- Aluminum Aluminum Chrome:
aluminum piston, running in a chrome plated aluminum sleeve. Typically used
in pylon racing engines. Advantages: low
friction and tight fit, when properly run. Disadvantage: more expensive and
more sensitive to foreign object damage. see also: ABC.
- Aluminum Brass Chrome:
aluminum piston, running in a chrome plated brass sleeve. see also: AAC.
- Angle of Attack
- Angle between the reference axis (x-axis) of an airfoil and the onset flow
direction. Variable, depending of flow direction and flight condition.
- Angle of Incidence
- Angle between the reference axis (x-axis) of an airfoil and the reference
axis of the aircraft (e.g. fuselage center line). Constant, built into the
- Bernoulli, Daniel (1700-1782)
- Is credited for Bernoulli's equation, although it seems to be Euler,
who really derived this equation (see ).
- Drag Coefficient
- Normalized drag force, makes the comparison of the aerodynamic properties
of different sized objects possible; Definition.
- Euler, Leonhard (1701-1783)
- Well known for the Euler differential equations. Probably also origin of Bernoulli's
equation, which relates pressure and velocity of a fluid:
where: v ... velocity, p ... pressure, and rho ... density.
- This equation can be applied to transform pressure distributions into velocity
distributions and vice versa.
- Féderation Aeronautique Internationale (french): International
- FAI class prefix for uncontrolled models (free flight):
||FAI class for outdoor, free flight glider models.
||FAI class for outdoor, free flight rubber powered glider
||FAI class for outdoor, free flight combustion engine
powered glider models.
||FAI class for indoor, free flight rubber
powered glider models.
- FAI class prefix for control line models:
||FAI class for control line speed models.
||FAI class for control line aerobatic models.
||FAI class for control line team racing models.
||FAI class for control line fox hunt models.
- FAI class prefix for radio controlled models:
||FAI class for acrobatic models with combustion engines.
||FAI class for allround sailplanes.
||FAI class for helicopter models.
||FAI class for piston engine pylon racing models.
- FAI class prefix for scale models:
||FAI class for control line scale models with combustion
||FAI class for radio controlled scale models with
- FAI class prefix for models powered by electric motors.
||FAI class for electric powered acrobatic models.
||FAI class for electric powered sailplanes.
||FAI class for electric powered pylon racing models.
- Laminar Flow
- State of fluid flow, where the particles move along parallel, ordered
paths. Results in low friction on submerged surfaces, but has problems to
follow retreating shapes (e.g. fuselage tails, airfoil behind location of
maximum thickness). see also: Turbulent Flow.
- Lift Coefficient
- Normalized lift force, makes the comparison of the aerodynamic properties
of different sized objects possible; Definition.
- Mach, Ernst (1838-1916)
- Born in Austria, he became became a professor in Prague in 1867. There he
worked as a Physicist and Philosopher for 28 years. He was one of the first
who made supersonic flow visible and who understood the importance of the
speed of sound for supersonic flows.
- In honor of him, the ratio v/a is called Mach number
(where a is the speed of sound, which is about 340 m/s
at sea level).
- Moment Coefficient
- Normalized torque moment, makes the comparison of the aerodynamic
properties of different sized objects possible; Definition.
- Abbreviation for Polar Exchange Format.
Look here for a description.
- Pitot Tube
- An L-shaped, open tube, one end connected to a pressure measuring device,
the other end placed in a flow with the opening facing the wind. Can be used
to measure the total pressure of a flow (stagnation pressure).
In conjunction with a static pressure measurement the flow velocity can be
calculated, if the density of the fluid is known. A device, which combines
both pressure measurements is a pitot-static tube (at least in
Germany also called a Prandtl-tube).
- Named after a Frenchman, Henri Pitot (1695-1771).
- A sign, marking the corner of the racing course. May be a tripod like
structure or a simple pole with an oil drum on top of it.
- Reynolds, Osborne (1842-1912)
- Worked for 37 years as a professor of engineering at the university of
Manchester, Great Britain. In 1883 his experiments lead him to the
definition of a dimensionless parameter, which indicated transition from
laminar to turbulent flow in pipes. This parameter was later known as
- For the flow inside a tube of diameter l he determined the
critical value of this parameter to be 2300.
- Reynold's number is a very important parameter in fluid dynamics. Flows at
the same Reynolds number are similar, which make it possible to use smaller
models (length l) for tests at higher velocities (velocity v) to achieve the
same Reynolds number as the full scale airplane.
- Turbulent Flow
- State of fluid flow, where the particles move in irregular, wavy paths.
Results in high friction on submerged surfaces, but can more easy follow
retreating shapes (e.g. fuselage tails, airfoil behind location of maximum
thickness). see also: Laminar Flow.
- A region of a flow field located behind a body, which is moving through
the air. The velocity and the pressure in the wake region can be very
different from the external flow field. The wake contains information about
the lift and the drag of the body that generated it. Usually the pressure in
the wake behind a body is lower than the pressure in the surrounding flow
field. The pressure difference corresponds to the drag of the body. Lift
forces can create strong vortices in a wake, which can make the wake exist
for a long time, until it gets dissolved through friction effects.
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