CHAPTER 4 - APPROACH

    a. Department Of Defense (DoD) Procedures. The Department of Defense (DOD) Instrument Approach Procedures are printed in two variations in CONUS; Terminal Low Altitude United States (VOL 1 through 15), and Terminal High Altitude United States (NE, NW, SE, SW). Overseas HI/LOW IAP’s are combined. DOD FLIP is the official publication medium for terminal information for use by the U.S. Army, U.S. Navy and U.S. Air Force.

    b. Civil Procedures. DOD FLIP does not contain approach procedures for all airfields or all available instrument procedures for a specific airfield. Civil and military users of civilian procedures must refer to the Government Instrument Approach Procedures publications published by the NOS for non-standard or restrictions to IFR Alternate Minimums. DOD policy for inclusion of civil instrument procedures in DOD FLIP products is to provide only those procedures to meet mission requirements. Procedures required for training can be obtained from the NOS procedures books. It is permissible to reproduce these NOS procedures and issue them to aviators for their missions. Civil procedures supporting U.S. Army requirements may be added to DOD FLIP with justification by direct contact with Director USAASA.

    d. Jeppesen Procedures. Jeppesen Sanderson, Inc. of Englewood, Colorado; a privately owned and operated company, publishes instrument approach procedures and other related flight information publications on a worldwide basis. The use of Jeppesen Approach Procedures are only approved for specific overseas AIRPORTS after a review of the procedure by Director USAASA or commander USAASD-E.

    b. The five approach categories (A thru E) are based on 1.3 times the stall speed in the landing configuration. If it is necessary to maneuver at speeds in excess of the upper limit of the speed range for the aircraft's category, the minima for the next higher approach category will be used. For example, an aircraft which falls into Category C but is maneuvering to land to a speed in excess of 140 knots, but less than 166 knots, will use approach Category D minima.

APPROACH SPEED CATEGORY

NOTE: All US Military Helicopters may utilize the aircraft approach Category A minima published in authorized FLIP publications. Since aircraft speeds are used in determining turning radii and obstacle clearance areas for circling and turning missed approaches, helicopters operating at speeds greater than CAT A will use the higher category minima. Procedures containing the word "COPTER" in the procedure title, i.e, COPTER VOR 190, are approved under TERPs Helicopter Criteria for helicopter use only and are restricted to 90 knots indicated airspeed unless a lesser speed is annotated on the approach plate..

4-6. IAP Legend Pages. The legends shall define and depict all symbols used in the presentation of IAP's and Airport Diagrams, and provide information pertaining to general items of interest and a listing of all abbreviations. Figures 5 - 11 are examples of legend pages taken from instrument approach procedures charts.

Figure 5. Example Legend Page (Plainview Symbols)

Figure 6. Example Legend Page (Profile)

Figure 7. Example Legend Page (Airport Diagram/Airport Sketch)

Figure 8. General Information and Abbreviations

Figure 9. Example Legend Page (DP Charts - Miscellaneous Symbols))

Figure 10. Example Legend Page, Cont’d

Figure 11. Example Legend Page, Cont’d

4-7. Chart Format. Each chart consists of five sections: margin identification, plan view, profile view, landing minimum section (and notes) and airport sketch (Figure 12).

Figure 12. Chart Format

    a. Margin Information. Information included in the margin of the approach plates includes procedure identification, reference number and approving authority, airport name, coordinates, and miscellaneous other information (Figure 13).

Figure 13. Margin Information

    b. Plan View. The Plan View provides a bird's eye view of the entire procedure. Information pertaining to the initial approach segment including procedure turn, minimum safe altitude for each sector, and obstructions is portrayed in this section. Navigation and communication frequencies are also listed on the plan view. The following paragraphs in this section describe plan view information in more detail. Figures 14 - 16 graphically illustrate the location of the information.

