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.
.
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(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
Chap 3 Page 3-11 based on en route facilities. The radar operator obtains weather information and other relevant data for the landing area, identifies the destination area approach target and landing site, determines the FAP and missed approach clear zone, and discusses the approach with the other pilot before arrival at the intermediate approach fix.
(2) Approach. The radar operator vectors the helicopter from the intermediate approach fix 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:
(a) All equipment required for the approach is operating properly.
(b) The final approach track does not overlay any obstacles other than the approach target, and when descending to the RA, the clear sector is clear of all obstacles.
(c) The missed approach clear zone is free of obstacles.
f. Missed Approach and Holding. A missed approach is a climbing turn into the clear zone (figure 3-3) then a climbing turn to the MEA direct to the intermediate fix or as directed by ATC. Holding is on the IF on the inbound course with one-minute legs or as directed by ATC.
g. A missed approach will be initiated immediately if:
(1) A flight crewmember has not established visual contact with the approach target at the authorized minimum visibility distance as shown on the radar display; or
(2) During final approach, if there is any malfunction of equipment required for the approach, unless the helicopter is in VFR conditions and can continue to the landing site in VFR conditions; or
(3) The approach 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.
h. Lost communication procedure after the missed approach: Execute the published missed approach procedure and then proceed direct to the alternate at the MEA.
i. 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.
j. Landing Minimums: Landing minimums shall 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
Page 3-12 Chap 3 course bearing cursor for approaches 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:
(a) Lateral clearance of 1.0 NM cannot be maintained.
(b) Required offshore heliport facilities are not operational.
(c) A required radio altimeter is inoperative.
(3) RA MDA. The RA is the lowest altitude that a descent is authorized in procedures using airborne radar in the mapping mode, an operational radio altimeter, and for cluster approaches, a course bearing cursor. It 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 is 3/4 SM.
(4) Barometric MDA. The barometric MDA is the lowest altitude that descent is authorized when 1.0 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 site. The maximum distance for a remote altimeter setting source from a landing site is 75 NM.
The barometric MDA visibility is 1/2 SM.
k. Alternate Minimums and Requirements. Standard alternate minimums of 800 ft ceiling and 2 SM visibility for nonprecision approaches apply for ARA’s 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 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 4 Page 4-1 CHAPTER 4. HELICOPTER EN ROUTE DESCENT AREAS
4-1. HEDA SYSTEM COMPONENT REQUIREMENTS. The system component requirements stated in paragraph 2-1 of this AC apply.
4-2. AIRWORTHINESS. Airworthiness as stated in paragraph 2-2 of this AC applies.
4-3. MAINTENANCE. Maintenance as stated in paragraph 2-3 of this AC applies.
4-4. INSPECTION AND TEST PROCEDURES. Inspection and test procedures as stated in paragraph 2-4 of this AC apply.
4-5. WEATHER REPORTING AND PREFLIGHT ACTION REQUIREMENTS. FAA Order 8400.10, Volume 4. Aircraft Equipment and Operational Authorizations, Chapter 7. Air Navigation and Communications, and Title 14 CFR Part 91, Subpart B-Flight Rules/General, provides guidance for weather reporting requirements and preflight action.
4-6. TRAINING PROGRAM. See appendix 4.
4-7. PROCEDURE DEVELOPMENT CRITERIA.
a. Procedure Construction:
(1) Criteria: A sample HEDA chart is in appendix 5, figure 5-5. A separate chart for each HEDA is not required. 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. (See appendix 1. Request For Approval of OSAP, ARA, or HEDA Procedures.)
(a) Apply paragraph 2-7a of this AC for en route criteria.
(b) The plan view of the intermediate segment and HEDA descent areas are shown in figure 4-1. The IF is the last fix prior to the HEDA. The intermediate area is the same width dimensions as the en route segment at the IF. The outside edges of the intermediate segment at the IF is drawn tangent to the HEDA area. The HEDA area is a circle that has a radius of 4 NM. The HEDA must be free of all obstacles and must be located over the water. The ROC for the intermediate segment is 500 ft with a descent charted to no lower than 900 ft MSL or no lower than the barometric MDA adjusted for the RASS.
