Appendix D to regain course alignment when a turn is required over the final approach waypoint. Table 1, Appendix D, shall be used to determine the minimum length needed to regain the course.
MINIMUM LENGTH OF THE FINAL APPROACH SEGMENT (MILES)
APPROACH CATEGORY Magnitude of turn over the Final Approach Waypoint (FAWP) 10° 20° 30° 40° 50° 60°
1.0 1.5 2.0 3.0 4.0 5.0
1.5 2.0 2.5 3.5 4.5 5.5
2.0 2.5 3.0 4.0 5.0 6.0 D 2.5 3.0 3.5 4.5 5.5 6.5 Table 1
(b) Width. The final approach primary area is centered longitudinally on the final approach course. The primary area is † 2 miles wide either side of the final approach course at the final approach fix. It narrows to the width of the fix displacement area at the runway threshold. See Table 4, Appendix D. A secondary area one mile in width is established on each side of the primary area. Figure 4 illustrates a typical final approach area.
FIX DISPLACEMENT AREAS
SECONDARY AREA + 2 MI PRIMARY AREA AT FAF IFWP FAF (ATD) RWY WP FIGURE 4. TYPICAL INTERMEDIATE/FINAL AREAS * Page 12 Par 4
Appendix D
(c) Obstacle Clearance. The minimum obstacle clearance in the primary area is 250 feet. In the secondary area the full obstacle clearance of the adjacent primary area is provided at the inner edge, tapering uniformly to zero at the outer edge of the secondary area.
f. Missed Approach Segment. A missed approach procedure shall be established for each instrument approach procedure. The missed approach shall be initiated no later than the runway threshold waypoint. The missed approach should be simple and shall specify an altitude and a clearance limit. The missed approach altitude specified in the procedure shall be sufficient to permit holding or enroute flight.
Straight Missed Approach Area. The straight missed approach area may be used when the missed approach track does not differ more than 15 degrees from the final approach track.
The area starts at the plotted position of the missed approach waypoint and has the same width as the final approach primary and secondary areas at the MAWP. The primary missed approach area splays at 15 degrees each side of the missed approach * track until it reaches the width of the appropriate terminal or enroute obstacle clearance area. The secondary areas expand uniformly from one mile to the width of the appropriate enroute secondary areas. See Figure 5.
FINAL APPROACH AREA
SECONDARY AREA MISSED APPROACH POINT SECONDARY AREA_ 15° SPLAY
TERMINAL OR
ENROUTE AREA FIGURE 5. STRAIGHT MISSED APPROACH AREA * Par 4 Page 13
Appendix D Straight Missed Approach Obstacle Clearance. Within the primary missed approach area no obstacle may penetrate the 40:1 missed approach surface. This surface begins at the plotted position of the MAWP when the along-track error at the MAWP is one mile or less. When the along-track error (Table 4, Appendix D) at the MAWP exceeds one mile, the surface begins at a distance past the plotted position of the MAWP equal to the amount of along-track error in excess of one mile. The missed approach surface beginning height is determined by subtracting the required final approach obstacle clearance from the minimum descent altitude.
the secondary area, no obstacle may penetrate a 12:1 slope which extends upward and outward from the 40:1 surface at the inner boundaries of the secondary area. See Figure 5.
NOTE: Helicopter procedures use a 20:1 missed approach surface with 4:1 slopes in the secondary areas.
(Ref. TERPS 1119 & 1120) Turning Missed Approach. The turning missed approach will be as prescribed in FAA Handbook 8260.3A (TERPS) except that * the starting point for the 40:1 obstacle clearance surface will be prescribed in the preceding paragraph (4.f.(2)).
