Aerodynamics Chapter: Load Factor and Turns

Theory of Flight

• Four forces act on an airplane: thrust, lift, weight, and drag.
• Thrust is the forward force propelling the airplane.
• Lift is the upward force supporting the airplane.
• Weight is the downward pull of gravity.
• Drag is the backward force resisting the airplane's movement.

Introduction

• Students will be able to describe the relationship between lift, weight, thrust, and drag.
• Students will be able to describe glide ratio.
• Students will be able to describe steady-state flight and performance.
• Students will be able to describe the theory of the turn.
• Students will be able to describe load factor and its influence on stalling, flight envelope, and structural limitations.
• Students will be able to describe methods of lift augmentation.

Four Forces of Flight

• Lift is produced by airflow over and under wings.
• Weight opposes lift, caused by gravity.
• Thrust moves the aircraft forward, determined by engine power.
• Drag opposes thrust, limiting speed.

Vectors

• Arrows representing forces are called vectors.
• Vector length indicates magnitude, and orientation shows direction.
• Several forces acting simultaneously combine to create a resultant force.

Lift

• Lift is the key aerodynamic force opposing weight.
• Airplane is in equilibrium when lift equals weight.
• Wing design creates a pressure differential (high below, low above) creating lift.

Weight

• Weight acts downward through the center of gravity (CG).
• Lift counteracts weight to maintain altitude.
• CG is the point where all the aircraft's weight is concentrated.

Center of Gravity

• CG is the point where the weight of the aircraft acts.
• Maintaining balance between lift and weight keeps the airplane in straight-and-level flight.

Adverse Forward Center of Gravity

• Too much weight forward shifts the CG forward.
• This can lead to increased tendency to dive, difficulty raising the nose, oscillations, and issues with flap operation, spin characteristics.

Adverse Rear Center of Gravity

• Too much weight aft leads to a rearward shifted CG.
• The possible consequences include decreased flying speed, decreased range, increased stalling tendency, spin characteristics, and poor stability.

Effect of Stall Speed on Centre of Gravity

• This topic is about how stall speed is affected by the location of the center of gravity (CG).

Imbalanced Centre of Gravity

• An imbalance in center of gravity position affects the stability of the aircraft.

Effect of Forward Centre of Gravity on Aircraft Performance and Stability

• Forward CG decreases performance and increases stability.
• Forward CG increases drag and indicated stall speed.

Effect of Aft Centre of Gravity on Aircraft Performance and Stability

• Aft CG increases performance and decreases stability.
• Aft CG decreases drag and indicated stall speed.

Lifting Forces

• Airflow over an airfoil (curved surface) creates a pressure difference.
• High pressure under the wing, low pressure above the wing.
• Resultant force pushes the aircraft upwards.

Center of Gravity Limits

• Each aircraft has specific CG limits (typically 15% to 40% of wing chord).
• CG position changes during flight due to fuel consumption and passenger/cargo movement.
• CG location affects pitch attitude.

Straight and Level Flight

• Lift equals weight, and thrust equals drag in straight-and-level flight at constant airspeed.
• Thrust changes are required for acceleration or descent.

Forces in a Climb

• Thrust balances drag plus a portion of the weight.
• Higher climbing angles result in lower lift and require greater thrust.

Forces in a Descent

• Gravity aids thrust in reducing the required thrust.
• Lift is less than weight, drag balanced by reduced thrust.

The Glide

• Thrust is removed, lift and drag counteract weight for a steady glide.
• Glide angle is influenced by lift/drag ratio.
• Optimal glide angle corresponds to max lift/drag ratio.

Glide Angle

• A glider's glide angle is determined by the change in altitude divided by the horizontal distance flown during descent.

Aircraft Glide Ratio

• Glide ratio relates horizontal distance traveled to altitude lost.
• Lower sink rate, higher glide ratio.
• A glide polar allows estimation of glide ratio at various speeds.

Aircraft Glide Ratio (continued)

• Airspeed and sink rate are used to determine minimum sink speed.
• The graph is used to find the minimum sink speed and related airspeed.

Aircraft Glide Ratio (continued)

• Best glide speed (or best L/D speed) is the airspeed for the highest glide ratio.
• Glide ratio can be calculated from a graph of sink rate vs. airspeed.
• Glide speed maximizes the distance flown for each unit of altitude lost.