The HEDA procedure requires special authorization and equipment. Chart the following note in the plan view of chart:
“ SPECIAL AUTHORIZATION REQUIRED.
WX RADAR IN MAPPING MODE, AND GPS OR LORAN C REQUIRED.”
(c) The IF is established at not more than 20 NM from the HEDA coordinates.
(d) The FAP is established on the HEDA circle. A descent is made at the FAP to the MDA.
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Chap 4 Page 4-3
(2) Altitude Minimums.
(a) Equipment Requirements. All required flight and navigation equipment must be installed and operative to descend to the 400 ft RA minimums.
(b) Chart the following notes: (See appendix 5, figure 5-5)
1. “The MDA is 700 ft MSL with radio altimeter or airborne radar mapping mode inoperative.”
2. “The MDA is 700 ft MSL with obstruction in HEDA.”
3. “Altimeter source more than 5 NM but less than 75 NM, increase MDA 5 ft for each NM over 5 NM from HEDA coordinates.”
4. “Descent below 700 ft is not authorized unless HEDA is clear of all obstructions.”
5. “Descent from MEA to 900 ft MSL is not authorized until within 20 NM of the HEDA coordinates.”
(3) Visibility Minimums. Chart the following note on the published procedure: “PROCEED VFR TO THE LANDING SITE.”
(4) Missed Approach Procedure.
(a) A missed approach procedure is made when VFR conditions cannot be established and maintained at the HEDA coordinates.
(b) Chart the following missed approach procedure instructions: “Climb to 900, then climbing turn to the MEA, direct to the HEDA coordinates. Remain within 10 NM and hold or as directed by ATC.”
(c) Chart the following missed approach holding instructions: “Hold over the HEDA coordinates on the inbound course, 3 NM legs, maintain the MEA or as directed by ATC.”
(5) Filing a HEDA as an alternate in an IFR flight plan is not authorized. Chart the following note: “Filing HEDA as an alternate not authorized.”
4-8. OPERATIONAL APPLICATIONS.
a. 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 based on en route facilities. In the Gulf of Mexico the last en route waypoint prior to destination is the last en route waypoint prior to the HEDA. The radar operator obtains all relevant data for the landing area, identifies the destination area and landing site, and determines the FAP and missed approach clear zone. The radar operator then briefs the approach procedure to the other pilot before arrival at the IF.
b. Intermediate Segment.
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(1) A descent below the MEA is not authorized at any point in the HEDA until the helicopter has departed the last en route fix and is offshore. The en route fix is established prior to the intermediate segment at no more than 20 NM from the HEDA coordinates. A descent to an altitude no lower than 900 ft MSL is made on this segment (See figure 3-3).
(2) The FAP altitude is no lower than 900 ft MSL or the barometric MDA adjusted for the RASS. The FAP is established at 4 NM from the HEDA coordinates.
(3) Upon arrival at the IF, the radar operator will enter the GPS or LORAN C published coordinates.
(4) Within 20 NM or at the established IF, a descent is made to 900 ft MSL.
(5) Confirmation is made by airborne radar that the HEDA is clear of obstacles.
(6) The radar operator will assure that the airborne radar and radio altimeter are operating correctly prior to descending below 900 ft MSL or the minimum intermediate altitude adjusted for RASS.
The lowest barometric MDA is 700 ft MSL.
(7) The heading from the HEDA coordinates to the landing site should be confirmed in the intermediate segment.
c. Final Descent.
(1) Before descending below 700 ft MSL, the radar operator selects the lowest appropriate scale on the airborne radar, confirms the descent area is still clear, and the radio altimeter is still operative.
(2) A descent continues to 400 ft RA. Upon reaching VFR conditions, the pilot proceeds to the landing site. If the pilot cannot proceed under VFR conditions to the landing site, a missed approach procedure is executed.
d. Special Limitations.
(1) The descent area must be entirely over water.
(2) Descent below 700 ft MSL is not authorized whenever any of the following conditions exist:
(a) Any obstruction is detected in the HEDA.
(b) Radio altimeter is inoperative.
(c) Airborne radar is inoperative.
(3) Lowest altitude used for IFR flight in any HEDA shall not be lower than 400 ft RA.