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A Glossary of Aviation Terms
and Abbreviations as related to Experimental Aviation, building and designing.
This will be a "living
document" that will be updated on a regular basis. Your comments and
participation are
necessary to maintain and grow this list as accurately as possible. Although we
are also aviators, this list will pertain more to building and designing than
flying. ABSOLUTE CEILING - A less often used term
– the highest altitude an airplane can sustain level flight, or altitude above
which the cabin pressurization system can no longer maintain a sufficient oxygen
level for passengers and crew, and where the pressure differential is so great
as to put severe stress on the pressure cabin of the aircraft. Most commercial
jetliners have a ceiling of about 42,000 feet (12,802 meters) while some
business jets can reach 52,000 feet or higher (15,850 meters.) Also see
SERVICE CEILING.
ACCELERATED STALL - Any stall made
to occur at other than 1g. Also see HIGH-SPEED STALL and SECONDARY STALL |
|
ACCESSORIES - Mechanical and electrical
units mounted on an engine necessary for its operation such as starter,
magnetos, fuel pump or the operation of other
systems such as an alternator, vacuum pump, etc.
ADVERSE YAW - Yaw generated when the
ailerons are used. The lifting wing generates more drag, causing an airplane to
yaw (turn) toward it.
AGL - Above Ground
Level, as a measurement of altitude above a specific land mass, and
differentiated from MSL.
AILERON - The movable
areas of a WINGFORM that control or affect the roll of an aircraft by
working opposite one another—up-aileron on the right wing and down-aileron on
the left wing.
AIRSPEED INDICATOR – (ASI)
An instrument or device that measures the air speed of an aircraft through an
air mass, but not its ground speed.
ALODINE - A non-anodic
protective coating. Alodine {aka Iridite, aka Chromate Conversion} is a
microscopic thin film commonly prescribed on aluminum to provide an excellent
surface prep for paint, aid in corrosion resistance and to impose desired
electrical resistance characteristics, (commonly prescribed for radio and
amplifier cabinets.) The the process requires an initial acid etching before the
AL applying the alodine conversion coating. Alodine is a strong oxidizer and
produces a chemical conversion of the surface (oxidizes it). Paint is reported
to bond to the alodine'd surface well.
ALCLAD - Trademark of
Alcoa used as a generic term to describe corrosion resistant Aluminum sheet
formed from high-purity aluminum surface layers metallurgically bonded to high
strength Aluminum Alloy core material. These sheets commonly used by the
aircraft industry.
Described in NACA-TN-259, of
August 1927, as "a new corrosion resistant aluminum product which is markedly
superior to the present strong alloys. Its use should result in greatly
increased life of a structural part. Alclad is a heat-treated aluminum, copper,
manganese, magnesium alloy that has the corrosion resistance of pure metal at
the surface and the strength of the strong alloy underneath. Of particular
importance is the thorough character of the union between the alloy and the pure
aluminum. Preliminary results of salt spray tests (24 weeks of exposure) show
changes in tensile strength and elongation of Alclad 17ST, when any occurred, to
be so small as to be well within the limits of experimental error."
ANGLE OF ATTACK – (AOA)
The acute angle at which a moving airfoil meets the airstream.
ANGLE OF INCIDENCE – (AOI)
The angle at which an airfoil is normally fixed in relation to the longitudinal
axis of an aircraft.
ANHEDRAL - The downward
angle of a wing in relation to a horizontal cross-section line; aka CATHEDRAL.
See DIHEDRAL.
ANODIZE - or anodising,
is an electrolytic passivation process used to increase the thickness of the
natural oxide layer on the surface of metal parts. Anodizing increases corrosion
resistance and wear resistance, and provides better adhesion for paint primers
and glues than bare metal. Anodic films can also be used for a number of
cosmetic effects, either with thick porous coatings that can absorb dyes or with
thin transparent coatings that add interference effects to reflected light.
Anodizing is also used to prevent galling of threaded components and to make
dielectric films for electrolytic capacitors. Anodic films are most commonly
applied to protect aluminium alloys, although processes also exist for titanium,
zinc, magnesium, and niobium.
ARM - In aircraft weight
and balance, as well as load distribution, it is the distance from the CENTER
OF GRAVITY (CG or CofG) to some point. For computations, arms measured
forward from the c/g are positive (+n) and those measured aft of the c/g are
negative (-n).
ASPECT RATIO - The ratio
of the span to the chord of an airfoil—a high-aspect ratio wing has wide span
and narrow chord, and vice-versa for a low-aspect ratio wing.
AUTOGYRO, AUTOGIRO - An
aircraft, often wingless, with unpowered rotary airfoil blades that auto-rotate
and serve as wings as they move through the air when mounted on a powered
aircraft (or, in some cases, a glider). The latter spelling is a trademark of
the Autogiro Corporation.
AUTO-ROTATION -
Automatic rotation of rotary blades from a HELICOPTER in an unpowered
glide or the forward movement of an AUTOGYRO.
