What NTSB Reports Say About Impossible Turns and AOA (Part I)

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Editor’s Note:  Air Facts is pleased to present a two-part series by Dr. Ed Wischmeyer on visual angle of attack indicators and executing a 180 degree, low-level turn back to the airport following an engine failure (the impossible turn). The first installment focuses on data and methodology while the second installment focuses on analysis and additional questions raised.

What NTSB Reports Say About Impossible Turns and Angle of Attack—Part 1:  Data, Methodology, and Next Steps

The objective of this research is to invite and challenge the greater general aviation safety community to expand their focus to all aspects of general aviation safety, and not to be content with seemingly cool approaches to very limited scope problems. This broad scope approach is ultimately needed to help keep our friends, created in the image of God, alive.

emergency return

The current emphasis in general aviation (GA) safety is on visual angle of attack (AOA) indicators and impossible turns (return to the airport following engine failure). The many analyses and videos on these topics have been done in what can best be described as laboratory conditions, carefully selected optimum conditions of pilot, airplane, and environment.

In contrast, this study sought to examine AOA in the context of all accidents. This approach gives perspective on all factors, including those that might otherwise be ignored or unrecognized. This, in turn, helps address the question of whether the current emphasis on AOA indicators and impossible turns is justified.

Instead of concentrating on standard accident causations and progression, this study concentrated on these major questions:

  • Was AOA a major factor in the accident, either in the causality or progression?
    • Would a visual AOA indicator have helped?
  • Was this a power loss after takeoff, whether or not the pilot chose to fly an impossible turn? Details?
  • Did the data suggest anything new?

Any good safety study ultimately addresses the question of how to most effectively allocate safety resources including training, regulations, publications, videos, and other areas. That question is addressed in the second article of this series.

angle of attack indicators

The current emphasis in general aviation (GA) safety is on visual angle of attack (AOA) indicators.

NTSB Reports Studied

The NTSB reports studied were all of the single engine events from 2021-2022 operating under FAR Part 91. These were flights not for hire, but included flight instruction.

NTSB data was accessed with the CAROL database. The Excel download of the data had 44 columns describing the aircraft, pilot, event statistics, and the NTSB report itself.

Some of that report data was processed data as opposed to raw data. For example, broad phase of flight and probable cause (being somebody else’s opinions) were not analyzed directly and were accessed only as memory and sorting aids. Similarly, the summary cause classifications and findings were not even read.

Fields of particular interest were the Highest Injury Level, i.e., fatal or not, and links to the event narrative and the event docket which includes supporting documents, diagrams, interviews and sometimes videos.

A derived parameter for each event was whether the word “stall” was present in the event summary.

As would be expected, the NTSB data were not completely consistent and error-free:

  • The completeness of the NTSB reports varied;
  • Several reports stated that stall speed depends on bank angle, ignoring the real factor, the G-load of the turn;
  • The term “stall/spin” was sometimes used as a default causal factor;
  • Go arounds were sometimes classified as landing events, but other times as takeoff events.

Additional Parameters Generated

Five more parameters were generated to help facilitate the analysis. Again, because of the wide range of accident circumstances and variations in the NTSB reports, these parameters were not and could not be completely precise. However, given that the primary objective of this study was to examine AOA, not to perform a traditional causality study, such variations were tolerable.

The first parameter was the quick summary, used as event descriptors rather than for generating statistics. There were 45 different entries in this category, some overlapping, but the most numerous of these was No Stall/Spin. Others included Failed Impossible Turn, Impossible Turn OK/Crash, IMC LOC, Overloaded, Stall, Stall/Spin, Water in Gas, and Windshear.

The other quick look parameters are:

Instigating Event Where event started Result Stall warning
Aircraft performance Approach CFIT Irrelevant to accident
Bird strike Climb Crash Might have helped
Carb Ice Cruise Forced landing Not an accident
CFIT FASF (see below) LOC Sounded
Density altitude Final approach Midair collision Unknown
Fuel mismanagement Go around Normal landing Would not have helped
Gust Impossible turn Spin
IMC Runway
Mechanical problem Traffic pattern
Midair collision
Note-worthy
Other
Pilot miscontrol
Reckless
Unknown
Unsuitable surface

 

A Surprise in the Data: Failure to Achieve Sustained Flight

As hoped for, there was a surprise in the NTSB data. That phenomenon is best named Failure to Achieve Sustained Flight (FASF). An incomplete summary description of FASF is whether the airplane made it out of ground effect.

FASF events included running off the side of the runway, failed takeoff abort, mechanical problems, fuel problems, gusts/tailwind/shear, hit obstacle, unable to climb, carb ice (especially in older planes), unlicensed pilots, rudder pedal jammed after total knee replacement surgery, student pilot/dual instruction, bird or deer strikes, first flights in that airplane, and pretty much anything you can think of. Some FASF events made it past the airport property before a ground collision or forced landing. And some made it as high as 100 feet but were still consistent with the spirit of FASF.

But from an angle of attack perspective, the unifying factor in all of these was that angle of attack was not a factor either because the wing never generated lift, or, if the plane became airborne, the flight situation was so precarious that the pilot’s attention would have been 100% outside the airplane, looking to keep it in the air without running into something. In all cases, stress made the pilot cognitively unavailable to watch any flight instruments, even if they could have provided any useful information.

Another consequence of the FASF concept is that, in any accident analysis, FASF or not, it’s worth considering whether stress made the pilot cognitively unavailable to watch any flight instruments. This is in line with well-known stress phenomena, such as aural cues being dropped.

