Slow Flight

Definition of Slow Flight

Slow flight is defined as flight at an airspeed approximately 5 knots above the stalling speed. At this speed, the airplane is fully controllable but operating near the lower boundary of its performance envelope.

To understand slow flight, you need to know two key stalling speeds:

V_S0 — Stall Speed (Landing Configuration)

The bottom of the white arc on the airspeed indicator. This is the stalling speed at maximum weight, full flap, power off. It represents the slowest speed at which the airplane can maintain controlled flight in landing configuration.

V_S1 — Stall Speed (Clean Configuration)

The bottom of the green arc on the airspeed indicator. This is the stalling speed at maximum weight, no flap, power off. It represents the slowest speed in clean (cruise) configuration.

Forces in Slow Flight

At slow speed, the airplane must fly at a significantly higher angle of attack to generate sufficient lift. In cruise, the angle of attack is approximately 4 degrees. In slow flight, it increases to approximately 10 degrees or more.

This high angle of attack has several consequences:

• Increased induced drag: Induced drag is inversely proportional to speed squared — at half the cruise speed, induced drag is four times greater
• More power required: The airplane needs significantly more power to maintain altitude at slow speed than at cruise
• Speed-unstable region: Below the minimum power required speed, the airplane enters a region where slowing down requires MORE power, not less

Typical Angle of Attack vs. Flight Condition

Flight Condition	Approximate AoA	Relative Drag
High-speed cruise	2°	Low
Normal cruise	4°	Moderate
Slow flight	10°	High
Approaching stall	12–15°	Very high

Effect of Controls

At slow speed, the reduced airflow over the control surfaces makes all controls less effective. You will notice:

• Sloppy feel: The controls feel mushy and unresponsive compared to cruise. Larger control movements are needed to achieve the same result.
• Adverse yaw more pronounced: Because the ailerons are less effective but still creating differential drag, adverse yaw becomes much more noticeable. Coordinated rudder use is essential.
• Slipstream effect more noticeable: With high power settings needed for slow flight, the propeller slipstream creates a stronger asymmetric effect, requiring more right rudder to maintain coordinated flight.

Maneuvering at Slow Speed

The fundamental relationship Power + Attitude = Performance still applies in slow flight, but the roles are reversed from normal cruise:

• Attitude controls airspeed: Lowering the nose increases speed; raising it decreases speed
• Power controls altitude: Adding power arrests descent; reducing power causes descent

When turning in slow flight:

• Limit bank angle to 15 degrees maximum — steeper banks increase load factor, which increases stalling speed
• Keep the airplane in balance — use the ball indicator and stay coordinated
• Add a small amount of power in the turn to compensate for the increased load factor and maintain altitude

Distractions

Inadvertent slow flight is one of the most dangerous situations in general aviation. It typically occurs when the pilot becomes distracted and allows airspeed to decay without noticing. Common distractions include:

• Radio calls: Listening for or making transmissions while in the traffic pattern
• Passengers: Conversation or passenger emergencies diverting attention
• Map reading / GPS programming: Looking inside the cockpit for extended periods
• Looking for traffic: Head-down time searching for reported traffic

Principles of Flight Supplement

To fully understand slow flight, you need to understand the aerodynamic concepts behind it.

Angle of Attack

The angle of attack (AoA) is the angle between the chord line of the wing and the relative airflow. The chord line is an imaginary straight line drawn from the leading edge to the trailing edge of the wing.

Increasing the angle of attack increases the coefficient of lift — up to a point. The airplane does not know its pitch attitude relative to the horizon; it only responds to the angle of attack relative to the air flowing over the wing.

Critical Angle of Attack

The critical angle of attack is approximately 12 to 15 degrees for most light aircraft wings. Beyond this angle, the smooth airflow over the upper surface of the wing can no longer follow the surface contour. It separates from the wing, destroying lift and causing the stall.

Coefficient of Lift (C_L) Curve

The relationship between angle of attack and lift coefficient is shown on the C_L curve:

• From 0° to approximately 12–15°, C_L increases roughly linearly with AoA
• At the critical angle, C_L reaches its maximum value (C_{L max})
• Beyond the critical angle, C_L drops sharply — the wing is stalled

Airflow Separation

As the angle of attack increases toward the critical angle, the airflow begins separating from the upper surface of the wing starting at the trailing edge. This separation point moves progressively forward as AoA increases. When separation reaches approximately the quarter-chord point, the wing stalls.