AVGAS - A high-octane
aviation fuel used for aircraft. Avgas is a portmanteau for aviation gasoline,
as distinguished from MOGAS (motor gasoline), which is the everyday
gasoline used in cars.
Avgas is used in aircraft that
use piston or Wankel engines. Gas turbines can operate on avgas, but typically
do not. Turbine and diesel engines are designed to use kerosene-based jet fuel.
AXIAL - Motion along a
real or imaginary straight line on which an object supposedly or actually
rotates.
BALANCED CONTROL SURFACE
- A movable control surface, as an aileron or rudder, having an added physical
extension or weights forward of the hinge-point to reduce forces on a joystick
or yoke and to lessen the chance for aerodynamic FLUTTER. See ELEPHANT
EARS.
BERNOULLI EFFECT or LAW
or THEOREM - Since the pressure of a fluid is proportional to its velocity,
airflow over the upper surface of an airfoil causes suction [lift] because the
airstream has been speeded up in relation to positive pressure of the airflow on
the lower surface.
BLEED AIR - Hot air at
high pressure, usually from the bypass section of a AUTOGYRO engine, for
de-icing, heating, and other uses.
BOUNDARY-LAYER CONTROL -
The design or control of slotted or perforated wings with suction methods to
reduce undesirable aerodynamic effects caused by the boundary layer—that region
adjacent to the boundary where shear stresses dominate in the airflow over a
WINGFORM.
BUMPED COWLING - An
engine FAIRING, generally circular, with welts or compound shapes in its
surface to accommodate cylinder heads.
CABANE STRUT - Wing
strut attached to the fuselage.
CALIBRATED AIRSPEED (CAS)
- The indicated airspeed of an aircraft, corrected for position and instrument
error. CAS is equal to true airspeed in standard atmosphere at sea level.
Compare INDICATED AIRSPEED (IAS) and TRUE AIRSPEED (TAS).
CAMBER - The convex or
concave curvature of an airfoil.
CANARD - An arrangement
in which the horizontal stabilizer and elevators of an aircraft are mounted in
front of the wing(s).
CATHEDRAL see
ANHEDRAL
CEILING - (1) The
heights above the earth's surface of the lowest layer of clouds or obscuring
phenomena that is reported as "broken," "overcast," or "obscuration," and not
classified as "thin" or "partial". (2) The maximum height above sea level in
STANDARD AIR attainable by an aircraft under given conditions—see
ABSOLUTE CEILING, SERVICE CEILING.
CENTER OF GRAVITY (CG or
CofG) - The longitudinal and lateral point in an aircraft where it is stable;
the static balance point.
CHORD - The measurable
distance between the leading and trailing edges of a WINGFORM.
COAMING - A padded,
protective rim around an open cockpit.
COLLECTIVE PITCH - A
cockpit control that changes the PITCH of a helicopter's rotor blades; used in
climbing or descending.
COLLECTOR RING - A
circular duct on a radial engine into which exhaust gases from its cylinders are
safely discharged.
CONSTANT-SPEED PROPELLER
- A hydraulically or electrically controlled propeller that can change its blade
pitch to take better advantage of the power supplied by an engine in much the
same way that a transmission in a car takes better advantage of its power
source. The mechanism varies depending on the aircraft, but the desired effect
is to change the angle of attack of the propeller blades to take a smaller or
larger "bite" of air as it rotates.
CONTACT! Magazine - An
independant, non-profit experimental aviation magazine started by Mick Myal in
1991. It's published bimonthly by it's editor, Patrick Panzera.
Read More
COWL, COWLING - A
removable FAIRING around an aircraft engine for the purposes of
streamling or cooling.
COWL FLAP - A
controllable louver to regulating airflow through an engine's COWLING.
DEADSTICK - Descending
flight with engine and propeller stopped.
DECALAGE - The
difference in angular settings [Angles of Attack] of the wings of a biplane or
multiplane.
DELTA-WING - A
triangularly-shaped aircraft wing having a low aspect ratio, a sharply-tapered
leading edge, a straight trailing edge, and a pointed tip.
DEPARTURE STALL - A
stall in the takeoff configuration with power.
DIHEDRAL - The acute
angle, usually upward, between the wing of an airplane and a horizontal
cross-section line. Opposite of ANHEDRAL.
DOPE - Preservative and
pigmented coloring for fabric aircraft covering and paints, generally nitrate
lacquer but generically used to denote all early shellac and coal-tar mixtures
on up to present-day acrylics.
DORSAL FIN - A lateral
fin/rudder extension on the top of a fuselage. Opposite of VENTRAL FIN.
DOWNWASH - The air
deflected perpendicular to the direction of movement of an airfoil.
DOWNWIND TURN - Long a
point of contest among pilots, there is in reality no such thing as far as the
airplane is concerned. Proponents claim that airplanes lose air speed and gets
pushed from behind (potentially causing a stall) when turning downwind, while
opponents (and the laws of physics) argue that an airplane, like a boat in a
river whose speed is only relative to the water and not the shore, is unaffected
within the movement of an air mass and that it gains only ground speed.
