We Need Stick Shakers

The FAA recently announced streamlined procedures to allow installation of angle of attack (AOA) systems in general aviation airplanes. That’s good news because the STC process for approving an AOA system in a standard airplane can be so cumbersome and costly that few equipment manufacturers want to undertake it, and few airplane owners want to pick up the extra cost.

Homebuilders can, of course, install an AOA system without specific FAA approval just as they can put other avionics in their airplanes without TSOs or STCs. And many builders are doing just that.

Many safety experts believe AOA indication systems can prevent low speed loss of control accidents by showing a pilot the actual AOA and margin above the stalling AOA. It makes sense. If you avoid the stall you avoid losing control, and maintaining AOA below the stalling angle means you can’t stall no matter what the attitude or airspeed.

But I believe measuring AOA is only part of the safety advantage. The other element is how to make the pilot aware of AOA, particularly when the angle is nearing stall. And I firmly believe only a stick shaker can deliver the warning in a meaningful way to actually improve safety through stall avoidance.

There are unlimited methods of displaying AOA to a pilot, particularly if a flat glass display is in the panel. Some of my favorite display techniques are marks or chevrons that show the stalling AOA on the PFD and indicated which way to push the nose to reduce AOA. There are also basic vertical displays that can be mounted close to the pilot’s line of sight over the glareshield that simply point down when AOA is approaching a stall.

But whatever display is installed they all have one thing in common—you have to look at them and make an interpretation of what the display means. And that’s why I don’t believe visual display of AOA will do much good to prevent the typical stall-spin accident.

When pilots unintentionally stall airplanes they are usually distracted by something, often a loss of power, or they have, as the safety experts say, become task saturated. In those situations the pilot is not looking at the information in the panel or at least not interpreting it correctly. The distracted brain is paying attention to something other than AOA, and in a situation, such as a forced landing, where so much is happening so fast and so confusingly our brains just can’t process everything.

That’s why the stick shaker warning is so important. A shaker vibrating the controls in your hand cuts through the distractions and information overload better than any aural or visual warning can. A shaker is intuitive. It requires no interpretation. The learning curve is straight up.

If you don’t believe me drive one of the several new luxury cars that have shakers in the seat to warn of collision threats. Even when you have no idea that a warning shaker is installed, such as when driving a rental car, when the shaker goes off on the side of the seat you look instinctively in that direction.

I even read a story about a company making clothing with shakers. The shakers are connected to a navigation system so you can be guided soundlessly by the position of the shaker in your vest.

The stick shaker has decades of proven success in jets. Jet pilots simply aren’t stalling and spinning and the shaker gets some credit. But the more convincing demonstration of the effectiveness of the shaker is when flying a wind shear escape.

The stick shaker warning is calibrated to fire at an AOA safely above the stall. That also happens to be the most efficient AOA for maximum climb gradient in most airplanes. So in the simulator pilots are taught when trying to escape a severe wind shear encounter to pull the nose up until the shaker fires. Then you relax back pressure just enough to keep the AOA going in and out of the shaker. That’s the AOA at which the wing can produce the most lift and offers you the best chance to get away from the ground.

During a wind shear encounter the airspeed is all over the place and the optimum pitch angle is constantly changing. There is so much to look at and interpret on the instruments that the shaker becomes the intuitive way to find best angle of climb when your brain is in overload.

A stick shaker is an electric motor with an eccentric weight attached. A shaker for GA need not be complex or expensive. It can be attached to the control column or stick almost anyplace and still deliver the unmistakable vibration to your hands.

I hope and expect to see more AOA systems for GA introduced soon since the FAA changed its certification policies. I just hope stick shakers are part of the new systems. Shakers can make a difference.

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36 Responses to We Need Stick Shakers

  1. James Butler says:

    Mac, the last thing we need is another gadget with all of the initial and recurring maintenance costs involved to compensate for an untrained pilot. We all have a device on our airplanes that sends signals through the airframe and controls when the wings are nearing a stall and it is called the horizontal stabilizer. All we need is some training to fly for an extended time on the edge of the critical angle of attack and feel the feedback the airframe is sending us. Once you have received that training, you become more in-tune with the airplane and when your body senses those signals you immediately recognize the problem and compensate without even realizing it. We have what we need, we just need to learn how to interpret and us it.