Center of Pressure Movement

The center of pressure is the point on the wing where the total aerodynamic force effectively acts. As the angle of attack increases, the center of pressure moves forward along the chord. At the stall, it moves rapidly rearward, causing a nose-down pitching moment — this is actually a built-in safety feature that helps the airplane recover from the stall naturally.

HASELL Checks

Before practicing any slow flight or stalling exercise, you must complete the HASELL check. This ensures you are in a safe environment to explore the edges of the flight envelope.

H — Height

Sufficient altitude to recover safely. Minimum 3,000 feet AGL for training exercises.

A — Airframe

Configuration appropriate for the exercise: flaps as required, landing gear (if retractable), brakes off, trim set.

S — Security

Harnesses tight, loose articles stowed, hatches and doors secure.

E — Engine

Temperatures and pressures in the green, fuel on fullest tank, mixture set, carburetor heat as required.

L — Location (ABCC)

Away from controlled airspace, Built-up areas, Clouds, and Congested traffic areas. Choose a practice area with clear terrain below.

L — Lookout

Complete a clearing turn (180° or two 90° turns) to ensure the area is free of other traffic above, below, and all around.

Entering Slow Flight

The procedure for controlled deceleration to critically slow airspeed follows the Power-Attitude-Trim sequence:

Step 1 — POWER: Reduce

• Smoothly reduce power toward idle (or a low power setting as briefed)
• The airplane will begin to decelerate

Step 2 — ATTITUDE: Pitch Up to Maintain Level Flight

• As the airspeed decreases, progressively raise the nose to maintain altitude
• The pitch attitude will be noticeably higher than cruise — this is normal
• As speed continues to decrease, you will need to add power to maintain altitude (speed-unstable region)

Step 3 — TRIM

• Trim to relieve control pressure as you stabilize at the target speed
• Target: approximately 5 knots above V_S1 (or V_S0 if flaps are extended)

Maneuvering in Slow Flight

Once stabilized in slow flight, practice:

• Maintaining altitude and heading — notice how much attention it requires
• Gentle turns (15 degrees bank maximum) — add a touch of power to compensate for the increased load factor
• Climbing and descending using power changes while maintaining slow airspeed

Recovery to Normal Flight

Recovery from slow flight to normal cruise uses a positive, sequential procedure:

Step 1 — POWER: Steadily Increase to Full

• Apply power smoothly and progressively — avoid slamming the throttle open, which can cause a yaw to the left
• Maintain balanced flight with right rudder as power increases

Step 2 — ATTITUDE: Maintain Altitude Until Airspeed Increases

• Hold altitude — the nose will need to come down slightly as speed builds
• Once airspeed reaches normal climb speed (V_Y), pitch to the climb attitude if a climb is desired
• Or maintain level flight as speed increases toward cruise

Step 3 — TRIM

• Re-trim for the new flight condition (climb or cruise)
• Retract flaps in stages once safely above V_S1

What You Have Learned

You can now recognize the symptoms of critically slow airspeed and control the aircraft safely at minimum controllable airspeed. You understand how the airplane behaves differently near the stall and can maneuver confidently in this regime.

Key takeaways from this lesson:

• Slow flight is speed-unstable: Below minimum power required speed, you need MORE power to fly SLOWER — the back side of the power curve
• Controls are less effective: Larger inputs needed, adverse yaw more pronounced, coordination is critical
• Attitude controls airspeed, power controls altitude — the reversed relationship at slow speed
• Turns limited to 15 degrees bank — load factor increases stalling speed, and you have very little margin
• Never raise flaps below V_S1 — doing so will cause an immediate stall
• Fly the airplane first — no distraction is worth losing airspeed awareness

Skills for What Comes Next

The awareness you have built in this lesson is directly applicable to two critical areas of your training:

Pattern flying: Every approach and landing happens in the slow flight regime. The airplane is configured with flap, flying at relatively low speed, close to the ground. Your ability to maintain precise airspeed control at slow speed — while managing radio calls, checklists, and traffic — is exactly what pattern flying demands.

