Here is a list of commonly used terms which relate to aeromodeling. Many of them are used frequently here and in building instructions and logs and I hope this glossary of terms will provide a reference for those unfamiliar with the terminology of aeronautics.
Aeronautics - The science and art of designing, constructing, and operating aircraft.
Aileron - The movable surface usually on the trailing edge of each wing which control movement around the roll axis or to instigate banking maneuvers.
Airbrake - A flight control used to increase drag and reduce speed while making little change to lift and used during landing, not generally incorporated on gliders or sailplanes.
Airfoil - The cross-sectional profile of an aircraft's wing or tail planes used to create lift.
Airframe - Describes the entire structure of an aircraft.
Angle of Attack - the angle of the mean chord line of an aircraft's wing relative to the general direction of thravel of the aircraft through the atmosphere. As this angle increases in flight due to changes in lift or sink or pilot induced controls, the wing can become stalled or loose its ability to create lift.
Anhedral - a negative orientation of two wings relative to the horizontal plane in which the tips are lower than the roots in normal flight. See also Dihedral, Polyhedral and Gull Wing.
Area - The total measurement of the surface of a wing or flying surface expressed in ft.2 and in models generally expressed as square inches. Calculated by multiplying the total span of the wing by the average chord (using the same dimenional units). See also Wing Loading. In the diagram below you may substitute inches for feet in the calculations to arrive at the area in square inches.
Aspect Ratio - The square of the span (s) divided by the wing area (A) and used to measure how long and slender a wing is from tip to tip. For a rectangular wing, this reduces to the ratio of the span to the chord length (c). Aspect ratio is a determining factor in performance and higher numbers yield lower drag and a higher lift to drag ratio (L/D) resulting in better glide angles.
AR = s2 / A = s2 / (s x c) = s / c.
Balance - Used to describe the state of an aircraft or control surface about its center of gravity in which weight or mass is configured to produce a particular level of stability.
Camber - The measurement of the greatest distance between the chord line and the mean camber line.
Camber-Changing - The ability to change the shape of the airfoil (and wing) in flight to produce more or less lift or more drag such as in the use of flaps.
Canopy - The glazing surrounding the cockpit for pilot visibility.
Carry-through- Describes the structural component of the airframe in which the loads generated by the two wings are borne within the fuselage.
Center of Gravity - The point on a aircraft about which its mass is balanced.
Chord - The measurement of a wing from leading to trailing edge at a described point on the wing or tailplane.
Chord Line - The straight line drawn from the leading to trailing edges of an airfoil.
Chord-wise - Used to describe the orientation of a measurement along a wing or tailplane in this case from leading to trailing edge.
Cockpit - The area of the fuselage in which the pilot is seated and where control surfaces are actuated using a stick or yoke, pedals and levers and is generally protected by a windscreen or canopy.
Control - To direct the movements of an aircraft with particular reference to changes in attitude and speed.
Control Horn - A fixture attached to a control surface at which cables or rods are attached and lead back to the cockpit to allow pilot-induced deflections of of the surfaces to affect changes in the pitch, yaw and roll attitude of the aircraft.
Control Surface - One of several movable planes used to control an aircraft's direction of flight or orientation to the airstream.
Crab- A pilot-induced modification of the aircraft's attitude to compensate for cross-wind in order to maintain a particular heading.
D Section - The forward section of the wing from leading edge to the main spar shaped like the letter D when boxed with shear webs and surface sheeting resists both bending and twisting moments.
Decalage - The angle described by measuring the difference between the mean chord line of the wing and the horizontal stabilizer.
Deflection- Describes the angle of movement or positioning of a control surface relative to its trimmed (undeflected) position.
Dihedral - A positive orientation of two wings relative to the horizontal plane in which the tips are higher than the roots in normal flight. See also Anhedral, Polyhedral and Gull Wing.
Dive Brake - A movable control surface generally on the wing which when deflected into the airstream reduces the aircraft's top speed and therefore the lift generated by the wings, allowing controlled descent as in the case of final approach to landing or rapid descent from a strong thermal.
Drag Spar- A secondary and aft spar oriented span-wise within a wing and in some cases used as a mounting and hinge point for flaps or ailerons.
Elevator - The movable aft portion of the horizontal tailplane which is used to affect pitch or the climbing or descending attitude of the aircraft.
Empenage- Used to describe the entire aft structure of an airframe which is made up of the vertical and horizontal tailplanes both fixed and movable.
Fin - Generally describes the vertical fixed portion of the tailplane which provides yaw stability.
Flap- A movable surface at the trailing edge section of the wing used to change the camber of the airfoil thus generating more lift at lower speed sometimes used to control angle of descent through provision to deflect upward offering greater speed over the ground in transitioning between thermals to reduce time spent in a sink.
Fuselage- Describes the center section of the airframe about which are oriented and attached the wing(s) and empenage.
Gull Wing - A polyhedral wing arrangment in which the center or inboard panels have dihedral and the outer or tip panels have anhedral relative to them, mimicking the frontal view of a gull's wing. See also Anhedral, Dihedral and Polyhedral.
Incidence - The angle of the wing measured from the centerline of the fuselage.
Instruments - Devices used to indicate aircraft position, orientation, and performance to the pilot or ground operators.