Comparing AOA Videos to the Real World and Real World Pilots

It is no surprise that videos purporting to show the advantage of AOA indicators are shot under ideal conditions. Such videos may contain these elements:

  • Calm air, no gusts
  • Stable flight paths, constant g load
  • Power on approaches
  • Optimum calm air glides
  • No forced landing glides as in a glide to a point in the windshield
  • No birds or planes to avoid
  • No aural distractions, radio or cockpit communications
  • Skilled, safety conscious pilot
  • Technically sophisticated pilot
  • Rational, unstressed pilot, cognitively available for all cues
  • High situational awareness
  • Non-emergency flight
  • Relaxed flight, no time pressure

In contrast, there are conditions in which visual AOA guidance is unlikely to add value:

  • When the pilot is so task saturated that she has is unable to read any flight instruments
  • When the pilot is cognitively unavailable due to distractions, startle, or surprise
  • When the law of primacy kicks in and the pilot reverts to airspeed
  • When the pilot simply does not understand AOA. A credible source emailed me that, “A long-time PPC (EAA Pilot Proficiency Center) sim instructor observed that the visual AOA was not as intuitive for a number of the pilots as he thought it would be.”
  • In maneuvering flight such as turns in the pattern. (I once flew downwind, base, and final at a constant AOA. To get the extra lift required for the turns, I had to dive to get extra airspeed so that the plane could turn at that same AOA. That produced a strange traffic pattern with roller coasters at the corners.)
  • When the precision of flying with AOA is insignificantly greater than indicated airspeed, as described in NASA TN D-6210
  • When turbulence makes the AOA indication unreadable as readings bounce all over the scale
  • Landings other than at best glide, e.g. spot in windshield techniques as is required in some forced landings
  • In ground effect:  stall AOA is different, eyes are outside. This is more theoretical than practical for visual AOA, but can affect some proposals such as a general aviation stick shaker.
  • Aircraft where installation is unlikely such as ultralights, Ercoupes, Taylorcraft, J-3 Cubs, and low hull value aircraft
  • Where the pilot perceives no need for AOA, the panel is already full, and AOA training is required but not be readily available
  • When the pilot’s learning style does not adapt to abstractions or complexity
  • When the pilot has such a good feel for the airplane that visual AOA adds little to the pilot’s innate sense of what the airplane is doing

But beyond these points, the general pilot population includes the unreachables and unteachables (as somebody put it). In my own flying career, I’ve seen plenty of small airport pilots unconcerned with safety messages, to put it mildly. One more gadget in the cockpit cannot remedy deficits in skill, judgement, and attitude.

Drs. Neelakshi Majumdar and Karen Marais extensively documented the demographics and experience of pilots who experienced loss of control accidents (see https://arc.aiaa.org/doi/10.2514/1.D0432). Their Figure 3 tends to support to my supposition that real world loss of control pilots are substantially less accomplished than those who promote visual AOA guidance.

It’s also interesting that the technique of flying a visual AOA approach never seems to be explained beyond, “It’s simple. I can teach you in five minutes.” Contrast this purported simplicity to the never-ending discussions of pitch/power for airspeed/altitude.

Two Obvious Questions

So if the pilot is in an accident situation and is so stressed, too cognitively unavailable to watch the airspeed indicator, how likely is it that the same pilot can watch AOA?

That question, in turn, raises a more fundamental question:  Is the safety community’s continued focus on AOA the best way to reduce overall accident rates? Or does that focus on AOA just distract the safety community from more fruitful safety efforts?

angle of attack

Is the safety community’s continued focus on AOA the best way to reduce overall accident rates?

Is Optimum Glide Always the Objective?

Visual AOA is touted as the way to get “optimum” glide, but there are a number of interesting facets to this discussion.

Glider pilots know that best glide speed for distance covered over the ground varies with wind:  faster into the wind, slower downwind. AOA indicators do not permit this compensation. And in the very high-tech world of competition sailplanes, they are not equipped with AOA indicators.

glider

Glider pilots know that best glide speed for distance covered over the ground varies with wind.

An interesting question is how much performance benefit a perfectly calibrated AOA indicator would give over an airspeed indicator. NASA TN D-6210, “Flight evaluation of angle of attack as a control parameter in general-aviation aircraft” indicated that the advantage was not operationally significant. Given all the elements of human factors, sensor noise, and filtering lag, I suspect that modern AOA systems would give the same result. That study would make an interesting thesis topic, however.

Tedious numerical interpolation is not required when adjusting airspeed for weight, contrary to the claims of some AOA advocates. Airspeed variations with weight in light general aviation aircraft are only a handful of knots, so it’s easy to fly the published slow speed when light, the faster speed when heavy, and something in the middle when the aircraft weight is something in the middle. No math required. What computational errors there might be would not be more significant than the piloting skills or other errors.

The standard glide estimation technique, as would be used in a forced landing, turned up again when landing at my home field on the way back from Oshkosh. On downwind, ATC had me at 3,000 feet going over the departure end of the crossing runway. Turning final, I was still way, way high. Even with full flaps, the issue at first seemed in doubt but glide estimation, taught to student pilots, was used.

I could see that the spot on the ground in the windshield that was not moving was short of the runway. This meant that I could land normally on the runway, not overshoot, and did not need to be concerned with the airliners on the crossing runway. “Optimum” glide was not the issue here, and a visual AOA indicator would have had no value. This descent used the same technique that (would have) had value in many of the NTSB accidents involving engine failure after takeoff.

Approximate Statistics

As noted in the many caveats above, precise statistics are not attainable from this data set and are not the goal, anyway. And recall that successful power loss outcomes are not in the data.

Given these limitations, here are very rough—very rough—estimates, realizing that if airspeed already provided sufficient information but was ignored, a visual AOA indicator was unlikely to help.