    • Bill Tomlinson says:

      Amen. We should stop trying to use technology as a crutch for crap pilots.

      Anything certificate above a basic PPL should require the applicant to demonstrate competence in aerobatics. The need for stick shakers etc will vanish like the morning dew.

  2. I have flown many single engine airplanes, but for me only one would have benefited from a stick shaker and that was a modified GP-4. In pitch, it had no breakout force ot pitch gradient.

    I put several thousand hours on a Beech Debonair. (aerodynamically the same as the F33 series). All of those planes save the GP-4 gave lots of warning as to an impending stall and I did not need the stall warning horn to tell me. As the plans approached the stall, there was a decided and difficult to ignore loss of back pressure on the yoke or stick. It was something that triggered an instinctive response of moving the yoke in the opposite direction. I’ll admit that I experienced that several times, and that sensation over rode all other inputs. Even on a soft field takeoff, the transition out of ground effect was entirely by feel.

    I don’t think I would have benefited from a “shaker” because that sensation was like grabbing an electric fence. Not something I could miss or ignore, but I’m all for anything to help the safety record. I realize many pilots never learn the feeling of the entire flight envelope in what they fly and it took me, many hours to become attuned to that feel.

    I’d vote for the AOA indicator and the stick shaker.

  3. Mac,
    Sorry – in my opinion you are way off base here. A properly calibrated AOA goes a LONG way toward educating pilots as to what the wing is really “feeling” throughout many flight regimes. That education is what creates a good pilot – one that does not have to rely on a mechanical sensation to alert him/her to the fact that the airplane is near the end of it’s lift curve.

    Your crowning example of windshear training completely misses the point. Yes – airline crews for years have used the stick shaker for escape maneuver training and execution. But the reason they have is BECAUSE there was no AOA installed. Watch the crew of a modern Boeing training for windshear escape and you will see that by using the installed AOA they do not need stick shaker to derive maximum escape performance.

  4. stan sanders says:

    What we need are my patented pivot( free wings) that are always at optimum angle of attack and variable angle of incidence that cannot be stalled. The FAA and the NTSB are considering recommending the pivot wings for all future aircraft designs to eliminate the possibility of stall/spin accidents. The Verticraft can be seen at gust.com or on youtube at http://www.youtube.com/watch?v=HbcUae_-Qc0

  5. JR says:

    We have become such a lawsuit happy society I’d be afraid to make and sell aircraft paint much less some add-on safety device. Seriously though, I think a simple stick shaker tied to either an AOA sensor or a factory stall warning device would be a great idea.

  6. Patrick Sieders says:

    Mac,

    Great idea however… are we flying an airliner or are in General Aviation ? I do enjoy all those bells and whistles on my big 120,000 lbs Max T/O workhorse, however I do not see a need to put it on my puddlejumper. The reason : I have in 13 years never had my stickshaker go off, other than during level flight at FL350, and that due to a bad connection.

    Lets stick with simple solutions : Let’s focus our bi-annuals on pitch power descents with constant rate, AOA is a very simple tool that seems to be easy to understand for all and easy to implement. And it takes standardized landing procedures, and practice to do it the same way EVERY time…

    Yes, there are other phases of flight than close to the ground when a stickshaker could be a handy tool, but again, with the tools already at hand, pilots need to build a feeling for their airplane, train and practice and have a procedure ready for when a sudden response is required. I am also afraid that the stickshaker going off at low level might become such a distraction for pilot with no recent recurrent training, that disaster can follow.

    If we overload GA pilots with all this Geewhiz stuff, the fun of flying is gone. We might as well request a typerating and IFR competency before ever flying.

  7. jethro says:

    Let’s not stop with a stick shaker. Why not a stick pusher for the times when a pilot fails to fly properly.

