Ground school

Stalls happen at an angle, not a speed.

OnSpeed is an aural angle-of-attack system. It tells you, by tone, where the wing is operating — slow, on speed, fast, or approaching the stall — without the pilot reading a gauge. Four lessons below: physics, energy, technique, and emergency.

01 — Basics

The wing stalls at one angle, every time.

Angle of attack is the angle between the wing's chord and the relative wind. The wing stalls when that angle exceeds a critical value — typically 15 to 20 degrees on most general-aviation airfoils. The stalling angle does not change with weight, bank, load factor, or density altitude. The stalling airspeed does. That's why airspeed indicators put pilots into accelerated stalls and AOA does not.

OnSpeed measures angle of attack directly from the differential pressure on an AOA-equipped pitot or boom probe, then maps it to a tone in your headset. You don't read it. You hear it. Eyes stay outside the airplane, where they belong on takeoff, in the pattern, and during the engine-out forced landing.

Four references the system gives you

Carson's speed

About 1.32 × L/Dmax. The cruise efficiency point — a little more fuel burn for a useful gain in speed.

L/Dmax

Best glide and best climb angle. The most lift per unit drag the wing produces. The bottom of the drag curve.

ONSPEED

The minimum-power AOA — where thrust and drag balance. The band the system is named for. Approach speeds are tied to it; landings are short and stable here.

Stall

Critical AOA. A progressive warning tone leads up to it, with margin of about 1.5 to 2 degrees before the wing actually lets go.

In flight, you only need to know three positions on this scale: Fast, On-Speed, and Slow. The tone tells you which one you are at. Fast means low workload and excess margin. On-Speed is the reference condition for landing and maneuvering. Slow means lift demand is high, the wing is approaching its limit, and you are losing energy fast. The framework is from carrier aviation. The Navy has flown by it for half a century.

02 — Energy

Know where you are on the power curve.

Drag is not a single number. It rises at high speed (parasite drag, scaling with the square of airspeed) and rises again at low speed (induced drag, scaling with the inverse square). The bottom of that curve is L/Dmax — the airspeed at which the airplane is most efficient and the power required to hold altitude is at its minimum.

Slower than L/Dmax, the airplane is on the back side. More power is required to hold altitude as you slow further. Pull more without adding thrust, and you trade altitude for nothing. This is where many short-final stall accidents live.

"On speed" is an angle, not a number on the ASI

Approach airspeed in the POH is calibrated for one weight, one configuration, one center of gravity, and zero G. Solo, half fuel, and a thirty-degree bank to final, that number is wrong. The ONSPEED tone is right at every weight and every load factor, because it tracks the angle the wing actually sees.

Total energy is the sum of altitude (potential) and airspeed (kinetic). The pilot trades between them with the stick. The throttle adjusts the total. AOA tells you whether the wing is handling the trade efficiently. With the tone in your ear, energy management stops being an arithmetic problem and becomes a sound.

03 — In flight

Rotate, climb, and land by ear.

Takeoff. Hold the nose down through acceleration. As the wing reaches flying speed, you'll hear ONSPEED. Rotate to that tone and hold it. The airplane is now climbing at the AOA the wing wants, regardless of weight, density altitude, or runway gradient.

Vx — best angle of climb — is a higher AOA than Vy. Both are tones. Pull until you hear Vx for obstacle clearance. Lower the nose to Vy once the obstacle is behind you. Eyes can stay outside; AOA does not require an instrument scan.

Approach. From downwind through final, fly the ONSPEED tone. The airplane will arrive at the threshold at the slowest safe airspeed for its current weight and load factor — which is exactly what the airfoil wants for the shortest, most controlled landing.

Fly the pattern by tone.

Abeam the numbers, power back, configure, hold ONSPEED. The airplane stabilizes at approach AOA and the tone tells you it's there. Turn base when the runway is at the picture you've trained for; tone holds. Final is more of the same. If the tone shifts toward fast, you have energy to spend; toward slow, add throttle. No mental math, no peeking at the airspeed indicator while the runway is moving.

04 — Engine out

Push, then pull. Fly the airplane to the crash.

The engine quits. The first move is forward stick — push to L/Dmax. That AOA is the tone you've been training to. It is the longest glide the airplane is capable of, and it gets you the most options for a forced landing.

Pulling back on the stick at this moment — the instinctive response — costs you airspeed, then altitude, then the airplane. The tone tells you when you've gone past L/Dmax toward the stall. If you hear the slow tone, you are throwing away glide range every second.

On short final to the field, transition from L/Dmax to ONSPEED. The airplane crosses the fence at the slowest airspeed it can fly at that weight, with full control authority. Touchdown is short. Walk away.

The 180 power-off and the SFO patterns

The 180-degree power-off approach — pull the throttle abeam the numbers, glide to the runway, no power added — is the building block. Flown to L/Dmax until short final, then ONSPEED to the flare, it lands every time on the same spot. Pilots who fly the 180 monthly land it on the same spot every time.

Higher altitude engine failures use the SFO (Simulated Flameout) patterns — high key, low key, base key, geometry borrowed from military single-engine procedures. The geometry is altitude-dependent. The AOA discipline is the same: L/Dmax in the glide, ONSPEED in the flare.

The phrase Vac uses in his seminars is "fly the airplane to the crash." The point is not pessimism. It is that the wing keeps lifting until you stop flying it. The tone is the input that keeps you flying it.

05 — Origin

A military framework brought to general aviation.

Aural angle of attack came out of carrier aviation. The Navy needed pilots to put their airplanes on a moving deck at night, in weather, at the slowest speed the wing would still fly — without taking eyes off the ball. Airspeed indicators couldn't answer the question; the wing's angle could. The framework standardized as Fast / On-Speed / Slow.

The Air Force adopted it for the F-4 Phantom in the early 1960s. Every U.S. fighter since has used aural AOA as a primary control reference. Loss-of-control accidents in military operations dropped sharply once the framework, the cueing, and the training came together.

General aviation never adopted it. The FAA dropped spin training in 1949, citing training accidents. Since the NTSB began tracking accident data in 1962, loss-of-control has remained 40 to 50 percent of GA fatalities, year after year. The cause has not been a mystery. The fix was proven on aircraft carriers in the late 1950s and has been in continuous military use ever since. We are bringing it across.