g - Published civil RNAV approach minimums shall meet the criteria for nonprecision approach systems as specified * in FAA Handbook 8260.3A (TERPS). Table 6 criteria which relates * minimum visibility to distance from station shall be applied as a variation of cross-track displacement area (Table 4, Appendix D) Cross-track area 0.6 - 0.8 NM use Column 0-10 " 0.9 - 1.0 NM 11 " 1.1 - 1.2 NM " " 1.3 - 1.6 NM " 11 Over 1.6 NM " Over 25
h. Approach Waypoint Displacement Area. The approach waypoint displacement area is a rectangular or square area formed around the plotted position of the waypoint. The dimensions of the area are derived from the appropriate along-track and cross-track error values. See Table 4, Appendix D. The approach waypoint * displacement area shall be considered for each waypoint used in developing RNAV final approach procedures including the FAWP, MAWP, and any stepdown WP or ATD fixes used on final. * Page 14 Par 4
ENROUTE AREA FIX DISPLACEMENT ERROR (95% Probability) DISTANCE ALONG TRACK FROM TANGENT POINT 2/21/75 10 20 30 40 50 60 70 80 90 100 110 120 130 140 150 200 ° (x1g tik) 2.5 2.5 2:5 2.8 3. 2 1:é 1:3 2:½ 3:3 3:⅞ 5:3 2:3 12.6
1.> 1.> 1.. 1.0 6.0 2,5 2.5 ... 2.8 1:3 1:} 2: 9 2:90 3:3 2:б 12.0 alg trk 1.- 1.5 1.9 trk) 1:S 1:5 1:3 1:3 2:1 2:3 2:8 1:₴ 3:8 . 9 2: g +z:2 Ł:§ 2:1 2:2 2:3 2:S 2:3 3:3 2:9 12: S 2:ł 2:5 4:3 2:3 3:3 FROM TANGENT POINT TO VORTAC 3:½2 }:½ 3:3 4:3 4: S 9.1 3:7 1⅔:8 trk) 5,4 3:3 3:8 }:в }:% ¼:1 2: 2 0. 9 3:2 8.0 8.6 9.2 9.8 1½:§
5.0 5.4 5.6 5.8 6.0 trk) 2:2 2:0 1:2 2:5 4: 8 3:9 S: d 8: 3 2:3 2:3 12:2 30 (x erk) 3:3 $:2 $ :3 3: 5 6:½ 8:3 6: 169 12:8 90(x 3:6 3:7 4 - 0 0. 0 6: 2 2:3 10:4 13.0
5.7 6.1 3:2 2:3 6: 3 1:2 10 ..
DISTANCE : rk) 2: 8 4:2 4:3 6:3 $:3 ⅜:İ 1:3 8:3 8:3 2: 8 18:2 19:ă 1}:₴ 1½:3 ฿ :2 в:3 з:2 8: 5 6: 8 в:} $:8 +9:5 10:4 ·:3 З:& 3:2 7:3 8: 5 1Q:$ 10.6 13-
10.0 150 (x 1:₴ 18:3 18:1 10. - 10:6 11:4
10.5 TANGENT DISTANCE TO FIND THE CROSS TRACK AND ALONG TRACK CROUND ERROR ELEMENTS Appendix D AC 90-45A ERROR AT THIS POINT, ENTER TABLE WITH TANGENT VOR 1.90 DISTANCE AND DISTANCE ALONG TRACK FROM AIRBORNE DAS 0I INM TANGENT POINT, i.e., when the distance to TP = VOR 3.00 30 and the along track distance = 60, the X track OME 37 or 0.5 NM error is14,4 NM and the along track error ist2.7 NM. RNAV SYSTEM 0.5 NM PILOT CROSS-TRACK 2.0 DISTANCE ALONG TRACK TABLE 2 ALONG-TRACK ZERO
Appendix D * TERMINAL AREA FIX DISPLACEMENT ERROR (95% PROBABILITY)
DISTANCE ALONG TRACK FROM TANGENT POINT 10 20 30 40 50 60 70 80 90 100 0(x trk) 1:1 2. 2 1:⅓ 1:9 §:з (alg (rk) TO VORTAC 10(x tIk) 1:1 1:3 1:½ 2:$ 1:3 2:8 2:3 2:6 2:9 alg tIk) 20(x Erk) 1:3 1:¾ 1:§ 1:3 2:1 4.0 2:6 2:3 S:4 (alg trk) 2.3 DISTANCE FROM TANGENT POINT 30(x trk) 2:1 2:3 2:3 2:5 3:2 5: S (alg trk) 40(x trk) 2:8 2:9 3:4 3:₴ 3:8 4:б (alg trk) 50 (x trk) 3:2 3:2 3:3 3:2 З:в 5: 3 (alg trk)
TO FIND THE CROSS TRACK AND ALONG TRACK ERROR ELEMENTS TANGENT DISTANCE ERROR AT THIS POINT, ENTER TABLE WITH TANGENT DISTANCE AND DISTANCE ALONG TRACK FROM GROUNO VOR D ME 1.90 0. 1 NM TANGENT POINT, i.e., when the distance to TP = AIRBORNE
- - . 30 and the along track distance = 60, the X track error is 4.0 NM and the along track error ist2.7 NM. RNAV SYSTEM 0.5 NM VOR 3.0° 3% or 0.5 NM PILOT CROSS-TRACK I.O
ALONG-TRACK ZERO
DISTANCE ALONG TRACK TABLE 3 Terminal waypoint displacement errors apply to waypoints used in arrival and departure procedures including Initial and Intermediate approach waypoints.
