### Introduction
Generally, we spend most of our time flying in a "cruise" configuration, with a low [[Angle of Attack]] (AOA). But airplanes perform in a significantly different way when the wing is at a high AOA. We experience this condition during the takeoff, landing, and go-around phases of flight, and it's important for a pilot to be comfortable with these flight characteristics, since some of the control inputs you need to make are counterintuitive. For this reason, we practice "[[slow flight|Slow Flight]]." This lesson covers the mechanics of slow flight, as well as its aerodynamics.
This lesson also covers Power-Off Stalls, another maneuver you're required to demonstrate on your checkride. In a power-off stall, we will exceed the critical angle of attack, and feel the nose of the airplane sag or drop. This maneuver will teach us to recognize the signs of an impending stall, as well as the simple procedure to recover from one.
**Pre-Lesson Reading/Homework:** [[~ PPL Pre-Lesson Reading]]
**Builds On:** [[PPL1.2 Four Fundamentals of Flight]]
**Schedule:** Ground 1.5 hr, Flight 1.5 hr
### Lesson Elements
#### Slow Flight
1. What is slow flight? Why do we practice this?
1. Flight at high [[AOA]], close to [[stall]], or stall warning
1. > [!youtube] Published by [University of Iowa](https://www.youtube.com/@universityofiowa)
3. We experience this during takeoffs, landings, go-arounds
2. Aerodynamics of slow flight
1. Angle-of-Attack ([[AOA]]), airspeed ([[Angle of Attack vs Speed.jpeg|image]]), [[Load Factor]] (such as in turn, [[Forces in Level Turn.jpeg|image]]), aircraft configuration, weight, attitude
1. ![[Angle of Attack Impact to Pressure on Airfoil.jpeg]]
2. Types of drag
1. [[Parasite Drag]]
2. [[Induced Drag]]
3. The [[drag]] curve and power curve. Flying "behind the power curve". ("[[pitch for airspeed, power for altitude]]")
1. ![[Drag vs Speed.svg]]
2. ![[Power Required Curve.svg]]
4. Stall warning devices and other indications of impending stall (mushy controls, buffeting)
5. Difference between attitude and AOA
6. [[Static vs Dynamic Stability and How Trainer Planes Are Designed]]
3. Introduction to [[Weight and Balance]]
- > [!note] [[WVFC]] requires W&B as part of solo ground review form
- Is this covered earlier already?
4. Slow flight maneuvering
1. Set Up ([[CHAPS]])
1. Clear the area - perform clearing turns
2. Heading - choose a prominent landmark, and set the heading bug
3. Altitude - choose a safe altitude and set the bug
1. ACS calls for 1500' AGL minimum recovery, but this is too low to start! -- start at > 2500' AGL (3000' MSL in our local practice areas)
2. Be careful of overlaying Bravo
4. Place to land - Identify an emergency landing location
5. Set power and configuration - Reduce power, maintaining altitude while aircraft slows down, extend gear and flaps at appropriate speeds if applicable
2. Reduce speed to ~5 knots above stall or stall-warning^[Can find this speed by continuing to slow until first indication of stall, then flying at 5kts faster]
3. Add power as necessary to maintain altitude
4. Maintain rudder coordination
5. Adjust trim as necessary
6. S&L, turns, climbs, descents at various configurations (flaps and power)
7. Emphasize rudder coordination, and divide attention between aircraft control, traffic avoidance, and orientation
8. Reestablish cruise flight: Full power, reduce pitch, hold altitude as plane accelerates, set cruise power, trim
> [!maneuver]- 3D Visualizer: Slow Flight
> <iframe src="https://maneuvers.cfijack.com/?embed&m=slow-flight" width="100%" height="520" style="border:0;border-radius:12px"></iframe>
#### Power-Off Stalls
1. Aerodynamics of stalls
1. [[Stall]] occurs when you exceed the **critical angle of attack** ([[AOA]])
2. Stall can occur at ANY airspeed, attitude, or power setting!
3. Aircraft designed to pitch down at stall
1. ![[Longitudinal Stability.svg]]
2. ![[Effect of Speed on Downwash.svg]]
4. Discuss effect from
1. Change wing shape
2. Vs, Vs0
1. flaps: wing generates more lift -> can fly at lower angle of attack w/ flaps -> lower stall speed
3. Change wing loading
1. ![[CL and CG and Tail Down Force.jpeg]]
2. weight, [[CG]], [[Load Factor]], bank angle, gear
5. Our airplane stalls from the inside back ([[Stall Progression for Various Wing Planforms.svg|regular wing]]), but still ailerons will be less effective in a stall^[See [How Wing Washout Makes Your Airplane More Stable](https://www.boldmethod.com/learn-to-fly/aircraft-systems/how-wing-washout-makes-your-airplane-and-wings-more-stable-when-flying/) for additional info.]
2. Situations where risk of stalls increase
1. Landing approach, especially skidding base to final turn
2. Climb-out, trying to clear an obstacle, especially at high density altitude
3. Emergency landing, power-off glide, trying to stretch the glide
4. Exceeding max gross, CG out of limits
5. Ice or frost accumulation on wings
3. Stall recognition
1. Sight - high pitch attitude (not always)
2. Sound - reduced airflow, less wind noise
3. Feel - mushy controls, less effective, buffeting
4. Power Off Stall Maneuver
1. Simulates stall during approach to landing
2. Clearing Turns, ID Emergency Field, Outside Reference ([[CHAPS]])
3. Enter slow flight in landing configuration
4. Descend at approach speed
5. Pitch up slowly for full stall, establish gentle turn if requested
6. Verbally acknowledge stall horn
7. Continue holding pitch to full stall
8. Recover: pitch down just below horizon, full power, raise flaps one notch, then incrementally up. Climb [[Vy]].
5. Common errors
1. Poor rudder coordination, drifting off altitude, heading, etc
2. Using excessive bank angle
3. Unintentional stall
4. Improper use of trim
5. Not maintaining rudder coordination, causing wing to drop during stall, entering spin!
6. Delay in stall recovery, causing excessive altitude loss or spin entry
7. Secondary stall due to aggressive pitch up during recovery
> [!maneuver]- 3D Visualizer: Power-Off Stall
> <iframe src="https://maneuvers.cfijack.com/?embed&m=power-off-stalls" width="100%" height="520" style="border:0;border-radius:12px"></iframe>
> [!maneuver]- 3D Visualizer: Power-Off Stall (Turning)
> <iframe src="https://maneuvers.cfijack.com/?embed&m=power-off-stalls-turning" width="100%" height="520" style="border:0;border-radius:12px"></iframe>
### Completion Standards
**Slow Flight**
Client should be proficient at entering slow flight, maneuvering, and recovering.
> [!success]- Tolerances (Partial) from [[Private Pilot ACS|ACS]]
> ±100', heading ±10°, airspeed +10/-0 knots, specified bank angle ±10°
**Power-Off Stall**
Client must be able to demonstrate power-off stalls, to ACS standards.
> [!success]- Tolerances (Partial) from [[Private Pilot ACS|ACS]]
> Recovery no lower than 1500' AGL, heading ±10° before stall, or specified bank angle ±10° (and <20°), acknowledge cues of impending stall and recover promptly with proper procedure
### Resources
- [[Private Pilot ACS]] Section VII.A and VII.B
- [[POH]]
### Required Homework
None
### Recommended Homework
- [ ] Chair fly slow flight
- [ ] Chair fly power off stall
*Return to [[~ PPL Lesson Plan Outline|Table of Contents]]^*