For 175 events in the data that were fatal, where the NTSB report included the word “stall,” or both:

  • 99 Stall Events, both fatal and non-fatal
    • 16 visual AOA might have helped, 83 unlikely to help (16% might)
  • 34 Fatal Stall Events
    • 25 takeoff or initial climb; 5 visual AOA might have helped (20% might)
    • 9 approach and landing; 1 visual AOA might have helped (11% might)
  • 76 Fatal Events, NTSB says No Stall
    • 1 might have helped, 75 visual AOA unlikely to help (1% might)

For 342 events that were neither fatal nor stall:

  • 327 visual AOA unlikely to have helped (95%)
  • 13 visual AOA might have helped (4%)
  • 1 event where the pilot wrote that airspeed sufficed
  • 1 event where the stall warning sounded—early flap retraction, quartering tailwind

The Most Important Question:  Where Are Safety Resources Best Expended?

For the industry as a whole, would safety resources be better expended on visual angle of attack indicators or on addressing other issues, such as teaching fundamentals of airmanship, basic piloting skills, or forced landing practice?

There is an impressive surge of AOA rhetoric—“lifesaving,” “correct,” “optimum”—but such language can be misleading. “Correct” and “optimum” may fit the context of the speaker but not necessarily apply to the situations of the listener, who may be considering other flight operations, or having to deal with real world scenarios, as is discussed in Part 2.

While the decision on where to expend safety resources will vary from pilot to pilot, the NTSB reports of this study do not support visual AOA indicators for impossible turns as a silver bullet to address overall safety issues.

Next Steps

Technical solutions that do not acknowledge the realities of operational environments and ranges of pilot skills and motivations will not achieve the degree of change required. This is especially true of visual angle of attack indicators, despite their popularity.

Those who attend flight instructor conferences and talk to DPEs know that there is a crisis in the quality of new pilots and CFIs, including graduates of universities and commercial flight training companies. The long-term effects of poorly-trained pilots is sobering. Addressing this problem is a desperate and worthy challenge for the safety community.

There are similar problems with those who have not kept up with change, aging pilot populations, second owners of homebuilts and older airplanes, those content with minimum standards, and those who do not understand or respect the crafts and oral traditions of general aviation flying and aircraft upkeep. I have encountered many such over the years.

A big part of any solution will be adapting to the extremely wide variety of pilots, airplanes, and operations that comprise general aviation. That variety may require multiple initiatives.

I think that currently, the most improvable aspects of general aviation safety likely will include improving basic flying skills including rudder usage and stall and slow flight well beyond ACS standards. Pilot psychology and human factors also need to be taught. Those “soft” psychological areas are easily disdained by pilots unless carefully presented.

All training should be as affirming and student focused as possible. After all, the objective is not to make pilots be subject matter experts on technical details, but rather for pilots to understand the implications of those technical details and apply them in flight. Angle of Attack for Dummies in an example of how a technical subject can be simplified for low experience pilots.

Fundamentally, improving safety and upgrading the pilot population’s flying skills is a marketing problem, a motivational problem, a problem that will require the whole industry to address. Until the industry as a whole, including training, publications, social media, and presentations all address the problem with positive reinforcement of pilots, it will not be reasonable to expect improvement.

There are already courses and training that address pilot skills. These include Patty Wagstaff’s Upset Prevention and Recovery Training, Rich Stowell’s spin training, my own Expanded Envelope Exercises®, SAFE CFI-PRO™, and numerous books and articles. Back in 1971, the EAA published the “EAA Pilot Proficiency.” All these indicate direction but are not enough in and of themselves enough to resolve the larger issues.

Ed Wischmeyer
Latest posts by Ed Wischmeyer (see all)
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36 replies
  1. Ray Johnston
    Ray Johnston says:

    Thank you for this very interesting article! I will look at this data for sure. To me the key to AOA indicator utilization is the prevention of stall during “normal” operations (without aircraft failure). The biggest killer by far in general aviation is the stall-spin accident in which there is no altitude for recovery for what is otherwise a normally operating airplane, so stall prevention is key. Often the stall occurs because increased load factor in the turn-to-final significantly reduces the stall margin for a given airspeed and pilots are often focused on an airspeed that is more appropriate for straight-in approaches. The airspeed will also drop in the turn if altitude in maintained and power is not added or there is compensating altitude loss (double whammy). I believe there is a significant benefit to AOA indicators in GA airplanes for this reason. Yes, training may be necessary. A secondary benefit is the ability to use the AOA indicator as a backup for failed airspeed indication in a VFR-only airplane. You make valid points about not being able to fix stupid with respect to safety enhancing equipment (no replacement for judgement, skill, or attitude). These same people probably don’t fully understand the substantial increase in stall speeds during turns either. An AOA indicator going into the “red” may actually help these so uninclined….

    Reply
  2. Ed Wischmeyer
    Ed Wischmeyer says:

    Thanks for your comments. What data there is suggests that base to final accidents are not always stall/spin, hence, may be low AOA botched steep turns. And in those cases, AOA will give no warning.

    Reply
  3. Daniel Slowikowski
    Daniel Slowikowski says:

    Ed,

    Appreciate the effort.

    From your conclusion:

    “ Until the industry as a whole, including training, publications, social media, and presentations all address the problem with positive reinforcement of pilots, it will not be reasonable to expect improvement.”

    TRAINING to the equipment installed is the most important solution to this issue!

    I have been flying military aircraft for 42 years – retired Navy F/A-18 pilot currently flying the T-1 (Beechjet 400) as an instructor pilot training USAF Combat System Officers. Never flew an airplane before my navy flight training which focused on the critical importance of AOA in all phases of flight and especially landing aboard ships. As a product of my training, the AOA indicator is THE Primary airspeed (safety) indicator that I monitor in slow flight regimes. When landing on ships pilots are debriefed after every landing by Landing Signal Officers (LSOs) on their approach and landing. Lineup (left/right of centerline), glideslope (high/on/low), and speed (fast/onspeed/slow). Fast is low AOA, Onspeed is proper AOA, and Slow is high AOA. The is no reference to indicated airspeed in knots (although a given weight and flight condition will establish an indicated airspeed for onspeed AOA).

