little reason not to equip most of the GA fleet (in many airplanes the cost is $500 plus 2-4 hrs labor).

    When I was learning to fly over 30 years ago I was taught a little about AoA and that stalling speed goes up with weight and g-force but when I got my PPL I really had no clear understanding of the relationship between AoA and stalling. Nor did I have the ability to “sense” AoA, that was always confused with pitch angle and airspeed in my mind. As a result I’m now convinced that having AoA during primary training would result in a much improved understanding ot this critical performance factor in addition to reducing the chances for inadvertent stalls. And putting AoA in the cockpit would very likely continue to reinforce it’s importance and relationship to the wing’s performance when the pilots are out of the training regime.

  28. Shane C Says:

    As and aircraft owner and CFI, I am as sensitive to the cost of equipment as anyone. I have found AOA indicators to be of great value during all phases of flight. More exposure to, and training with, these devices is needed. To everyone who thinks they are too expensive, do you wonder what the Bonanza (or the families) pilot who crashed thinks of the expense now?

  29. Dave Eberhardt Says:

    Interesting questions posed by Bruce’s article. I was an instructor pilot in Air Force T-38s and KC-135s back in the 80s. T-38 had AOA indicators and KC-135 did not. In the T-38 you could still get into trouble with high sink rates which AOA did not warn you about; you had to sense high sink by other means. I never had problems in KC 135 without AOA and I was an IP in those also.

    In my opinion, it’s all about training (practice slow flight and stalls) and prioritizing the cross check (monitor pitch and airspeed) and not using too much rudder to help turn the aircraft. FAA examiners and Instructors could be tougher on check rides and bi-annuals to identify those pilots who do not have enough familiarity with aircraft control at slow speeds.

    I routinely go out to pratice area and work on my slow flight and stall work. I’ve noticed that my approaches and landings are superior when I’ve done my practice work. I’ve emphaisized the slow flight practice exercises more this past year. It has lead to a really good feel for the airplane at slow speeds.

  30. John D Says:

    I’ve been trying to get an A.O.A. installed on my plane for more than a year now but was told by my service center “John, I spoke with Aloha systems and got a copy of the 337 used on N****
    passed all this all thru the Teterboro FSDO, and after
    speaking with **** we don’t feel comfortable installing the AOA right now.
    With the flight testing needed, the heating element installation and the
    problems that (Alpha) has had with NY FSDO’s in the past it is not very likely to get this thru the Teterboro FSDO for field approval. ”
    When I pursued the reasoning I received this follow up “Well, From talking to our FSDO here they believe this really should be a STC due to the flight testing that needs to be done to calibrate the unit. If you want to chat with the Local FSDO inspector ……”
    So much for the FAA making flying safer!

  31. Robert Forker Says:

    Stall spin accidents do continue to take lives. Yes, AOA is a much more definitive measure of the nearness of a stall than airspeed. But I believe that the real problem is that too many instructors are trained today without a thorough grounding in high AOA operations. As a result, they avoid maneuvers that put the aircraft near a critrical AOA. The lack of a spin training requirement for students and a very minimal requirement for instructors, almost ensures that the student has never flown an airplane to the ragged edge of envelope, much less had to demonstrate a clear recognition of a spin actually developing. I know the flight schools, for a variety of reasons, don’t want to teach spins. Today if you want to get that sort of instruction you need to enrole in an aerobatics course.
    The disorientation resulting from the student’s first spin entry is pretty overwhelming. After a dozen spins or so, not all in the same lesson, the sensations become routine and for some pilots, even enjoyable. Turning students loose in spinable aircraft without proper training is nothing short of criminal. Extra gadgets in the cockpit are a rubber crutch.

  32. Fred Scott Says:

    John, for almost ten years, we have not needed Form 337 field pre-approvals for minor alterations. The IAs are making these determinations now, and the vast majority of them see the AlphaSystemAOA (as well as the competing LRI) as the minor alterations they, in fact, are.

    There is no FAA guidance that prevents the installation of a totally independent secondary AOA advisory system. None.

    Especially for a minor alteration with a <1Amp load. If you want a heated probe, then have your IA calculate an Electrical Load Analysis and if your charging system can handle it with reserves, you are good to go.

    Calibration flight? If there is a calibration flight required for any OEM stall vane, i have never seen or heard of any. Can you recall the last time you heard of our stall vanes being re-calibrated? (or Airspeed Indicators, for that matter). That's a red herring. Common sense needs to come into play. Calibrate it to the recommended OAA (or to any setting you like. It's a secondary advisory system, for gosh sakes), then placard that setting so the next pilot will know what it's set for.

    There are plenty of smart FAA people who "get it". The REALLY wise ones wrote…46 years ago, in the Flight Instructors Handbook … that very costly AOA systems made it "not practicable" to teach pilots an "accurate conception of AOA" … 46 years ago, in the 1964 Flight Instructors Handbook, the FAA publicly bemoaned the lack of reliable and affordable devices that we can entirely legally install now as independent secondary advisory alerts…because great engineering and modern electronics now make prices quite affordable.