Figure 14. Plan View

        (1) Format. Normally, all information within the plan view is shown to scale. Data shown within the 10 NM distance circle (inner ring) is always shown to scale (Figure 14). The dashed circles, called concentric rings, are used when all information necessary to the procedure can not fit to scale within the limits of the plan view area. These circles then serve as a means to systematically arrange this information in their relative position outside and beyond the 10 NM distance circle. These concentric rings are labeled Enroute Facilities and Feeder Facilities and are normally centered on the approach facility.

            (a) ASR - Airport Surveillance Radar instrument approach procedure is available at the airport.

Figure 16. Plan View, Cont’d

                        (3) When a holding pattern replaces the procedure turn, the standard entry and the holding pattern must be followed except when RADAR VECTORING is provided or when NoPT is shown on the approach course. As in the procedure turn, the descent from the minimum holding pattern altitude to the final approach fix altitude (when lower) may not commence until the aircraft is established on the inbound course.

        (2) Stepdown fixes in non-precision procedures. A stepdown fix may be provided on the final, i.e., between the final approach fix and the airport, for the purpose of authorizing a lower MDA after passing an obstruction. This stepdown fix may be made by an NDB bearing, fan marker, radar fix, radial from another VOR, TACAN, or by DME when provided for as shown in Figure 17.

Figure 17.  Profile Views

        (3)  Normally, there is only one step-down fix between the final approach fix (FAF) and the missed approach point (MAP). If the step-down fix cannot be identified for any reason, the altitude at the step-down fix becomes the MDA for a straight-in landing. However, when circling under this condition, you must refer to the Minimums Section of the procedure for the applicable circling minimum.

         (4)  Missed approach point (MAP).  Missed approach points are different for the ILS (with glide slope) and the localizer only approach. The MAP for the ILS is at the decision height (DH) while the localizer only MAP is usually over the (straight-in) runway threshold. In some non-precision procedures, the MAP may be prior to reaching the runway threshold in order to clear obstruc­tions in the missed approach climb-out area. In non-precision procedures, the pilot determines when he is at the missed ap­proach point (MAP) based on time from the final approach fix (FAF) or by use of DME. The FAF is clearly identified by the Maltese cross symbol in the profile section. The distance from FAF to MAP and a time and speed table, for easy calculation, are found below the aerodrome sketches.  This does not apply to the use of DME required procedures, or when the facility is on the airport and the facilitv is the MAP.

    d.  Minimums Section.  Minimums apply to both day and night operations unless specified at the bottom of the minimum box in the space provided for symbols or notes.  The minimums for straight-in and circling appear directly under each aircraft category (Figure 18). When there is no division line between minimums for each category on the straight-in or circling lines, the minimums apply to two or more categories under the A, B, C, or D.  In Figure 18, the S-ILS 21 minimums apply to all four categories. The S-Localizer 21 minimums are the same for Categories A and B, and individually different for Categories C and D. The circling minimums are the same for A and B and individually different for C and D.  The VOR Rwy 35 procedure authorizes minimums for aircraft with a VOR receiver. Lower minimums are authorized if the aircraft also has a DME receiver or the intersection is identified. Off tuning from the approach NAVAID to identify an approach fix is authorized, except in the case of an NDB.  Extreme caution should be used when the fix is within two miles of the missed approach point.

Figure 18.**Examples of Minimums Section

        (1)  Straight-In Minimums.  Straight-in minimums are shown on instrument approach procedure charts when the final approach course of the instrument approach procedure is within 30º of runway alignment and a normal descent can be made from the IFR altitude shown on the instrument approach procedures to the runway surface.  When either the normal rate of descent or the runway alignment factor of 30º is exceeded a straight-in minimum is not published, and a circling minimum applies.  The pilot must be cleared to land straight when conducting a circling approach.  The fact that a straight-in minimum is not published does not preclude the pilot from landing straight-in if he has the active runway in sight in sufficient time to make a normal landing.  Under such conditions and when Air Traffic Control has cleared him for landing on that runway, he is not expected to circle even though only circling minimums are published.  If he desires to circle at a controlled airport, he should advise ATC.  

