Robert, I agree. Of course, envelope protection is more expensive than an AOA indicator. And when you multiply that expense by 10x for certification, it becomes unaffordable.
So, what you're saying is that we need the regulators to get out of the way of safety devices, like envelope-protecting autopilots!
I'm not one to usually weigh in here but after reading this post I feel i need to. It is very apparent that the author has never flown with an AOA because if he had, I'm sure he would agree with most of the industry that this one tiny gauge is the most important instrument in the cockpit regarding the speed of the aircraft.
I have flow for over 20 years in light ga and small turbo jet aircraft. Having spent the first 10 years with out an AOA, and the last 10 using one, I can safely compare the use of this instrument. I think the concept that a pilot can just use their internal AOA is ridiculous. The factors that effect stall speed are constantly changing. Do the passengers really weight what I planned, did I pick up any ice in the decent, and how about the gusty cross wind, these are the real world factors that an AOA can help you safely navigate.
This is the most simply gauge in the cockpit. It works at 2000 or at 32000 feet. It simply tells you if your too fast or slow. You don't need to go through a complicated thought process to decide what your angle of attack is , thinking about the weight of the aircraft vs bank angle. What it helps you do is focus on flying the airplane by managing these factors for you. This is a real time unit and can give you constant, instant information as you maneuver for landing so that you don't get slow.
I have hired numerous young pilots moving them from light aircraft to jets. In most cases they could explain what angle of attack was but could do nothing to apply it in the real world under changing conditions.
This unit is the single best unit to reduce spin stall accidents and I am constantly amazed that we aren't putting them in light ga aircraft.
I would encourage this author to fly with an AOA before making statements that could shape the minds of young aviators leading them away from such a useful instrument.
In 1944 Wolfgang Langewiesche wrote in Stick And Rudder about AOA and how important for us pilots it is to understand AOA to prevent accidentally stalling an airplane.
Proper training on how to use AOA indicator during flight is very simple.
AOA indicator tells always correct "speed" regardless of weight and Center of Gravity which is what a pilot needs especially during approach.
With aural and visual warning of excessive AOA a lot of unnecessary GA accidents could be prevented
I agree with your sentiments. AOA gauges certainly are a tool that could enhance safety, if couple with proper training. I don't feel like people fully understand the aerodynamic forces at play when it comes to exceeding the critical angle of attack. The challenge is getting that training out into the system and somehow keeping it fresh.
Thomas Boyle stole my thunder. Excellent point!
The issue with the new envelope-protecting autopilots is that it will be many years if ever that they're available for installation on even a large minority of used aircraft. Then after that you can talk about the huge price difference between an AOA and an envelope-protecting autopilot. Would I add that type of autopilot to my plane? Sure! I'd love it! But, since I own a 1966 Meyers 200D I doubt they'll ever be certified for such a rare, high-performance, complex plane.
I'm in agreement with Gsbchiefpilot in advocating AOA in GA aircraft. It is apparent inadequately trained pilots continue to dot the landscape with crash sites. FAA studies show that 85% of pilots involved in serious or fatal accidents would fail a check ride for their level of certification on the day of the crash. These same pilots would, in my experience consider themselves ace of the airport and eschew continuing aviation education, either in flight or seminars. They might however invest in and use an AOA for better control for take off and landing.
I'm going to swing back and reiterate my agreement with Robert: there's nothing wrong with AOA - they're an unquestioned good idea - they probably won't prevent as many smoking holes as we'd like (not that there's anything wrong with preventing some of them).
Although we'd all like to think that people who stall/spin from low altitude were poorly trained and otherwise people not-like-us, the distressing fact is that some of those stall/spin accidents have involved some very highly-trained, experienced pilots. Pilots who had flown literally thousands of hours in sailplanes, constantly thermaling on the edge of a stall, have spun in from the landing approach. One of them did it a couple of years ago at an airshow in the UK (fortunately, he lived).
No-one with a certificate in their pocket and even a vestige of the will to live, looks at an ASI that's dropping out the bottom of the white arc and doesn't know what to do about it. The problem is that, at the critical moment, they're not looking at the ASI. Their attention is elsewhere. We see what we're looking for, not what we aren't. There's a famous video ("selective attention test" on YouTube) that makes the point very powerfully. Bottom line: no matter how good you are, if your brain is paying attention to something other than flying the plane, it doesn't matter how good you would have been, if your brain had actually been paying attention to flying the plane.
An AOA will let you fly with more precision, no question, but it won't reach out and grab your attention in an emergency any better than an ASI would.
That's where envelope protection comes in. It's like the Arnie Terminator. It can't be bargained with. It can't be distracted. It doesn't feel hunger, or pressure, or fear. And it absolutely will not stop, until you are on the ground.
While I support the use of AOA in GA airplanes, several factors must be considered regarding their effectiveness and potential widespread use.