    My hope is that we'll soon hear something like the FAAs highly intelligent way of dealing with shoulder harness retrofits. That precedent is precisely the same:

    "Makes sense. Will save lives. Minor alteration. Have at it!" said the FAA.

    Someone deserves a "Really Big Award" for that decision.

  33. Craig Says:

    Excellent article on someones experience in installing, testing and usage of an AOA Indicator:

  34. Marc Rodstein Says:

    Years ago I bought an R/Stol Aztec that had AOA installed. The airplane was incredible. It could take off and land on a postage stamp, and a big part of the reason for that was the AOA indicator. It allowed me to fly approaches SAFELY not at 1.3 VSO but 1.1 VSO. And whereas I have been uncomfortable flying 1.3 VSO in many airplanes, the AOA-informed 1.1 VSO was flown with complete confidence. I have since owned a number of airplanes, none of which had an AOA indicator. I miss having it and I am convinced that it is a great safety tool. It should be considered indispensable for anyone looking to optimize short field performance. If I were designing any new aircraft, I would make it standard equipment. The cost of factory installation be very low, and the resulting increase in safety would make it more than pay for itself.

  35. Russell Turner Says:


    I am sure you are aware that any item added to the airplane adds to the expenses of the airplane operator. Apparently, the less airplanes sold my the manufacturer, the higher the initial cost to the operator for an airplane.

    Until a group of airplane manufacturers lowers the cost of entry into the new airplane market we will probably see a continuing reduction in the number of new students and older pilots with a corresponding rise in cost of an airplane. Instead of all of the glass panel improvements, I would enjoy seeing several airplanes which are simple and affordable. Then addition of the AOA indicator would be a welcome addition to all airplanes.

    Start serving your members more than the manufacturers. We do not need a monthly siphoning of d0llars from our pockets. We need simplicity, dependability and more utility.

  36. Elbie Mendenhall, EM Aviation, LLC Says:

    I’ve flown AOA for years in various aircraft from KitFox to 767 and my company has been producing AOA systmes for the homebuiolt industry for 15 years and cannot seem to get the major A/C companies interested. We use a Vane, no computed values, Push a button the system memorizes the vane and flap position and illuminates the appropriate LED. Systems flying on hundreds of homebuilt aircraft and a few production ones such as the Wipaire Fire Boss, PBY,Cessna 421, Helio Stallion. We have custom designed angle measuring instruments for the military used in helicopter engine upgrades. Airspeed sounds like speedometer, so regardless of errors the “keep it simple” attitude by the major companies presists. Our systems correct up to 5 flap positions automatically and can be totally self contained with a small battery pack (8 aaa batteries) which will last approx 100 hours of flight. Simple setup! Had partial certification completed when major electronic component went out of production. New system totally redesigned.
    Best $ spent “Fly the Safe Angle with the RiteAngle

  37. John Townsley Says:

    I installed an Alpha Systems AOA indicator in my C172 about two years ago. It’s a great instrument! Not only does it make my landings (and takeoffs) more precise and therefore better, it also is a real time indication of just how close I am to the edge when I’m doing slow flight, steep turns, etc. Bottom line, it is another tool (and a very valuable one!) for managing my aircraft. I read recently of a C206 that stalled at low altitude and spun in with four aboard near Truckee, CA. The NTSB cited the pilot for “failure to maintain airspeed…” Very few details could be gleaned from the very sparce narrative report that accompanied the probable cause statement. With a 10 kt crosswind and warm temperatures it is possible the pilot encountered wind shear while operating very close to the envelope while coping with high density altitude. GPS data mentioned in the report showed ground speed fluctuations from around 77 to 90 kts as the aircraft made an anemic climbout. Post crash investigation by the NTSB and Cessna determined that the stall warning had a defective switch, and only operated intermittently. IMHO an AOA indicator would have been very helpful to the pilot, since she was possibly unaware of how close to stall her aircraft was flying. Installing an aftermarket AOA is completely optional. But it’s one of those instruments that adds significant safety… a good value for the investment.

  38. Ken Luke Says:

    I received my Private Pilot license in 1965 and trained extensively for a few years afterward, getting to CMELI CFI before 1970. I learned about AOA, and trained my students that this is the critical factor in stalls. During this time I read at least one article similar to the one I am reading now, about how useful an AOA indicator was, and how it was likely to become a standard light aircraft flight instrument “soon”. Unfortunately, the industry chose form (i.e. digital readouts and glass cockpits) over function in coming up with instrumentation improvements.

  39. Steve Reinsch Says:

    The AoA is “only” 2 to 4 thousand installed? This is on top of upgrading our ELT to the new frequency. The average plane is over 30 years old with 7,000 hours. Manufactures and the FAA have to realize we can’t even afford decent airplanes much less high tech gadgets to add to them. I sold our plane. The dollar cost per enjoyment ratio was not bearable anymore.