        (2)  Circling Minimums.  The circling minimums published on the instrument approach chart provide adequate obstruction clearance and the pilot should not descend below the circling altitude until the aircraft is in a position to make final descent for landing.  Sound judgment and knowledge of his and the aircraft capabilities are the criteria for a pilot to determine the exact maneuver in each instance since the airport design, the aircraft design, position, altitude and airspeed must all be considered.  The following basic rules apply: 

            (a)  Maneuver the shortest path to the base or downwind leg as appropriate under minimum weather conditions.  There is no restriction from passing over the airport or other runways. 

            (b)  It should be recognized that many circling maneuvers may be made while VFR flying is in progress at the airport.  Standard left turns or specific instruction from the controller for maneuvering must be considered to land when circling to land.  

            (c)  At airports without a control tower, it may be desirable to fly over the airport to determine wind and turn indicators, and to observe other traffic which may be on the runway or flying in the vicinity of the airport.

        (3)  Remote Altimeter Settings.  The weather planning minimums must be computed when the pilot knows that a MDA or DH has been raised due to having to use a remote altimeter setting .  In some cases, the new minimums will be shown in the minimum box (Figure 19 below).  When not shown, the method illustrated in Figure 19 will be used to compute the new weather planning minimums.

  Figure 19:  Recomputing MDA and DH

    e.  Airport Sketch.  The airport sketch (Figure 20) contains specific data about runways, elevations, etc,  It also provides information on approach times from the FAF to the MAP.

  Figure 20: Airport Sketch

4-8.  Procedural Component Operation. 

    a.  Operative runway lights are required for night operation.

    b.  When the facility providing course guidance is inopera­tive, the procedure is not authorized.  VOR/DME procedures are not authorized if either VOR or DME is inoperative.

     c.  When the ILS glide slope is inoperative or not used, the published straight-in localizer minimum applies.

    d.  Compass locator, precision radar, or DME may be substituted for the ILS outer marker.  

    e.  Surveillance radar may be a substitute for the ILS outer marker.  DME, at the glide slope site, may be substituted for the outer marker when published on the ILS procedure to identify the localizer FAF.

    f.  Facilities that establish a stepdown fix, i.e., 75 MHz FM, off course VOR radial, etc.  are not components of the basic approach procedure, and applicable minimums for use, both with or without identifying the stepdown fix, are published in the minimums section (Fig.  19 above). 

    g.  Runway Visual Range (RVR) Minimums.  To authorize RVR minimums, the following components and visual aids must be available in addition to basic components of the approach procedure:

        (1)  Precision approach procedures.

            (a)  RVR reported for the runway.

            (b)  HIRL.

            (c)  All weather runway markings

        (2)  Non-precision approach procedures.

            (a)  RVR reported for the runway.

            (b)  HIRL.  

            (c)  Instrument runway markings.

        (3)  Inoperative RVR minimums.  Where RVR visibility minimums are published and the runway markings become unusable, the necessary adjustment will be accomplished by NOTAM and by air traffic advisory.  RVR minimums for take-off or landing are published in an instrument approach procedure and departure procedure.  If RVR is inoperative and cannot be reported for the runway at that time, it is necessary that the RVR minimums which are specified in the procedure be converted and applied as ground visibility in accordance with the METAR Conversion Chart located in IAP volumes.

4-9.  Simplified Direction Finding Approach (SDF).  The SDF provides a final approach course similar to that of the ILS localizer.  It does not provide glide slope information.  A clear understanding of the ILS localizer and the addi­tional factors listed below completely describe the operational characteristics and use of the SDF (Figure 21).  

    a.  The SDF transmits signals within the range 108.10 to 111.95 MHz.  

    b.  The approach techniques and procedures used in an SDF instrument approach differ from a standard localizer approach in that the SDF course may not be aligned with the runway and the course may be wider, resulting in less precision.  

Figure 21:  Example SDF Approach

          c.  Identification consists of a three letter identifier transmitted in Morse Code on the SDF frequency.  The appropriate instrument approach chart will indicate the identifier used at a particular airport. 

10.  Global Positioning System (GPS).  The (GPS) consists of a worldwide signal and monitoring network and a broad array of military and civilian equipment.  