    Short anecdote: on my first training flight transitioning the the T-1 10 years ago, my IP (C-5 pilot) commended me in the debrief on my airspeed control base turn, final and landing. She asked me how I did that. I replied that I maintained onspeed AOA indexer (similar to the AOA indicators pictured in your article). Her response, “you look at that?!” Obviously, she was not trained to monitor AOA.

    T-1 procedures are to add 10KIAS to Vref for turns up to 30 degrees AOB. Onspeed AOA naturally adds 10 KIAS at 30 AOB.

    That’s the beauty of AOA – simplicity. Optimal AOA maximizes performance (power on or off). Higher AOA invites stall and departure from controlled fight.

    But pilots have it and train to use it!

    Fair skies and following winds,
    Slow

    Reply
    • Ray Johnston
      Ray Johnston says:

      When I first read the article I somehow just knew that a Navy pilot might chime in about flying AOA indicators! Interesting take.

      Reply
      • Loren L Banko
        Loren L Banko says:

        Not a Navy Pilot but the basic understanding that any wing can/will stall at any speed at any attitude or bank angle, but only one AOA, melds with my post about understanding the concept of flight…powered or unpowered.

        Reply
    • Don Golding
      Don Golding says:

      Most high performance, high wing loaded jets use AOA strictly during landing, due to the wide range of gross weights and configurations possible, where IAS and AOA are not closely related. However for most light, GA aircraft, IAS and AOA are very closely related, making AOA indicators relatively less valuable as an aid.

      Reply
  4. Ed Wischmeyer
    Ed Wischmeyer says:

    HI Slow –

    Thanks for your comments.

    I come from a GA background, and in the same sense that your C5 pilot didn’t understand AOA, I find that the ex-military pilots I’ve flown with did not always understand the flexibility and variability of GA. In GA, there are so many factors that come into play that a theoretical “optimal” AOA is often operationally irrelevant. Part 2 (tomorrow) will give a few examples, and there are many more.

    Also, AOA may be unusable if the air is not calm enough. (https://www.youtube.com/watch?v=bWSzptdQyFk)

    While I agree that training is crucial, if there’s no motivation to train pilots beyond the bare minimum of ACS, training will not occur. Training is, of course, required to fully and safely exploit the versatility and variability of GA, because one size, one AOA mantra, does not fit all.

    Fly safe!

    Ed

    Reply
  5. Loren L Banko
    Loren L Banko says:

    Those who attend flight instructor conferences and talk to DPEs know that there is a crisis in the quality of new pilots and CFIs, including graduates of universities and commercial flight training companies. The long-term effects of poorly-trained pilots is sobering.
    ———————-
    The above paragraph perfectly states the primary purpose and reason for this entire article and discussion. No student will ever understand the concept of powered flight if the occupant of the right seat has minimal ,if any , concept of powered flight. “Driving” a desktop simulator around does not a pilot make either.

    This retired 35K hr airline pilot has seen these deficiencies manifest themselves in everything from my personal Just SuperStol to Boeing 737’s…..sobering indeed.

    Safe/Smooth flying to all,

    Loren

    Reply
  6. RichR
    RichR says:

    Many good points here about understanding AOA concepts, situational benefits, trng req’d. and mentioned in passing but also critical, continued calibration and maintenance of AOA system.

    As alluded to, one reason for TACAIR/transport AOA is to accommodate hugely varying aircraft weights (and resulting v speeds) compared to bugsmasher GA due to fuel weight burn and ordnance expenditure. One reason not addressed is the development of fully hydraulic “irreversible” flt controls required for large/high speed acft that provide no airload feedback to the pilot thru the controls. That said, even then, the airframe will talk if you are listening…buffet, wing rock, control effectiveness, perceived AOA (pitch angle vs flt path) but one doesn’t learn any of that flying every flt fat/dumb/happy in the middle of the flt envelop on autopilot.

    Not having an unlimited flying budget, for me, any equipment upgrade cost is converted into in flight hours not flown, few “upgrades” exceed the value of getting out there and really flying your acft to its limits or expanding (and maintaining) your limits to match it.

    Regularly flying your aircraft at the stall limit edges of the performance envelop and learning to feel what the aircraft is telling you is the most important investment you can make, in GA an AOA indicator may be helpful in confirming/calibrating your feel, but unless incorporated in every flight has no more use than the “ball” (as in “step on the ball”) already ignored by most of GA.

    As a USN TACAIR NFO I relied AOA to monitor, but also learned to listen subconsciously to the acft as it tried to tell you to “pay attention!”

    Bottom line is nothing will help the complacent, get out there and really fly and learn what your airplane is telling you thru the controls and its response.

    Reply
  7. Robert Thomas
    Robert Thomas says:

    I just a guy that bangs around small airports in small cheap aircraft. My take is this is a stick and rudder issue combined with lack of seat time.
    1. If you want to attempt the “impossible turn” you should practice it at altitude. Learn it for the aircraft you are flying.
    2. 30-40 hrs in a traditional taildragger with minimal instrumentation and preferably no flaps. Recurrent training 10hrs per year.
    Why? The modern flying computers don’t know the computers are in board. They are just aircraft. The laws of aerodynamics are universal. We are learning to fly the electronics, instead of learyto fly the aircraft.

    Reply
  8. Gibertoni Jim
    Gibertoni Jim says:

    I think the additional risk after engine failure on take off to complete an impossible turn maybe far greater than not doing the impossible turn and landing somewhat ahead. Furthermore, practicing
    A “real” impossible turn maybe a greater threat.

