One more time—It’s the Wing!!

July 25, 2013 by Bruce Landsberg

AoA indicatorThe big news last week was that Icon is finally giving the angle of attack indicator its due by positioning it smack dab in front of the pilot. This is on its new light sport aircraft (LSA), which appears to be a very interesting aircraft. Regular sufferers of this blog and the Safety Pilot columns know that I’ve been a fan of angle of attack (AOA) for years and have wondered frequently why the industry has persisted in relying on that tired old derivative, airspeed, to measure wing performance.

In the speculative mode, briefly, it would appear that the recent Asiana B777 crash in SFO will be attributed to trying to make the wing do something that it wasn’t designed to do. If that is the determination, then that will make this the third fatal air carrier accident in less than five years that was caused by the crews’ aeronautical equivalent to walking on water. It’s been proven too many times that AOA is perhaps the essence of aeronautical life. So back to my tired old refrain:  if it’s so danged important, why don’t we measure it?

Icon, with a well done video, is making the same point and it becomes so obvious you wonder why the rest of the business hasn’t gotten in line sooner.  Here is what I like—you’ll have your own opinion:

  • The AOA is located directly in the pilot’s view. On takeoff, landing, and maneuvering when one should be looking mostly out the window the wing lift indicator is visible. No need to fumble in depth of the panel or buried somewhere on the PFD.
  • It’s analog! Some things are best described pictorially not numerically. Icon displays, of all things, a wing that points to green, yellow, and red pie shaped wedges—exactly as CFIs attempt to explain AOA to new students. This will irritate some of my left-brained engineering and accountant friends who have a strong preference for numbers and believe all things digital to be inherently better than analog. You won’t find many digital speedometers on cars these days and mostly the aforementioned are the only ones still wearing digital watches.

As written before, some of the best human factor types in the business, NASCAR, put the most important instrument right in front of the driver, and the tachometer is analog not digital so that critical information can be seen without shifting away from the primary task of not smacking the wall or the driver in front of you. (They do a lot of tailgating but the polite term is drafting.) While we like to blame the FAA for all kinds of things, and in many cases they richly deserve it, I suspect that there is nothing prohibiting aircraft manufacturers of all stripes from doing exactly what Icon did although it might take some reconfiguring. We hope to find out shortly.

It’s the wing that sustains us, and all pilots—from the newest student to the most seasoned air carrier type—should know exactly how that wonderful device is performing!



Bruce Landsberg
Senior Safety Advisor, Air Safety Institute

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  • John hey

    Isn’t that’s what the string in the nose of our gliders is for?YE3

  • Bruce Landsberg

    I’m probably mistaken but I think that’s for yaw. Glider types?

  • Charlie Branch

    The toughest thing for many to grasp is that the airplane and its wings fly in relationship to the airflow, and relationship to the ground is relatively unimportant (except for making sure the airplane touches down on its “alighting gear” when it stops flying).
    Spins, unusual attitudes, aerobatics and gliding… It’s all about the airflow.

  • Craig Maiman

    On gliders it’s a *yaw* string.

  • Overkill33

    Correct, that’s why they call it a “Yaw String”. AoA would be a great safety tool. It must be taught and included in the scan. CFIG ATP

  • Craig Maiman

    What would be even better than an AoA detector/indicator is *two* AoA detectors, one of each wingtip and a single indicator showing the worse AoA of the two (and maybe an indication that you’re flying uncoordinated if the two measurements differ).

  • John Morgan

    Some early ASI were actually AOA indicators, consisting of a paddle vane working against a spring out on a wing strut.

    Some glider pilots have tried using yarn attached to the canopy sides to indicate AOA, but with generally marginal results. The indications tend to be skewed by the wing to fuselage intersection (drag) and any slip caused cross flow at the canopy.

    I used to think airspeed worked just fine to avoid stalls, but I’m slowly coming around. When maneuvering down low, as is often done when back country flying, unlike an ASI, the AOA automatically accounts for different loading and bank angle.

  • Howard Riley

    For at least 50 years sailboats have used AOA indicators on top of the mast. The most popular is the “Windex”, invented by a great soaring plane designer!

    I agree that one on each wing would give the best information.

  • Finbar Sheehy

    Agree with all of it: large, primary instrument, analog, in line of sight – all so that the pilot can be aware of AoA while looking out the window. These teeny-tiny “standard” AoA displays are far too small, and AoA indications being added to glass panels are both too small and too low on the display to be helpful. The direction indicator gets far more real estate…

  • Craig Zgraggen

    Hmmmm, maybe those dumb Navy pilots know something after all. How long have they been using AoA?

  • Pranesh Dey

    Nothing like GA — the simplest form of aviation perhaps after gliders — to stay current with basics.

  • Rob Spencer

    Most glider pilots are familiar with the yaw string, a slip/skid indicator taped to the center of the canopy. It is used like the “ball” slip/skid indicator installed in most planes. However, few pilots have heard of a “side-string” which is a very simple inexpensive AOA indicator for gliders that could probably be used on other aircraft without a propeller up front. After installing the “side-strings” low on each side of the canopy, I calibrated the placement of taped marks on the inside of the canopy for just above stall, best L/D (least drag which is also best glide ratio angle of attack) and also for maneuvering speed in level flight. See for more information about the side-string AOA.

    Rob Spencer, CFI (glider)

  • Rob Spencer

    Must have missed John Morgan’s earlier post in which he mentions the side string. (sorry). But I have been using the AOA side string for a couple of years with good results. Yes, in a slip, would not be accurate. Also would not trust it if it got wet. But overall, a good safety tool and one that I see automatically when clearing my turns or looking at the runway turning base to final (when most stall/spin fatalities occur).

  • MeStall?Never!

    I really don’t get why an AoA indicator is not standard equipment on all fixed wing aircraft. It would be great to have and is a relatively simple and inexpensive piece of equipment. I have never stalled an airplane without that being my intent, but I have often wondered how close I may have come on some of my not so stable approaches. I can only guess. Last year I suggested to some members of my flying club that we consider installing one of the not too expensive kits on our planes, but was met with surprisingly negative feedback. Comments like “stalls are not really a serious risk for us” or “that’s what we have stall warning horns for”. Yes we have warning horns, but they only alert you when a stall is eminent and that is not a sound I really want to hear as I am turning base to final. Having an AoA indicator would really help the pilot to be situational aware of the wing and its reserve of lift at any given moment, under any flight condition. Having that information would make us all better and more enlightened pilots.

  • Dan Tootle

    Us fixed-wing CV types found out a long time ago thatif you want to avoid smacking into the round-down, you better pay good attention to your AOA. And better yet, the LSO is looking at it also from the AOA indicator lights on your very expensive reusable fuel container. not only does the AOA indicator in the cockpit (which is right in front of you) keep you honest, but the LSO can see the AOA trend you are flying and make critical decisions concerning landing gear position and whether or not you should continue your approach. Those who don’t use this indication properly, just DON’T continue to enjoy the ready room movies.

  • Tom Harnish

    Hooray! The FAA says today that they’re going to make getting AoA indicators approved easier and quicker.

    “Although they have been available for some time, the effort and cost associated with gaining installation approval has limited their use in general aviation. The streamlined requirements are expected to lead to greater use of the devices and increased safety in general aviation.

    “We have eliminated major barriers so pilots can add another valuable cockpit aid for safety,” said FAA Administrator Michael Huerta. “These indicators provide precise information to the pilot, and could help many avoid needless accidents.”