3-6 adjustment is made for the RASS when the source is more than 5 NM from the landing site. The barometric MDA visibility is ½ sm.
3.6.3 Cluster Approach Target Procedure Construction. This 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 procedure selected by the flightcrew.
A plan view for a cluster instrument approach target area is shown in Figure 3-2.
3.6.3.1 IF. 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.
3.6.3.2 ROC. The ROC for the intermediate operation segment is 500 ft above the highest known obstacle in the intermediate operation area. The lowest intermediate altitude is 700 ft MSL and is charted as follows: “700′ 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.
3.6.3.3 Intermediate Approach Area. 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.
3.6.4 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.
3.6.4.1 Final Approach Area. 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.
3.6.5 Cluster Approach Target Landing Minimums (see Figure 3-2).
3.6.5.1 Radio Altimeter. The RA is the highest of the following: 200 ft RA, 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 ¾ sm.
3.6.5.2 Barometric MDA. 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 operation 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.
Note: The barometric MDA visibility is ½ sm or ¾ sm.
• If the lowest descent altitude is above obstructions, the lowest visibility is ½ sm.
• If the lowest descent altitude is below obstructions, the lowest visibility is ¼ sm.
3.6.5.3 Proceeding Visually. 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."
3.6.5.4 Chart Note. Chart the following note for a RASS for the single and cluster operation target operations using barometric MDAs: iAltimeter source more than 5 NM but less than 75 NM, increase MDA 5' for each mile over 5 NM from operation target."
Figure 3-2. Cluster Approach Target Area Plan View NOT TO SCALE Minimum Descent Altitude (MDA) Add 250 ft to the Highest Obstacle in the Final Approach Area. Round Up to the Next 20 ft Increment.
Example:
7 NM Obstacle Height = 166 ft MSL ROC = +250 ft MDA = 416 ft MSL Round To: 420 ft MSL Nearest Platform in Cluster More Than 20 NM from Not Less Than 10 NM or Intermediate Area FAPS (Includes Final (Approach Target) Landing Site -- (FAP- At Any Point on tadli and Tangent Line Approach Area nto the Wind Intermediate * Fix (IF) →*- 6 NM Landing sites - 6 NM Maintain MEA Until Crossing the IF
3.7 Missed Approach Segment.
3.7.1 Missed Approach Construction. The missed approach is constructed for the single and cluster procedures in the same way. The missed approach begins at the missed approach point (MAP) and ends at an appropriate point or fix where intermediate approach or en route obstacle clearance is provided.
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3.7.1.1 MAP. The MAP is no closer to the approach target than the minimum authorized visibility for landing, as observed on the radar display.
3.7.1.2 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, Clear Zone and Clear Sector).
3.7.1.3 Recording the Missed Approach. 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.”
3.7.2 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.”
Figure 3-3. Clear Zone and Clear Sector
3.8 Op erational Requirements.
3.8.1 Approved Weather Observation and Reporting Requirements. Refer to FAA Order 8900.1 Volume 4, Chapter 7, Section 1, Instrument Flight Rules Offshore Operations.
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3.8.2 Offshore Environment Operation. Operators approved to conduct IFR operation in the offshore environment in accordance with parts 91, 91K, and 135 for the appropriate operational approval (e.g., letter of authorization (LOA) or operations specification (OpSpec)) may comply with the requirements by any one of the following methods or one with an equivalent level of safety approved by the Administrator:
1. One station: The operation coordinate shall be within 10 NM of an approved weather reporting station.
2. Two stations: The operation coordinates shall fall within an observed area defined by the location of two approved weather reporting stations.
• The observation area centerline is established by the actual bearing between the two stations. The actual distance between the two stations is not to exceed 40 NM.
The centerline shall continue on either side of each weather station by a distance of 10 NM.
• The lateral width of the observed area may not be greater than 40 NM on either side of the established centerline.
• The resultant maximum observation area is a rectangle 60 NM by 80 NM.
