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Aviation definitions

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These definitions come directly from Federal Aviation Regulations parts 1 and 91, unless noted.

aircraft - large
means aircraft of more than 12,500 pounds maximum certificated takeoff weight.
aircraft - small
means aircraft of 12,500 pounds or less, maximum certificated takeoff weight.
airspeed - calibrated
Indicated airspeed of an aircraft, corrected for position and instrument error. Calibrated airspeed is equal to true airspeed in standard atmosphere at sea level.
airspeed - indicated
means the speed of an aircraft as shown on its pitot static airspeed indicator calibrated to reflect standard atmosphere adiabatic compressible flow at sea level uncorrected for airspeed system errors.
airspeed - true
means the airspeed of an aircraft relative to undisturbed air.
category - aircraft
As used with respect to the certification of aircraft, means a grouping of aircraft based upon intended use or operating limitations. Examples include: transport; normal; utility; acrobatic; limited; restricted; and provisional.
category - pilot certification
As used with respect to the certification, ratings, privileges, and limitations of pilots, means a broad classification of aircraft. Examples include: airplane; rotorcraft; glider; and lighter-than-air.
ceiling
the height 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".
CFI
means Certificated Flight Instructor.
class - aircraft
As used with respect to the certification of aircraft, means a broad grouping of aircraft having similar characteristics of propulsion, flight or landing. Examples include: airplane; rotorcraft; glider; balloon; landplane and seaplane.
class - pilot certification
As used with respect to the certification, ratings, privileges, and limitations of airmen, means a classification of aircraft within a category having similar operating characteristics. Examples include: single engine; multiengine; land; water; gyroplane, helicopter; airship; and free balloon.
controlled airspace
means an airspace of defined dimensions within which air traffic control service is provided to IFR flights and to VFR flights in accordance with the airspace classification. Note: Controlled airspace is a generic term that covers Class A, Class B, Class C, Class D, and Class E airspace.
crewmember
means a person assigned to perform duty in an aircraft during flight time.
day
means the period of time between the beginning of morning civil twilight and the end of evening civil twilight. (Implied by FAR 1.)
FAR
Federal Aviation Regulations, Title 14 of the U.S. Code of Federal Regulations.
flight level
means a level of constant atmospheric pressure related to a reference datum of 29.92 inches of mercury (1013.25 hPa). Each is stated in three digits that represent hundreds of feet. For example, flight level 250 represents a barometric altimeter indication of 25,000 feet; flight level 255, an indication of 25,500 feet.
flight plan
means specified information, relating to the intended flight of an aircraft, that is filed orally or in writing with air traffic control.
flight time
means pilot time that commences when an aircraft moves under its own power for the purpose of flight and ends when the aircraft comes to rest after landing.
flight time - cross-country
means flight time on any flight in which the point of departure is a straight-line distance of 92 km (50 Nmi) from the point of arrival. FAR 61.1(b)(3)(ii)(B)

The FARs are unclear about whether this means the point of first arrival or all legs of a round-robin flight, but it appears—and we log it so—that after the first 50 Nmi leg, all subsequent legs of the same flight count as cross-country time. We would appreciate your comments on this point.
flight time - dual
means flight time during which a (CFI) is present. A pilot with the proper certificates and ratings for the aircraft flown may still log pilot in command time while flying dual.
flight time - instrument
A person may log instrument time only for that flight time when the person operates the aircraft solely by reference to instruments under actual or simulated instrument flight conditions. FAR 61.51(g)
flight time - pilot in command
A recreational, private, or commercial pilot may log pilot-in-command time only for that flight time during which that person (i) is the sole manipulator of the controls of an aircraft for which the pilot is rated; (ii) is the sole occupant of the aircraft; or (iii) except for a recreational pilot, is acting as pilot in command of an aircraft on which more than one pilot is required under the type certification of the aircraft or the regulations under which the flight is conducted.

