Chap 2 Page 2-13
5. When the radar operator determines the helicopter's track will not avoid all obstacles by at least 0.5 NM.
(f) When within close proximity of the MAP, if visual contact is not established, make only minor heading changes to avoid flight closer than 0.5 NM to any radar returns while following GPS or LORAN C course guidance during a missed approach.
(g) Lost communication procedure after the missed approach: Execute the published missed approach procedure and then proceed direct to the alternate at the MEA.
(7) Minimums:
(a) Takeoff Minimums:
1. The standard takeoff visibility for offshore landing sites is 1/2 SM.
2. When departing an offshore landing site, avoid all obstructions by at least 0.5 NM when below 900 ft MSL.
3. For departures from platforms that have no approved procedure, maintain VFR until able to climb through an obstacle clear area to the MEA.
(b) Landing Minimums:
1. RA 200 & 3/4 SM visibility.
2. 250 MSL & 3/4 SM visibility.
3. Requirements for charting the MDA:
• 200 ft RA: Radio altimeter must be operative.
• 250 ft MSL: Barometric altitude for use when radio altimeter is not available.
When the barometric altimeter setting is received from a source that is more than 5 NM from the landing site, increase the MDA by 5 ft for each mile in excess of 5 NM. The maximum distance for a remote altimeter setting source from a landing site is 75 NM.
(c) Alternate Minimums and Requirements: Standard alternate minimums of 800 ft ceiling and 2 SM visibility for nonprecision approaches apply for OSAP’s to be used as an alternate.
Requirements to establish an alternate are listed below:
Page 2-14 Chap 2
1. Approved source of weather observations and reports.
2. Two-way communications with aircraft making an approach.
3. Any required onshore alternate requires a standard or special instrument approach procedure other than GPS or LORAN C that is anticipated to be operational at the estimated time of arrival.
Chap 3 Page 3-1 CHAPTER 3. AIRBORNE RADAR APPROACHES
3-1. ARA SYSTEM COMPONENT REQUIREMENTS. (See appendixes 2 and 3 for sample LOA’s and OpsSpecs). This section applies to helicopter ARA procedures for offshore landing sites conducted under IFR. The procedures criteria in this AC apply to airborne weather radar with mapping mode that has a demonstrated navigational capability acceptable to the Administrator for ARA procedures.
The airborne weather radar systems that have proved suitable for use as primary instrument approach aids are short-range pulse radars, manufactured and approved for the purpose of weather avoidance rather than navigation. Minimum system components for procedures based on airborne radar only (with or without beacon capability) are as follows:
a. Airborne Radar. Radar system minimum requirements:
(1) Stabilized 120°/ 60° sector scanning antenna with scan rates of no less than 12 per minute and 24 per minute respectively.
(2) Adjustable light display.
(3) Alphanumeric display for selected ranges and azimuth markers; however, alphanumeric display for selected ranges is not required when:
(a) A positive means for determining selected scale is available, and
(b) The radar operator is appropriately trained.
(4) The indicated range error should not exceed ± 0.2 NM for display ranges of 5 NM or less.
(5) The lowest selectable range display should be at least 2.5 NM with a range mark display of 0.5 NM to meet the authorized landing minimums. Equipment that provides a lowest range display of 5 NM with a range mark display of 1 NM may be used, but a 1/4 NM penalty is imposed on established visibility minimums.
(6) Tilt control ±± 15°.
(7) Test pattern.
(8) Primary mode (beacon mode may be necessary for cluster approach).
(9) Fault monitor or self-test.
(10) An operational course bearing cursor that provides course guidance is required to fly cluster approaches below obstacles.
(11) With zero pitch and roll signals applied to the antenna scanner representing level flight attitude, the indicator update strobe line should indicate the antenna beam center to within ± 3° at any scan angle.
Page 3-2 Chap 3 NOTE: A radio altimeter must be installed and operational before descent to the RA MDA is authorized.
b. Radio Altimeter. The radio altimeter must meet the requirements of TSO C87.
c. Offshore Heliport Facilities.
When required to ensure positive identification of targets, a radar transponder beacon should be evaluated during the approval process.