    Reply
  9. Loren L Banko
    Loren L Banko says:

    Regularly flying your aircraft at the stall limit edges of the performance envelop and learning to feel what the aircraft is telling you is the most important investment you can make, in GA an AOA indicator may be helpful in confirming/calibrating your feel, but unless incorporated in every flight has no more use than the “ball” (as in “step on the ball”) already ignored by most of GA.
    ——————————-
    ^^^^^^^^THIS^^^^^^^

    Go to any airport on any day and watch people “drive” C150’s thru Cirrus’ onto the runway waaaay above VSO……

    When asked why….they’re scared of being “slow” because their exposure to flight at MCA was minimal in their training because their instructors exposure was minimal and generationally so was his/her instructor’s….etc, etc, etc

    Flew with a Dr. in his very well equipped C182 who was crossing the threshold at 90 mph! He’s got a wrinkled/repaired firewall, a prop strike and multiple nose gear rebuilds in the logbook too.

    He nearly had a heart attack when I took the airplane to altitude and flew it at MCA with the stall warning chirping and freaked out when I demonstrated a gentle touchdown on the mains with the stall warning screaming.

    All goes back to initial training or lack there of IMH(umble)O

    Reply
    • Jong Lee
      Jong Lee says:

      Sir,
      Totally different topic. But during your 35k flight hours, how much time during t/o and landing you do estimate you spent with less than three wheels on the runway?
      Thank You,
      Jong

      Reply
  10. Ran Powers
    Ran Powers says:

    Ed – I’m 72, long time CFI, ex-military background (which in my experience can be more of a hindrance than a help with GA). I want to thank you, I read a EEE article you wrote several years ago, and it helped me focus on maneuvers beyond the ACS, both from your articles and my own experience. As a result, I offer a “EEE Flight” to the CFI’s at my flight school when they reach 50hrs dual given, and the owner picks up the tab. I also offer it to certificated pilots at normal cost. It’s a fun flight, and has been well-received. I frequently make changes to the profile. I want to show you, here’s the latest on the maneuvers I do, usually in a C-172: Wingovers-“Unload”, Fishtail, Coord. Ex.’s, AY Demo, Fwd&Side Slip, Stall Series, Pwr On Stall w/bank (ACS), Spin Aw. Stall, Stall Recov. w/o Pwr, Falling Leaf Stall, Wingover w/Sec.Stall, X-Ctl Stalls, 60/90 Turns, Fwd Slip w/Full Flaps, Rndout/FlareTng-LoApp. Brief Airsick, Bag, Seat, ?’s. The preflight briefing takes about 45 minutes. I cover up or turn off all the flight instruments (maybe leave HI), attach the maneuver list to the fuel selector, and I do all the ground ops and takeoff. I demo the maneuver first, then “help” the other pilot with it, and continue based on pilot performance (and airsickness), just like normal dual instruction. I liken it to “VFR unusual attitude recoveries”, and do this in flight – look out the window and set level flight, power to cruise. These are really about the only flights I do nowadays, no paperwork, no checkride standards to meet, I just try to improve a pilot’s confidence and feel of aerodynamic pressures and energy management for an object in the air, and have some fun! Again, I want to thank you for inspiring me to come up with this profile.
    P.S. I have flown with an AOA indicator, I totally agree with your evaluation of them. I would say direct more effort to explaining what those “foot rests” are for!

    Reply
  11. Ed Wischmeyer
    Ed Wischmeyer says:

    Hi Ron –

    And thanks for the affirmations! And I’d never thought of military background as “more of a hindrance than a help with GA.” Not sure I could argue with that, though…

    I don’t have an article on line about the Expanded Envelope Exercises®, but here’s a presentation given at the AOPA tent at Oshkosh a few years ago: https://www.youtube.com/watch?v=7C2xfFNb1sQ (At the AOPA tent at AirVenture, 3,400+ views). Glad you’ve found E3 useful and that you’ve adapted it to your own needs.

    Fly safe!

    Ed

    Reply
  12. Ray
    Ray says:

    Read all the comments before and agree with all.
    Equate this to my past over North Viet Nam when SAMs were after me from 2 directions. At low altitude and low energy, maybe 6,000 ft I just rolled over again perpendicular to the attack in a split S, pushing stall buffet. Did not even look at the (Navy) AOA. It was that or get hit and an out the window judgement. I’m still here! The impossible turn is much the same. I know my Swift requires 900ft at 5,000ft density altitude turning into a crosswind to get back in line with the runway. No stall warning horn, no AOA, no best glide speed, just shove the nose down quick with lots of bank angle. If there is lots of headwind you can easily overshoot the runway, now how much altitude is now required? All possible, but you might just consider almost straight ahead to a place where you will survive and collect your insurance.

    Reply
    • RichR
      RichR says:

      The point of the article, and most highly experienced commenters, is that AOA is just another input, ignored if not proficient in its use.

      Experience, training and continued proficiency flying at the performance limits required in that scenario are the “decision making aids”. No equipment will make a difference if not incorporated into regularly flying that part of the performance envelop. If you haven’t, any/all “aids” fall away as ignored distractions when task saturated or worse, panicked. If you learn to feel your airplane’s aero feedback and are proficient flying near stall, you will already have have subconscious tactile cues much more readily absorbed in an extremis situation…riding a bike is a good example of that tactile feedback readily absorbed.

      By all means, pick whatever you think works for you, but then go train with it and maintain proficiency with its use in that part of the performance envelop…and don’t forget to maintain/calibrate it properly, and learn its quirks/limitations/assumptions (balanced vs unbalanced flt?) or it just becomes another bad data distraction.