Leading Edge - The forward or entry point to the airstream of a flying surface.
Lift-to-Drag - The lift divided by drag is called the L/D ratio (L over D). The higher the L/D, the lower the glide angle, and the greater the distance that an aircraft can travel across the ground for a given change in altitude and so measures an aircraft's efficiency.
Main Gear- The primary landing wheel and tire assembly and the fixture to which they are attached to the fuselage or airframe.
Mean Camber Line - A plot of points that lie halfway between the upper and lower surfaces of the wing or airfoil cross section. See also Airfoil, Camber and Chord.
Monocoque - Construction method in aircraft in which formed aluminum skins are applied with rivets or adhesives over a series of station point bulkheads to make the fuselage or other structures.
Panel - Used to describe a portion of a wing generally from a point of attachment at the fuselage or another dissimilar shaped portion that may be attached separately as in inner and outer sections of a single left or right wing or as in the left and right portions of wings that can be removed for transport or ease of assembly.
Pitch- The angle of the aircraft's heading relative to the longitudinal axis and about the axis in the plane of the wings, generally controlled by the pilot using the elevator and for which stability is provided by the fixed or non-movable stabilizer.
Planform- in aviation used to describe the shape of wing wing when viewed from above. See also Wing Area. See Area diagram for illustrations of three different wing planforms.
Polyhedral - A configuration of more than two wing sections in which both wings are elevated above the horizontal plane and the outboard sections are further elevated. See also Anhedral, Dihedral and Gull Wing. See also Anhedral, Dihedral and Gull Wing.
Rib - That part within the wing attached to the spar that gives the wing its airfoil shape.
Roll - The movement of an aircraft around the fuselage longitudinal axis which elevates one wing or the other and used to initiate turning maneuvers.
Root- The inboard end of a wing or tailplane generally where it joins the fuselage.
Rudder - The vertically oriented movable control surface used to yaw the aircraft.
Ruddervator- In Vee tailed aircraft serves the function of both rudder and elevator and so when actuated through a mechanical or other mixing apparatus provides for changes in aircraft pitch and yaw from fewer movable surfaces and may be conventionally fixed and hinged arrangement or two full-flying surfaces.
Skid- A wooden or metal sprung plate along the lower forward fuselage or tail which take up landing loads and provide for movement along the ground until the aircraft comes to rest during landing.
Slip - A maneuver in which the aircraft is yawed to compensate for cross-wind forces in order to maintain a ground heading to a particular point or to bleed off lift and control angle of descent.
Span - The total length of the wing measured from one tip to the opposite tip.
Span-wise - Used to describe the orientation of a measurement along a wing or tailplane in this case from root to tip.
Spar - The main structural load-bearing element of a wing or tailplane from which the rest of that structure is constructed and attached to the fuselage or airframe.
Spoiler - A device which reduces lift in an aircraft generally on the upper surface of a wing and when deployed into the airstream reduces lift while moderately increasing drag. Used to control rate of descent and thus landing at a desired spot.
Stability - The property of an aircraft to maintain its attitude or to resist displacement, and if displaced, to develop forces and moments tending to restore the original condition.
Stabilator - A full-flying or single piece tailplane in which the entire surface deflects about its thickest point to create pitch movement of the airframe.
Stabilizer - The horizontal tailplane which is fixed and from which the elevator hinges.
Tailplane - The flying surface at the aft or tail section of an aircraft used with horizontal or vertical to describe the axis of control or stability.
Thickness- Used to describe the total frontal area of an airfoil and generally represented as a percentage of the chord for a given airfoil or wing section.
Tip - the outboard end of a wing or tailplane.
Trailing Edge - the aft or termination point of a flying surface.
Trim - describes a state of the aircraft or control surface in which settings are fixed to produce a particular attitude of the aircraft in flight while no control inputs are being introduced by the pilot.
Undercamber - The characteristic of an airfoil in which the lower surface is concave which generally creates higher lift at lower speeds.
Variometer - Also known as a rate-of-climb indicator, this instrument informs the pilot of changes in altitude as they continouslby as they occur by visual or audible means.
Webbing- A material placed between two structures to increase the shear or bending load-bearing characteristics of such structure as in the case of spar construction.
Wing - The primary flying or lifting surface of an aircraft.
Winglet - A small vertically-oriented surface at the tip of the wing used to modify the lifting characteristics of a wing by changing the airflow across the primary surface.
Wing Joiner - Generally the rod or blade and associated sleeve, tube, (box or lugs and pins or bolts in full size aircraft) in which the wings are borne and/or attached to the fuselage or carry-through structure.
Wing Loading - the loaded weight of the aircraft divided by the area of the wing nearly always given in either lb/ft2 or kg/m2 (full size aircraft or oz/ft2 for models) and one of the determining factors or indicators of aircraft performance. See also Area.
Yaw -The angle of the aircraft's heading relative to the vertical axis and generally controlled by the pilot using the rudder and in which stability is provided by the fixed or non-movable fin.
NASA Beginner's Guide to Aerodynamics
http://www.grc.nasa.gov/WWW/K-12/airplane/bga.html
NASA Wing Geometry Definitions
http://wright.nasa.gov/airplane/geom.html
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