    Remember, it is all about safety.

  8. James L says:

    I disagree with this article. As others have said, this will not do anything but increase costs, and provide another item to file a lawsuit over.

    If an electronic device were the answer, we would have stopped having gear up landings long ago. Gear warning lights were supposed to make sure people put the gear down. ” I didn’t notice the red light”. I know, lets make an audio alarm, there is no way someone could miss that. Oh yes they can!

    The Q400 in the Colgan crash had a stick shaker. When it when off, the pilot pulled BACK on the controls. It also had an automatic system to push the nose down, which it did three times. In the end, none of it was enough.

    You can add all the gadgets you want but in the end, a human being is going to find a way around it. The following statement says it all.

    NOTHING is foolproof to a sufficiently talented fool.

    • Bill Tomlinson says:

      Never mind. It won’t be long now before commercial drones take over, and they won’t need stick pushers or AOA….

  9. Will Fox says:

    Hi Mac,
    I think you are right on. A stick shaker is a life saver. A little research reveals that stick shakers elicit a response from pilots 99% of the time as compared to 65% of the time for stall horns and the pilots response time is almost halved with the little shaking wonders. Pilots who think that such devices can be easily replaced with more training and developing a feel for the aircraft must come from the planet Vulcan, because we mere humans are subject to certain physiological limitations. As you pointed out, there are unexpected situations or emergencies, where humans exhibit Selective Attention or become Task Saturated. In these situations, pilots need all the help they can get to keep their skins intact, and stick shakers have proven to be effective in eliciting the correct response. However if your blood is green and your ears are pointed, feel free to argue that you are immune to these human weaknesses, and you have my best wishes that you will live long and prosper.

  10. Josh Johnson says:

    Of the aircraft I’ve flown, only a couple had barely recognizable stall characteristics – they were either experimentals or larger twin engine aircraft. There is probably merit to stick shakers on those. If you fail to recognize a stall in a 172 or Bonanza, might be time for some remedial training.

  11. TedK says:

    Most of the smaller GA airplanes I have flown have an aerodynamically powered stick shaker factory installed. What the bigger jets with electrical stick shakers are doing is mimicking what exists naturally when you can feel the control surfaces. Perhaps some pilots have been distracted from its feed back through the controls is masked by a annoying horn.

  12. Thomas Boyle says:

    I think Mac is broadly right, in the sense that something is needed to grab the pilot’s attention when it is NOT on the angle of attack. The “classic” stall-spin happens on the turn from base to final, when at least 9 out of 10 pilots are looking at the runway over the left wingtip, not watching the AOA indicator (or ASI – either one would save many lives). I propose, however, that sound can be equally effective, more easily installed than a stick shaker, and more intuitive to the majority of today’s lightplane pilots, who grew up in Cessnas.

    Those of us who learned to fly in Cessnas recall the simple, effective, AOA-based stall warning in those aircraft. Not only was it AOA-based (and not IAS-based), it offered audio information on the AOA as it approached stall. The first indication of high AOA would be a “hiss” or sucking sound from the reed. Then it would begin a medium-pitched buzzing moan, transitioning to a nasal whine at about the right AOA for touchdown. Take the AOA even higher, past stall, and the reed would move to what I remember as a frantic scream.

    Those sounds can easily be replicated electronically today, tied to the output of an AOA instrument, and fed into the audio system. Set the “low moan” to best AOA for the landing approach: lower and you have silence (too fast), higher and it moves up the scale. Fly your approach by “feathering” at the edge of the sound. No (failure-prone, heavy) mechanical stick shakers. Cessna-trained pilots will know instinctively what the sounds mean, and – let’s face it – that’s most of us right there. The rest will learn. And AOA control on the approach will become intuitive, a background task being managed by the brain at all times, no matter what else the pilot’s conscious attention is on.

    This kind of analog audio feedback is already used in aviation: glider pilots can tell you the value of their audio variometers in allowing them to know what’s happening to their rate of climb even when their attention is on something else entirely (like avoiding other gliders in the thermal).

