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Basic Aviation Terms - ASTB-E

Terms in this set (90)

Airfoil
A wing or helicopter blade that generates more lift than drag as air flows over its upper and lower surfaces. A propeller is also an airfoil. Airfoil are carefully designed and can be made of non-metallic materials such as composites.
Angle of attack
The angle between the chord line of an airfoil and it's direction of motion relative to the air (i.e., the relative wind) AOA is an aerodynamic angle
Angle of incidence
In the context of fixed-wing airplanes, the angle of incidence is the inclination of the wing or tail surface attached to the fuselage relative to an imaginary line that is parallel to the aircraft's longitudinal axis
Anhedral angle
The downward angle of an airplane's wing and tailplane from the horizontal is called the anhedral angle, of negative cathedral angle
Attitude
An aircraft's position relative to its three axes and a reference such as the Earth's horizon
Center of gravity (CG)
An aircraft's center of mass, the theoretical point through which the entire weight of the machine is assumed to be concentrated
Chord
The distance between the leading and trailing edges along the chord line is an airfoil's chord. In the case of a tapered airfoil, as viewed from above, the chord at its tip will be different than at its root. Average chord describes the average distance.
Chord line
An imaginary straight line from the airfoil's (front) edge to its trailing (aft) edge
Constant speed propeller
A controllable-pitch propeller whose angle is automatically changed in flight by a governor in order to maintain a constant number of revolutions per minute (rpm) despite changed aerodynamic loads
Controllability
A measure of an aircraft's response relative to flight control inputs from the pilot.
Controllable pitch propeller
A propeller that can be varied in terms of its blade angle by the pilot via a control in the cockpit
Coordinated flight
When the pilot applies flight and power control inputs to prevent slipping or skidding during an aircraft maneuver, the flight is said to be coordinated
Critical angle of attack
The angle of attack at which an airfoil stalls (loses lift) regardless of the aircraft's airspeed, attitude, or weight
Dihedral angle
The upward angle of an airplane's wings and tailplane from the horizontal
Dihedral effect
The amount of roll moment produced per degree of sideslip is called Dihedral effect, which is crucial in terms of an aircraft's rolling stability about its longitudinal axis
Directional stability
An aircraft's initial tendency about Ithaca (vertical) axis. When an aircraft is disturbed yaw-wise from its equilibrium state during to a gust, for example, and returns to that state (i.e. aligned with the relative wind) because if the aerodynamic effect of the vertical stabilizer, it is said to be directionally stable.
Downwash
Air the is deflected perpendicular to an airfoil's motion
Drag coefficient
A dimentionless quantity that represents the drag generated by an airfoil of a particular design
Drag curve
A constructed image of the amount of aircraft drag at different airspeeds
Dynamic stability
Describes the tendency of an aircraft after it has been disturbed from straight-and-level flight to restore the aircraft to its original condition of flying straight and level by developing corrective forces and moments
Equilibrium
In the context of aviation, equilibrium is an aircraft's state when all opposing forces acting on it are balanced, resulting in accelerated flight at a constant altitude.
Feathering propeller
A controllable-pitch propeller that can be rotated sufficiently by the pilot (via a control lever in the cockpit connected to a governor in the propeller hub) so that the blade angle is parallel to the line of flight, thereby minimizing propeller drag
Forward slip
A pilot-controlled maneuver where the aircraft's longitudinal axis is inclined to its flight path
Glide ratio
The ratio between altitude lost and distance traversed during non-powered flight (e.g., following and engine failure, in a sail plane)
Glide path
An aircraft's path across the ground while approaching land
Gross weight
An aircraft's total weight when it is fully loaded with aircrew, fuel, oil, passengers and or cargo (if applicable), weapons, etc.