3.8.3 Parts 91 and 135 Operators—Authorized Areas of En Route Operations, Limitations, and Provisions.
1. Operators conducting IFR operations in areas authorized by OpSpec B050, Authorized Areas of En Route Operations, Limitations, and Provisions, will comply with the requirements of the OpSpec.
2. Part 91 operations within oceanic airspace are covered in LOA H104, Helicopter Offshore Instrument Operations, and the applicable International Civil Aviation Organization (ICAO) Annex.
3.9 Course Guidance.
3.9.1 Use of Radar. 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 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 ensured by adherence to specified minimum altitudes. Missed approach obstacle avoidance is provided by an immediate climbing turn to a clear zone.
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3.10 Planning.
3.10.1 ARA Procedure. 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 the potential for operator error. This 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.
3.10.2 Target Identification. Prompt and positive identification of the landing site solely by the use of ground 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 ensured in ground mapping mode and approved air navigation facilities are unavailable to resolve target ambiguity, the approving authority should, as an option, consider whether to require installation of a radar beacon.
3.10.3 Approach Planning. To ensure obstacle-free flightpaths on final and missed approach, it is necessary to thoroughly scan and evaluate these areas before the operation is initiated.
3.10.4 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. Therefore, it is 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.
3.10.5 Use of Course Bearing Cursor. A final approach flown by maintaining the operation 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.
3.10.6 Flexibility. An offshore ARA requires procedural flexibility to provide options for the crew in planning the approach. The approach must provide a transition from an en route fix to a downwind position before beginning the final approach. This requires a provision in the approach for selection of a FAP that accounts for variations in wind conditions. On a cluster operation, where the close proximity of other targets does not permit sufficient lateral clearance for an ARA directly to the landing site, the operation can be made to a more suitable operation 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 approved ARA operation will provide an into-the-wind final descent to a cluster perimeter or to a single landing site from any direction.
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3.11 System Limitations and Procedural Consideration.
3.11.1 Blind Flightpath Segments. If the FAP is not established directly downwind and the final 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 0.3 of the airspeed, segments of the flightpath may not be visible to the radar operator when using a 40-degree sweep angle. When using a 120-degree 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:
sweep anglesin = 2
3.11.1.1 No-Wind Conditions. In a no-wind condition, a target return 1 NM to the left or right of the 0-degree azimuth mark will disappear from the radar display at the following ranges as the distance to the target decreases:
Table 3-1. No Wind Sweep Angle Range 120 degrees 0.58 NM 80 degrees 1.19 NM 60 degrees 1.73 NM 40 degrees 2.75 NM
3.11.1.2 Cross-Wind Conditions. When a wind causes a 10-degree crab, or in a 10-degree offset approach, a target 1 NM to the side of the 0-degree azimuth mark away from the crab or offset will disappear at the following ranges:
Table 3-2. Cross Wind Sweep Angle Range 120 degrees 0.84 NM 80 degrees 1.73 NM 60 degrees 2.75 NM 40 degrees 5.67 NM
3-12 Note: Lateral obstacle clearance is accomplished by radar and therefore it is important that the FAP is clearly established.
3.12 Missed Approach Area.
3.12.1 Clear Zone. 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/NM (355 ft/min).
3.13 Flightcrew Duties.
3.13.1 Development of Approach Procedures. Operators using airborne radar for offshore instrument flight should develop detailed approach procedures to ensure clearly defined flightcrew member 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 the National Aeronautics and Space Administration (NASA) and the FAA.
3.13.2 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 IF and is based on en route facilities. The radar operator obtains weather information and other relevant data for the landing area, identifies the destination area operation target and landing site, determines the FAP and missed approach clear zone, and discusses the operation with the other pilot before arrival at the IF.
3.13.3 Approach. The radar operator vectors the helicopter from the IF to a position downwind from the landing site and provides all further vectors to the MAP. The pilot makes no heading changes except to those vectors specified by the radar operator. At the FAP, the crew confirms the final approach course is clear of all obstacles by at least 1 NM before a descent is made to the RA MDA. Descent on final approach may not begin until the radar operator confirms that all of the following conditions exist:
1. All equipment required for the approach is operating properly.
2. The final approach track does not overlay any obstacles other than the operation target, and when descending to the RA, the clear sector is clear of all obstacles.
