1 of 11

Forces of Flight

An introduction to

2 of 11

Objective

Purpose

To ensure the applicant learns the purpose of and and can exhibit a clear understanding of basic aerodynamics.

A basic understanding of aerodynamics. When flying, pilots need to understand the four forces acting on an airplane and why a wing stalls. This lesson in basic aerodynamics will introduce pilots to the four forces, airfoils, and lift; fundamentals to other aspects of flying.

3 of 11

The Four Forces

In straight and level flight:

Weight - Downward Force

Lift - Upward Force

Thrust - Forward Force

Drag - Rearward Force

4 of 11

All Moving Objects Create Drag

Induced Drag - Drag that is created by the production of lift

Parasite Drag - Drag that is created unrelated to the production of lift

Form Drag - Created by the shape

Interference Drag - Created by disturbed air from two different features interacting with one another

Skin Friction Drag - Drag created by the friction between the air and the surface of the object

5 of 11

Airfoil Design Features

Leading Edge

Trailing Edge

Chord Line

Upper & Lower Camber

Mean Camber Line

6 of 11

How Airfoils Produce Lift

Bernoulli’s Principle - As the velocity of a moving fluid increases, the pressure within the fluid decreases.

7 of 11

Wingtip Vortices

Also known as Wake Turbulence

High pressure air moves over the wing tip spilling into low pressure area.

Decrease in lift in the area

8 of 11

Dangers of Wake Turbulence

Strength largely depends on how much lift is being produced

Properties

Move Outward

Move Downward

Start and stop with the production of lift

Affected by wind

The strength of Wake Turbulence largely depends on how much lift is being produced. Heavier aircraft require more lift, thus create stronger wake turbulence. A small airplane which encounters these invisible vortexes can roll violently and without warning.

Somethings to keep in mind about Wake Turbulence is that the vortices move Out and Down, be cautious flying underneath the flight path of a larger aircraft.

These vortices begin with the production of lift. When taking off behind a larger aircraft, rotate before the point they did and fly above their flight path. Wake turbulence also ends when lift is no longer being produced. When landing behind a larger aircraft, fly the approach above their flight path and land beyond their touchdown point.

Wingtip vortices can be affected by wind. When landing parallel runways, keep in mind the direction of the wind - In a mild crosswind situation, the downwind vortex moves rapidly away from the runway, but the movement of the upwind vortex is slowed, or stalled, and it may linger over the runway.

9 of 11

How Airfoils Produce Lift

Angle of Attack (AOA) - Angle between the Chord Line and the relative wind

The higher the AOA the more lift (and drag) is produced

Critical Angle of Attack - Where the lift produced is not enough to sustain flight

10 of 11

Aerodynamic Stalls

Critical AOA is exceeded

Air no longer flows smoothly over airfoil and separates

Lift decreases, drag increases

Can happen at any speed

11 of 11

Changing an Airfoil Design

Done with Flaps

Lengthens the cord line and changes the wing camber

Adds lift, but also increases drag

Produces more lift for given AOA

Decreases critical AOA