Applied AOA
- vac023
- Jul 8
- 5 min read
Updated: 5 days ago
With the late 2024 FAA SAIB publication advocating for adoption of AOA by all GA, there has been much discussion about mitigating loss of control (LOC) risk by providing accurate AOA feedback to the pilot in one form or another. What hasn’t been discussed as widely, is the increased precision that AOA brings to daily flying operations.
An easy way to apply AOA today in GA is the way the military has successfully since the late 1950’s. Both the RN and USN were early adaptors as it was quite difficult to land first generation jets on an aircraft carrier with precision using airspeed as a reference. Later, it’s use expanded to include energy management awareness, primarily in air combat maneuvering. Another way to describe ACM is “maximum performance maneuvering” and whether we think in those terms or not, that’s exactly what we do in GA every time we take off and land.
The concept the military developed was simple: the optimum condition for landing was “on speed” and the pilot needed a simple means to assess whether they were “fast” or “slow” relative to that condition. In other words, trend information. What’s important to understand is that on speed isn’t a speed, it’s a small range of AOA that produces a cue the pilot uses for VREF. The exact AOA range varies slightly, but the result when properly displayed to the pilot is a directive cue that maintains within about 2 to 2.5 knots of VREF at 1 g, non-maneuvering appropriate for gross weight. Because an on speed condition is based on AOA, it’s not affected by gross weight or g-load. Just like the airplane always stalls at a single, critical AOA, it is always on speed at the same AOA. From a loss of control stand point, this means that if we maintain on speed, we maintain a constant stall margin when we maneuver. Our actual airspeed will increase with g-load, but our AOA will remain constant. The simple “on speed, fast or slow” relative to on speed feedback provided by AOA cuing makes it easy to do that.
The reason for this is intuitive: AOA and power control energy, and energy is some combination of airspeed and altitude. An easy way to picture this is trimmed, level flight. Assuming the airplane has positive stability, if we pull back on the stick and pitch up a bit, say to reduce IAS by 10 knots, the airplane will naturally pitch forward and undergo a series of oscillations over a couple of minutes and eventually return to trimmed condition. It does this because the wing is trimmed for an AOA, and the airplane simply maintains that AOA until the motion damps.
AOA also provides “power required” feedback when we maneuver. This also makes sense intuitively, since we all know that if we are “slow” relative to a desired condition, one of the ways we can fix that problem is by adding power. In the military, we use the concept of “excess specific power” when we teach energy management, and we can apply a simplified version of that concept (thankfully without any math) in GA as well. If we think back to our private pilot written examination, we all had to learn the four forces that effect the airplane in flight: lift, weight, thrust and drag. We use AOA and power to manipulate lift, thrust and drag to counter weight. That weight is a function of load and g’s. Our basic gross weight changes throughout the flight as fuel is burned, and every time we maneuver, we pull some amount of g’s. Both factors impact the speed associated with VREF and stall, but do not affect the AOA for on speed or stall.
Let’s look at two charts that show all of this graphically, a flight envelope depiction and something we are calling the “power required” envelope. We are all familiar with airplane flight envelopes, and the only thing different about this one is that we’ve plotted some other AOA’s besides stall. In this case, we can see our three conditions (on speed, fast and slow) depicted. This envelope is for a Van’s RV-4; but any AOA depiction will look similar. Notice the small red box. That is the airspeed and g region we operate in the traffic pattern. Note the entire traffic pattern is expressed as an AOA.
The second chart is a plot of power required (the lower curve) and power available (the upper limit) for the RV-4 with a 160 HP engine and fixed pitch propeller. Again, all airplanes will have such an envelope, and the size of this envelope will shift and vary with gross weight, density altitude and configuration; but the basic AOA relationships will always be the same. Again, we can see that our three standard military cues (on speed, fast and slow) encompass a good deal of the envelope, and where they don’t, we’ve got plenty of energy to maneuver, just like the flight envelope.

Figure 1. The flight envelope with on speed AOA added. Note that the entire traffic pattern can be expressed as an AOA.

Figure 2. The airplane “power envelope” where on speed becomes an “energy neutral” condition—which is a fancy way of saying thrust and drag are balanced. The pilot pushes something when slow, either the throttle, the yoke or both. The envelope is a “snap shot in time” and the actual size and orientation relative to airspeed varies with weight, density altitude and configuration. The light dashed lines are g-load and show how the envelope shrinks, but basic AOA relationships hold no mater what the size of the envelope is.
How do we apply this feedback in flight? Let’s look at landing an airplane because that is a requirement every time we fly. Specifically, if we are interested in precision landing, let’s look at how the Navy applies the on speed, fast or slow matrix. It’s quite simple. The pilot uses pitch to control AOA, power to control glide path and bank angle to control ground track. Although when we fly, we tend to blend those tasks, it’s easier to fix one issue at a time, precisely. The AOA information is directive and tells the pilot whether the airplane is slow or fast relative to desired condition. Push or pull the stick or throttle based on AOA feedback. The same thing you do now with the airspeed indicator but automatically adjusted for variation in weight. If you dutifully maintain VREF +/- 2 knots, that will work right up until you pull 1.4 g’s. If you allow yourself to get slow, all bets are off as to when you will lose control of the airplane based on how hard you turn. That’s because VREF is simply a stand in for on speed AOA, and it’s based on maneuvering limits which if not adhered to, result in possible unintentional stall. But our emphasis here is on precision landing and maneuvering.
Another concept that on speed makes easy is something we call maximum sustained turn rate. That means exactly what it sounds like—the airplane can not turn any faster (turn rate) or harder (g-load) without losing airspeed and increasing angle of attack. The way we apply this in GA is to think of an on speed condition as “optimum” turn, you can’t do any better. It also means that for whatever our effective weight is (that’s our current gross times our current g-load), thrust and drag are balanced.
Airplanes take off on speed, they approach on speed and they achieve optimum turn performance on speed. By knowing exactly when you are on speed, or fast or slow relative to that condition, you have all of the directive feedback you need to fly with precision and maintain positive aircraft control.
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