3. The missed approach clear zone is free of obstacles.
3.14 Missed Approach and Holding.
3.14.1 Climbing Turn. A missed approach is a climbing turn into the clear zone (Figure 3-3) then a climbing turn to the Minimum IFR Altitude (MIA) direct to the IF or as directed by air traffic control (ATC). Holding is on the IF on the inbound course with 1-min legs or as directed by ATC.
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3.14.2 Conditions for Missed Approach. A missed approach will be initiated immediately if:
1. A flightcrew member has not established visual contact with the approach target at the authorized minimum visibility distance as shown on the radar display;
2. During the inbound segment, if there is any malfunction of equipment required for the operation, unless the helicopter is in visual conditions and can continue to the landing site in visual conditions;
3. The operation target is lost during any single radar scan when the helicopter is within 2.5 NM of the target; or
4. Visual reference is lost while maneuvering to the landing site.
3.14.3 Lost Communication Procedure After the Missed Approach. Execute the published missed approach and then proceed direct to the alternate at the MIA.
3.14.4 Takeoff Minimums:
1. The standard takeoff visibility for offshore landing sites is ½ sm.
2. When departing an offshore landing site, avoid all obstructions by at least
0.5 NM when below 900 ft MSL.
3.14.5 Landing Minimums. Landing minimums must be specified as a barometric MDA based on vertical obstacle clearance, or an RA specified for use by operators with an operative radio altimeter and a course bearing cursor for operations to a cluster area. The altitude that descent is authorized depends on the following conditions:
1. All required equipment must be operational before descent to the RA MDA.
2. Descent below the barometric MDA is not authorized if:
• Lateral clearance of 1 NM cannot be maintained;
• Required offshore heliport facilities are not operational; and/or
• A required radio altimeter is inoperative.
3.14.6 RA MDH. The RA is the lowest altitude that a descent is authorized in operations using airborne radar in ground mapping mode, an operational radio altimeter, and for cluster approaches, using a course bearing cursor. It is the highest of the following: 200 ft RA, 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 MDH visibility is ¾ sm.
3.14.7 Barometric MDA. The barometric MDA is the lowest altitude that descent is authorized when 1 NM lateral obstacle clearance is not maintained, the offshore heliport facilities are not available, or the radio altimeter is not operative. The minimum barometric MDA is increased 5 ft for each NM over 5 NM from the altimeter setting source to the landing
3-14 site. The maximum distance for a remote altimeter setting source from a landing site is 75 NM. The barometric MDA visibility is ½ sm.
3.14.8 Alternate Minimums and Requirements. Standard alternate minimums of 800 ft ceiling and 2 sm visibility for nonprecision procedures apply for ARAs to be used as an alternate. Requirements to establish an airport or landing site as an alternate are listed below:
1. Approved source of weather observations and reports;
2. Two-way communications with aircraft making an operation; and
3. Any required onshore alternate requires a standard or special instrument operation other than GPS-based that is anticipated to be operational at the estimated time of arrival, unless the aircraft is equipped with approved TSO-C145( ) or TSO-C146( ) avionics and STC for instrument operations, then the onshore can have GPS-based operation.
3.15 Training.
3.15.1 Experience. Before conducting ARA procedures in IMC, each flightcrew member should have:
1. Ten hours of flightcrew experience operating IFR (at either crew station) in the offshore route structure.
2. A minimum of ten ARAs and at least four from each crewmember position.
This may be reduced by the POI for the certificate holder based on the flightcrew experience and proficiency.
3.15.2 Training.
3.15.2.1 All training must be a matter of record.
3.15.2.2 After completing ARA training, each flightcrew member 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 ½ sm above the lowest established visibility minimums. Each crewmember must then fly and record ten additional ARAs 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 the total crew experience provided the pilot in command (PIC) meets all the conditions of this paragraph.
3.15.2.3 The flight proficiency check is an annual requirement.
3.15.2.4 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.
