the Aviation Dictionary

visibility . visual inspection
visibility - The ability, as determined by atmospheric
conditions and expressed in units of distance, to see
and identify prominent unlighted objects by day and
prominent lighted objects by night. Visibility is
reported as statute miles, hundreds of feet or meters.
a. Flight Visibility - The average forward horizontal
distance, from the cockpit of an aircraft in flight, at
which prominent unlighted objects can be seen and
identified by day and prominent lighted objects can be
seen and identified by night.
b. Ground Visibility - Prevailing horizontal visibility
near the Earth's surface as reported by the United
States National Weather Service or an accredited
observer.
c. Prevailing Visibility - The greatest horizontal
visibility equaled or exceeded throughout at least half
the horizon circle that need not necessarily be
continuous.
lights delineating the runway or identifying its centre
line.
visible light - Light wavelength between 4,000 and
7,700 angstroms (.4 - .77 pM) that can be seen by the
eye.
visible line - A line on an engineering drawing that
represents a portion of an object that can be seen.
visual approach - An approach conducted on an
instrument flight rules (IFR) flight plan that authorizes
the pilot to proceed visually and clear of clouds to the
airport. The pilot must, at all times, have either the
airport or the preceding aircraft in sight. This approach
must be authorized and under the control of the
appropriate air traffic control facility. Reported weather
at the airport must have a ceiling at or above 1,000 feet
and visibility of three miles or greater.
d. Runway Visibility Value (RVV) - The visibility visual approach (ICAO)- An approach by an IFR
determined for a particular runway by a flight when either part or all of an instrument approach
transmissometer. A meter provides a continuous procedure is not completed and the approach is
indication of the visibility (reported in miles or executed in visual reference to terrain.
fractions of miles) for the inway: RVV is used in lieu
of prevailing visibility in determining minimums for a
visual approach slope indicator (VASI)- An airport
particular runway.
lighting facility providing vertical visual approach
e. Runway Visual Range (RVR)- An instrumentally
slope guidance to aircraft during approach to landing
derived value, based on standard calibrations, that
by radiating a directional pattern of high intensity red
represents the horizontal distance a pilot will see down
and white focused light beams that indicate to the pilot
the runway from the approach end. It is based on the
that he is "on path if he sees redwhite, "above path"
sighting of either high intensity runway lights or on the
if whitelwhite, and "below path" if redked. Some
visual contrast of other targets whichever yields the
airports serving large aircraft have three-bar VASIs
greater visual range. RVR, in contrast to prevailing or
that provide two visual glide paths to the same runway.
runway visibility, is based on what a pilot in a moving visual climb over the airport (VCOA)- An option to
aircraft should see looking down the runway. RVR is allow an aircraft to climb over the airport with visual
horizontal visual range, not slant visual range. It is reference to obstacles to attain a suitable altitude from
based on the measurement of a transmissometer made which to proceed with an IFR departure.
near the touchdown point of the instrument runway and
is in hundreds of feet. RVR is used in lieu of visual descent point (VDP)- A defined point on the
R W and/or prevailing visibility in determining final approach course of a non-precision straight-in
minimums for a particular runway.
approach procedure from which normal descent from
I. Touchdown RVR - The RVR visibility readout values the MDA to the runway touchdown point can be
obtained from RVR equipment serving the runway commenced, provided the approach threshold of that
touchdown zone. runway, or approach lights, or other markings
2. Mid RVR - - The RVR readout values obtained from identifiable with the approach end of that runway are
RVR equipment located midfield of the runway.
clearly visible to the pilot.
3. Rollout RVR - The RVR readout values obtained visual flight rules (VFR) - 1. The procedures for
from RVR equipment located nearest the rollout end of conducting flight under visual conditions according to
the runway.
Federal Aviation Regulations (FARs). The FARs
visibility (ICAO) - The ability, as determined by specify minimum cloud clearance and visibility
atmospheric cond~tions and expressed in units of requirements. 2. VFR is also used to describe weather
distance, to see and identify prominent unlighted conditions and is often used interchangeably with the
objects by day and prominent lighted objects by night. term VMC (visual meteorological conditions).
Flight Visibility is the visibility forward from the visual holding - The holding of aircraft at selected,
cockpit of an aircraft in flight. Ground Visibility is the prominent geographical fixes that can be easily
visibility at an aerodrome as reported by an accredited recognized from the air.
observer. Runway Visual Range (RVR) is the range
over which the pilot of an aircraft on the centre line of visual inspection - The inspection of a part or
a runway can see the runway surface markings or the component by visual means.
Aircraft Technical Book Company
346 P.O. Box 270
Tabernash, CO 80478
http:llwww.ACTechbooks.com