DRAG - The resisting
force exerted on an aircraft in its line of flight opposite in direction to its
motion. Compare THRUST.
DRAG WIRE - A wire
designed to resist DRAG forces, usually running from a forward inboard
point to an outboard aft point.
DRY WEIGHT - The weight
of an engine exclusive of any fuel, oil, and coolant.
DURAL - Originally a
tradename for a wrought aluminum-copper alloy created by Bausch Machine Tool Co,
now fallen into generic use as any aluminum alloy containing 3.0-4.5% copper,
0.4-1.0% magnesium, and 0.1-0.7% manganese. Alcoa's version is commonly referred
to as "Duraluminum," popularly used in aircaft manufacture.
DZUS FASTENER - ("Zoose")
Very singular to aircraft, a patented slotted screw that binds to a wire for
fast release and securing of cowlings and inspection plates, requiring no
special tool other than a quarter coin.
EAA - (The Experimental
Aircraft Association) is an international organization of aviation enthusiasts
based in Oshkosh, Wisconsin. Since its inception, it has grown internationally
with over 170,000 members.
ELEPHANT EAR - (1) An
air intake characterized by twin inlets, one on each side of the fuselage. (2) A
type of balanced aileron in which the outer edges are noticeably larger than the
control itself. See BALANCED CONTROL SURFACE and example Travel Air 4000.
ELEVATOR - The movable
part of a horizontal airfoil which controls the pitch of an aircraft, the fixed
part being the STABILIZER.
ELEVON - A hinged device
on the rear portion of an aircraft wing combining the functions of an elevator
and an aileron. Usually found on delta-wing aircraft, it can be moved in the
same direction on either side of the aircraft to obtain longitudinal control, or
differentially to obtain lateral control. Also see FLAPERON.
ELT - Emergency Locator
Transmitter, a type of distress beacon used
in aircraft
EMPENNAGE - An
aircraft's tail group, includes rudder and fin, and stabilizer and elevator. Old
French: empenner, to feather an arrow, from Latin penna, feather.
ETA - Estimated Time of
Arrival.
ETD - Estimated Time of
Departure.
FAIRING - An added
streamlining structure or auxiliary member, most often of light metal, whose
only purpose is to reduce drag. Fairings are not load-bearing and, therefore,
are not meant to carry any principal air loads placed on the airplane structure.
FBO - Fixed-Base
Operator (or Fixed Base Operation). A commercial operator supplying fuel,
maintenance, flight training, and other services at an airport.
FEATHERING - In the
event of engine failure, the process of adjusting a controllable-pitch propeller
to a pitch position where the blade angle is about 90° to the plane of rotation
in order to stop its windmilling and lessen drag.
FEDERAL AIR REGULATION
(FAR)
FAR Part 91 - General
Aviation (portions apply to all operators)
FAR Part 103 - Ultralight
Vehicles
FAR Part 105 - Parachute
Jumping
FAR Part 108 - Airplane
Operator Security
FAR Part 119 - Certification:
Air Carriers and Commercial Operators
FAR Part 121 - Domestic, Flag,
and Supplemental Air Carriers and Commercial Operators of Large Aircraft
FAR Part 123 - Travel Clubs
FAR Part 125 - US Civil
Airplanes, seating 20 or more passengers or a maximum payload capacity 6,000# or
more
FAR Part 127 - Air Carriers
using helicopters for scheduled interstate flights (within the 48 contiguous
states)
FAR Part 129 - Foreign Air
Carrier and Foreign Operators of US registered aircraft engaged in common
carriage
FAR Part 133 - Rotorcraft
External Load Operations
FAR Part 135 - Air Taxi
Operators and Commercial Operators
FAR Part 137 - Agricultural
Aircraft Operations
FAR Part 141 - Pilot School
FERRY FLIGHT - A flight
for the purpose of (1) returning an aircraft to base; (2) delivering an aircraft
from one location to another; (3) moving an aircraft to and from a maintenance
base. Ferry flights, under certain conditions, may be conducted under terms in a
special flight permit.
FIN - The fixed part of
a vertical airfoil that controls the yaw of an aircraft; the movable part being
the RUDDER. Sometime referred to as Vertical Stabilizer.
FIREWALL - A
fire-resistant bulkhead that isolates the engine from other parts of an
airplane's structure.
FISHTAILING - A
rudder-controlled side-to-side [yawing] motion to reduce air speed, generally
prior to landing.
FLAP - A movable,
usually hinged AIRFOIL set in the trailing edge of an aircraft wing,
designed to increase LIFT and/or DRAG by changing the CAMBER of
the wing or used to slow an aircraft during landing by increasing lift. Also see
FOWLER FLAP, SLOTTED FLAP, and SPLIT FLAP.
FLAPERON - A control
surface combining the functions of a FLAP and an AILERON.