3-2. AIRWORTHINESS. As a minimum, ARA systems shall meet the airworthiness requirements of TSO C63 or C102. Installation of an ARA system for IFR use is a major change in type design, and the provisions of 14 CFR Parts 21.97, 43.5, and 43.7 apply. System installation requirements are:
a. System controls and data displays must be conveniently accessible and visible to radar operators at their duty stations. The system controls should be protected against inadvertent operation.
b. Electrical power for the system should be obtained from a bus that provides maximum reliability for electrical power without jeopardizing other essential or emergency loads.
c. The ARA system should not be a source of objectionable electromagnetic interference and shall not be adversely affected by electromagnetic interference from other helicopter equipment.
d. Any probable malfunction of the ARA system should not adversely affect the normal operation of other systems or equipment installed in the helicopter.
e. System performance should not be adversely affected by helicopter attitude, altitude, or main rotor RPM normally encountered in flight operations.
3-3. MAINTENANCE.
a. Airborne weather radar and radio altimeter maintenance shall be performed in accordance with 14 CFR Part 43 and the manufacturer's instructions or in accordance with a manual under an FAA-approved maintenance program. Records of maintenance should be entered in the helicopter maintenance records required by 14 CFR Part 43.9 or in the records required by the operator's approved maintenance program. Following repair or alteration, the system should be checked by appropriate ground and flight evaluations before predicating any operation on its use. Compatibility of replacement parts and components should be assured. Ground-based radar beacon or reflector maintenance will be performed in accordance with the manufacturer's instructions and must be under an FAA-approved maintenance program.
b. Each operator’s maintenance program must be approved by the FSDO issuing the ARA authorization before any ARA operations in instrument IMC may be conducted.
3-4. INSPECTION AND TEST PROCEDURES. IFR ARA systems that are not under an FAA-approved maintenance program should be maintained under inspection and test procedures that ensure the equipment continues to be capable of navigation with at least the degree of accuracy required for original approval. These procedures should include methods for analyzing malfunctions and defects to
Chap 3 Page 3-3 determine that established inspections and tests reasonably assure maintenance of equipment accuracy.
Procedures and intervals for tests and inspections should be adjusted in accordance with results of the analysis. In addition to the equipment manufacturer's recommendations, the following test and inspections should be included:
a. A visual inspection to determine condition and security of equipment mounting, electrical wiring and connectors, radome, antennas and cables, wave guide and couplings, indicator mounts, knobs, etc.
b. A functional test of the airborne weather radar mapping mode and radio altimeter to determine operating conditions. Tests should be performed in accordance with appropriate manufacturer's procedures.
c. Other appropriate tests and inspections to determine whether the complete system is operating properly.
3-5. APPROVED WEATHER OBSERVATION AND REPORTING REQUIREMENTS. Refer to FAA Order 8400.10, Volume 4, Aircraft Equipment and Operational Authorizations, Chapter 7. Rotorcraft Authorizations and Limitations, Section 1. IFR Offshore Operations, and Title 14 CFR Part 91, Subpart B - Flight Rules/General.
3-6. TRAINING PROGRAM AND FLIGHT CREWMEMBER EXPERIENCE. Before conducting ARA operations in IMC, each flight crewmember should have:
a. Ten hours of flight crew experience operating IFR (at either crew station) in the offshore route structure.
b. A minimum of ten ARA’s and at least four from each crewmember position. This may be reduced by the POI for the certificate holder based on the flight crew experience and proficiency.
c. All training must be a matter of record.
d. After completing ARA training, each flight crewmember must pass an ARA flight proficiency check. They may then be authorized to use the ARA to 100 ft above the lowest established ceiling minimums and 1/2 SM above the lowest established visibility minimums. Each crewmember must then fly and record ten additional ARA’s before receiving authorization to conduct operations to the lowest established ceiling and visibility minimums required by the operator. The POI may reduce these requirements based on total crew experience provided the pilot-in-command meets all the conditions of this paragraph.
e. The flight proficiency check is an annual requirement.
f. Helicopter flight simulators specifically approved for ARA training by the National Flight Simulator Evaluation Team and the POI assigned to the operator may be used for any amount of required training.
g. Operators requesting authority to use ARA’s are required to satisfactorily train their flight crewmembers under an FAA-approved training program before beginning ARA operations. Operators
Page 3-4 Chap 3 should submit a proposed training program to the CHDO for approval. (See appendix 4 for sample training program.)