The foundation is solid. You know what the airplane feels and sounds like when it is running out of airspeed. That awareness will protect you throughout your entire flying career.

Aviator.NYC Lesson Plan

Briefing Topics

• Aviation weather tools
• NYC-area training airports overview
• Decision-making strategies

Simulator Session

1. Pre-Flight Weather Briefing — TAF and METAR
2. Depart KFRG or KCDW into deteriorating weather
3. Diversion to alternate airport (KMMU or KHPN)
4. Simulated Radio Failure — NORDO landing procedure
5. Go-Around from 200 ft AGL

Debrief

Review decision-making under pressure and airport familiarity.

Pilot Preparation

• Practice weather briefing on aviationweather.gov
• Review NORDO (no radio) procedures

Skill Items

Skill	D P 1 2 3 4 5 6
Preflight Inspection
Engine Starting
Taxi & Before Takeoff Check
Radio Communications
Normal Takeoff and Climbs
Climbing & Leveling Off With Turns
Straight & Level Flight/Various Airspeeds
Steep Turns
Slow Flight (With & Without Flaps)
Use of Trim Flaps Mixture Carb Heat
Clean Stall Entry & Symptoms
Recovery With & Without Power
Incipient Recovery of Clean Stall
Go Around Procedure (At Altitude)
Descent & Leveling Off
Ground Ref Maneuvers
Approach Planning & Altimeter Setting
Normal Landing
After Landing Parking and Securing

Date

Aircraft

Student

Instructor

Remarks

Radio Communication Scenarios

Practice VFR radio calls for this lesson. Listen to the scenario, formulate your response, then reveal the full exchange.

1 PIREP — Icing Report KIRK

You are in N106ST and have just taken off from Kirksville Regional in Missouri. After a few minutes, you see that you are experiencing unforecast light icing. You decide to go back to Kirksville, but want to give a PIREP to Flight Watch. Tune 122.0 and make the report.

AirportDeparted Kirksville Regional (KIRK)

Position10 NE of Kirksville, 4,500 ft

FrequencyFlight Watch 122.0

TypeEn route

Your Turn

Contact Flight Watch on 122.0 and give a PIREP. Include: callsign, location, altitude, aircraft type, and the icing conditions you're experiencing. State your intentions.

• You (Pilot) "Flight Watch, november-one-zero-six-sierra-tango, PIREP."
• Flight Watch "november-one-zero-six-sierra-tango, Flight Watch, go ahead with your PIREP."
• You (Pilot) "november-one-zero-six-sierra-tango, PA-28, one-zero miles northeast of Kirksville, four thousand five hundred. Light rime icing, unforecast. Returning to Kirksville."
• Flight Watch "november-one-zero-six-sierra-tango, roger, PIREP received. Kirksville altimeter two-niner-niner-two. Weather, ceiling three thousand broken, visibility five."
• You (Pilot) "Two-niner-niner-two, six-sierra-tango. Thank you."

2 Position Update to FSS KGRI

You are in N106ST on a long cross-country to Central Nebraska Regional Airport. You've filed an open VFR flight plan. You pass the Ponca City VOR at 1830 Zulu and decide to update Flight Service with your current position.

AirportEn route to Central Nebraska Regional (KGRI)

PositionOver Ponca City VOR, 5,500 ft

FrequencyFSS 122.2

TypeEn route

Your Turn

Contact Flight Service to update your VFR flight plan with a position report. Include: callsign, that you have an open VFR flight plan, your current position, altitude, and time over the fix.

• You (Pilot) "Radio, november-one-zero-six-sierra-tango, position report on open VFR flight plan."
• FSS (Radio) "november-one-zero-six-sierra-tango, Radio, go ahead."
• You (Pilot) "november-one-zero-six-sierra-tango, over Ponca City VOR at one-eight-three-zero Zulu, five thousand five hundred, en route Central Nebraska Regional."
• FSS (Radio) "november-one-zero-six-sierra-tango, roger, position report received. Ponca City altimeter three-zero-zero-five."
• You (Pilot) "Three-zero-zero-five, six-sierra-tango."