About 60 years ago, John Boyd and his team at Eglin AFB Test developed a method to directly compare the performance of two fighter aircraft. The purpose was to determine areas of the performance envelope where one airplane has a maneuvering advantage or deficit relative to a different type. This work caused a fundamental shift in the fighter community and the way we taught folks to dogfight. It also led to integration of better energy management tools in the cockpit as well as revisions to the training syllabus—i.e., how we taught folks to fly. This shift improved combat efficacy and resulted in reduction in loss of control mishaps.
Before you stop reading because “military flying isn’t general aviation” please consider that airplanes are airplanes and physics is physics
Let’s take a brief look at what “specific power” (abbreviated Ps and pronounced “p sub s”) is and why the pilot cares…
…Ultimately, it’s just an easy way to analyze the four forces that you learned about for your private pilot written test. Technically it’s thrust x velocity minus drag x velocity divided by gross weight x G-load. As stick-actuators, all we need to know is the relationship between thrust and drag for our current G-load as we maneuver the airplane.
Using Ps is an easy way to do that if you have a properly calibrated AOA system in the airplane. It eliminates math in public and tells us what to do with the stick and throttle to avoid a negative energy state or optimize performance.
In my initial post, I’m substituting Ps for “energy state." AOA (whether you look at it or listen to it) is the key to knowing where you are on the power required curve since there are specific AOAs associated with minimum power and maximum lift to drag ratio. AOA also tells you exactly how far from a stall you are. Us knuckle-dragging stick apes refer to this situational awareness as “knowing our aerodynamic margin” which makes us sound smart at the bar (and engineers cringe), but just means “how hard can I pull right now?”
Key performance AOAs are built into the airplane and don’t change except during flap deployment. That means your approach and landing reference AOA remains the same regardless of gross weight, density altitude or G-load. The three-tone pattern is just a simple way to convey “onspeed, fast or slow” to the pilot during maneuvering. It allows instantaneous determination of Ps, correlates with Vapp/Vref (1.3 Vs), and Vx. If the objective is to maintain onspeed for approach and landing, the tone is a simple “push/pull” cue. The same is true during maneuvering flight. Unless the intention is to add drag using G, or maneuver at the aerodynamic limit of the airplane, there isn’t any reason for the pilot to spend any time in the slow tone.
We use the throttle to “make energy” and the elevator to manage it. If we know AOA, we know specific power and how we can use the elevator to trade that throttle position for altitude, airspeed, optimum approach or optimum turn performance, real-time. That performance SA and progressive stall warning are what AOA bring to the fight. It's a simple, efficient way to manage energy and maintain control of an airplane with manual flight controls.