3-7. PROCEDURE DEVELOPMENT CRITERIA. Approach chart examples are in appendix 5, figures 5-3 and 5-4. A certificated air carrier submits a written request with the proposed chart through the CHDO POI to the FSDO having jurisdiction over the area of intended operation. All other operators submit requests directly to the FSDO having jurisdiction over the area of intended operation. The FSDO having jurisdiction forwards the procedure to the regional AWO program manager for approval of the procedure and coordination with air traffic elements and the regional Flight Procedures Office (FPO).
Coordination with the FPO is required when expenses are incurred by the FAA for the development and/or flight check of a procedure. (See appendix 1, Request For Approval of OSAP, ARA, or HEDA Procedures.) The following note is charted in the plan view of the procedure:
“SPECIAL AUTHORIZATION REQUIRED.
WX RADAR IN MAPPING MODE REQUIRED.”
a. Procedure Identification. The procedure is identified as “Copter ARA” with the name of the cluster or rig, e.g. “WINTR 120.” If the procedure requires beacon capability, the procedure will be annotated “Beacon Required.” A note specifying the platform containing the beacon is printed on the plan view of the chart, e.g. “Beacon on Platform 1.” (See appendix 5, figure 5-4.)
b. Procedure Construction. For ARA procedures, obstructions 50 ft or higher above the surface are considered obstacles. Where landing sites or approach targets are less than 100 ft above the surface, all obstacles within 50 ft of the site’s height shall be charted. An ARA procedure to an offshore site has two areas, the intermediate area and the final approach area. Missed approach airspace is contained within the two areas (see figures 2-4 and 3-1). Determine whether the procedure is for a single landing site or for a cluster of landing sites. Identify the final approach area. Connect it to the en route structure by an overlying intermediate area that is used for transition. The procedure shall also contain the land side navigation facility, the route designation, and the location of the destination site or landing site cluster. For en route construction, apply paragraph 2-7a of this AC. The ARA chart contains a table to determine the time required to fly an outbound 4 NM leg for a teardrop procedure turn. The intermediate and final segment construction is described in paragraph 3-7c. Sample ARA approach charts are contained in appendix 5, figures 5-3 and 5-4.
c. Single Approach Target Procedure Construction. This procedure provides for an into-the-wind final descent to the landing site from any direction, depending on the surface wind reported in the approach target area and the operating procedures selected by the flight crew (see figure 3-1).
(1) The IF is located on the en route course centerline not less than 10 NM or more than 20 NM from the approach target.
(2) The required obstacle clearance (ROC) for the intermediate approach area is 500 ft above the highest known obstacle in the intermediate approach area until arrival at the FAP inbound. The lowest charted minimum altitude is 600 ft MSL and is charted as follows:
“600 ft MSL or no lower than the barometric MDA adjusted for RASS.”
This note is required to assure that the FAP altitude is no lower than the MDA adjusted for the RASS.
Chap 3 Page 3-5
(3) The intermediate approach area is centered on a straight course between the IF and the approach target. The intermediate approach area is bounded by an arc having a 7 NM radius centered on the approach target. Straight lines drawn tangent to the arc extend the area to the en route boundaries at the IF. The intermediate approach area overlies and includes the entire final approach area.
(4) Final Approach Area. The final approach area is the area contained within a circle with a 4 NM radius centered on the approach target.
d. Single Approach Target Landing Minimums:
(1) The RA is the higher of:
RA 200 ft or 50 ft above the landing site.
The RA MDA visibility is 3/4 SM.
.
Page 3-6 Chap 3
(2) The barometric MDA minimums are computed by adding 250 ft to the highest obstacle in the final approach area and this value is rounded up to the next 20 ft increment. In figure 3-1, the highest obstacle in the final approach area is a 120 ft oil derrick. A ROC of 250 ft is added to the MSL height of this derrick. The MDA is rounded up to 380 ft MSL. An adjustment is made for the RASS when the source is more than 5 NM from the landing site. The barometric MDA visibility is 1/ 2 SM.
e. Cluster Approach Target Procedure Construction. The procedure provides for an into-the-wind final descent to the cluster area from any direction, depending on the surface wind reported in the cluster area, and the operating procedures selected by the flight crew. Procedures for a cluster approach target area are shown in figure 3-2.
