Forces Acting on an Aircraft

Forces Acting on an Aircraft

• Four main forces act on an aircraft: Thrust, Lift, Drag, and Weight.
• Thrust propels the aircraft forward, opposing drag.
• Lift counters weight, allowing the aircraft to stay aloft.
• Drag is the force that resists the aircraft's motion through the air.
• Weight is the force of gravity acting on the aircraft.

Lift Augmentation

• Trailing-edge flaps increase lift and decrease stall speed, allowing for slower flight speeds while maintaining control.
• They are particularly important during approach and landing.
• This helps maintain control at lower speeds.

Lift Augmentation - Slats

• Slats are leading-edge devices that delay airflow separation at higher angles of attack.
• They prevent stalls by maintaining airflow over the wing.
• Using a slot in the wing also delays airflow separation.

Slat Types

• Some slats are automatically deployed at predetermined angles of attack.
• Another slat type can be controlled manually by the pilot.
• Both are positioned ahead of the ailerons to maintain lift past the wing root.

Lift Augmentation Graph

• The graph displays how lift coefficient (Cl) changes with angle of attack (α).
• Different configurations of flaps and leading-edge slats impact the lift coefficient and angle of attack.
• The graph demonstrates that the lift coefficient increases with flaps and slats deployed.
• Different flap and slat combinations have different outcomes on the lift generated.

Deflection of Flaps

• Deflecting flaps effectively increases the camber, or curvature, of the wing.
• This camber creates a virtual increase in the angle of attack, resulting in more lift.

Impact of High-Lift Devices

• High-lift devices increase the maximum lift coefficient (Cl,max) of an aircraft.
• These devices shift the lift curve to the left, decreasing the stall speed (Vstall).
• This means the aircraft can fly at a lower airspeed during takeoff and landing.
• The increase or decrease in lift depends on the position of the high lift devices.

Aerodynamic Effect of Flap Models

• Various flap types (plain, split, slotted, and Fowler) have different effects on lift and drag characteristics.
• The type of flap affects the lift coefficient and drag coefficient at various angles of attack.
• Different flap types generate varying drag and lift outputs.

Figures of Merit

• L/D (lift-to-drag ratio) represents aerodynamic efficiency, a higher ratio is desirable.
• Range is directly proportional to L/D.
• Cl,max (maximum lift coefficient) determines stall speed, higher values are beneficial.
• High Cl,max is important for take-off and landing performance.

Types of Flaps

• Plain flaps, split flaps, slotted flaps, and Fowler flaps are different flap types on an aircraft.
• Each type has different characteristics and uses.
• Specific diagrams illustrating each flap type's appearance on an aircraft are presented.

Plain Flap

• Boundary layer separation over the wing results in wake turbulence.
• A plain flap is a simple extension of the trailing edge.

Split Flap

• Boundary layer separation and wake turbulence occur over the wing trailing edge.
• A split flap is a simple extension of the trailing edge.

Slotted Flap

• High-pressure air flows through the slot, minimizing boundary layer separation over the wing trailing edge.
• Delaying airflow separation with a slot.

Fowler Flap

• High-lift device that effectively increases lift and camber.
• Extension extends the chord and moves downward or forward of the wing trailing edge.

Slat

• Leading-edge device, commonly used to delay stall.
• Deployed position and effect on airflow over the wing.
• Used in modern airplane design to effectively control lift and stall speed.

Leading Edge High-Lift Devices

• LE slat, LE droop, and Kruger flap are types of leading-edge devices.
• These devices extend in front of the leading edge of the wing.
• They extend the maximum lift curve to higher angles of attack, delaying stall.

The Effect of Leading Edge Slat Deflection

• Extending a slat extends the maximum lift coefficient and extends the region where lift can be achieved to higher angles of attack.
• No change to alpha zero.
• No change to the lift coefficient at zero degrees of angle of attack.

High Lift Devices

• High lift devices increase the maximum lift coefficient which then decreases the stall speed, useful during take off and landing operations.
• Different configurations for high lift devices are illustrated and explained.

Three Configuration of High Lift Devices

• High lift devices are deployed for different flight phases.
• Illustrations of high lift devices during various flight conditions.
• The effect of the high lift devices on the aircraft lift coefficients under various flight conditions

Driving Mechanism of Slat

• Diagrams of mechanical components involved in slat deployment and retraction.
• Different components for controlling the slat extension/retraction.

Leading Edge High Lift Devices

• Detailed diagrams showcasing different leading-edge high-lift device types.
• Illustrative diagrams of devices, both retracted and extended.
• Information comparing the features of the different devices.

Kruger Flap - B737

• Kruger flap on a B737 is illustrated and described
• Diagrams illustrate the structure of the Kruger flap (B737).

Kruger Flap VS Fowler Flap

• Comparison between the Kruger and Fowler flaps, diagrams highlighting the structural differences.

Slat Driving Mechanism (using slat track):

• Mechanism for deploying slats is shown.
• The illustrations show the components in detail.

Conclusion

• Summary of topics covered in the section.
• Students should be able to apply the knowledge.

This quiz covers the fundamental forces that act on an aircraft, including thrust, lift, drag, and weight. It also explores lift augmentation techniques such as trailing-edge flaps and slats that enhance aircraft performance during different flight stages. Test your knowledge of these essential aviation concepts.