Slow Flight Mastery: Flying on the Back Side of the Power Curve

Slow flight training develops the skills and awareness needed to operate safely near the stall—the region where the aircraft becomes less responsive, control inputs produce different effects, and margin for error disappears. Understanding the back side of the power curve transforms slow flight from a checkride maneuver into genuine safety preparation.

What Is the Back Side of the Power Curve

The power curve relates airspeed to the power required for level flight. At higher airspeeds, parasite drag dominates—power required increases with speed. At lower airspeeds, induced drag dominates—power required increases as speed decreases. The point where these effects balance, requiring minimum power for level flight, divides the curve.

On the “front side” of the curve (higher speeds), reduced airspeed means reduced power required. You can slow down by reducing power. On the “back side” (lower speeds), reduced airspeed means increased power required. Maintaining level flight while slowing requires adding power. This counterintuitive relationship creates the slow flight environment.

Characteristics of Flight on the Back Side

Flying on the back side of the power curve differs fundamentally from normal cruise flight.

Reversed Power Effects

In normal flight, adding power causes the aircraft to climb; reducing power causes it to descend. On the back side, this relationship reverses to some extent. Adding power causes acceleration and a tendency to climb. But reducing power causes deceleration, increased induced drag, and potential for rapid descent—the aircraft is “behind the power curve.”

Maintaining altitude while slow requires significant power—often near maximum available thrust. Any further reduction leads to descent that cannot be arrested without accelerating.

Reduced Control Effectiveness

Control surfaces develop force proportional to airflow velocity. At slow airspeeds, control effectiveness decreases. Inputs that produce immediate, crisp response at cruise speeds produce sluggish, delayed response when slow. Pilots must anticipate the need for larger inputs and accept delayed response.

Increased Propeller Effects

At slow speeds with high power settings, propeller effects become dominant. P-factor, torque, and slipstream create strong left-turning tendencies requiring significant right rudder to counteract. Pilots unused to slow flight often underestimate the rudder pressure required.

Stall Proximity

By definition, slow flight occurs near the stall. The margin between controlled flight and stall may be only a few knots. Turbulence, an abrupt control input, or a momentary lapse in airspeed awareness can cause the aircraft to stall.

ACS Standards for Slow Flight

The current ACS requires demonstrating slow flight at an airspeed at which the aircraft exhibits controllability at the point the stall warning is activated. This is slower than older standards that allowed somewhat higher speeds. The aircraft must be controlled in straight-and-level flight and turns while in this configuration.

Tolerances include altitude ±100 feet, heading ±10 degrees (straight flight) or a specified bank ±10 degrees (turning flight), and maintaining the stall warning or specified airspeed ±10 knots. Coordination must be maintained throughout.

Establishing Slow Flight

Entry to slow flight requires smooth, gradual deceleration to the target airspeed while maintaining altitude.

Power Reduction

Begin by reducing power to an appropriate setting. The aircraft will begin to slow. As speed decreases, induced drag increases and the aircraft will start to descend unless attitude and power are adjusted.

Pitch Adjustment

As the aircraft slows, gradually increase pitch to maintain altitude. This requires continuous adjustment—the attitude that maintains altitude at one speed differs from the attitude needed at a slower speed.

Power Addition

As speed approaches the target, you’ll need to add power to maintain altitude. The slower you fly, the more power required. At the minimum controllable airspeed with stall warning active, power may be near maximum.

Configuration

The ACS allows slow flight in various configurations. Typically, examiners specify flaps extended and gear down if applicable. Know the stall warning speed in your chosen configuration and establish airspeed that activates the warning.

Maneuvering in Slow Flight

Once established, slow flight requires constant attention and different technique than normal maneuvering.

Straight and Level

Maintaining straight-and-level slow flight requires continuous small corrections. Airspeed, altitude, and heading interact—a small pitch change affects all three. Make small corrections early rather than waiting for larger deviations that require larger corrections.

Turns

Turns in slow flight must be shallow—typically 10-15 degrees of bank. Steeper banks increase load factor, raising stall speed and potentially causing the aircraft to stall. Add power when turning to maintain altitude against the increased load factor. Reduce power and relax back pressure when rolling out.

Coordination becomes critical in slow flight turns. The tendency to slip or skid is more pronounced, and the consequences near the stall are more severe. Use coordinated aileron and rudder, and verify with the ball.

Climbs and Descents

Slow flight climbs require accepting even slower speeds or very high power settings. The performance available is limited. Descents may require power reduction, which will also accelerate the aircraft—maintaining slow flight in a descent can require an unusual combination of pitch and power.

Recovery to Normal Flight

Recovering from slow flight to normal cruise should be smooth and controlled.

Standard Recovery

Smoothly add power while relaxing back pressure. The aircraft accelerates while the pitch attitude decreases toward normal. As speed builds past the region requiring high power, reduce power to cruise setting. Retract flaps and gear as appropriate for the speed and conditions.

Minimum Altitude Loss Recovery

If at the stall warning and needing to recover immediately, the technique resembles incipient stall recovery: reduce angle of attack (lower the nose slightly), add power smoothly, and accelerate away from the stall. This recovery may result in momentary altitude loss but establishes safe airspeed quickly.

Why Slow Flight Matters

Slow flight training provides more than checkride preparation. The traffic pattern approach and landing phases occur on the back side of the power curve. Go-arounds from slow configurations require adding power to arrest descent. Understanding power/pitch relationships at slow speeds makes these normal operations safer.

The awareness developed in slow flight—constant monitoring of airspeed, recognition of control feel changes, understanding of the proximity to stall—transfers directly to the most critical phases of every flight. Pilots comfortable in slow flight remain aware and in control when conditions demand operation near the edges of the envelope.

Practice slow flight regularly throughout your flying career. The skills developed prevent the low-altitude stalls and loss of control that continue to cause fatal accidents. Master the back side of the power curve, and you’ll fly more safely at all speeds.