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in a specific type of aircraft, the crew training, and the
type of equipment installed at a particular airport, these
operators can depart from appropriately equipped runways with as little as 300 feet RVR. Additionally,
OpsSpecs outline provisions for approach minimums,
alternate airports, and weather services in Part 119 and
FAA Order 8400.10, Air Transportation Operations
Inspector’s Handbook.
HEAD-UP GUIDANCE SYSTEM
As technology improves over time, the FAA is able to work
in cooperation with specific groups desiring to use these
new technologies. Head-up guidance system (HGS) is an
example of an advanced system currently being used by
some airlines. Air carriers have requested the FAA to
approve takeoff minimums at 300 feet RVR. This is the
lowest takeoff minimum approved by OpsSpecs. As stated
earlier, only specific air carriers with approved, installed
equipment, and trained pilots are allowed to use HGS for
decreased takeoff minimums. [Figure 2-9]
CEILING AND VISIBILITY REQUIREMENTS
All takeoffs and departures have visibility minimums
(some may have minimum ceiling requirements)
incorporated into the procedure. There are a number
of methods to report visibility, and a variety of ways to
distribute these reports, including automated weather
observations. Flight crews should always check the
weather, including ceiling and visibility information,
prior to departure. Never launch an IFR flight without
obtaining current visibility information immediately
prior to departure. Further, when ceiling and visibility
minimums are specified for IFR departure, both are
applicable.
Weather reporting stations for specific airports across
the country can be located by reviewing the A/FD.
Weather sources along with their respective phone
numbers and frequencies are listed by airport.
Frequencies for weather sources such as automatic terminal information service (ATIS), digital automatic
terminal information service (D-ATIS), Automated
Weather Observing System (AWOS), Automated
Surface Observing System (ASOS), and FAA
Automated Flight Service Station (AFSS) are published on approach charts as well. [Figure 2-10]
RUNWAY VISUAL RANGE
Runway visual range (RVR) is an instrumentally
derived value, based on standard calibrations, that
represents the horizontal distance a pilot will see down
the runway from the approach end. It is based on the
sighting of either high intensity runway lights or on the
Figure 2-9. HGS Technology.
Figure 2-10. Frequencies for Weather Information are listed on
Approach and Airport Charts.
2-9
visual contrast of other targets whichever yields the
greater visual range. RVR, in contrast to prevailing or
runway visibility, is based on what a pilot in a moving
aircraft should see looking down the runway. RVR is
reported in hundreds of feet, so the values must be converted to statute miles if the visibility in statute miles is
not reported. [Figure 2-11] This visibility measurement
is updated every minute; therefore, the most accurate
visibility report will come from the local controller
instead of a routine weather report. Transmissometers
near the runway measure visibility for the RVR report.
If multiple transmissometers are installed, they provide
reports for multiple locations, including touchdown
RVR, mid-RVR, and rollout RVR. RVR visibility may
be reported as RVR 5-5-5. This directly relates to the multiple locations from which RVR is reported and indicates
500 feet visibility at touchdown RVR, 500 feet at mid-
RVR, and 500 feet at the rollout RVR stations.
RVR is the primary visibility measurement used by Part
121 and 135 operators, with specific visibility reports
and controlling values outlined in their respective
OpsSpecs. Under their OpsSpecs agreements, the operator must have specific, current RVR reports, if available,
to proceed with an instrument departure. OpsSpecs also
outline which visibility report is controlling in various
departure scenarios.
RUNWAY VISIBILITY VALUE
Runway visibility value (RVV) is the distance down
the runway that a pilot can see unlighted objects. It is
reported in statute miles for individual runways. RVV,
like RVR, is derived from a transmissometer for a particular runway. RVV is used in lieu of prevailing visibility in determining specific runway minimums.
PREVAILING VISIBILITY
Prevailing visibility is the horizontal distance over
which objects or bright lights can be seen and identified
over at least half of the horizon circle. If the prevailing
visibility varies from area to area, the visibility of the
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Instrument Procedures Handbook (IPH)仪表程序手册上(45)