FLARE - A simple
maneuver performed moments before landing in which the nose of an aircraft is
pitched up to minimize the touchdown rate of speed.
FLIGHT ENVELOPE - An
aircraft's performance limits, specifically the curves of speed plotted against
other variables to indicate the limits of speed, altitude, and acceleration that
a particular aircraft cannot safely exceed.
FLOATPLANE - A
water-based aircraft with one or more mounted pontoons, as differentiated from a
hulled SEAPLANE [Flying Boat], but often used generically.
FLYING WIRES -
Interplane bracing wires that help support wing loads when the plane is in
flight. Direction of travel is upward and outward from the fuselage to the
interplane struts. Also known as LIFT WIRES, the opposite of LANDING
WIRES.
FLUTTER - A
self-starting and potentially destructive vibration where aerodynamic forces on
an object couple with a structure's natural mode of vibration to produce rapid
periodic motion.
FOWLER FLAP - Trademark
name of a flap attached to a wing's trailing edge with a system of tracks and
rollers to slide backwards before hinging downwards, thereby increasing both
camber and chord, creating a larger wing surface better tuned for lower speeds.
Named for its inventor, USAF engineer Harland D Fowler.
FRISE AILERON - A type
of aileron that has a beveled or contoured leading edge projecting beyond its
inset hinges. When the trailing edge is lowered, it forms an extension of the
wing surface; when raised, its nose protrudes below the wing surface, protruding
into the airflow increasing DRAG and reducing YAW. Named for its
inventor, British engineer Leslie George Frise.
Unfortunately, as well as
reducing adverse yaw, Frise ailerons will increase the overall drag of the
aircraft, and therefore they are less popular in aircraft where minimizing drag
is important (e.g. in a glider)
FUSELAGE - An aircraft's
main body structure housing the flight crew, passengers, and cargo and to which
the wings, tail and, in most single-engine airplanes, engine are attached.
French: fuselé, tapering.
g or G - see
LOAD FACTOR
GAP - The distance
between two adjacent wings of a biplane or multiplane.
GAS TURBINE - An
internal-combustion engine consisting essentially of an air compressor,
combustion chamber, and turbine wheel that is turned by the expanding products
of combustion.
GLASS COCKPIT - Said of
an aircraft's control cabin which has all-electronic, digital and
computer-based, instrumentation.
GLIDER - An unpowered
aircraft capable of maintaining altitude only briefly after release from tow,
then gliding to earth. Compare SAILPLANE.
GROSS WEIGHT - The total
weight of an aircraft when fully loaded, including fuel, cargo, and passengers;
aka Takeoff Weight.
GROUND CUSHION see
GROUND EFFECT
GROUND EFFECT -
Increased lift generated by the interaction between a lift system and the ground
when an aircraft is within a wingspan distance above the ground. It affects a
low-winged aircraft more than a mid- or high-winged aircraft because its wings
are closer to the ground; aka GROUND CUSHION.
GROUNDSPEED - The actual
speed that an aircraft travels over the ground—its "shadow speed"; it combines
the aircraft's AIRSPEED and the wind's speed relative to the aircraft's
direction of flight.
GULL-WING - Descriptive
of wing in frontal view bent as the wing of a seagull; a distinctive shallow,
inverted "V" shape—see Stinson SR-10 or inverted gull-wing Vought F4U.
GYROPLANE - A rotorcraft
whose rotors are not engine-driven, except for initial starting, but are made to
rotate by action of the air when the rotorcraft is moving and whose means of
propulsion, usually a conventional propeller, is independent of the rotor
system. Similar to AUTOGYRO.
HELICOPTER - A wingless
aircraft acquiring its lift from revolving blades driven by an engine about a
near-vertical axis. A ROTORCRAFT acquiring its primary motion from
engine-driven rotors that accelerate the air downward, providing a reactive lift
force, or accelerate the air at an angle to the vertical, providing lift and
thrust.
HIGH BLOWER - A
blower-type SUPERCHARGER set at high rpm.
HIGH-SPEED STALL - Any
stall made to occur at more than 1g, such as pulling out of a dive or while
turning. Also see SECONDARY STALL or ACCELERATED STALL.
HORSEPOWER – (HP) The
motive energy required to raise 550# one foot in one second, friction
disregarded. With any rotating engine HP can be determined by multiplying the
torque and the revolutions per minute (RPM) and dividing by 5,252.
Torque (ft. lbs) x
RPM
HP = --------------------------------
5252
HYPERSONIC - Speed of flight at
or greater than Mach 5.0, exceeding SUPERSONIC.
INDICATED AIRSPEED (IAS) - A
direct instrument reading obtained from an air speed indicator uncorrected for
altitude, temperature, atmospheric density, or instrument error. Compare
CALIBRATED AIRSPEED and TRUE AIRSPEED.
INDUCED DRAG - is caused
by that element of the air deflected downward which is not vertical to the
flight path but is tilted slightly rearward from it. As the angle of attack
increases, so does drag; at a critical point, the angle of attack can become so
great that the airflow is broken over the upper surface of the wing, and lift is
lost while drag increases.