    • Thomas Boyle says:

      I should add, I am NOT talking about a scare-you-out-of-your-skin stall horn. Anything “alarming” in an airplane is a distraction and probably shouldn’t happen at all.

      I’m talking about audio feedback, which needs to be set at a suitable level to be considered “background”. You should be able to listen to it throughout the approach, while making radio calls, etc.

    • Joseph Truncale says:

      I second Mr. Boyles calm and reasoned response to an idea with enough merit to keep the conversation going. As a present builder of an Experimental, AoA is high on my list of must-haves. And since all Experimentalists can install whatever we want, I think a simple stick-shaker is also going in.

  13. James Butler says:

    My airplane is equipped with a angle of attack instrument, displaying the chevrons and the donut for the optimal angle. It also has a pleasant sounding female voice that announces “Angle, Angle, Push” when the AOA becomes too low. We have all seen/heard the retractable gear pilots flying all the way to the runway with the gear horn blaring in the background. If we make the audio too much in the “background” we will the same thing only with the stall horn blaring. When my AOA instrument starts squawking “Angle, Angle, Push, Angle, Angle, Push” it is difficult not to notice.

  14. James Butler says:

    I mis-spoke when I stated “…when the AOA becomes too low.” I should have said, when the AOA approaches the critical angle.

  15. Boyd says:

    Severe wind-shear recovery in our airline flight simulators was exactly like Mac said: “Pull the nose up until the shaker fires. Then you r

  16. Bob says:

    Mr. Gorrell has it right–the true value of an AOA indicator isn’t to be the actual warning device. It’s to teach pilots what AOA *actually is* and what the airplane is *actually doing*. You can blather on about feeling the airframe all you want, but that sensation changes in every airplane and requires constant practice that a lot of pilots just can’t get. Having a good visual indicator is a great training aid, and it would be even better if it was paired with stall training while maneuvering in realistic scenarios (at safe altitudes, of course) instead of the straight-and-level power-off stalls at given airspeeds. We could train pilots properly and teach them about stalls during maneuvers with the airspeed covered up, so they know what the AOA is going to do before they do it, or we can continue to beat our heads against the wall and insist on doing things the way they were done in the past because they were done that way in the past.
    I firmly believe that every airplane should have AOA indication; it’s no more complex than an airspeed indicator, and yet so much more valuable in the pattern and when maneuvering.

  17. Larry Zepp says:

    Hi Mac,
    In spite of all of the macho pilots that don’t think they need it, I am convinced this is a valuable safety addition. I have a working prototype of a simple stick shaker for experimental aircraft. I am developing plans for this to be published in experimenter magazine.
    The wind shear is one situation that pilots don’t realize they need AOA help until they are in it. Another is a steep climb and low speed turn when they are traveling and happen to be at a much higher density altitude than they are used to. Hang in there- you are right! Best regards, Larry Zepp, EAA Ch. 2, Smith Field, Fort Wayne, IN

  18. Howard Riley says:

    Mac, a few months ago you wrote a five page article on AOA awareness with no mention of stick shakers, and now you are advancing to stick shakers-a new awakening in such a short time? Do you have a problem reinforcing the dynamics of flight for all pilots to be diligent of? An example being if the wind is blowing toward the runway when on the downwind, stay farther away from the runway so your turn from base leg to final won’t over shoot causing you to do a steep turn at low speed and a potential stall/spin in to earth. AND would a stich shaker help here? Please!

  19. Gary R. Watson says:

    We do not need stick shakers. We need competent pilots! We need pilots who understand airplanes and who understand stick and rudder piloting. The seat of your pants tells you when you are approaching a stall, if you are paying attention. Neither my Globe Swift nor my Christen Eagle even has a stall warning device. The airplanes give me a clear and unmistakable signal when a stall is approaching. Even a stall warning in a Cessna is annoying, rather than reassuring. Many very enjoyable aerobatic procedures begin with a stall. Incidentally, if you pay attention to the seat of your pants, you do not even need a turn and bank indicator to know if your controls are coordinated. If you do not know how to recognize an impending stall or how to deal with it, get training or stop flying. A stick shaker will not make up fpor incompetence or inexperience.

