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Questions and Answers
What is the purpose of a vortex generator?
What is the purpose of a vortex generator?
Stall strips are used to ensure wing root stall before the wing tip at high angle of attack.
Stall strips are used to ensure wing root stall before the wing tip at high angle of attack.
True
What is the purpose of riblet films on an aircraft wing?
What is the purpose of riblet films on an aircraft wing?
Reduce skin friction and prolong laminar flow
Wing fences are designed to control the ________ flow of the boundary layer over the top of the wing.
Wing fences are designed to control the ________ flow of the boundary layer over the top of the wing.
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Match the following wing modifications with their purpose:
Match the following wing modifications with their purpose:
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What is the primary function of the elevator on an aircraft?
What is the primary function of the elevator on an aircraft?
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The rudder of an aircraft controls the roll movement.
The rudder of an aircraft controls the roll movement.
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What are control surfaces on an aircraft used for?
What are control surfaces on an aircraft used for?
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The flight envelope is defined by the aircraft's design and ______ characteristics.
The flight envelope is defined by the aircraft's design and ______ characteristics.
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Match the following control surfaces with their functions:
Match the following control surfaces with their functions:
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Study Notes
Boundary Layer
- A thin layer of air at the surface of an airfoil where velocities are reduced due to skin friction.
- Velocity changes from zero at the surface to the free stream value away from the surface.
- Air can flow smoothly (laminar) or in a random pattern (turbulent) depending on air viscosity and surface roughness.
Stall
- Occurs when smooth airflow over the wing's surface breaks away and becomes turbulent.
- Associated with high angle of attack flight conditions or shock waves that form when aircraft speed approaches its critical Mach number.
- Shock waves cause air separation at the upper surface of the wing, leading to buffeting of the aircraft's controls.
Vortex Generators
- Short, low aspect ratio aerofoils arranged in pairs and extended into and above the boundary layer.
- Attached to the aerofoil surface by adhesive, they induce high-energy air from the free stream airflow into the boundary layer.
- Energize the air to prevent air separation, and can be fitted in various ways and locations.
Stall Strips
- Inverted triangles used to break the airflow over the root section to create stall at high angle of attack.
- Fitted on the leading edge at the wing root, ensuring wing root stall before the wing tip at high angle of attack.
- Turbulence created may strike the tailplane, resulting in vibration warning to the pilot of an approaching stall.
Riblet Films
- Microgrooves with V-shaped cross-sections that reduce skin friction and prolong laminar flow over the wing.
- Force turbulent air through the narrow passage of the grooves, increasing air velocity to flow as laminar airflow.
Wing Fences
- Fitted about mid-span on the leading edge of the wing and extending rearward.
- Designed to control the spanwise flow of the boundary layer over the top of the wing.
- Straighten the airflow over the ailerons, improving their effectiveness, and prevent air spillage from beneath the wing to the top.
Saw Tooth or Notch Leading Edge
- A small increase in wing chord on the outer portion of the wing.
- Forms an 'invisible wall' of high-velocity air that flows over the wing and straightens the spanwise flow.
- Similar in function to the wing fence but removes the extra drag and weight penalty.
Winglets
- Give better airflow control and reduce drag produced by the wing by using the up-flow from below the wing to produce a forward thrust.
- Work best at higher speeds, but add weight to the aircraft and increase parasitic or profile drag.
- Compensated by the large reduction in induced drag at the wingtip, resulting in a significant fuel saving.
Primary Flight Control
Elevator
- Located on the tail section of an aircraft, controlling pitch (up and down movement)
- Moves the aircraft's nose up or down to change altitude
- Controlled by the control yoke or stick
Rudder
- Located on the tail section of an aircraft, controlling yaw (left and right movement)
- Moves the aircraft's nose left or right to change direction
- Controlled by the rudder pedals
Control Surfaces
- Consist of ailerons, elevators, and rudder
- Create aerodynamic forces by moving parts on the aircraft
- Control aircraft's orientation and direction
- Shaped to produce a difference in air pressure above and below the surface
Flight Envelope
- Defines the range of speeds and altitudes within which an aircraft can operate safely
- Determined by the aircraft's design and performance characteristics
- Includes limits on speed, altitude, and maneuverability
- Essential to operate within the flight envelope to avoid loss of control or structural damage
Aileron
- Located on the wings of an aircraft, controlling roll (banking left and right)
- Moves the aircraft's wings up or down to change direction
- Controlled by the control yoke or stick
- Used to maintain balance and stability during turns
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Description
Learn about the boundary layer, a thin layer of air near an airfoil's surface, and stall, a phenomenon that occurs when airflow breaks away and becomes turbulent.