INERTIA FORCE - A force
due to inertia, or the resistance to acceleration or deceleration.
JOYSTICK or STICK
- A single floor- or roof-mounted control stick—sideways movement produces ROLL,
and forward/backward movement produces PITCH (rudder pedals produce YAW).
KNOT - One nautical
mile, about 1.15 statute miles (6,080'); eg: 125kts = 143.9mph.
LAMINAR-FLOW AIRFOIL - A
low-drag airfoil designed to maintain laminar (smooth, continuous) flow over a
high percentage of the CHORD about itself. Often relatively thin, especially
along the leading edge, with most of its bulk near the center of the chord.
LANDING WIRES - Interplane
bracing wires that help support wing loads when the plane is on the ground.
Direction of travel is downward and outward from the fuselage. Opposite of
FLYING WIRES.
LIFT - The force exerted on the
top of a moving airfoil as a low-pressure area [vacuum] that causes a
WINFGFORM
to rise. AIRFOILs do not "float" on air, as is often assumed—like a boat hull
floats on water—but are "pulled up" [lifted] by low air pressures trying to
equalize.
LIFT-DRAG RATIO - The lift
coefficient of a wing divided by the drag coefficient, as the primary measure of
the efficiency of an aircraft; aka L/D Ratio (L over D).
LIFT WIRES - Interplane bracing
wires that help support wing loads when the plane is in flight. Direction of
travel is upward from the bottom of the fuselage to the top of the interplane
struts. Also known as FLYING WIRES, the opposite of LANDING WIRES.
LIGHT SPORT AIRCRAFT - Special
FAA certification class (LSA) for an aircraft other than a helicopter or
powered-lift—single-engine aircraft, airship, balloon, GLIDER, GYROCOPTER,
ROTORCRAFT, weight-shift-control aircraft. While limiting the types of aircraft
that could be flown by a SPORT PILOT, it simplified requirements for a obtaining
a pilot license and did not require a medical examination.
LOAD FACTOR (g) - The
proportion between lift and weight commonly seen as g (sometimes capitalized)—a
unit of force equal to the force of gravity times one.
LOFTING - Design or fabrication
of a complex aircraft component, as with sheet metal, using actual-size patterns
or plans, generally laid out on a floor. The term was borrowed from boat
builders.
LONGERON - A principal
longitudinal member of a fuselage's framing, usually continuous across a number
of supporting points.
LTA - Lighter-than-air craft,
generally referring to powered blimps and dirigibles, but often also includes
free balloons.
MACH or m. - A number
representing the ratio of the speed of an object to the speed of sound in the
surrounding air or medium in which it is moving.
MAGNETO, MAG - An accessory
that produces and distributes a high-voltage electric current for ignition of a
fuel charge in an internal combustion engine.
MAGNUS EFFECT - The effect on a
spinning cylinder or sphere moving through a fluid, in which force acts
perpendicular to the direction of motion and to the direction of spin. This is
used to advantage in baseball, in which the trajectory of a pitched ball is a
distinct curve. Applied to aeronautics in experimental wingforms, the Magnus
Theory states that if air is directed against a smooth, revolving cylinder,
whose circumferential speed is greater than that of the air current, a force is
directed against one side of the cylinder—air compressed on one side and vacuum
formed on the other—creating lift. Named for physicist Heinrich Gustav Magnus
(1802-70).
MEAN SEA LEVEL see MSL
MOGAS – An aviation nickname
for everyday automobile gasoline intended by the purchaser for aircraft use.
Mogas is a portmanteau for autoMObile gasoline, as distinguished from AVGAS
(aviation gasoline) which is specifically blended for aviation use and not
intended nor legal to use in land-based internal combustion engines.
MONOCOQUE - Type of fuselage
design with little or no internal bracing other than bulkheads, where the outer
skin bears the main stresses; usually round or oval in cross-section. Additional
classifications are (1) Semi-Monocoque, where the skin is reinforced by
LONGERONS or BULKHEADs, but with no diagonal web members, and (2) Reinforced
Shell, in which the skin is supported by a complete framework or structural
members. French: monocoque, single shell.
MSL - Mean Sea Level. The
average height of the surface of the sea for all stages of tide; used as a
reference for elevations, and differentiated from AGL.
NACELLE - A streamlined
enclosure or housing to protect something such as the crew, engine, or landing
gear. French: nacelle, from Latin, navicella, little ship.
PANTS - A popular word for
streamlined, non-load bearing fairings to cover landing wheels. Also sometimes
called Spats or, when fully enclosing the wheel struts, Skirts.
PATTERN - The path of aircraft
traffic around an airfield, at an established height and direction. At
tower-controlled fields the pattern is supervised by radio (or, in non-radio or
emergency conditions by red and green light signals) by air traffic controllers.
PAYLOAD - Anything that an
aircraft carries beyond what is required for its operation during flight,
theoretically that from which revenue is derived, such as cargo and passengers.
