Theory of Flight Loads and Load Factor References

Theory of Flight Loads and Load Factor References: FTGU pages 28 -29

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 (C of G) of the a/c

Weight What happens if… • Weight is greater than lift? • Lift is greater than weight?

Wing Loading Aircraft Gross Weight divided by Wing Area or Lifting Surface = Load Types of Loads • Live Load • Dead Load

Dead Load v. Live Load Dead Load • The load put on the aircraft when it is sitting on the ground • Weight due to gravity Live 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 -33 a Max Load = 4. 67 G C 152 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 factor during flight Speed to reach critical angle of attack 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 into the centre of the turn Pulls plane to outside 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 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 1 G force?

CP 140 Aurora