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GYROPLANE GLOSSARY
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Advancing Blade
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The portion of the rotor disc in which the rotation of the blade is moving
in the direction of the aircraft's travel.
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Aerodynamics
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Hydrodynamics and aerodynamics are both branches of fluid dynamics, which is
the study of fluids in motion. The fundamental laws governing the movements
of gases, such as air, and liquids, such as water, are identical. Although
many liquids are almost incompressible.
The equations representing these natural laws are, however, so complex that
although formulated over a hundred years ago, they cannot be easily solved
to account for all situations and conditions. The equations which describe
in a general fashion the motion of fluids were developed in 1820 and
subsequently perfected by G.G. Stokes.
At the beginning of the present century, aerodynamics was introduced with
the possibility of flight in air. It started with the same assumption as
hydrodynamics with the added assumption of incompressibility replacing what
was a fact for water.
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Airfoil
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A surface designed to produce lift from the movement of air over it.
Ideally, it should present the greatest amount of lift with the least amount
of drag.
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Anodizing
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Anodizing is the deposition of a thin film of synthetic oxide on a light
metal, such as aluminum, to prevent the further access of air to the
surface, preserving the luster and preventing corrosion. The article is made
to anode in 3% solution of cromic acid at about 104 degrees F. The voltage
is gradually increased to a maximum of 50 volts and the process may take an
hour. Sulphuric and oxalic acid processed are also used, and the anodic film
may be dyed various colors.
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Autogyro
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A heavier-than-air flying machine which derives its lift from a rotor system
mounted above the machine, with blades rotating more or less horizontally.
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Autorotation
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A flight condition made possible by the vertical or horizontal movement of
air through the rotor system.
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Blade Loading
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The load placed on the rotor blades of a gyroplane, determined by dividing
the gross weight of the craft by the total combined areas of all blades (not
the disc area, but the blade area).
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Balance
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Rotor blades that are equal in weight will balance each other. Unbalanced
rotor blades may cause control stick shake and instability when in flight.
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Bank
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Sideward tilt of the aircraft in flight. When correctly executed, the bank
compensates for centrifugal force, and the passengers will be pressed
straight down in their seats.
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Ceiling
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The maximum altitude to which a gyroplane can climb. Because of thin air,
the engine decreases in power, or the rotor blades no longer provide lift to
climb.
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Center of Gravity
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Called CG. A point where the resultant of all weight forces will hang evenly
from this point Usually at or very near to the main mast.
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Center of Pressure
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An imaginary point on the cord lines of all the rotor blades where all the
aerodynamic forces of the airfoil surfaces are concentrated.
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Centrifugal Force
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The force caused by the rotation of an object with mass.
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Chord
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A straight line between the exact center of the leading and trailing edge of
the rotor blade.
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Chordwise Balance
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A term that refers to the mass balance of an airfoil. It is designed to be
in the center of lift.
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Compressibility
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Forces acting on a rotor blade when its tip speed approaches the speed of
sound.
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Coning
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The blades tend to bend upward in flight, when they are lifting the weight
of the aircraft. Referred to as the coning angle.
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Cruise Speed
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An airspeed that usually results in the best fuel economy and is usually
between 112 and 2/3 of full power.
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Density Altitude
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Pressure altitude calculated from air temperature, altitude and humidity.
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Disc
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The area swept by the blades of the rotor.
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Disc Loading
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The gross weight of the gyroplane divided by the rotor disc area. The
greater the disc loading, the gyroplane's sinking speed will increase, and
its glide-angle will become steeper.
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Dissymmetry of Lift
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The unequal lift across the rotor disc, caused from the advancing blade
creating more lift than the retreating blade.
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Dynamic Roll Over
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A roll over on the ground caused by violent rotor flapping. Caused by
insufficient rotor rpm combined with excessive ground speed.
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Downwind
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Flying with the wind direction. Flying downwind near the ground is
dangerous, true airspeed is lower than groundspeed and the aircraft's lift
is less.
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Endurance
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The maximum length of time a gyroplane can stay aloft on its fuel supply.
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Flapping
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The up and down motion of the rotor blade on its hinge. Without flapping, a
gyroplane would roll over on its side during flight because of the unequal
lift of the rotor disc.
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Flare
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A landing maneuver performed near the ground to slow the gyroplane's rate of
descent and air speed. The gyroplane is in a nose-high attitude during the
execution of this maneuver.
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Flutter
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A self-induced oscillating motion of improperly designed rotor blades.
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Ground Effect
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Also known as ground cushion, A beneficial increase in lift near the ground.
Readily apparent when the rotor height is one-half of the rotor's diameter
over the ground. Less engine power is required due to the air being thrust
downward to meet the ground. This denser air is partially trapped beneath
the rotor disc.
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Ground Vortex
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The horizontal whirlwind thatforms at the forward edge of the rotor wake
when the gyroplane flies at low speeds close to the ground.
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Gyroplane
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An aircraft whose lift is developed by the rotor blade system using the
principles of autorotation.
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Horsepower Loading
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The ratio of gross weight to horsepower, obtained by dividing the total
weight by the engine's horsepower rating.