PILOT IN COMMAND (PIC) -
The pilot responsible for the operation and safety of an aircraft during flight
time.
PITCH - (1) Of the three
axes in flight, this specifies the vertical action, the up-and-down movement.
Compare ROLL and YAW. (2) The angle of a propeller or rotor blade in relation to
its arc; also the distance advanced by a blade in one full rotation.
PITOT TUBE - More
accurately but less popularly used, Pitot-Static Tube, a small tube most often
mounted on the outward leading edge of an airplane wing (out of the propeller
stream) that measures the impact pressure of the air it meets in flight, working
in conjunction with a closed, perforated, coaxial tube that measures the static
pressure. The difference in pressures is calibrated as air speed by a panel
instrument. Named for French scientist Henri Pitot (1695-1771).
PLANFORM
- or plan view is a vertical orthographic projection of an
object on a horizontal plane, like a map. In aviation, a
planform is the shape and layout of an airplane's wing and
fuselage. Of all the myriad planforms used, they can typically
be grouped into those used for low-speed flight, found on
general aviation aircraft, and those used for high-speed flight,
found on many military aircraft and airliners.
POBEREZNY, PAUL
HOWARD (b. September 14,
1921 in Leavenworth County/Kansas) is a US aviator and aircraft
designer famous for his work in establishing the Experimental
Aircraft Association (EAA) in 1953 and promoting
homebuilt aircraft.
POWER LOADING - The
GROSS WEIGHT of an airplane divided by the rated horsepower, computed for
Standard Air density.
PROPELLER SPEED REDUCTION UNIT (PSRU) - A
gearbox or a belt and pulley device used to reduce the output rotational speed
(rpm) when compared to the higher input rpm of the powerplant. These
arrangements allow the use of relatively small' displacement, high-revving,
internal combustion automotive engines to turn propellers within an efficient
speed range. Certified aircraft engines, where the propeller most commonly is
fastened directly to the engine crankshaft, develop peak power near the peak
safe and efficient speed for the propeller--2,500 to 3,000 rpm. This speed is
considered the typical maximum rpm for a single engine aircraft propeller. Note
that there are examples of factory certified aircraft that have used a PSRU. The
Cessna 170 used a a geared unit during its production run the 1970s.
PUSHER - A propeller
mounted in back of its engine, pushing an aircraft through the air, as opposed
to a TRACTOR configuration.
QUADRAPLANE, QUADRUPLANE
- An aircraft having four or more WINGFORMS.
RAMJET - An aerodynamic
duct in which fuel is burned to produce a high-velocity propulsive jet. It needs
to be accelerated to high speed before it can become operative.
ROGALLO WING - A
flexible, delta-wing plan in which three rigid members are shaped in the form of
an arrowhead and joined by a flexible fabric, which inflates upward under flight
loads. Originally specific to paragliders, but now found on some powered
aircraft.
ROLL - Of the three axes
in flight, this specifies the action around a central point. Compare PITCH and
YAW.
ROTARY ENGINE - A
powerplant that rotates on a stationary propeller shaft. An American invention
by Adams-Farwell Co (1896), it was first used for buses and trucks in the US
(1903), then copied by French engineers for early aircraft engines (1914).
Other rotary engines: Besides
the configuration described above, with cylinders moving around a fixed
crankshaft, several other very different engine designs can also be described as
rotary engines. The most notable pistonless rotary engine, the Wankel rotary
engine has also been used in cars (notably by Mazda in cars such as the RX-7 and
RX-8), as well as in some experimental aviation applications.
Although the GAS TURBINE
produces rotary motion directly, it is not generally considered a rotary engine.
ROTORCRAFT - A
heavier-than-air aircraft that depends principally for its support in flight on
the lift generated by one or more rotors. Includes helicopters and gyroplanes.
RUDDER - The movable
part of a vertical airfoil which controls the YAW of an aircraft; the fixed part
being the FIN.
SAILPLANE - An unpowered,
soaring aircraft capable of maintaining level flight for long periods of time
after release from tow and of gaining altitude using wind currents, as opposed
to a GLIDER.
SCRAMJET - Acronym for
supersonic combustion ramjet, in which combustion occurs at supersonic air
velocities through the engine.
SEAPLANE - A water-based
aircraft with a boat-hull fuselage, often amphibious. The term is also used
generically to define a similar Flying Boat and a pontoon FLOATPLANE.
SECONDARY STALL - Any
stall resulting from pulling back too soon and too hard while recovering from
any other stall. Usually a HIGH-SPEED or ACCELERATED STALL.
SERVICE CEILING - The
density altitude at which flying in a clean configuration, at the best rate of
climb airspeed for that altitude and with all engines operating and producing
maximum (available) continuous power, will produce a 100 feet per minute climb.
Margin to stall at service ceiling is 1.5g.