A student pilot may log pilot-in-command time when the student pilot (i) is the sole occupant of the aircraft... (ii) has a current solo flight endorsement as required under FAR 61.87; and (iii) is undergoing training for a pilot certificate or rating. FAR 61.51(e)
flight time - solo
A pilot may log as solo flight time only that flight time when the pilot is the sole occupant of the aircraft. FAR 61.51(d) A supervised solo is a solo flight in which a CFI observes the student from the ground while the student conducts traffic pattern operations.
IFR
Instrument Flight Rules, FAR 91.167 et seq. An IFR flight is a flight for which the pilot files an IFR flight plan and conforms to the appropriate Instrument Flight Rules. It doesn't mean that the pilot can't see the ground, or that the flight even requires instruments. However, any time the pilot does not have a visual reference to the ground, IFR applies. Cf. VFR, MVFR.
IFR conditions
means weather conditions below the minimum for flight under visual flight rules. (Also called "IMC," for "Instrument Meterological Conditions.")
METAR
A meteorological aviation report, formatted according to the Federal Meteorological Handbook.
MSL
Altitude above mean sea level.
MVFR
Marginal Visual Flight Rules. When visibility and ceilings are close to, but not below, VFR minimums, pilots can still fly for certain purposes. Usually pilots can only conduct traffic pattern operations under MVFR.
night
means the time between the end of evening civil twilight and the beginning of morning civil twilight, as published in the American Air Almanac, converted to local time.

When referring to logged flight time, night means the time beginning one hour after sunset and ending one hour before sunrise.
pilotage
means navigation by visual reference to landmarks.
pilot in command
means the person who (1) has final authority and responsibility for the operation and safety of the flight; (2) has been designated as pilot in command before or during the flight; and (3) holds the appropriate category, class, and type rating, if appropriate, for the conduct of the flight.
special VFR conditions
(SVFR) mean meteorological conditions that are less than those required for basic VFR flight in controlled airspace and in which some aircraft are permitted flight under visual flight rules.
standard atmosphere
The combination of temperature and pressure used as a universal reference, equal to 1013.25 hPa (29.92 in/Hg) at sea level with a temperature of 15°C (59°F). (dab)
speed - best angle of climb
(noted as VX) means the speed at which the airplane will climb at the steepest angle. (dab)
speed - best rate of climb
(noted as VY) means the speed at which the airplane will climb at fastest rate. (dab)
speed - flap extended
(noted as VFE) means the highest speed permissible with wing flaps in a prescribed extended position. Corresponds to the upper limit of the white arc on an airspeed indicator.
speed - ground
The speed of an aircraft relative to the ground.
speed - landing gear extended
(noted as VLE) means the maximum speed at which an aircraft can be safely flown with the landing gear extended.
speed - landing gear operating
(noted as VLO) means the maximum speed at which the landing gear can be safely extended or retracted.
speed - never exceed
(noted as VNE) means the maximum speed at which an aircraft can be safely operated. Corresponds to the upper limit of the yellow arc, and the red line, on an airspeed indicator. (dab)
speed - normal operating
(noted as VNO) means the maximum structural cruising speed of an aircraft. Corresponds to the upper limit of the green arc on an airspeed indicator. (dab)
speed - stall
(noted as VS0) means the speed at which the airplane stall with flaps down; i.e., the slowest indicated airspeed the airplane can fly and still remain airborne. Corresponds to the lower limit of the white arc on an airspeed indicator. (dab)
speed - stall - clean
(noted as VS1) means the speed at which the airplane stall with flaps (and landing gear) up. (dab)
traffic pattern
means the traffic flow that is prescribed for aircraft landing at, taxiing on, or taking off from, an airport.
twilight - astronomical
means that period of time when the center of the sun's disc is higher than 18° below the horizon. Nautical twilight roughly corresponds to the period beginning 90 minutes before sunrise and ending 90 minutes after sunset. During this period, the atmosphere does not scatter any sunlight, making ground-based visual astronomy possible. (dab)
twilight - civil
means that period of time when the center of the sun's disc is higher than 6° below the horizon. Civil twilight roughly corresponds to the period beginning one half-hour before sunrise and ending one half-hour after sunset. (dab)
twilight - nautical
means that period of time when the center of the sun's disc is higher than 12° below the horizon. Nautical twilight roughly corresponds to one hour before sunrise to one hour after sunset. (dab)
VFR
Visual Flight Rules. In most classes of airspace, VFR operation requires a specific minimum visibility and ceiling, and requires the pilot to maintain specific distances from clouds. Cf. IFR, MVFR.
visibility - flight
means the average forward horizontal distance, from the cockpit of an aircraft in flight, at which prominent unlighted objects may be seen and identified by day and prominent lighted objects may be seen and identified by night.
visibility - ground
means prevailing horizontal visibility near the earth's surface as reported by the United States National Weather Service or an accredited observer.

Submitted by reader D.B.