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Induced Power
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The power associated with developing rotor thrust from the movement of air
passing the rotor blade.
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Induced Velocity
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The downward air velocity generated in the process of developing rotor
thrust.
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Laminar Flow &
Turbulent Flow
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The air flow immediately against the rotor blade (boundary layer) is of most
importance in the efliciency of the blade. Two kinds of fluid flow are
possible - laminar and turbulent. In laminar flow, the fluid moves as a
series of sheets or laminae, sliding one over the next where there is a
difference of speed between them (velocity gradient).
In turbulent flow, particles of fluid (air) can move in any direction - only
the mean velocity and direction being defined. This flow can be caused by
the overall shape of the object (rotor blade) or disturbances in the surface
polish have a noticeable effect on efficiency.
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Laminar Flow Blades
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Laminar Flow Blades are fiberglass blades which cause unusually low drag in
the rotorcraft operation. During World War II when experimental planes began
to approach the speed of sound, laminarAlow wing sections contributed to
their success. In the beginning development stages, thin gauges of sheet
metal were used in forming the "skin". It was determined that the slightest
buckle forming in the "skin", caused by a counter sunk rivot, could nullify
the advantages of the blade section. With the advent of fiberglass, it was
determined that the blade could carry as much load as aluminum-alloy sheets,
but had a much greater resistance to damage and guaranteed a smoother
surface. Continuing development of these materials has resulted in stronger
bonding methods and resins which in turn have led to the laminar-flow rotor
system currently being offered for rotorcraft.
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Lead-Lag
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The tip movement needed to adjust the rotor blades in a two-bladed system to
get the weight of the whole rotor exactly equal on each side of the main
shaft laterally.
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Life
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The recommended safe duration (in hours or measurable wear on the component)
of any part on an aircraft. This length of time is determined by either
fatigue or the operational wear on the part.
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Load Factor
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The ratio of rotor thrust to gross weight of the gyroplane. Mast - The main
structural member of the gyroplane. The mast is the vertical assembly that
connects the rotor blades to the airframe.
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Parasite Power
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The power used to overcome the drag of all nonlifting components of the
rotorcraft.
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Pattern
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The in-plane alignment of all rotor blades so they perfectly balance each
other.
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Period
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The time it takes for an oscillating system to complete one full cycle.
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P.I.O.
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Pilot induced Oscillation - Caused by delays in the human reaction time.
Also known as porpoising, which is caused by over control and inexperience.
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Pitch
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The angle between a blade's chord line and a plane perpendicular to the
rotor bearing.
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Power Loading
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The ratio of the gross weight to the horsepower rating of the rotorcraft's
engine.
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Pull Out
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A flight maneuver at the bottom of a dive or descent.
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Push Over
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A flight maneuver at the top of a climb or a nose-down dive from level
flight.
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Radius of Action
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The maximum distance a gyro-plane can fly down and return to without
refueling.
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Range
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The maximum distance a gyroplane can fly without landing or refueling.
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Redundancy
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A fail-safe design which provides a secondary standby structural member.
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Retreating Blade
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This blade is on the opposite side of the advancing blade. It travels with
the wind created by the forward motion of the rotorcraft.
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Roll
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Tilt of the gyroplane along its longitudinal axis. Controlled by lateral
movements of the joystick.
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Rotor
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The lift-producing airfoil system of a rotorcraft. Rotor blade refers to a
single blade only.
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Service Ceiling
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The altitude at which the rotorcraft still maintains the potential to climb
at 100 feet per minute.
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Side Force
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The force on the side of a rotorcraft due to a side slip.
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Slip
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The controlled flight of a rotorcraft in a direction not in line with its
fore and aft axis.
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Solidity Ratio
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The portion of the rotor disc which is filled by the rotor blades. A ratio
of the total blade area to the total disc area.
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Spar
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The main load-carrying member of the rotor blade's structure. It carries the
centrifugal force as well as loads from the root attachments to the tip of
the blade.
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Speed Stability
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The tendency of the rotorcraft to pitch up or down when the forward speed is
changed.
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Stall
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The separation of the airflow from the surface of the airfoil or any other
component. The resulting loss of lift is a stall.
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Static Stability
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The tendency of a rotorcraft to return to its original flight condition
after a disturbance.
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Teetering Rotor
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A two-bladed rotor with a single horizontal hinge for flapping.
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Thickness Ratio
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The ratio of maximum thickness of the airfoil to the chord length of the
airfoil.
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Thrust
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The rotor force perpendicular to the tip path plane.
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Tip Path Plane
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The plane in which the tip paths travel when the blades are rotating.
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Tip Speed
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The airspeed at the top of the rotor blade in flight.
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Tip Stall
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The stall condition of the retreating blade which occurs at high forward
speeds (approx. 150mph).
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Torque
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A rotary force. A reaction to the turning effort supplied by the engine is
an example.
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Tracking
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Rigging the rotor so that each blade passes through the same slot of air.
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Yaw
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Turning of the gyroplane to the right or left by changing the direction of
the airflow over the tail surface through the use of the foot petals.
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