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3.15.2.5 In accordance with Order 8900.1, operators requesting authority to use ARAs are required to satisfactorily train their flightcrew members under an FAA-approved training program before beginning ARA operations. Operators should submit a proposed training program to the CHDO or appropriate Flight Standards office, as applicable, for approval. (See Appendix A for a sample training program.)
4-1 CHAPTER 4. HELICOPTER EN ROUTE DESCENT AREAS
4.1 Applicability. This chapter applies to HEDA procedures for offshore landing sites conducted under instrument flight rules (IFR). The procedure criteria in this AC apply to airborne weather radar with ground mapping mode that has a demonstrated navigational capability acceptable to the Administrator for HEDA operations.
4.2 Helicopter Requirements.
4.2.1 Radar and Radio Altimeter. Before being authorized to conduct HEDAs, each operator who applies must have at least one helicopter equipped with airborne radar approved for ground mapping mode use (see paragraph 4.2.4 below), an IFR-approved Global Positioning System (GPS) navigation receiver, and a radio altimeter (RA).
4.2.2 Navigation Equipment Requirements. The navigation equipment must meet the minimum requirements of Technical Standard Order (TSO)-C129, Airborne Supplemental Navigation Equipment Using the Global Positioning System (GPS); TSO-C145, Airborne Navigation Sensors Using the Global Positioning System (GPS) Augmented by the Wide Area Augmentation System (WAAS); or TSO-C146, Stand-Alone Airborne Navigation Equipment Using the Global Positioning System (GPS) Augmented by the Wide Area Augmentation System (WAAS); with an external course deviation indicator (CDI) or horizontal situation indicator (HSI) mounted in the pilot’s primary instrument scan.
(Refer to AC 91-70( ), Oceanic and Remote Continental Airspace Operations.)
4.2.3 Reference System Requirements. The reference coordinate datum system used for all operations must be World Geodetic System 1984 (WGS 84) or North American Datum of 1983 (NAD 83).
4.2.4 Airborne Radar.
4.2.4.1 Suitable for Use as Primary Instrument Operation Aid. 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 operations based on airborne radar only (with or without beacon capability) are as follows:
1. Meet the requirements of either TSO-C63, Airborne Weather Radar Equipment, or TSO-C102, Airborne Radar Approach and Beacon Systems for Helicopters.
2. Contain a stabilized 120-degree/60-degree sector scanning antenna with scan rates no less than 12/min and 24/min respectively.
3. Contain an adjustable, bright display.
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4. Contain an alphanumeric display for selected ranges and azimuth markers; however, alphanumeric displays of selected ranges are not required when a positive means of determining the range that has been selected is available and the radar operator is appropriately trained.
5. Contain an indicated range error that does not exceed ±0.2 NM for display ranges of 5 NM or less.
6. Contain a lowest selectable range display of 2.5 NM and a range mark display of 0.5 NM increments or smaller.
7. Contain tilt control of ±15 degrees.
8. Display a test pattern.
9. Be operable in the primary mode.
10. Be equipped with a fault monitor or self-test function.
Note: An operational course bearing cursor that provides course guidance may be used to supplement navigation track accuracy.
4.2.5 Radio Altimeter.
4.2.5.1 TSO Requirement. The radio altimeter must meet the requirements of TSO-C87, Airborne Low-Range Radio Altimeter.
Note: A radio altimeter must be installed and operational before descent to the radio altitude (RA) minimum descent height (MDH) is authorized.
4.3 Airworthiness.
4.3.1 Minimum Airworthiness Requirements. As a minimum, systems used for HEDA operations must meet the airworthiness requirements of TSO-C63 or TSO-C102. The selected equipment components must, as a minimum, meet the referenced TSO applicable to each requirement and be specifically approved for HEDAs by the appropriate Flight Standards office. Equipment not meeting these standards requires further evaluation and approval by FAA engineering before it may be used.
4.3.2 Installation Requirements. Installation of a systems used for HEDA operations for IFR use is a major change in type design, and the provisions of 14 CFR part 21, § 21.97 and part 43, §§ 43.5 and 43.7 apply. The following are requirements for system installation:
1. 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.