(1) The IF is located on the en route course centerline not less than 10 NM and/or more than 20 NM from the nearest landing site or approach target in the cluster.
(2) The ROC for the intermediate approach segment is 500 ft above the highest known obstacle in the intermediate approach area. The lowest intermediate altitude is 700 ft MSL and is charted as follows:
“700 ft MSL or no lower than the barometric MDA adjusted for RASS.”
This note is required to assure that the FAP altitude is no lower than the MDA adjusted for the RASS.
(3) The intermediate approach area is bounded by arcs whose radii are centered on each outlying landing site or approach target in the cluster. Each radius is 7 NM. Straight lines drawn tangent to arcs at the lateral extremities of this area extend the area to the en route boundaries at the IF. The intermediate approach area overlays and includes the entire final approach area.
(4) FAP. The FAP can be any point on the arcs defining the limits of the final approach area.
The FAP is a point inbound to the landing site or approach target at 4 NM on the radar display.
(5) The final approach area is bounded by arcs whose radii are centered on each outlying landing site or approach target in the cluster. Each radius is 4 NM.
f. Cluster Approach Target Landing Minimums. See figure 3-2.
(1) The RA is the highest of the following:
200 ft RA or 50 ft RA above the landing site elevation or 100 ft RA above the highest obstruction located within a cluster if a course bearing cursor is not used.
The RA MDA visibility minimum is 3/4 SM.
(2) The barometric MDA minimums are computed by adding a ROC of 250 ft to the highest obstacle in the final approach area and this is rounded up to the next 20 ft increment. In figure 3-2, the highest obstacle in the final approach area is a 166 ft oil derrick. A ROC of 250 ft is added to this value.
The MDA is rounded up to 420 ft MSL.
*The barometric MDA visibility is 1/2 SM or 3/4 SM.
Chap 3 Page 3-7 *(a) If the lowest descent altitude is above obstructions, the lowest visibility is 1/2 SM.
*(b) If the lowest descent altitude is below obstructions, the lowest visibility is 3/4 SM.
After visual reference with the landing site or approach target is established, the pilot proceeds visually to the landing site. Chart the following note:
“PROCEED VISUALLY TO THE LANDING SITE.”
Chart the following note for a remote altimeter setting source for the single and cluster approach target procedures using barometric MDA’s:
“Altimeter source more than 5 NM but less than 75 NM, increase MDA 5 ft for each mile over 5 NM from approach target.”
Page 3-8 Chap 3
g. Missed Approach Segment. The missed approach procedure is constructed for the single and cluster approaches in the same way. The missed approach begins at the MAP and ends at an appropriate point or fix where intermediate approach or en route obstacle clearance is provided.
(1) MAP. The MAP is no closer to the approach target than the minimum authorized visibility for landing, as observed on the radar display.
(2) Missed Approach Area. The missed approach area is the clear zone left or right of the final approach course, 1.5 NM long and 2.0 NM wide (see figure 3-3).
(3) Chart the following missed approach: “Climbing turn into the clear zone, then climbing turn to the MEA direct to the IF, or as directed by ATC.”
h. Missed Approach Holding. Chart the following holding instructions:
“Hold over the intermediate fix on the inbound course, 1 minute legs, maintain the MEA or as directed by ATC.”
Chap 3 Page 3-9
3-8. OPERATIONAL APPLICATIONS.
a. Course Guidance. The radar operator interprets radar returns on the cockpit display and vectors the helicopter clear of observed targets to the MAP. The nature of offshore operations is such that numerous permanent or transient targets may be displayed on radar. For ARA procedures, obstructions 50 ft or higher above the surface are considered obstacles. Where landing sites are less than 100 ft above the surface, all obstacles within 50 ft of the landing site's height are charted. Those obstacles depicted within the final approach area on the ARA approach chart will include known height; however, those objects not shown on the chart must be considered moving obstacles of unknown height that radar provides means of lateral rather than vertical clearance on final approach. Before final approach, vertical clearance over surface obstacles is assured by adherence to specified minimum altitudes. Missed approach obstacle avoidance is provided by an IMMEDIATE climbing turn to a clear zone.
b. Planning. Operational experience has shown that an ARA procedure to a single landing site is a relatively uncomplicated operation. However, operations to and from a landing site cluster increase potential for operator error. This potential can be reduced by careful evaluation of the procedure during the approval process, adequate training by the operator, proper approach planning, and use of aids such as a course bearing cursor to supplement basic airborne radar.