       GPS includes a constellation of 24 satellites, in six orbit planes (four satellites per plane) in 10,898 NM orbits.  This equates to an orbit period of 12 hours, or two orbits per day.  This satellite constellation guarantees that at least five satellites are in view from any point on the earth 24 hours a day, providing three-dimensional (latitude, longitude and altitude) position and time reference information.  GPS receivers validate signal information through what is called receiver autonomous integrity monitoring (RAIM).  Isolation of a corrupt signal requires signal augmentation with local area barometric pressure or six satellites to be in view of the receiver and Fault Detection Error (FDE). 

        In order for the aviation community to take advantage of the benefits provided by GPS, aircraft operators must have the necessary certified airborne equipment (TSO C-129 or military equivalent, i.e.  AMCOM certification) approved and installed in their aircraft and published instrument approach procedures available to the user.  Non-U.S.  Government instrument approach procedures have to be reviewed and validated for compliance with TERPS criteria or equivalent level of safety before use by military aviators. 

    a.  GPS Nonprecision Approach Procedure Development.  GPS instrument approach procedures are based on GPS airborne equipment meeting the enroute, terminal and non-precision requirements. 

        (1)  Procedure Identification.  Instrument Approach Procedures based on GPS are identified by the prefix RNAV followed by the runway number or letter, as appropriate; such as RNAV RWY 12 for a straight-in, or RNAV-A which signifies a circling approach (Figure 22).  See also Appendices 1 & 2.

Figure 22.  GPS Approach

Figure 23  Volpe Format (Replacement for present format)

        (2)  Segments.  GPS RNAV segments begin and end at a WP.  WPs are used to identify the point at which GPS navigation begins and the point at which the procedure ends.  WPs are also used to identify where routes change course; holding fixes; the final approach fix (FAF); and the missed approach point (MAP).  Step-down fixes are defined as Along Track Distance (ATD) fixes, and there is no maximum number in any segment .  Each WP is defined by latitude and longitude to nearest hundredth of a second, and identified with a five letter name. 

        (3)  Enroute.  Standard enroute criteria applies to GPS enroute segments.

        (4)  Feeder Routes.  When the initial approach WP (IAWP) is not part of the enroute structure, feeder routes will be designated from the enroute structure to another feeder WP or to the IAWP.  Enroute obstacle clearance applies in the feeder.

        (5)  Initial Approach Segment.  The initial approach segment begins at the IAWP and ends at the intermediate WP (IWP) or the intermediate ATD fix.  Normally, the IAWP will overlie an enroute fix or NAVAID.  The length should not exceed 50 NM.  When the IAWP is more than 30 NM from the airport reference point (ARP), the procedure is annotated with a note to advise the pilot to ensure the approach mode has been activated, i.e.  Arm Approach Mode Prior to IAF.  The angle of intercept between the initial and intermediate segments should be the minimum required for the procedure, and will not exceed 120°.  A minimum of 1,000 feet of obstacle clearance, or 1,500 feet above terrain for airspace is provided in the initial segment.  The optimum descent gradient is 250 feet/NM, and the maximum is 500 feet/NM in the initial segment.

        (6)  Course Reversal.  When a course reversal is required, a holding pattern is provided in lieu of a PT.  A minimum obstacle clearance of 1,000 feet is provided within the holding pattern area when the altitude permits a departure from holding at a normal descent to the Final Approach Waypoint (FAWP) altitude at a descent rate not to exceed 300 feet/NM.  Course change at the FAWP or IWP will not exceed 15°. (Holding in lieu of a PT is at the IF/IAF) 

        (7)  Intermediate Segment.  The IWP may be shown as an ATD fix if no turn is required at the IWP.  The intermediate should be aligned with the final.  Course change at the FAWP will not exceed 15°.  The minimum length is 5 NM, and the optimum is 10 NM.  A minimum of 500 feet of obstacle clearance is provided in the intermediate segment.  The optimum descent gradient is 150 feet/NM, and the maximum is 300 feet/NM in the intermediate segment.