Gyroscopes precession
The attribute of rotating bodies to manifest movement ninety degrees in the direction of rotation from the point where a force is applied to the spinning body
Heading
The direction in which the aircraft's nose is pointed
Inertia
A body's opposition to a change of motion
Internal combustion engine
A mechanical device that produces power from expanding hot gases created by burning a fuel-air mixture within the device
Lateral stability (rolling)
An aircraft's initial tendency relative to its longitudinal axis after being disturbed, it's design quality to return to level flight following a disturbance such as a gust that Causes one of the aircraft's wings to drop
Lift coefficient
A directionless quantity that represents the lift generated by an airfoil of a particular design
Lift/drag ratio
A number that represents an airfoil efficiency, the ratio of the lift coefficient to the drag coefficient for a specific angle of attack
Lift-off
The act of rising from the earth as a result of airfoil lifting the aircraft above the ground
Load factor
The ratio of load supported by an aircraft's lift-generating airfoil (wings, main rotor blades) to the aircraft's actual weight, including the mass of its contents. Load factor is also known as G-loading ("G" meaning gravity).
Longitudinal stability
An aircraft's initial tendency relative to its lateral axis after being disturbed, it's designed quality to return to its trimmed angle of attack after being disrupted due to a wind gust or other factor.
Maneuverability
An aircraft's ability to change directions in three axes along its flight path and withstand the associated aerodynamic forces
Mean camber line
An imaginary line between the leading and trailing edges and halfway between the airfoil's upper (curved) and lower (flat) surfaces
Minimum drag speed (L/D MAX)
The point on the total drag curve where total drag is minimized and lift is maximized (I.e. where the lift-to-drag ratio is greatest).
Nacelle
An enclosure made of metal or another durable material that covers an aircraft's engine
Non-symmetrical airfoil (cambered)
When one surface of an airfoil has a specific curvature that the opposite side does not, the airfoil is described as non-symmetrical, or clambered. The advantage of a non-symmetrical wing, for example, is that it produces lift at an AOA of zero degrees (as long as airflow is moving past the blade). More over, the lift-to-drag ratio and stall characteristics of a cambered airfoil are better than those of a symmetrical airfoil. It's disadvantages are center of the pressure movement chord-wise by as much as in-flight the chord-line distance, which causes undesirable airfoil torsion, and greater product costs.
Normal category
An airplane intended for non-acrobatic operation that seats a maximum of nine passengers and has a certified takeoff weight of an 12,500 pounds or less
Payload
In the context of aviation, the weight of an aircraft's occupants, cargo, and baggage
P-factor (precession factor)
A propeller-driven aircraft's tendency to yaw to the left when the propeller rotates clockwise (as seen by the pilot) because the descending propeller blade on the right produces more thrust than the ascending blade on the left. If the propeller rotated counter-clockwise, the yaw tendency would be to the right
Piston engine
Also known as a reciprocating engine, it is a heat engine that uses one or more pistons to convert pressure created by expanding, hot gases resulting from a blockbuster fuel-air mixture, or steam pressure, into a rotating motion
Pitch
An airplane's rotation about its lateral axis, or the angle of a propeller blade as measured from the vertical plane of rotation
Power lever
The cockpit lever connected to a turbine engine's fuel control unit, which changes the amount of fuel entering the combustion chambers
Power plant
And engine and its accessories (i.e., starter-generator, tachometer drive) and the attached propeller (usually via a gearbox)
Propeller blade angle
The angle between the chord of an airplane and propeller blade and the producer's plane of rotation.