(1) Target Identification. Prompt and positive identification of the landing site solely by the use of mapping mode can be difficult when returns from moving targets confuse the pattern of the targets depicted in a cluster area. Where identification of a cluster cannot be assured in the mapping mode and approved air navigation facilities (NAVAID’s) are unavailable to resolve target ambiguity, the approving authority should, as an option, consider whether to require installation of a radar beacon.
(2) Approach Planning. To assure obstacle-free flightpaths on final and missed approach, it is necessary to thoroughly scan and evaluate these areas before the approach is initiated.
(3) Overshooting the MAP. Range errors caused by the time required for target update, possible equipment malfunctions, equipment accuracy, and crew reaction time may cause the MAP to be closer to the landing site than the desired MAP. While turning during the missed approach, airborne radar cannot be relied upon to provide lateral obstacle avoidance. It is, therefore, imperative that crews be trained to execute an immediate climbing turn toward a clear zone at the MAP. To ensure obstacle clearance, it is necessary to initiate the missed approach at the designated MAP. Otherwise the flightpath could transgress an area that does not provide missed approach obstacle clearance.
(4) Use of Course Bearing Cursor. A final approach flown by maintaining the approach target on the course bearing cursor increases the probability that the helicopter will be on the final approach course upon arrival at the designated MAP.
c. Flexibility. An offshore ARA requires procedural flexibility to provide options for the crew in planning the approach. The procedure must provide a transition from an en route fix to a downwind position before beginning the final approach. This requires a provision in the procedure for selection of a FAP that accounts for variations in wind conditions. On a cluster approach, where the close proximity of other targets does not permit sufficient lateral clearance for an ARA directly to the landing site, the approach can be made to a more suitable approach target located on the perimeter of the cluster and proceed visually to the landing site. Selection of an approach target depends upon existing wind conditions that in turn determine the location of the FAP, landing site selection, and missed approach clear zone. An
Page 3-10 Chap 3 approved ARA procedure will provide an into-the-wind final descent to a cluster perimeter or to a single landing site from any direction.
d. System Limitations and Procedural Consideration.
(1) Blind Flightpath Segments.
(a) If the FAP is not established directly downwind and the approach course is not directly upwind, a homing approach will result. A homing approach can result in blind flightpath segments. This means that, with wind speeds as low as one-third of the airspeed, segments of the flightpath may not be visible to the radar operator when using a 40° sweep angle. When using a 120° sweep angle, a wind speed of 0.9 of the airspeed may cause blind flightpath segments. Homing approaches can occur whenever the wind speed to airspeed ratio is greater than or equal to: Sin sweep angle2 .
(b) In a no-wind condition, a target return 1.0 NM to the left or right of the 0° azimuth mark will disappear from the radar display at the following ranges as the distance to the target decreases:
Sweep Angle Range 120° 0.58 NM 80° 1.19 NM 60° 1.73 NM 40° 2.75 NM
(c) When a wind causes a 10° crab, or in a 10° offset approach, a target 1.0 NM to the side of the 0° azimuth mark away from the crab or offset will disappear at the following ranges:
Sweep Angle Range 120° 0.84 NM 80° 1.73 NM 60° 2.75 NM 40° 5.67 NM
(d) Considering that radar is used to avoid obstacles laterally, the importance of establishing an accurate FAP should be apparent.
(e) Missed Approach Area. The clear zone in figure 3-3 is designed to protect the missed approach. The dimensions of this figure are based on a helicopter being on track at the MAP with a ground speed of 70 knots and a climb gradient of no less than 304 ft per NM (355 ft per minute).
e. Operators using airborne radar for offshore instrument flight should develop detailed operational procedures to ensure clearly defined flight crewmember duties for a two-pilot operation.
Confusion or misunderstanding with respect to responsibility and authority during an airborne radar operation can be detrimental to safety. The following operating procedures were found both safe and usable during procedural development testing by NASA and the FAA.
(1) En Route. Offshore en route navigational guidance may be based upon any approved system appropriate to the route flown. The last en route fix is also the intermediate approach fix and is