      Reply
  14. Ed Wischmeyer
    Ed Wischmeyer says:

    The first paragraph declares that, “The objective of this research is to invite and challenge the greater general aviation safety community to expand their focus to all aspects of general aviation safety, and not to be content with seemingly cool approaches to very limited scope problems. This broad scope approach is ultimately needed to help keep our friends, created in the image of God, alive.”

    Reply
  15. Terry Lutz
    Terry Lutz says:

    For those of us who have used AOA for years in situations where our lives depended on it, there are many aspects of this article that are both incorrect and misleading. For example, the movement of AOA in turbulence, which does not occur as mentioned in the article. The author did not participate in the AOA training events at AirVenture 2024, and is not aware of the positive aspects of the training many pilots received. NOW WAIT FOR IT. The author will summarily pound me into the ground for making these straightforward comments.

    Reply
    • Ed Wischmeyer
      Ed Wischmeyer says:

      Terry –

      A few factual, non-judgmental replies:
      * General aviation AOA indicators can indeed show movement in turbulence, as the article stated. https://www.youtube.com/watch?v=bWSzptdQyFk was shot in my RV-9A with winds reported as 9G14, and the AOA indicator was calibrated by the book. I have made this video public multiple times in the past.
      * Your comments indicate that you had not yet read Part II of the article, wherein I related my observations of the 2024 AOA training event. I did not greet you then because there was so much stress and confusion surrounding the start of the event, including people chatting noisily at the back of the room. To confirm that I was in fact present, at the first half of the first session, you gave pitch cues such as 2° and 8° nose down to help pilots fly the AOA impossible turn more easily.

      Terry, almost all of us have strongly held beliefs and opinions. What we all sometimes do, you and me both, is consider counter-examples to those abstract beliefs as a personal affront when, in fact, none was offered nor intended.

      Why should I want to “pound you into the ground”? I’d much rather join you, and the rest of the GA safety community, in helping keep our friends, created in the image of God, alive.

      Reply
      • Mike "Vac" Vaccaro
        Mike "Vac" Vaccaro says:

        Hi Ed,

        Couple of points to ponder…

        First, what what you done is heterodox opinion based on poor quantitative analysis, not actual research or experimental test flight. It’s not peer reviewed, nor has it ever caught a three wire on a pitching deck or been based on empirical data derived from a properly instrumented airplane flown by a trained test pilot. I’m actually not sure what you are trying to achieve.

        Reply
  16. T Boyle
    T Boyle says:

    Great article – thanks for taking the time! It’s a lot to think about.

    The point you make about spending more time training stalls and slow flight; I’m unsure about that. We’ve been trying to do that – to various degrees – throughout the history of GA. And there are a lot of dead people. The airlines don’t, though: they teach techniques that (as I understand it) mean the wing normally never exceeds about 8 degrees AOA. That translates to staying roughly at 1.37 x actual stall speed at the aircraft’s weight. And their stall/spin accident record is MUCH better than light GA’s. What I’m wondering is whether we are doing the wrong thing, when we teach students that slow flight / stalls are perfectly normal and nothing to be afraid of. Maybe we should be teaching them that slow flight is a maximum performance technique that needs to be done quite deliberately for takeoff and landing but never treated casually, and stalls are something to be treated like the pointy end of a firearm – perfectly safe when properly managed but capable of being suddenly lethal otherwise, and absolutely not something to mess with.

    Reply
    • Mike “Vac" Vaccaro
      Mike “Vac" Vaccaro says:

      Ed,

      I’m violent agreement regarding Turnback analysis, but find your AOA conclusions flawed, I don’t have a PhD , but am a trained test pilot and former fighter weapons school instructor, and have some flying experience in light planes, fighters and heavies.

      This low altitude stall and recovery was flown under controlled conditions, and the right answer for recovery is “go around” but the point of the drill is the sheer amount of SA provided by AOA (I.e., how hard the wing is working right now): https://youtu.be/BPD5xk1wgOw?feature=shared

      By the same token, if you don’t properly coordinate and simultaneously pooch up a turn in the pattern, it’s easy to depart controlled flight: https://youtu.be/2QSZTPFwEuw?feature=shared

      But the physics and compute are sufficient that we can design a system that accommodates gust loads and g onset rates—we call that “transient response.” Again sufficient to land a fighter on a ship. Also sufficient to deal with wind shear: https://youtu.be/VQZYY5nIgjY?feature=shared.

      This AOA system is designed to handle a gust load of 64 knots/sec. I understand you observed noise in your Garmin system, but how do you quantify that observation? You are correct, AOA is inherently noisy, but it’s practical to damp the signal. What instrumentation besides the Garmin data do you have on board? It’s practical to equip an RV type with GNSS/INS as well as an air date boom.

      AOA is the only “gauge” to tell you how are the wing is working, You can’t see AOA. It also provides you with power control feedback, we still kill folks at the same as we did in the year I was born (1963) due to loss of control. The military broke the code a while back. Your choice to embrace that or bury your head in the sand ad go “what do we need that for?”

      Works well at high beta: https://youtu.be/5sgJZX-Tjps?feature=shared

      Helps with power control: https://youtu.be/V5sCflrjTb4?feature=shared

      Helps with energy maneuverability: https://youtu.be/Zfw7GlEzJz0?feature=shared

      Stop putting constraints around the argument, strap on an airplane fly some instructional demos, fully understand FAR 23 maneuvering speed constraints (control doublets), instrument your airplane, do some PhD quantitative analysis of empirical data, and get it peer reviewed. We can help with that if you want an assist with either aero engineering or experimental test flying.

      More training is a good thing. Also in violent agreement there, Just be careful with how you reverse flight controls in a normal category airplane at the g limit.