    • Bill Tomlinson says:

      I agree wholeheartedly. Many years ago, when I had about 150 hours TT, I went to fly a J-3 Cub, and found that an instructor had fixed a notice to it stating “Airspeed indicator inoperative”.

      I wasn’t sure what the implications of that might be, so asked another instructor who happened to be nearby. He was a real crusty old veteran of Mustangs in WW2 and Sabres in Korea. He looked me up and down, fixed me with a beady eye, and asked “You’ve got f***ing ears haven’t you?”.

      So off I went and had a delightful hour in a plane which was legally unairworthy. Even the landing was easy, the old veteran was right: you just listen to what the sound of the wings is telling you.

  20. Cary Alburn says:

    Since I’ve never flown an aircraft with a stick shaker installed, I’m not ready to say yea or nay on such things. Until I flew with my own AOA indicator, I did not realize what a benefit it is. After over 2000 hours in light singles, I thought the IA, the stall warner, and impending aerodynamic buffet, coupled with my decent skill level, was all I’d ever need. Well, I can get along without my AOA, just as I can get along without the IA and the stall warner, but with the AOA and with the IA and the stall warner, I’m unlikely to lose control, moreso even than without them. And I’m landing slower than I ever did with just the IA and stall warner to guide me.

    The biggest problem I see with adding a stick shaker is that no matter how simple it might be to install, how fundamentally simple it might be to construct, and how well it might work, it would be hampered by an outrageous price coupled with years and years before the FAA would approve it. So instead of marching down that road, I suggest that better instruction on the real meaning of angle of attack would be more beneficial, and install AOA indicators universally so that the better instruction would be more meaningful.

    Cary

  21. Carter Boswell says:

    Mac, thanks for taking this issue to heart. I’ve flown many departures and arrivals while undergoing windshear training in the sim. You just pull up into the stickshaker and go in and out of stick shaker right? Since the stickshaker is taking AOA information from the probe on the side of the jet why not just use a AOA gauge for windshear training? The big reason is cost, isn’t it always, Boeing doesn’t want to add another gauge to the plethora of instruments being displayed, or another symbol on its EFIS display. The current display system forces the pilot to go “Heads Down” to recover, if no HUD is available. (Not good) Finally, if your ever in a sim again, ask the instructor to select the “Unrecoverable Windshear” mode. Yes, this mode exist in some sims, instructors are not supposed to use it for obvious reasons, all of us are wondering what your last words might be?

  22. James Butler says:

    This is a typical bureaucratic response. When the first numerous layers of bureaucracy don’t work, we must surely need to add another layer, rinse and repeat. When will we get around to solving the original problem instead of piling on layer after layer of band-aids.

  23. Jerry says:

    I can’t speak to the usefulness of stick shakers, but I can vouch for AOA’s. Two years ago I installed an AOA, and have become convinced, that it was simply the best investment I have ever made.

    I’ve owned and flown this airplane for over 35 years, and literally thousands of hours and thousands of landings. I have a sense for what the plane is doing; feeling like it’s an extension of me in all phases of flight. But, I came to the realization, that all this familiarity could be a set-up for a base to final stall spin. I am simply too comfortable flying her, and at some point I could get bit by this comfort level. (It’s happened to pilots with 10X the experience and hours that I have.)

    After two years of using the AOA, it has become second nature. I’m unconsciously paying attention to the AOA light display, directly in my line of sight without, thinking about it. Most of the time, I am surprised that I am slightly faster turning final than I need to be. The system also has aural warnings at VS1.3 where a sweet lady’s voice softly announces, “Getting slow”, and at VS begins repeating “Too Slow, too slow.” I believe the combination of these should prevent any unintentional stall entry. And, the comfort level in hearing “Getting Slow” just as I cross the fence, and “Too slow” when flaring simply can’t be expressed. Now, it isn’t how far down the runway will I land, but where on the runway numbers do I want the wheels to touch, regardless of aircraft weight and density altitude.