Glider Fly

• This is about the operation and performance of gliders in flight.

Gliding Flight

• Power-off glide (T = 0) occurs with no thrust.
• Lift must balance drag and weight in a constant glide angle.

Equations of motion for power-off glide

• Equations that describe the forces acting on an airplane in a power-off glide related to glide angle.

Example

• Examples of calculations related to the topic of gliding in flight

Example 2

• Examples of calculation for different types of aeroplanes.

Centrifugal Force

• Outward force felt by an object moving in a circle.
• Centripetal force pulls objects inwards.

Centripetal Force

• Force needed to keep a body moving in a circle.

Aircraft Turn

• Inertia must be overcome to start a turn.
• Banking the aircraft creates a horizontal component of lift (centripetal force).

Turning Flight

• Turning requires overcoming inertia and tilting lift.
• Horizontal component provides centripetal force for turning.
• Maintaining altitude involves increasing lift component.

Sideslip

• Sideslip occurs when the aircraft bank angle is too great.

Skidding

• Sideslip is the opposite of a skid (which happens when the bank angle is too small for a coordinated turn).
• Centrifugal force causes an outward skidding tendency.

Sideway Landing

• Describing a sideway landing.

Cross Wind landing

• This section describes a cross-wind landing.

Balanced Turn

• During a balanced turn, the pilot experiences no sliding.
• Effective weight is equivalent to lift, magnified accordingly.

Turning Flight and The V-n Diagram

• Graph relating airspeed, load factor, and turning capabilities.

Level Turn (Coordinated turn)

• An airplane in a level turn experiences a constant altitude with a horizontal component of lift (centripetal force) providing the turning force to match the turn radius.
• A component of lift is to resist gravity (to hold altitude).
• The resultant force in level turn flight is the square root of the sum of the horizontal and vertical components of lift force.

Level turn

• The lift vector is tilted during a bank to provide necessary centripetal force for turn.
• A component of lift equals weight, maintaining altitude.
• The resultant centripetal force is calculated using a Pythagorean theorem.

Load Factor

• Ratio of lift to weight during a turn.
• Load factor increases with increased bank angle.
• Load factor affects structural loads on aircraft components.
• Increased bank angle leads to increased load factor and increased loads on aircraft components.

Load Factor During a Turn

• Lift on wings increases to counteract increased weight during turns.
• Increased angle of bank leads to substantial increases in lift.
• The struts and spars must be able to withstand the greatly increased loads during turning maneuvers.

Load Factor Angle of Bank

• Minimum speed during a bank is defined mathematically as W/L = cos e or L = W/Cos e.

Load Factor Angle of Bank(continued)

• There is a relationship between the stalling speed and angle of bank.

Wing Loading

• Wing loading is the ratio of weight to wing area.
• Lower wing loading corresponds to a lower minimum speed and higher wing loading to a higher minimum speed.

Wing Loading Stalling Speed

• Lower wing loading means a lower stalling speed.
• Higher wing loading means a higher stalling speed.

"g" Limit

• "g" limit represents the maximum load factor an aircraft can withstand to avoid structural failure.

How to survive high G force?

• Methods and techniques applicable to high-G force conditions.

"g" Limit from V-n Diagram

• Diagram depicting the relationships among airspeed, load factor, stall speed, and structural limits in flight.

V-n diagram

• A graph showing flight envelope limits, particularly for maneuverability.

Maneuver point

• A point in the V-n diagram where load factor and lift coefficient are at their maximum values during a turn.
• Point where maximum load factor and highest velocity for turn is possible.

Corner velocity (V*)

• Velocity at the maneuver point where load factor and lift coefficient are at their maximum in aircraft turns.

V-n diagram (Low speed)

• Graph describing the relationship between load factor, airspeed, and stall speed when limiting conditions are low speeds.

V-n diagram (High-speed)

• Graph describing the relationship between load factor, airspeed, and stall speed in high-speed flight.

Test your understanding of the load factor experienced during aircraft turns and its implications in flight dynamics. This quiz covers essential concepts such as stall limits, turn radius, and the significance of lift-to-drag ratios in gliding. Perfect for students and aviation enthusiasts wanting to sharpen their knowledge in aerodynamics.