      Fly safe,

      Vac

      Reply
  17. Terry Lutz
    Terry Lutz says:

    AOA is sensed by all civil airliners to protect against stall. If AOA was unstable in turbulence, the stall warning system would be sounding off mulitiple times on final approach. It’s the same thing in fighter aircraft. I flew from central Michigan to Duluth, MN today in a Cirrus, with the AOA gauge in full view. I intentionally flew through cumulus clouds just to watch the AOA indicator in the Perspective + avionics. It didn’t move, but my cell phone sure did while I was trying to make a video. I have the short video, but where do I updoad it?

    Reply
  18. Jim Van Laak
    Jim Van Laak says:

    Ed,

    Excellent article, as usual. Just celebrated 54 years of flying, and have tried to keep learning both in aviation and in my career (space systems design and operation).

    My flight experience began and will end in GA, with military and corporate flight mixed in the middle. During that time, I have been engaged in lots of challenging flight situations, some intentionally entered, some surprises. In most surprises, I found that ALL instrument indications were suspect, that I had to take stock of the situation and make judgements of what to trust, to what degree, and what to do about the indications they gave. When this is included in the discussion of AOA, it weakens the belief that people would perfectly follow the guidance of this (admittedly powerful) instrument. This is because the instrument, whether with visual or aural indication, can just be one more piece of data to analyze in a confusing situation.

    My military experience (F-106 and A-10) did include AOA instruments, but they were used as backups, not primary performance indicators. Their accuracy was unclear, and most of us only glanced at them to make sure they were in agreement with the airspeed and other indications we normally used. When they did not agree, I reverted to power and attitude to make sure I was in a safe performance envelope.

    Finally, I had three engine failures on takeoff in my life. The first was an ultralight that died 150 feet in the air. Went straight ahead and landed in a rough field. Tore the gear off, but otherwise fine. Second was a Cessna 180 that died about 600 feet in the air off the end of a 2000 foot grass strip. I did a quick rudder turn (think wingover) and landed the other direction with altitude to spare. The third was the partial loss of the left engine on my Twin Comanche at 300 feet from an airport well above the single engine ceiling. I immediately adjusted the “failed” engine for maximum thrust and turned back to land on the crosswind runway. In all three cases, instruments were of marginal use. My success was enabled by familiarity with the airplane and its performance.

    Jim

    Reply
  19. Dan Harrah
    Dan Harrah says:

    Hi Ed,

    I love the way all the military guys come in with criticism, thinking that their experience somehow equates to the weekend GA pilot with limited experience. The opening of the book Deep Survival by Laurence Gonzales describes a Navy carrier pilot who was so stressed and had tunnel vision (and hearing) to the point where he couldn’t hear the LSO waving him off, and he slammed into the stern of the carrier. For GA, AOA is seductive technology, blinking colored lights that are one more distraction from airmanship when things get tough. I have over 1,000 hours flying around SE Alaska, and knowing my airplane envelope in slow flight is way more important than another gadget. For GA pilots, reading the classic Stick and Rudder would be more helpful than an AOA indicator. Thank you!

    Reply
  20. Charles Lloyd
    Charles Lloyd says:

    In these articles I see no definition for “The Possible Turn.” An impossible turn can be defined as the altitude above flied elevation continuing a straight out departure to successfully return to the runway and land in the opposite direction from departure. Engine failure at any altitude below this value is an impossible turn to land safely. Another definition is that the aircraft has proceeded to far from the takeoff runway to turn and glide safety to the runway. Not enough altitude and too far from the departure end of the runway also make this an Impossible Turn. This has nothing to do with an AOA Indicator. It is not a magic bullet, and the focus needs to be on technique. You need to practice before you have to execute in an emergency and know your critical altitude.

    In the 70s there was a published article in a flying publication that defined how to do this in detail. There was no set altitude mentioned other than I was dependent on the specific aircraft. I owned a Piper Cherokee Lance at the time and decided to find out what my critical altitude was by flying to the practice area at a safe altitude and initialing the maneuver. What I did was: reduce power to flight, immediately lower the nose while initiating the turn, pitch to best glide speed and continuing to complete a 230 degree turn. The article did not discuss what happed the angle of attack in the recommended steep turn. I continued on this course (220 degrees turn) until I was where I thought I would be on course to turn again to line up for final to the runway. At this point the altitude lost was 900 feet. This maneuver help me a define critical altitude of 1,000 feet. An engine failure before this departure altitude was defined as an impossible turn and had nothing to do with an AOA.

    These articles never discuss emphasis the benefits of an AOA system in any type aircraft GA or heaver turbine aircraft. I was introduced to the Teledyne AOA that was installed on most all of the straight wing Citations and later became a certification item during later years. Its accuracy was spot on in determining best rate of climb speed and approach speed at 1.3 stall speed for any flap setting at any gross weight. You were looking out the windscreen in front of you and a heads up AOA indicator was located in the center of the glare shield. All you had to was look to the right side of your peripheral vision and keep the green donut glowing. No red or yellow chevron.

    Later, 2010, I installed an Alpha System AOA Heads Up Display in a Cessna 182J. I did not consider an in panel display a useful tool. This 182 had a Horton Stall Kit and Speed Mod Kit installed. The stall numbers were significantly lower that the aircraft’s original capabilities, so I did a new stall series. The Alpha System did not have flap compensation, and I ran the series at all flap settings. I chose to be conservative and calibrated the AOA system at the flaps up setting. The 1.3 Vs for the green donut was 67 KIAS. As far as lag in the Alpha System AOA there was a faster change in response to the system later in production. If you have a slow response system, you ought to contact Alpha Systems about having your unit updated.

    I was based at an 1,800 foot grass runway. Stabilized on speed approaches improved the consistency to hit the target touchdown point improved immensely using the Alpha System AOA as my primary speed source. Now, I did not have to continue to glance down in the panel to confirm airspeed.
    We need to continually learn more and keep the attitude that we are still student pilots no matter what ratings we have.