        (8)  Final Approach Segment.  The final segment begins at the FAWP and ends at the MAWP.  Any step-down fixes are defined as ATD fixes with reference to the next WP or runway.   Straight-in approaches will not exceed 15° from the runway centerline extended (RCL), and the optimum alignment is to the threshold (THR).  When the alignment exceeds 3° from the RCL, the optimum alignment is to a point 3,000 feet from the THR on the RCL.  The optimum length is 5 NM, and the maximum is 10 NM.  The minimum obstacle clearance provided in the final is 250 feet.  The optimum descent gradient is 300 feet/NM, and the maximum is 400 feet/NM.The final descent gradient is computed by dividing the difference between the FAF (or Step-down) altitude and the touchdown zone elevation (TDZE) by the length of the final approach segment.

        (9)  Circling Approach.  The optimum alignment is to the center of the landing area, but may be to any portion of the useable landing surface.  The location of the Missed Approach Waypoint (MAWP) can be anywhere along the final course between the FAWP and a point abeam the nearest useable landing surface.  A minimum of 300 feet of obstacle clearance is provided in the circling area.  The optimum descent gradient is 300 feet/NM, and the maximum is 400 feet/NM.  The descent gradient is computed by dividing the difference between the FAF (or Step-down) altitude and the MDA by the length of the final approach segment.

        (10)  Approach Minimums.  The standard criteria spelled out in the Terminal Instrument Procedures Manual (TERPS) apply to computing GPS instrument landing minimums.

        (11)  Missed Approach.  The missed approach segment begins at the MAWP and ends at a point designated as the clearance limit.  A straight, turning, or combination straight and turning missed approach may be developed.  A 40:1 or 152 feet/NM obstacle clearance surface is provided in the missed approach segment.  The missed approach surface begins at the MDA minus the obstacle clearance and any other adjustments in the final.  A IWP is designated at the MAP and at the end of the missed approach procedure.  The missed approach will specify a clearance limit and an altitude suitable for holding or continued enroute navigation.

        (12)  Minimum Safe Altitude.  A common safe altitude is established for a 25 NM radius around the MAWP or Runway Threshold.  The minimum safe altitude area provides 1,000 feet of clearance over the highest obstacle in the MSA.

NOTE - With Terminal Arrival Area (TAA) MSA’s will not be provided.

    b.  Helicopter RNAV Approaches.   Helicopter instrument approach procedures are based on the premise that helicopters are approach category A aircraft with special maneuvering characteristics.  Speed limitations incorporated in these procedures take advantage of the unique, slow speed capability of helicopters and allow the lowest possible landing minimums.  Military (“Not for civil use”) approach procedures are designed for an airspeed not to exceed 90 KIAS in the final and missed approach segments. 

        (1)  Procedure Identification.  Helicopter GPS instrument approaches to runways are identified by COPTER RNAV followed by the runway number or final bearing as appropriate; i.e.  COPTER RNAV RWY 30, COPTER RNAV 160.   A typical approach is shown at Figure 24.

        (2)  Approach Design.  The basic “T” configuration is considered the optimum.  It affords flexibility and standardization of procedure design.

        (3)  Initial Approach Segment.  The initial begins at the IAF and ends at the IF or ATD fix form the FAF.  Course change at the IF will not exceed 120°.  IAF’s originate within 25 NM of the airport (ARP) or heliport (HRP).  The length should not exceed 10 NM.  A minimum of 1,000 feet of obstacle clearance is provided in the initial, with an optimum descend gradient of 400 feet/NM.

        (4)  Course Reversal.  A holding pattern will be provided at the IF or FAF when a course reversal is required to execute the approach.  The holding pattern will be aligned within 30° of the intermediate or final course as appropriate.

        (5)  Intermediate Segment.  The intermediate begins at the IWP or ATD fix and ends at the FAF.  The maximum length is 5 NM, and the recommended is 3 NM.  The maximum course change at the FAF is 60°.  A minimum of 500 feet of obstacle clearance is provided in the intermediate, with an optimum descent gradient of 400 feet/NM.

