10.3 Slow Flight, Power-On/Off Stalls, and Spin Awareness

ACS Area of Operation VII is four tasks: PA.VII.A maneuvering during slow flight, PA.VII.B power-off stalls, PA.VII.C power-on stalls, and PA.VII.D spin awareness. The knowledge elements repeat the same list: angle of attack, airspeed, load factor, power, weight and CG, attitude, and yaw. Chapter 9 already defined a stall as exceeding critical AOA. This section is what you do with that fact in the airplane, and how a stall plus yaw becomes a spin. AC 61-67C is the stall/spin-awareness circular that sits behind the ACS language.

Slow flight — the ACS speed, not a folklore MCA

Older oral lore said “minimum controllable airspeed”: any further increase in AOA, load factor, or power cut produces an immediate stall. The current ACS is more precise and safer. PA.VII.A.S3 asks you to establish and maintain an airspeed at which any further increase in AOA, increase in load factor, or reduction in power would result in a stall warning (horn, buffet, or equivalent). You fly coordinated straight-and-level, turns, climbs, and descents without letting that warning trigger. Finish no lower than 1,500 feet AGL in a single-engine land airplane.

That speed lives on the back side of the power curve (region of reversed command). Induced drag is high; adding pitch without adding power makes you sink, not climb. Controls are mushy. The rudder is doing real work against left-turning tendencies. A small bank is a real load-factor change — remember √n — so the same indicated speed that was quiet wings-level can honk in a 20° turn. The skill is dividing attention: attitude, ball, altitude, and the warning system’s remaining margin.

You will hear “MCA” in the briefing. Translate it into ACS words for the knowledge test: stall-warning boundary, coordinated, specified configuration. Do not hold a blaring horn as a target. SAFO 17009 exists because teaching people to ignore the warning was a bad idea.

Power-off versus power-on stalls

Both stalls are still critical-AOA events. The pictures differ.

A power-off (approach) stall is the landing pattern: low power, often landing flaps, a moderate pitch attitude. Indicated stall speed sits near the AFM flaps-down 1g number. Buffet and horn are usually honest. Propeller effects are mild, so yaw is mostly whatever rudder you failed to use. Recovery is reduce AOA first (forward elevator / relax the back-pressure), then add power as appropriate, level the wings, and return to the desired flight path. Adding power while holding the stall pitch can raise the nose and deepen the stall.

A power-on (departure) stall is the takeoff/go-around picture: high power, takeoff flaps or clean, a much steeper pitch to get the wing to critical AOA. Two numbers move:

• A vertical component of thrust supports part of the weight, so the wing can reach critical AOA at a lower indicated airspeed than in the power-off stall.
• Slipstream over the inboard wing and tail can delay the break and keep the elevator effective — until it is not.

Left-turning tendencies are loud here. Torque, slipstream, and P-factor all peak. If the ball is out, you are building the yaw that PA.VII.D is about. If a wing drops, reduce AOA first, then pick the wing up with coordinated aileron and rudder. Holding the stall and “lifting the dead wing” with aileron is a textbook spin entry.

Recovery altitude: complete the task no lower than 1,500 feet AGL (ASEL). The first action is always AOA. Power is the second thought, not the first grab.

Spin awareness — stall plus yaw

PHAK and the Airplane Flying Handbook: a spin is an aggravated stall with autorotation. Both wings are stalled, or one is more deeply stalled than the other. The down-going wing has a higher AOA and more drag; that drag yaws the airplane into the low wing; the yaw keeps that wing buried. You need two ingredients: a stall and yaw. A coordinated stall that breaks straight ahead is not a spin. A steep spiral is not a spin either — in a spiral the wings are not stalled, airspeed rises, and load factor builds. Recovering a spiral like a spin (full opposite rudder and a shove) is how you overspeed or overstress the airframe.

AFH phases you must be able to identify:

• Entry — the stall plus the yaw input (or the neglected rudder) that starts rotation.
• Incipient — the transition from the stall break until the spin is fully developed. Aerodynamic and inertial forces are not yet in balance. This may last on the order of one to a few turns. This is where prompt, correct recovery is most likely to work with the least altitude.
• Developed — rotation rate, airspeed, and a near-vertical descent have stabilized. The airplane is in equilibrium and will keep autorotating until you break that equilibrium.
• Recovery — rotation stops and AOA is reduced below critical; then you recover from the resulting dive.

PA.VII.D on the Private Pilot Airplane practical test is knowledge and risk management. The skills column is N/A. Most ASEL PAR checkrides do not include a full spin demonstration. Flight-instructor applicants are the ones 14 CFR 61.183 sends out for spin training. You still have to explain the aerodynamics, the phases, and the recovery — and to avoid the entry in slow flight and stalls.

PARE — AFH teaching, not an aerobatic syllabus

When the AFM/POH publishes a spin recovery, that procedure wins. In the absence of a manufacturer procedure, the Airplane Flying Handbook and AC 61-67C teach a sequence students remember as PARE:

1. Power — idle. Power can flatten and tighten a spin.
2. Ailerons — neutral. Aileron into the low wing often deepens that wing’s stall.
3. Rudder — full opposite the rotation (confirm direction with the turn needle / turn coordinator’s airplane; do not trust the inclinometer ball — its location in the panel can make it lie).
4. Elevator — briskly through / forward of neutral to break the stall after the rudder has reached the stop.

Hold those inputs until rotation stops, then neutralize the rudder (or you can spin the other way), level the wings, and recover from the dive without a secondary stall or an airspeed blow-through VNE. Retract flaps if they were down, as the AFM directs.

That is awareness and recovery knowledge for PAR. It is not an invitation to practice developed spins, inverted spins, accelerated entries, or competition recoveries in a rental 172. Many normal-category trainers are not approved for intentional spins except in a utility envelope at a restricted weight and CG. If the POH prohibits the configuration, the configuration is prohibited.

Aft CG shortens the tail’s moment arm, reduces pitch stability, can make the stall more abrupt, and makes a spin flatter and harder to recover. Forward CG is the more stall-stable direction (at the price of a slightly higher stall speed). Loading behind the aft limit is how a “recoverable” trainer becomes an accident report. Configuration matters too: flaps can change spin mode; some POHs forbid spins with flaps extended.

Scenario: Nadia’s base-to-final skid

Nadia overshoots final, banks, and steps on inside rudder to yank the nose toward the runway — a skid. Airspeed is 70 knots, flaps down, power idle. The inside wing is more stalled; the airplane rolls and yaws into it. That is no longer a power-off stall to recover with a gentle pitch-down. It is an incipient spin at pattern altitude, where PARE does not have the altitude it needs. The PAR answer is never get here: coordinated rudder, reduce AOA, and accept a go-around. The knowledge-test answer is stall plus yaw, not “she got too slow for the flaps.”