Propeller lever
The cockpit control that controls propeller speed and angle
Propeller slipstream
Air accelerated behind a spinning propeller
Propeller
A relatively long and narrow blade-like device that produces thrust when it rotates rapidly. In aviation, the term typically includes not only the propeller blades but also the hub and other components that make up the propeller system
Rate of turn
The rate of a turn expressed in degrees per second
Reciprocating engine
An engine the converts heat energy created by combustion fuel mixed with air into reciprocating piston movement, which in turn is converted into a rotary motion via a crank shaft
Reduction gear
A gear or set of gears that turns a propeller at a speed slower than that of the engine
Relative wind
The direction of airflow relative to an airfoil, a stream of air parallel and opposite to an aircraft's flight path
Ruddervator
Two control surfaces on an aircraft's tail that forma "V". When moved together via the control wheel or joystick in the cockpit, the surfaces act as elevators. When the pilot presses his or her foot against one rudder pedal or the other, the reservation acts like a conventional plane's rudder
Sideslip
A flight maneuver controlled by the pilot that involves the airplane's longitudinal axis remaining parallel to the original flight path, but the aircraft no longer flies forward, as in normal flight. Instead, the horizontal lift component causes the plane to move laterally toward the low wing
Skid
A flight condition during a turn where the plane's tail follows a path outside of the path of the aircraft's nose
Slip
A maneuver used by pilots to increase an aircraft's rate of descent or reduce its airspeed, and to compensate for a crosswind during landing. An unintentional slip also occurs when a pilot does not fly the aircraft in a coordinated manner
Stability
An aircraft's inherent tendency to return to its original flight path after a force such as a wind gust disrupts its equilibrium. Aeronautical engineers design most aircraft to be aerodynamically stable
Stall
A rapid decrease in lift caused by an excessive angle of attack and airflow separating from an airfoil's upper surface. An aircraft can stall at any pitch attitude or airspeed
Standard-rate turn
A rate of turn of three degrees per second
Subsonic
Speed below the speed of sound, which varies with altitude
Supersonic
Speed in excess of the speed of sound , which varies with altitude
Swept wing
A wing platform involving the tips being further back than the wing root
Symmetrical airfoil
When an airfoil has identical upper and lower surfaces, it is said to be symmetrical and produces no lift at an AOA of zero degrees. The wings of very high performance aircraft tend to be symmetrical
Taxiway lights
Blue lights installed at taxi way edges
Taxiway turnoff lights
Green lights installed level with the taxiway
Throttle
A mechanical device that meters the amount of fuel-air mixture fed to the engine
Thrust line
An imaginary line through the center of an airplane's propeller hub and perpendicular to the producer's plane of rotation, or through the center of each jet engine
Total aerodynamic force (TAF)
Two components comprise the total aerodynamic force: lift and drag. The amount of lift and drag produced by an airfoil are primarily determined by its shape and area
Torque
A propeller-driven airplane's tendency to roll in the opposite direction of the producer's rotation. Some multi-engine airplane's have propellers that rotate in opposite directions to eliminate the torque effect
Trailing edge
The aft part of an airfoil where air that was separated as it hit the wing's front edge and was forced over the upper and lower surfaces comes together
Transonic
At the speed of sound, which varies with altitude
Trim tab
A small, hinged control surface on a larger control surface (e.g., aileron, rudder, elevator) that can be adjusted in flight to a position that balances the aerodynamic forces. In still air, a trimmer aircraft in flight requires no control inputs from the pilot to remain straight and level
T-tail
The description for an airplane's tail involving the horizontal stabilizer mounted on the top of the vertical stabilizer
Turbulence
The unsteady flow of a fluid (e.g. air)
Utility category
An airplane intended for limited-acrobatic operation that seats a maximum of nine passengers and has a certified take off weight of 12,500 pounds or less
Vector
A force applied in a certain direction. Depicted visually, a vector shows the force's magnitude and direction
Velocity
The rate of movement (e.g., miles per hour, knots) in a certain direction
Vertical stability
An aircraft's designed, inherent behavior relative to its vertical axis, it's tendency to return to its former heading after being disturbed by a wind gust or other disruptive force. Also called yawning or directional stability.
V-tail
A design involved two slanted tail surfaces that aerodynamically behave simular to a conventional elevator and rudder, i.e., as horizontal and vertical stabilizers
Wing
An airfoil attached to a fuselage that creates a lifting force when the aircraft has reached a certain speed
Wing area
A wing's total surface, including its control surfaces, and singlets, if so equipped
Wing in ground effect (WIG)
When an aircraft flies at a very low altitude, one roughly equal to its wing span, it experiences WIG. The effect increases as the airplane descends closer to the surface (runway, land, water) and supports the aircraft on a cushion of air best at an altitude of one half the wing span
Winglet
A surface installed on a Wingfield that is angled to the wing and improves its efficiency by smoothing the airflow across the upper wing near the tip and reducing induced drag. Winglets improve an aircraft's lift-to-drag ratio.
Wing span
The maximum distance between wingtips
Wingtip vortices
A spinning mass of air generated at a wing's tip created by outward-flowing high pressure air from underneath the wing meeting inward-flowing low air pressure on the wing's upper surface. The intensity of a wing vortex - also referred to as wake turbulence - is dependent on an airplane's weight, speed and configuration
Wing twist
A wing design feature that improves the effectiveness of aileron control at high angles of attack during and approach to a stall.
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