曝光台 注意防骗
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staggered separation of aircraft on the adjacent
localizer/azimuth course is required.
In order to successfully accomplish parallel,
simultaneous parallel, and converging ILS
approaches, flight crews and air traffic controllers
have additional responsibilities. When multiple
instrument approaches are in use, ATC will advise
flight crews either directly or through ATIS. It is
the pilot’s responsibility to inform ATC if unable or
unwilling to execute a simultaneous approach.
Pilots must comply with all ATC requests in a
timely manner, and maintain strict radio discipline,
including using complete aircraft call signs. It is
also incumbent upon the flight crew to notify ATC
immediately of any problems relating to aircraft
communications or navigation systems. At the very
least, the approach procedure briefing should cover
the entire approach procedure including the
approach name, runway number, frequencies, final
approach course, glide slope intercept altitude, DA
or DH, and the missed approach instructions. The
review of autopilot procedures is also appropriate
when making coupled ILS or MLS approaches.
As with all approaches, the primary navigation
responsibility falls upon the pilot in command. ATC
instructions will be limited to ensuring aircraft separation. Additionally, missed approach procedures are
normally designed to diverge in order to protect all
involved aircraft. ILS approaches of all types are
afforded the same obstacle clearance protection and
design criteria, no matter how capacity is affected by
multiple ILS approaches. [Figure 5-37]
ILS APPROACH CATEGORIES
There are three general classifications of ILS
approaches — CAT I, CAT II, and CAT III (autoland).
The basic ILS approach is a CAT I approach and
requires only that pilots be instrument rated and current, and that the aircraft be equipped appropriately.
CAT II and CAT III ILS approaches typically have
lower minimums and require special certification for
operators, pilots, aircraft, and airborne/ground
equipment. Because of the complexity and high cost
of the equipment, CAT III ILS approaches are used
primarily in air carrier and military operations.
[Figure 5-38]
CAT II AND III APPROACHES
The primary authorization and minimum RVRs
allowed for an air carrier to conduct CAT II and III
approaches can be found in OpsSpecs – Part C. CAT II
and III operations allow authorized pilots to make
instrument approaches in weather that would otherwise
be prohibitive.
While CAT I ILS operations permit substitution of
midfield RVR for TDZ RVR (when TDZ RVR is not
5-51
available), CAT II ILS operations do not permit any
substitutions for TDZ RVR. The touchdown zone
RVR system is required and must be used. Touchdown
zone RVR is controlling for all CAT II ILS operations.
200 Feet Current and
Previous
ILS Final Approach Criteria (for Primary Protected Airspace)
Final Approach Area
50,200 Feet Current
50,000 Feet Previous
1,400 Feet Current
1,000 Feet Previous
12,152 Feet Current
16,000 Feet Previous
Figure 5-37. ILS Final Approach Segment Design Criteria.
200
100
0 150 700 1,200 1,800 2,400
CAT II
CAT I
CAT III c
CAT III b
CAT IIIa
Runway Visual Range (feet)
Decision Height (feet AGL)
Photo Courtesy of Cessna
The lowest authorized ILS minimums, with all required ground and airborne systems components operative, are
• CAT I — Decision Height (DH) 200 feet and Runway Visual Range (RVR) 2,400 feet (with touchdown
zone and centerline lighting, RVR 1800 feet),
• CAT II — DH 100 feet and RVR 1,200 feet,
• CAT IIIa — No DH or DH below 100 feet and RVR not less than 700 feet,
• CAT IIIb — No DH or DH below 50 feet and RVR less than 700 feet but not less than 150 feet, and
• CAT IIIc — No DH and no RVR limitation.
NOTE: Special authorization and equipment are required for CAT II and III.
Figure 5-38. ILS Approach Categories.
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The weather conditions encountered in CAT III operations range from an area where visual references are
adequate for manual rollout in CAT IIIa, to an area
where visual references are inadequate even for taxi
operations in CAT IIIc. To date, no U.S. operator has
received approval for CAT IIIc in OpsSpecs.
Depending on the auto-flight systems, some airplanes
require a DH to ensure that the airplane is going to land
in the touchdown zone and some require an Alert
Height as a final crosscheck of the performance of the
auto-flight systems. These heights are based on radio
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Instrument Procedures Handbook (IPH)仪表程序手册上(136)