(para 3c) Page 16 Par 4
Appendix D * FINAL AREA FIX DISPLACEMENT ERROR (95% PROBABILITY)
DISTANCE ALONG TRACK FROM TANGENT POINT 5 10 15 20 25 30 DISTANCE FROM TANGENT POINT 0(x & tik) 1: & 1:0 5(x trk). (alg trk) 1.0 8 1:1 VORTAC 10(x trk) (alg trk) 1.0 • 9 1:3 1:5 1:1 15(x (alg trk) trk) 1:1 1:½ 1:½ 1:3 TO 20 (x trk) (alg trk) 1:3 1:0 1:¿ 1:4 1:≤ 25(x trk) (alg trk) 1:0 1:6 1:3 1:⅔ 30(x (alg trk) _ trk) 1:⅔ 1:⅔
TO FIND THE CROSS TRACK AND ALONG TRACK
TANGENT DISTANCE ERROR AT THIS POINT, ENTER TABLE WITH TANGENT ERROR ELEMENTS GROUNO
DISTANCE AND DISTANCE ALONG TRACK FROM VOR TANGENT POINT, i.e., when the distance to TP = AIRBORNE 5 and the along track distance = 10, the X track 3.00 error istl.0 NM and the along track error is*,8 NM. RNAV SYSTEM 0.5 NM 3% or 0.5 NM PILOT CROSS-TRACK 0.5
ALONG-TRACK ZERO
DISTANCE ALONG TRACK TABLE 4 Final waypoint displacement errors apply to the waypoints used in the Final approach segment. (para 4h) * Par 4 Page 17 (and 18)
Appendix D
SECTION II 3D RNAV CONSIDFRATIONS
5. BACKGROUND. Adding a third dimension of vertical guidance to the two dimensional RNAV system can achieve significant operational advantages.
Briefly, a 3D RNAV capability permits altitude change bv following vertical routes (tubes) of known dimensions thus vertical guidance is available for stabilized descent in instrument approach procedures using computed glide path information. In some cases, the computed glide path can make it possible to safely eliminate obstacles from consideration. This section discusses the operational problems and capabilities of 3D RNAV and provides criteria for vertical instrument flight procedures.
a. Level Flight RNAV Longitudinal and Vertical Errors.
(1) In level flight, the plus or minus vertical position error is due to altimetry and flight technical errors. Current standards for aircraft separation and obstacle clearance allow for these errors, and in addition, provide an allowance for atmospheric anomalies.
VERTICAL ERRORS
BASIC CONCEPT FIGURE 6. LEVEL FLIGHT VERTICAL ERROR Par 5 Page 19
Appendix D
(2) Also, in level flight the combination of ground station, airborne equipment, and computer errors produce a plus-or-minus longitudinal position error called along-track error. No flight technical error is involved.
HORIZONTAL PROBABILITY FIGURE 7. ALONG-TRACK ERROR
(3) Thus, providing airspace for aircraft in level flight using RNAV is simply a matter of containing the plus-or-minus vertical and longitudinal position errors as the aircraft progresses along the intended flight path.
