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Flight Advisory Service (Flight Watch), take weather
observations, issue airport advisories, and advise Customs
and Immigration of transborder flights.
Pilot Briefers at flight service stations render preflight,
in-flight, and emergency assistance to all pilots on
request. They give information about actual weather
conditions and forecasts for airports and flight paths,
relay air traffic control instructions between controllers
and pilots, assist pilots in emergency situations, and
initiate searches for missing or overdue aircraft.
FSSs/AFSSs provide information to all airspace users,
including the military. In October 2005, operation of
all FSSs/AFSSs, except those in Alaska, was turned
over to the Lockheed Martin Corporation. In the
months after the transition, 38 existing AFSSs are
slated to close, leaving 17 “Legacy” stations and 3
“Hub” stations. Services to pilots are expected to be
equal to or better than prior to the change, and the
contract is expected to save the government about
$2.2 billion over ten years.
FLIGHT PLANS
Prior to flying in controlled airspace under IFR conditions or in Class A airspace, pilots are required to file a
flight plan. IFR (as well as VFR) flight plans provide
air traffic center computers with accurate and precise
routes required for flight data processing (FDP 1
). The
computer knows every route (published and unpub-
1
FDP maintains a model of the route and other details for each aircraft.
Figure 1-9. Terminal Radar Approach Control.
1-11
lished) and NAVAID, most intersections, and all airports, and can only process a flight plan if the proposed
routes and fixes connect properly. Center computers
also recognize preferred routes and know that forecast
or real-time weather may change arrival routes.
Centers and TRACONs now have a computer graphic
that can show every aircraft on a flight plan in the U.S.
as to its flight plan information and present position.
Despite their sophistication, center computers do not
overlap in coverage or information with other Centers,
so that flight requests not honored in one must be
repeated in the next.
RELEASE TIME
ATC uses an IFR release time 2
in conjunction with
traffic management procedures to separate departing
aircraft from other traffic. For example, when controlling departures from an airport without a tower, the
controller limits the departure release to one aircraft at
any given time. Once that aircraft is airborne and radar
identified, then the following aircraft may be released
for departure, provided they meet the approved radar
separation (3 miles laterally or 1,000 feet vertically)
when the second aircraft comes airborne. Controllers
must take aircraft performances into account when
releasing successive departures, so that a B-747 HEAVY
aircraft is not released immediately after a departing
Cessna 172. Besides releasing fast aircraft before slow
ones, another technique commonly used for successive
departures is to have the first aircraft turn 30 to 40
degrees from runway heading after departure, and then
have the second aircraft depart on a SID or runway heading. Use of these techniques is common practice when
maximizing airport traffic capacity.
EXPECT DEPARTURE CLEARANCE TIME
Another tool that the FAA is implementing to increase
efficiency is the reduction of the standard expect departure clearance time 3
(EDCT) requirement. The FAA has
drafted changes to augment and modify procedures contained in Ground Delay Programs (GDPs). Airlines may
now update their departure times by arranging their
flights’ priorities to meet the controlled time of arrival.
In order to evaluate the effectiveness of the new software and the airline-supplied data, the actual departure
time parameter in relation to the EDCT has been
reduced. This change impacts all flights (commercial
and GA) operating to the nation’s busiest airports.
Instead of the previous 25-minute EDCT window (5
minutes prior and 20 minutes after the EDCT), the new
requirement for GDP implementation is a 10-minute
window, and aircraft are required to depart within 5 minutes before or after their assigned EDCT. Using reduced
EDCT and other measures included in GDPs, ATC aims
at reducing the number of arrival slots issued to accommodate degraded arrival capacity at an airport affected
by weather. The creation of departure or ground delays
is less costly and safer than airborne holding delays in
the airspace at the arrival airport.
MANAGING SAFETY AND CAPACITY
SYSTEM DESIGN
The CAASD is aiding in the evolution towards free flight
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Instrument Procedures Handbook (IPH)仪表程序手册下(16)