  40. Jon Hutchinson Says:

    100% in agreement.
    I have long believed AoA indicatoin should be porovided not only on commercial jet transports, but also on GA aircraft, and have published articles on the subject.
    The ideal for me is to have AoA & Flt Path Vector references included on a Primary Flt Display, preferably head-up. In the past cost has been the major obstacle to the application of AoA indication & HUDs in GA, but with the advanced avionic systems now available, this should no longer be the case.

  41. Jim Lied Says:

    AOA is a no brainer. If I had to choose Airspeed or AOA to make a landing, the AOA would be the winner every time! I have flown Citations in and out of every type of airport including Telluride, CO. The AOA takes all the variables of weight, density altitude, angle of bank, icing etc and blends them into one easy to use indicator that tells the truth without bias. Of all the safety devices out there, the AOA is the most under estimated in it’s value to prevent stall/spin accidents.

    Jim Lied ATP CFI MEI

  42. Charles Lloyd Says:

    The STOL capability is not the major reason for installing an Alpha AOA system. Here are questions to ask yourself:
    • What is the stall speed difference between flaps up and full flap configuration? Some heavy singles have a 20 knot variation is stall speed depending on flap configuration and landing weight.
    • Do you ever forget to set flaps for takeoff or landing?
    • Do you ever bank more than 20 degrees?
    • Do you want more consistent landings?

    These are the reasons I installed an Alpha AOA system in my Cessna 182 after flying Citations with AOA installed during my time at Cessna and NetJets. The AOA system is there to prevent a killer steep turn to final accident and provide consistent landing touchdown points and roll outs.

    No the FAA and Flight Safety don’t emphasize AOA but that is not reason to not adopt a safer method for flying our airplanes. AOA is a life saver.

  43. Don Arnold Says:

    To reply to Jack White, the stick postiion vs. AOA curve is not fixed, it changes with the power setting and with the trim tab setting. Sorry, you need an AOA to know AOA.

  44. Dan Rogers Says:

    Don, I’ll agree that there is slight variability of critical AOA as a result of power setting and flap position, but trim tab setting, don’t think so. Basically Mr. White is correct, the elevator position is a great indicator of AOA. Granted, an AOA indicator removes virtually all AOA guesswork. However stick position is a great indicator of when things can go south. Have a look at Alan Cassidy’s “Better Aerobatics.” In it, Mr. Cassidy, an aeronautical engineer and well-respected international aerobatic competitor, writes “Because elevator position and angle of attack are very closely interdependent during forward flght, the aircraft also always stalls at the same elevator control position.” He goes on to write, “Of course the feel of the elevator varies in all these positions [referring to various flight attitudes], both because of aerodynamic forces and because of different trim settings, but the stick/yoke position will always be the same.” If I had my druthers, I’d like to see an AOA indicator and an inclinometer in all aircraft. What a great combo.

  45. Peter Says:

    On a related note, why is the ball only ever found under the turn indicator? Given its importance in keeping a stall form becoming a spin, I’ve always thought that the ball should be at the top of the panel — ESPECIALLY in airplanes used mostly for VFR.

  46. Elbie Says:

    Naturally, I am a little biased on this, but to have an precise AOA you need a vane in the airflow, and it must correct for flap position if precision flying is desired. A stall warner is great, but why not get automatic bias of flap position, those of you that flew the Citation (I was an ATP designated examiner (CE-500 & 550 on it for 7 years and chief instructor) know how accurate it was, our AOA is within 1/2 degree, not to many of us can fly light aircrft that smooth. Some airfoils can get by without flap bias, but not that many.
    The AOA is the best instrument for safety ~~ even more so if properly trained. All of my competitors instruments will help prevent the Stall / Spin acidents, as I said I’m biased having produced the RiteAngle series of AOA’s for 15 years.

  47. Charles Lloyd Says:

    Elbie, the Alpha System AOA does not have flap compensation. However, when calibrated in the flaps up configuration for my Skylane the lower stall speeds for extended flap settings make the indication slightly conservative.

    Yes, it would be nice to have flap compensation similar to the Citation but for that you will pay even more bucks. Some of the responders are resistant at the current installed cost.

    The Alpha System AOA uses differential pitot pressures and can be just as good as the vane type AOA system for GA light aircraft. My experience is with the Alpha AOA and not the Right Angle System so both may be just fine for light GA aircraft.

  48. George hoselton Says:

    Bonanza’s with flaps down have sudden and full stall break. Keep it over 100 and only use necessary flaps on landing until on final. Type specific safety book taught me this.

  49. George hoselton Says:

    My opinion. Pilots are either by the numbers or they feel the flight characteristcs
    of the plane in flight. Someone not intouch with the flight and just flying by the numbers won’t feel the wing approaching stall at a higher speed than they expect due to flap position greater than normal. Going into a short field requires full flaps when bonanza’s need very little for 3000 foot runway or more.

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