VERTICAL-HORIZONTAL PROBABILITY ......
FIGURE 8. AIRSPACE IN LEVEL FLIGHT Page 20 Par 5
Appendix D Vertical Flight RNAV Errors. To provide vertical guidance during ascent or descent, the 3D RNAV equipment compares the indicated altitude with the desired altitude and presents the computer correction instrumentally; typically in the form offly up/fly down cross pointer information. The computation and comparison process produces vertical position errors which are additional to those affecting the aircraft in level flight.
ADDITIDNAL VERTICAL CONTRIBUTION USING VNAV FIGURE 9. ADDITIONAL ERROR ALLOWANCE FOR ASCENDING/DESCENDING FLIGHT.
The along-track error also has significance in vertically guided flight. When an aircraft is ahead or behind its assumed position, it will be either above or below its intended path.
FIGURE 10. EFFECTS OF ALONG-TRACK ERROR.
Par 5 Page 21
Appendix D
(2) The angle at which climb or descent is made also affects the required obstacle clearance because as the vertical angle increases, there is a corresponding increase in the effect of the along-track error on the thickness of the tube.
VARIATIONS OF VERTICAL CLEARANCE
LEVEL FLIGHT
SHALLOW ANGLE
STEEP ANGLE FIGURE 11. VARIATIONS OF TUBE SIZE TO CONTAIN POSITION ERRORS AS VERTICAL ANGLE INCREASES.
6. CONCEPT OF VERTICAL OBSTACLE CLEARANCE. In prescribing obstacle clearance for 3D RNAV, it is useful to think of the vertical route as being the center of a tube of airspace. The lateral dimension of the tube is the width of the RNAV route as described in Section I of this appendix. • The vertical dimension of the tube is sufficient to contain the combined 3D RNAV vertical errors. The longitudinal dimension of the tube is limited only by its operational use; for example: The distance required to climb 10,000 feet at a climb angle of 2°, or the descent from the final approach waypoint to the missed approach waypoint at a descent angle of 3°. For obstacle clearance, it is necessary to consider only that portion of the tube which is at and below the designed vertical flight path. An aircraft is protected from obstacles when no obstacles penetrate the tube from below.
Page 22 Par 5
Appendix D
7. OBSTACLE CLEARANCE REQUIREMENTS. 3D obstacle clearance requirements W1ll be included in FAA Handbook 8260.3A, "U.S. Standard for Terminal Instrument Procedures (TERPs).
NOTE: Use of 3D RNAV on 2D RNAV procedures is not prohibited. 2D RNAV procedures are annotated with Flight Path Angles measured from the TCH at the runway threshold waypoint to the altitude at the Final Approach ATD. These FPA may be flown as may any other FPA generated by the airborne equipment PROVIDED that the minimum and maximum altitudes specified in the flight procedures or in Air Traffic Control clearances are not violated.
Par 7 Page 23 (and 24)
Appendix E APPENDIX E. MAINTENANCE
1. MAINTENANCE. All maintenance will be performed in accordance with FAR 43 and the manufacturer's instructions, or in accordance with a manual under an approved maintenance procedure. Records of maintenance should be entered in the airplane maintenance records required by FAR 43.9, or in the records required by the operator's approved maintenance procedures. Following repair or alteration, the system should be checked before predicating any operation on its use.
Compatibility of the airborne area navigation system replacement components should be assured unless the replacement is of the same make and model as those upon which original approval was based.
2. INSPECTION AND TEST PROCEDURES. Operators using aircraft under IFR with an airborne area navigation system and not under an approved maintenance procedure should establish procedures which will be used to inspect and test the equipment periodically to determine that it is operating in accordance with at least the accuracy specified in Appendix A for minimum equipment. Such procedures should include a method for analyzing malfunctions and defects to determine that the established inspections and tests give reasonable assurance that the equipment is maintaining its accuracy. Test and inspection procedures and intervals should be adjusted in accordance with the results of the analysis.
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