First, although the GAJSC Loss of Control Working Group has recommended the use of AOA systems in GA airplanes, where is the research that supports the added benefits of such systems for GA? We must not assume that because AOA is beneficial in air transport and military applications that it will be similarly beneficial for GA. To my knowledge, no recent GA-specific research is available. On the other hand, several older studies conducted by FAA and NASA on the use of AOA in GA had mixed results. NASA TN D-6210, for example, concluded that the use of AOA "did not show a significant improvement in performance or safety." See http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19710008967_1971008...
Second, current GA AOA systems are likely not as robust as those found in air transport / military applications. Consequently, pilots need to understand the limitations in these systems. For example, I flew a homebuilt Europa equipped with an EFIS with integrated AOA. The system failed to function properly during one of a series of routine, wings level, power off stalls; it also never moved out of the yellow range and failed to annunciate during a series of slipping stalls wherein stall buffet was obvious and pronounced. A three minute iPhone video of some of those slipping stalls is available at http://www.youtube.com/watch?v=985BkVkRDUs&feature=plcp
Third, pilots must not think of their AOA system as a replacement for all of the other tools in their AOA awareness toolbox, but rather as a complimentary tool. In other words, all of the other AOA awareness skills must still be practiced and brought to bear.
Again, I support the use of AOA in GA provided the above factors are taken into consideration.
I believe I am in a very good position to comment in that I recently installed an Avidyne DFC 90 autopilot in my Cirrus SR22 along with an Alpha Systems Digital angle of attack indicator, with, as to the AoA system, only a log book entry as a minor alteration and no 337 necessary. What the angle of attack indicator provides to me at least is reassurance. Located directly between the PFD and MFD the indicator on climb out and glideslope (as well as loaded turns, etc) shows without any doubt the amount of available lift in any configuration. It has actually proven to me that I have been carrying too much of a "fudge factor" in airspeed during landing that, with practice and proficient use, has resulted in smoother, shorter landings and controlled, constant climb outs even on hot days with gusts and turbulence, when before, subconsciously (or consciously) there were worries - now proven to be misplaced, about getting up and out before the tree line. Agreed too, that the DFC90 is a great box, with envelope protection working to lower the nose when airspeed decays in climb (on autopilot) or raise nose when in a descent and the AP senses overspeed. Envelope "alerting" aurally advices the pilot as to low or high speeds even when hand flying and is again, great peace of mind. The unfortunate part of the equation? I spent a lot of money - more money in fact than I spent on my first airplane twenty five years ago! So whatever can be done to assist a pilot who wants these features in his/her airplane but finds the cost prohibitive, I am in favor of. The problem is cost of certification divided by number of end users. I find that this equation, both in counseling my aviation law clients over the years (which include the most well known LSA on the market), has been shrinking proportionately to the erosion of new pilots, students and owners.
I'm curious. Anyone know how AOA systems function in ground effect?
I am all for AOA systems and instrumentation. However, stall speed changes only a few knots between full gross and empty in most small aircraft. My aircraft has an AOA vane, but it is not something I can read directly. It simply tells the computer when I am approaching the stalling AOA and activates the stick shaker, and pusher if necessary as well as providing PLI indications- but no numbers are ever displayed. In the end though, the result is the same. The difference being that the computer actively informs me if the AOA is approaching critical, and takes action by itself in the event that I do not. I would love to see what my actual AOA is in the cockpit. When our aircraft are loaded with people and baggage we put the numbers in the FMS. As they say, garbage in, garbage out. And that garbage can be on the order of +/- 5,000lbs. An Alpha gauge would eliminate all estimation and rounding off that goes into picking approach speeds. Good article Goyer.
I'm all for technologically aided solutions but when Robert says,
"I think a more realistic approach, especially given the often marginal proficiency of pilots who don't or can't fly as much as they'd like to, is envelope protection . . ."
I think he sets up a false distinction. Modern autopilots control attitude almost perfectly but we still want attitude indicators, digital or steam. The same goes for an AOA indicator. Having one teaches pilots the size and shape of the envelope with greater precision than the proxy measures to which Robert refers. It is the only direct indicator of where one is at critical points along the flight envelope.
It boggles the mind to think that they are so inexpensive, easy to install, easy to use, and easy to maintain and yet are not an FAA requirement.
I looked at rstowell's iPhone video in which an integrated AOA indicator made it to yellow but not red even though well into a slipping stall. This is a nice video. Thanks for the work it took to put it together!
To your point, do you think that the failure in 1 out of 10 stall scenarios was due to (a) the position of the port on one wing, (b) a lack of calibration, or (c) the fact that AOA is not always a valid indicator?
It seems to me that the answer has to be 'a' or 'b' because AOA is logically tied to the physics of a stall. If true, your warning not to fully trust a specific indicator is good advice. I wonder though if this indicator's limitations are common.
Does anyone have any experience with a GA AOA that they have tested under various stall scenarios?