The one engine inoperative (OEI)
service ceiling of a twin-engine, fixed-wing aircraft is the density altitude at
which flying in a clean configuration, at the best rate of climb airspeed for
that altitude with one engine producing maximum continuous power and the other
engine shut down and feathered, will produce a 50 feet per minute climb. However
some performance charts will define the service ceiling as the pressure altitude
at which the aircraft will have the capability of climbing at 50 fpm with one
propeller feathered. Also see ABSOLUTE CEILING
SESQUI-WING - A
lesser-span additional wingform, generally placed below the main planes of an
aircraft, generally a biplane.
SHOULDER-WING - A
mid-wing monoplane with its wing mounted directly to the top of the fuselage
without use of CABANE STRUTs.
SINK, SINKING SPEED -
The speed at which an aircraft loses altitude, especially in a glide in still
air under given conditions of equilibrium.
SLATS - Movable vanes or
auxiliary airfoils, usually set along the leading edge of a wing but able to be
lifted away at certain angles of attack.
SLIPSTREAM - The flow of
air driven backward by a propeller or downward by a rotor. Compare DOWNWASH.
SLOT or SLAT- A
long, narrow, spanwise gap in a wing, usually near the leading edge, to improve
airflow at high angles of attack for slower landing speeds. A higher coefficient
of lift is produced as a product of angle of attack and speed, so by deploying
slats an aircraft can fly slower or take off and land in a shorter distance.
They are usually used while landing or performing maneuvers which take the
aircraft close to the stall, but are usually retracted in normal flight to
minimize drag.
SLOTTED FLAP - A flap
that, when depressed, exposes a SLOT and increases airflow between itself and
the rear edge of the wing.
SMOH - "Since Major
Overhaul," an acronym seen in reference to the operating hours, or time
remaining, on an engine.
SPLIT FLAP - A FLAP
built into the underside of a wing, as opposed to a Full Flap wherein a whole
portion of the trailing edge is used.
SPOILER - A long,
movable, narrow plate along the upper surface of an airplane wing used to reduce
lift and increase drag by breaking or spoiling the smoothness of the airflow.
SPORT PILOT - Special
FAA certification enabling "budget" pilotry; see LIGHT SPORT AIRCRAFT and LSA
feature.
SPONSON - A short,
wing-like protuberance on each side of a seaplane fuselage to increase lateral
stability.
STABILATOR - A movable
horizontal tail that combines the actions of a stabilizer and elevator,
increasing longitudinal stability while creating a pitching moment.
STABILIZER - The fixed
part of a horizontal airfoil that controls the pitch of an aircraft; the movable
part being the ELEVATOR.
STAGGER - The relative
longitudinal position of the wings on a biplane. Positive Stagger is when the
upper wing's leading edge is in advance of that of the lower wing [eg: Waco YKS],
and vice versa for Negative Stagger [eg: Beechcraft D17].
STALL - (1) Sudden loss
of lift when the angle of attack increases to a point where the flow of air
breaks away from a wing or airfoil, causing it to drop. (2) A maneuver initiated
by the steep raising of an aircraft's nose, resulting in a loss of velocity and
an abrupt drop.
STANDARD DAY (Standard
Atmosphere) - An arbitrary atmosphere established for calibration of aircraft
instruments. Standard Air Density is 29.92 inches of mercury and temperature of
59° F, equivalent to an atmospheric air pressure of 14.7# per square inch.
STATIC WIRE - A clip-on
wire used to ground an aircraft by drawing off static electricity, a potential
fire hazard, during refueling.
SUPERCHARGER - An air pump or blower in
the intake system of an internal combustion engine. Its purpose is to increase
the air-charge weight and therefore the power output from an engine of a given
size. In an aircraft engine, the supercharger counteracts the power loss that
results from the decrease of atmospheric pressure with increase of altitude.
Various types of pumps and compressors may be used as superchargers, which are
either mechanically driven by the engine crankshaft or powered by the engine
exhaust gas. Also see TURBOCHARGER
SUPERSONIC - Speed of
flight at or greater than Mach 1.0; literally, faster than the speed of sound.
SWEEPBACK - A backward
inclination of an airfoil from root to tip in a way that causes the leading edge
and often the trailing edge to meet relative wind obliquely, as WINGFORMs that
are swept back.
SWING-WING - A wing
whose horizontal angle to the fuselage centerline can be adjusted in flight to
vary aircraft motion at differing speeds.
TAILDRAGGER see
CONVENTIONAL GEAR.
TARMAC - (1) A
bituminous material used in paving; a trade name for Tar MacAdam. (2) An airport
surface paved with this substance, especially a runway or an APRON at a hangar.
TAS - True Air Speed.
Because an air speed indicator indicates true air speed only under standard
sea-level conditions, true air speed is usually calculated by adjusting an
Indicated Air speed according to temperature, density, and pressure. Compare
CALIBRATED AIR SPEED and INDICATED AIR SPEED.
THRUST - The driving
force of a propeller in the line of its shaft or the forward force produced in
reaction to the gases expelled rearward from a jet or rocket engine. Opposite of
DRAG.
