Theory of Flight

6.06 Loads and Load FactorReferences: FTGU pages 17-18, 34-35

6.06 Loads and Load Factor

• Definitions

• Load Factor changes

• Load Factor in Turns

• Forces in a turn

Weight

1. What is weight?

Weight

• The FORCE due to gravity that pulls the aircraft to the ground

• Acts through the centre of gravity (CG) of the a/c

Weight

What happens if…• Weight is greater than lift?

• Lift is greater than weight?

Wing Loading

Aircraft Gross Weightdivided by

Wing Area or Lifting Surface

Types of Loads• Live Load• Dead Load

= Load

Dead Load v. Live Load

Dead LoadDead Load• The load put on the aircraft when The load put on the aircraft when

it is sitting on the groundit is sitting on the ground• Weight due to gravityWeight due to gravity

Live LoadLive Load• Additional loads added in flight

due to acceleration or change in direction associated with manoeuvres

Load Factor

• Ratio of the actual load acting on the wings to the gross weight of the airplane

• Live Load : Dead Load

• In straight and level flight the load factor is 1

Load Factor

Is load factor a bad thing?

Normally, No

But load factors could cause problems…

Load Factor

1. Structural Limitation

• Each aircraft is designed with a max load factor that should never be exceeded, as permanent damage or structural failure may occur

SGS 2-33a Max Load = 4.67 G C152 Max Load = 4.4 G

Load Factor

2. Increased Stall speed• Increased load factor during manoeuvres in flight requires

increased lift to maintain level flight• Critical angle of attack is reached at an increased speed• Stall speed increases

Load factorduring flight

Speed to reachcritical angle ofattack

Stall speed

Load Factor Changes

The load factor is increased any time the aircraft is not in straight and level flight.

Examples:• Aircraft Performing manoeuvres• Wind Gusts• Turbulence

Load Factors in Turns

• As angle of bank is increased in a turn the load factor and amount of lift required also increases

• Load factor increases exponentially with angle of bank

Angle of Bank

Load Factor

15° 1.04 G

30° 1.15 G

45° 1.41 G

60° 2 G

Forces in a Turn

• In a turn lift is divided into two components

• Vertical component

• Horizontal component

Forces in a Turn

• Vertical component opposes weight

• Horizontal component causes the aircraft to turn– This horizontal component is

known as centripetal force

Forces in a Turn

Pulls plane to outside of the turn

Resulting liftdue to added

horizontalcomponents

Pulls plane into the

centre of the turn

Forces in a Turn

Centripetal v. Centrifugal Force

Centripetal Force Centrifugal Force

Pulls INTO the turn Pushes AWAY from turn

Genuine force Inertial (fictitious) force

This is the force you feel going around a corner in a

vehicle. It pulls in the opposite direction of a

turn.

Confirmation Check

Confirmation

1. Load factor =

2. What is the difference between live load and dead load?

Confirmation

3. Label where the centripetal and centrifugal forces are.

4. If this aircraft is doing a 60 degree of bank turn, how many Gs is it experiencing?

5. When does an aircraft experience a 1G force?

CP140 Aurora