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compared to airplane instrument flight. Many new helicopter instrument approach procedures have been
developed to take advantage of advances in both avionics and helicopter technology.
STANDARD INSTRUMENT APPROACH PROCE-
DURES TO AN AIRPORT
Helicopters flying standard instrument approach procedures (SIAP) must adhere to the MDA or decision altitude for Category A airplanes, and may apply the Part
97.3(d-1) rule to reduce the airplane Category A visibility by half but in no case less than 1/4 SM or 1200
RVR [Figure 7-10 on page 7-11]. The approach can be
initiated at any speed up to the highest approach category authorized; however, the speed on the final
approach segment must be reduced to the Category A
speed of less than 90 KIAS before the MAP in order to
apply the visibility reduction. A constant airspeed is
recommended on the final approach segment to comply
with the stabilized approach concept since a decelerating approach may make early detection of wind shear
on the approach path more difficult. [Figure 7-8]
When visibility minimums must be increased for inoperative components or visual aids, use the Inoperative
Components and Visual Aids Table (provided in the
front cover of the U.S. Terminal Procedures) to derive
the Category A minima before applying any visibility
reduction. The published visibility may be increased
above the standard visibility minima due to penetrations of the 20:1 and 34:1 final approach obstacle
identification surfaces (OIS). The minimum visibility
required for 34:1 penetrations is 3/4 SM and for 20:1
penetrations 1 SM (see Chapter 5). When there are
penetrations of the final approach OIS, a visibility
credit for approach lighting systems is not allowed for
either airplane or helicopter procedures that would
result in values less than the appropriate 3/4 SM or 1
SM visibility requirement. The Part 97.3 visibility
reduction rule does not apply, and you must take precautions to avoid any obstacles in the visual segment.
Procedures with penetrations of the final approach
OIS will be annotated at the next amendment with
“Visibility Reduction by Helicopters NA.”
Until all the affected SIAPs have been annotated, an
understanding of how the standard visibilities are
established is the best aid in determining if penetrations of the final approach OIS exists. Some of the
variables in determining visibilities are: DA/MDA
height above touchdown (HAT), height above airport
(HAA), distance of the facility to the MAP (or the
runway threshold for non-precision approaches), and
approach lighting configurations.
The standard visibility requirement, without any
credit for lights, is 1 SM for nonprecision approaches
and 3/4 SM for precision approaches. This is based on
a Category A airplane 250-320 feet HAT/HAA, and
for nonprecision approaches a distance of 10,000 feet
or less from the facility to the MAP (or runway
threshold). For precision approaches, credit for any
approach light configuration, and for non-precision
approaches (with a 250 HAT) configured with a
MALSR, SSALR, or ALSF-1 normally results in a
published visibility of 1/2 SM.
Consequently, if an ILS is configured with approach
lights or a nonprecision approach is configured with
either MALSR, SSALR, or ALSF-1 lighting configurations and the procedure has a published visibility of 3/4
SM or greater, a penetration of the final approach OIS
may exist. Also, pilots will be unable to determine
whether there are penetrations of the final approach
OIS if a nonprecision procedure does not have
approach lights, or is configured with ODALS, MALS,
or SSALS/SALS lighting since the minimum published
visibility will be 3/4 SM or greater.
As a rule of thumb, approaches with published visibilities of 3/4 SM or more should be regarded as having
final approach OIS penetrations and care must be taken
to avoid any obstacles in the visual segment.
Approaches with published visibilities of 1/2 SM or
less are free of OIS penetrations and the visibility
reduction in Part 97.3 is authorized.
Figure 7-8. Helicopter Use of Standard Instrument Approach Procedures.
Helicopter Use of Standard Instrument Approach Procedures
Procedure Helicopter Visibility Minima Helicopter MDA/DA Maximum Speed Limitations
The greater of: one half the
Category A visibility minima,
1/4 statute mile visibility, or
1200 RVR unless annotated
(Visibility Reduction by Helicopters NA.)
As published
As published
Copter Procedure
GPS Copter Procedure
As published for
Category A
As published
As published
The helicopter may initiate the final approach segment
　
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本文鏈接地址：Instrument Procedures Handbook (IPH)儀表程序手冊下(155)