HELICOPTER INSTRUMENT APPROACHES

Helicopter instrument flight is relatively new when 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 PROCEDURES 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]

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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 approachOIS 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.