    Finally, I agree improved safety in the impossible turn is not what I would use to justify installing an AOA Heads up System. There are many other benefits that I found using this system in many aircraft.

    Reply
  21. Ken Duncan
    Ken Duncan says:

    Interesting article and comments !
    Providing a platform for discussion and sharing of ideas and opinions is always a fun read when the topic is Aviation !
    I think any discussion on the usefulness/relevancy of AOA systems should include the aural as well as visual features. The aural feature provides the same immediate info without looking inside. It’s also useful if the pilots attention is focused on the terrain, obstacles or runway out the side canopy/window !
    I personally find the aural indications more valuable in a turning environment.

    FLY SAFE !! (;-))

    Reply
  22. Mike Vaccaro
    Mike Vaccaro says:

    https://3c039af6-63d7-4703-82ff-4bf98735a5a3.usrfiles.com/ugd/3c039a_d5c84a119a7d4696a1174627269acb2d.pptx

    This link is to a briefing that summarizes a three year effort by the EAA to study power loss on takeoff and develop techniques to assist pilots and instructors with dealing with this low frequency/high risk event. The project included a ten year mishap analysis based on NTSB reports (2011-2021), a survey of 1000 pilots (100 instructors), a controlled field study, a controlled simulator study and instrumented flight test. The EAA team consists of three experimental test pilots, two USAF weapons school instructors, a professional analyst, two PhD aerodynamicists, the FlyONSPEED (a volunteer, non-profit group dedicated to reducing LOC mishap risk) team of engineers and the EAA simulator team. All team members are current/qualified civilian pilots as well–specialized skill sets range from civilian flight instruction, bush flying to the space shuttle ops. Conclusions are presented in the briefing. The “impossible” turn isn’t, but it’s also only a “no other good alternative, planned, briefed and executed using a properly programmed technical aid” option. Experience and the Mark I eyeball are not sufficient, there are simply too many variables. And to be perfectly clear, a “turn-back” is not a 180 degree maneuver as implied by the title of this article. At a minimum at least 210 degrees of turn PLUS an alignment turn are required, and there can be as much as 360 degrees of turn involved, depending on geometry.

    We won’t argue with “more training required,” or “more training is good” conclusions, but the private pilot ACS are what they are, and civilian LOC mishap statistics remain depressing consistent. Easy enough to stand on the experienced end of the bar and point out that young pilots don’t know much, military guys have no clue how to fly in a GA environment and site examples of channelized attention where no technical aid (short of automatic flight control logic) was going to save the pilot. The topic itself always generates passionate discussion. For those that prefer to actually watch the briefing, it’s available on the NAFI website/archives. One of our survey questions is “are you nuts?” As in, no way I’d ever consider this. 5% indicated that they would never consider a turnback. They are correct, insofar as we can not refute that logic using the scientific method. The pilots that were not correct were those that “have a minimum altitude for a turnback attempt” (i.e., a hip pocket calculation) and those that said “a turnback is practical at some altitude.”

    This does not mean that there is no benefit from training, preflight planning or the use of a technical aid (i.e., a computer to do the physics).

    Ultimately the risk is loss-of-control, which remains the #1 killer in general aviation. That is not the case in the military or airline operations. In the military, the answer was wide-spread adoption of angle of attack systems and changes in the way we train pilots. In the airlines, the answer has been increased automation. Ultimately, the focus needs to be on reducing loss-of-control mishap risk. That occurs far more frequently and kills more pilots than loss of power during the takeoff/initial climb phase. If the objective is to loose fewer of our friends and colleagues, then we need to keep our eyes on the ball. We can continue to debate, beat our aged chests and claim we can intuitively feel AOA without a technical aid and do math fast enough to adjust indicated stall speed for gross weight at the square root of the g-load real time (because we flew in the bush, right?) and point out how inexperienced the new guys are due to poor training; or we can look to other flying communities that have cracked the nut and learn. Ultimately more awareness of “how hard the wing is working” and AUTOMATION will make their way to general aviation. Just as the ubiquity of GPS/moving map tech has reduced CFIT risk, we can also reduce LOC risk using technology.

    We are currently conducting operational test and evaluation of the power loss on takeoff teaching/execution techniques as well as an iOS based technical aid we’ve developed as the result of our work. Any active instructors are welcome to participate, and any constructive feedback is always welcome via email at [email protected]

    Fly safe,

    Vac

    Reply
    • Mike Vaccaro
      Mike Vaccaro says:

      A clarification to my previous comment: By making reference to private pilot ACS, I realize I implied that this cohort suffered increased risk when a power loss on takeoff occurs. That is not the case. Power loss on takeoff/during initial climb is an equal opportunity killer. We didn’t see any statistically significant difference based on pilot qualifications during our ten year study period.

      Fly safe,

      Vac

      Reply
  23. Bart Robinett
    Bart Robinett says:

    “In maneuvering flight such as turns in the pattern. (I once flew downwind, base, and final at a constant AOA. To get the extra lift required for the turns, I had to dive to get extra airspeed so that the plane could turn at that same AOA. That produced a strange traffic pattern with roller coasters at the corners.)” There was an old adage that described the guaranteed way to live to an old age as a pilot, “fly low, slow and keep the nose up in the turns”. All competent pilots recognized they were all guaranteed ways to die. Unfortunately many pilots trained in the past 20 years or so have learned only one mantra, “fly fast and you won’t die”.
    There’s a UTube channel I enjoy watching which is focused entirely on video of rubber band powered free flight models. You can learn a lot about pitch, power and airspeed by watching a fully uncontrolled aircraft fly from takeoff to landing.

    Reply

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