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8-27
Precision approaches use decision height (DH), which
is referenced to the height above threshold elevation
(HAT). Nonprecision approaches use MDA, referenced
to “feet MSL.” The MDA is also referenced to HAT for
straight-in approaches, or height above airport (HAA) for
circling approaches. On NACG charts, the figures listed
parenthetically are for military operations and are not used
in civil aviation.
Visibility figures are provided in statute miles or runway
visual range (RVR), which is reported in hundreds of feet.
RVR is measured by a transmissometer, which represents the
horizontal distance measured at points along the runway. It
is based on the sighting of either high intensity runway lights
or on the visual contrast of other targets, whichever yields
the greater visual range. RVR is horizontal visual range, not
slant visual range, and is used in lieu of prevailing visibility
in determining minimums for a particular runway. It is
illustrated in hundreds of feet if less than a mile (i.e., “24”
is an RVR of 2,400 feet). [Figures 8-19 and 8-20]
Visibility figures are depicted after the DA/DH or MDA in the
minimums section. If visibility in statute miles is indicated,
an altitude number, hyphen, and a whole or fractional
number appear; for example, 530-1, which indicates “530
feet MSL” and 1 statute mile visibility. This is the descent
minimum for the approach. The RVR value is separated
from the minimum altitude with a slash, such as “1065/24,”
which indicates 1,065 feet MSL and an RVR of 2,400 feet.
If RVR is prescribed for the procedure, but not available, a
conversion table is used to provide the equivalent visibility
in this case, of 1/2 statute mile visibility. [Figure 8-20] The
conversion table is also available in the TPP.
When an alternate airport is required, standard IFR alternate
minimums apply. For aircraft other than helicopters, precision
approach procedures require a 600-feet ceiling and two
statute miles visibility; nonprecision approaches require an
800-feet ceiling and two statute miles visibility. Helicopter
alternate minimums are a ceiling that is 200 feet above the
minimum for the approach to be flown and visibility of at
least one statute mile, but not less than the minimum visibility
for the approach to be flown. When a black triangle with a
white “A” appears in the notes section of the pilot briefing,
it indicates non-standard IFR alternate minimums exist for
the airport. If an “NA” appears after the “A,” then
alternate minimums are not authorized. This information is
found in the beginning of the TPP.
In addition to the COPTER approaches, instrument-equipped
helicopters may fly standard approach procedures. The
required visibility minimum may be reduced to one-half the
published visibility minimum for category A aircraft, but
in no case may it be reduced to less than 1/4 mile or 1,200
feet RVR.
Two terms are specific to helicopters. Height above landing
(HAL) means height above a designated helicopter landing
area used for helicopter IAPs. “Point in space approach”
refers to a helicopter IAP to a MAP more than 2,600 feet
from an associated helicopter landing area.
Airport Sketch /Airport Diagram
The airport sketch, located on the bottom right side of the
chart, includes many helpful features. IAPs for some of the
larger airports devote an entire page to an airport diagram.
Airport sketch information concerning runway orientation,
lighting, final approach bearings, airport beacon, and
obstacles all serve to guide the pilot in the final phases of
flight. See Figure 8-21 for a legend of airport diagram/airport
sketch features (see also Figure 8-10 for an example of an
airport diagram).
The airport elevation is indicated in a separate box at the
top left of the airport sketch. The touchdown zone elevation
(TDZE), which is the highest elevation within the first 3,000
feet of the runway, is designated at the approach end of the
procedure’s runway.
Beneath the airport sketch is a time and speed table when
applicable. The table provides the distance and the amount
of time required to transit the distance from the FAF to the
MAP for selected groundspeeds.
The approach lighting systems and the visual approach lights
are depicted on the airport sketch. White on black symbols
are used for identifying pilot-controlled lighting (PCL).
Runway lighting aids are also noted (e.g., REIL, HIRL), as
is the runway centerline lighting (RCL). [Figure 8-22]
The airport diagram shows the paved runway configuration
　
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