        (6)  Final Approach Segment.  The final approach begins at the FAF and ends at the MAWP.  Helicopters are considered to be in a visual mode from the MAWP to the landing area.  The final approach can be to a runway, to a heliport or to a point-in-space.  For approaches to a runway the alignment will not exceed 30° from the RCL.  The optimum length of the final is 3 NM.  A minimum of 250 of obstacle clearance is provided in the final with an optimum descent gradient of 400 feet/NM, and a maximum of 600 feet/NM.  Final segment descent gradient is computed from the FAF altitude to MDA.

        (7)  Missed Approach.  The missed approach segment begins at the MAWP and ends at a clearance limit designated by a missed approach holding waypoint (MAHWP).  Optimum routing is straight ahead to a direct entry into holding.  The MAHWP will be located within 25 NM of the ARP/HRP.  A 20:1 or 304 feet/NM obstacle clearance surface is provided in the missed approach segment.

        (8)  Landing Minimums.  Heliport Instrument Lighting System (HILS) or approved runway lighting is recommended for all helicopter GPS approach operations in order to receive the lowest possible landing minimums.

        (9)  Alternate Minimums.  A heliport or airport served only by GPS instrument approaches is not suitable for use as an alternate.

SEE ALSO APPENDICES 1 & 2

Figure 24.  Typical Helicopter GPS Approach.

          c.  Terminal Arrival Area (TAA) and Basic “T” Design.  Transition from the enroute structure to the terminal environment requires specific ground tracks defined by ground based navigational facilities.  These transitions can be difficult to develop in areas where terrain features interfere with signal radiation and reception.  With the development of navigation systems that are independent of conventional navigational aids the possibility of creating a new transition system has emerged.  Efforts to develop an efficient and standard instrument approach configuration has led to the development of the Terminal Arrival Area (TAA) concept.  The TAA utilizes a Basic T segment configuration as a standard for area navigation (RNAV) approach procedures.  The TAA combined with the Basic T is viewed as the optimum design for GPS procedures.  

          The TAA approach consists of an Initial, Intermediate, Final and Missed Approach segments.  In the Basic T approach configuration the alignment of the initial segment to the intermediate segment is 90° (See figure 25).  The initial segment length may vary to meet descent gradients.  The maximum length is 10 NM.  The intermediate segment is aligned with the final segment, and turns over the final approach fix (FAF) are not allowed.  If a course reversal is required holding will be established in lieu of a procedure turn (PT) at the IF (IAF).  The inbound holding course will be aligned with the inbound intermediate course.  The optimum missed approach is a straight ahead climb with a direct entry into a missed approach holding pattern.  If the missed approach routing is back to a T IAF, the missed approach holding pattern will be aligned with the initial inbound course, with a direct entry into holding. 

          The standard TAA contains three areas; a straight-in area, left base area, and a right base area.  MSAs are not published for a TAA.  The straight-in area is bounded by a 30 NM arc in each direction from the IF.  The left and right base areas are bounded by 30 NM arcs from the respective IAF.  Arc boundaries are equivalent to a feeder fix.  Obstacle clearance is considered for the entire TAA including a buffer area.  Ideally all the TAA areas should have the same minimum altitudes.  Appropriate obstacle clearance must be provided in all sectors.  Modifications to the standard TAA may be necessary to accommodate operational or terrain clearance requirements.  Variations may include eliminating one or both base areas, and/or changing the configuration of the straight-in area.  A course reversal pattern at the IF (IAF) may be used to meet descent criteria for the approach.  Normally a portion of the TAA will overlie an airway.  If not, a feeder will provide a route from an airway fix or NAVAID to the TAA boundary where the pilot can proceed direct to the appropriate IAF. 

          The TAA will normally be located in class E airspace (1,200’ floor) but may overlie class B airspace.  The TAA may also be modified to accommodate restricted, controlled or warning areas.  The basic “T” configuration is the first option in procedure design.  It affords flexibility and standardization of instrument approach design.

SEE ALSO APPENDICES 1 & 2

Figure 25.  Typical TAA  Approach.

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