TORQUE - A twisting,
gyroscopic force acting in opposition to an axis of rotation, such as with a
turning propeller; aka Torsion.
TRACTOR - A propeller
mounted in front of its engine, pulling an aircraft through the air, as opposed
to a PUSHER configuration.
TRAILING EDGE - The
rearmost edge of an AIRFOIL.
TRIKE - Nickname for a
weight-shift-control aircraft, such as a paraglider.
TRIM TAB - A small,
auxiliary control surface in the trailing edge of a WINGFORM, adjustable
mechanically or by hand, to counteract ("trim") aerodynamic forces on the main
control surfaces.
TRUE AIRSPEED (TAS)- The
speed of an aircraft along its flight path, in respect to the body of air (air
mass) through which the aircraft is moving. Also see CALIBRATED AIRSPEED,
GROUND SPEED, and INDICATED AIRSPEED.
TURBOCHARGER – (Turbo)
An air compressor or SUPERCHARGER on an internal combustion piston engine
that is driven by the engine exhaust gas to increase or boost the amount of fuel
that can be burned in the cylinder, thereby increasing engine power and
performance. On an aircraft piston engine, the turbocharger allows the engine to
retain its sea-level power rating at higher altitudes despite a decrease in
atmospheric pressure. Also see SUPERCHARGER.
TURBOJET - An aircraft
having a jet engine in which the energy of the jet operates a turbine that in
turn operates the air compressor.
TURBOPROP - An aircraft
having a jet engine in which the energy of the jet operates a turbine that
drives the propeller.
ULTRALIGHT - An
aeronautical vehicle, operated for sport or recreational purposes that does not
require FAA registration, an airworthiness certificate, or pilot certification.
Primarily single-occupant vehicles, although some two-place vehicles are
authorized for training purposes. Operation of an ultralight vehicle in certain
airspaces requires authorization from ATC.
UNDERCARRIAGE - The
landing gear of a land-based aircraft, including struts, frames, and wheels. A
very British word that has limited use in the USA.
UPWASH - The slight,
upward flow of air just prior to its reaching the leading edge of a rapidly
moving airfoil.
USEFUL LOAD - The weight
of crew, passengers, fuel, baggage, and ballast, generally excluding emergency
or portable equipment and ordnance.
V-SPEED – V, Velocity,
as used in defining specific air speeds at specific configurations or
conditions: Read More
VARIOMETER - A panel
instrument, often as simple as a tiny ball in a vertical tube, indicating subtle
vertical movements of an aircraft. Popular use in SAILPLANES.
VENTRAL FIN - A
fin/rudder extension on the bottom of a fuselage. Opposite of DORSAL FIN.
VENTURI TUBE - A small,
hourglass-shaped metal tube, usually set laterally on a fuselage facing into the
slipstream to create suction for gyroscopic panel instruments. Now outdated by
more sophisticated means.
VFR - Visual Flight
Rules that govern the procedures for conducting flight under visual conditions.
The term is also used in the US to indicate weather conditions that are equal to
or greater than minimum VFR requirements. Also used by pilots and controllers to
indicate a specific type of flight plan.
VFR ON TOP - Flight in
which a cloud ceiling exists but modified VISUAL FLIGHT RULES are in effect if
the aircraft travels above the cloud layer.
VISUAL METEOROLOGICAL
CONDITIONS (VMC) - Meteorological conditions expressed in terms of
visibility, distance from clouds, and ceiling equal to or better than specified
minima.
VSI - Vertical Speed
Indicator. A panel instrument that gauges rate of climb or descent in
feet-per-minute (fpm). Also Rate Of Climb Indicator.
WASHOUT - The terms
'wing twist' and 'washout' refer to wings designed so that the outboard sections
have a lower ANGLE OF INCIDENCE, 3 or 4° or so, and thus lower AOA
than the inboard sections in all flight conditions. One reason for wing twist is
to reduce INDUCED DRAG, the other is to improve the stall characteristics
of the wing. With twist, the sections near the wing root reach the stalling
AOA first, thus allowing effective aileron control even as the stall
progresses from inboard to outboard. This is usually achieved by building a
geometric twist into the wing structure by rotating the trailing edge so
providing a gradual decrease in AOA from root to tip, but of course
washout reduces the total lift capability a little but this disadvantage is more
than offset by the wing twist improving elliptical lift distribution and thus
decreasing induced drag.
WINGFORM - A wingform is
the shape and layout of an airplane's wings as vied from above or below. Also
see PLANFORM.
WINGLET - A small,
stabilizing, rudder-like addition to the tips of a wing to control or employ air
movement.
WING LOA
DING - The
maximum take-off gross weight of an aircraft divided by its wing area.
YAW - Of the three axes
in flight, this specifies the side-to-side movement of an aircraft on its
vertical axis, as in skewing. Compare PITCH and ROLL.
YOKE - The control wheel
of an aircraft, akin to an automobile steering wheel.
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