    After installing the system, I flew several flights to identify the AOA indications for all the other V speeds. (Vx, Vy, Best Glide, Best Range, etc.) I’ve subsequently found the Vx indication to be extremely useful for high density altitude take-offs. Simply accelerate to the Vx indication, and begin to rotate. The result is a smooth lift off. No more mushy take-offs, and no more wondering about climbing out of ground effect. It has simply become a decision that if Vx isn’t displayed half way down the runway, just pull the power.

  24. Stuart says:

    The stick shaker might be valuable on long final approaches but most fatal GA stall/spin accidents occur at low altitude while being distracted (overshooting final, circling the girlfriend’s house, etc). My experience has been that these spins happen very quickly; almost like a snap roll caused by a sudden yank on the yoke/stick while in a steep bank. Not sure the stick shaker would operate quickly enough in these cases. Interesting idea though.

  25. Hod says:

    “Earth Shaking” idea. I can see where Mac probably wants to go with this. With a few thousand dollars more in electronics and servos, we can also get auto-land and takeoff – problem solved. Oh yes, do we really need a PIC? Drones are so much simpler when you remove the human in the equation. Might I humbly suggest that Mac run his suggestion for a stick shaker past folks like Burt Rutan to get their feedback?

    I almost forgot – don’t forget to also add the radar altimeter for J3′s and up (you know – the ground thing), and also add the “stick-puller” to remind you to keep your nose up in the turns (Mac).

    AOA really is a great tool – stick shaker in GA – not so much (IMHO).

    • Bill Tomlinson says:

      You forgot the most important item: the alarm clock to wake the pilot if he happens to nod off on final approach.

  26. I would have to chime in a say while a shaker may be a nice idea, BUT, because it is for an “AIRCRAFT” it will cost big bucks for the $50.00 in parts you could build it yourself for. I would have to agree with others that TRAINING is the big item. When I learned to fly back in the 70′s. I remember one lessen where my instructor (Thank you TOM) had covered every instrument but the compass. That was the day I learned to fly. I was taught to hear the noise, listen to the engine, listen to the wind, use the rivets on the nose and other aircraft structure to judge my pitch, roll, and yaw. We did all sorts of stalls, each time I had to explain what I felt in the controls. I even had to make a simulated engine out landing that day. Funny how all these years later I still remember that lesson.
    Like cruise control in your car, you still have to steer and PAY ATTENTION.
    Bob

  27. Jan Miller says:

    I’ll bet the folks checking in against the AOA indicator/shaker are the same ones who insist that they also don’t believe in aircraft parachutes because “real pilots” don’t need them. It wasn’t too long ago that a fellow pilot rode his aircraft right into the ground (and into eternity), while in stall/spin, rather than deploy the aircraft’s parachute. I don’t remember how many rotations the report said he did before impact, but I’m pretty sure it was double-digits.

    As far as the added expense — remains to be seen just how much once the application is more readily available. And “lawsuits”? Really?? Sounds like the same arguments motorcyclists in California made about the helmet law, which has, demonstrably, saved lives.

    Just how much is “too much” to give your family/passengers additional safety?

  28. Earl Turner says:

    Some airplanes may need stick shakers, but most do not. Good light airplane design should include good stall characteristics, including natural stall warning. The J2 cub I used to fly would give you lots of warning before stalling – the whole airplane would shake, including the stick. If the right side window was unlatched, it would act as an angle-of-attack indicator , rising slowly as you increase the angle-of-attack and would rattle up against the wing just before stalling. What more could you ask for.

  29. I agree with all the comments on training. I am never quite sure how one can miss the mush before the stall. Nobody should have a PP cert. without having the push&power reaction instinctive.

    But if we install the AoA I do like the idea of the ball buzzer (sorry 99′s) it’s much simpler than the shaker and I imagine quite an attention geter.

    On a serious note the turboprops I have flown with AoA installed I found myself integrating it into the scan and it became the primary pitch indicator.

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