Appendix 2 Turn Height Above Airport (Feet) Standard Tailwind Component (Knots)* 500 25 Standard AFS-400 Approval 1,000 37.5 30 1,500 50 35 2,000 50 40 2,500 50 45 3,000 50 3,500 55 4,000 60 4,500 65 5,000 70 5,500 75 6,000 80 6,500 85 7,000 90 7,500 95 8,000 100 8,500 105 9,000 110 9,500 115 10,000 120 10,500 125 ≥11,000 130 Table 11. Tailwind Component (VKTW) for Turn Calculations A2-9
Appendix 2 *Other tailwind gradients may be used after a site-specific determination of wind based on that location’s meteorological history (using available information from other sources). Document the source and value used on the procedure form (the FAA uses Form 8260-9).
Note: A new tailwind component may be interpolated for turns initiated at an altitude located between the values in Table 11. The 0 ft value for wind is 15 knots if an interpolated value is ever used below 500 ft.
(3) Waypoint Resolution Error.
The navigation database must provide sufficient data resolution to ensure the navigation system achieves the required accuracy. Waypoint resolution error must be less than or equal to 60 feet, including both the data storage resolution and the RNAV system computational resolution used internally for flight plan waypoint construction. The navigation database must contain vertical angles (flight path angles) stored to a resolution of hundredths of a degree, with computational resolution such that the system-defined path is within 5 feet of the published path.
(4) Capability for a “Direct-To” Function.
The navigation system must have a “Direct-To” function the flight crew can activate at any time. This function must be available to any fix. The navigation system must also be capable of generating a geodesic path to the designated “To” fix, without “S-turning” and without undue delay.
Note: The applicant should identify any limitations associated with the operational use of the aircraft navigation system’s “Direct-To” functions. For example, if there are limitations associated with intercepting an RF leg segment, then the flight manual or aircraft qualification guidance should identify those limitations.
(5) Capability to Define a Vertical Path.
The navigation system must be capable of defining a vertical path by a flight path angle to a fix. The system must also be capable of specifying a vertical path between altitude constraints at two fixes in the flight plan. The navigation system must also define fix altitude constraints as one of the following:
(a) An “AT or ABOVE” altitude constraint (for example, 2400A, may be appropriate for situations where bounding the vertical path is not required);
A2-10
Appendix 2
(b) An “AT or BELOW” altitude constraint (for example, 4800B, may be appropriate for situations where bounding the vertical path is not required);
(c) An “AT” altitude constraint (for example, 5200); or
(d) A “WINDOW” constraint (for example, 2400A3400B).
(6) Altitudes and/or Speeds.
The navigation system must extract the altitudes and/or speeds defined in published terminal procedures from the onboard navigation database.
(7) Path Construction.
The navigation system must be able to construct a path to provide guidance from the current position to a vertically constrained fix.
(8) Capability to Load Procedures from the Navigation Database.
The navigation system must have the capability to load the entire procedure(s) to be flown into the RNAV system from the onboard navigation database. This includes the approach (including vertical angle), the missed approach, and the approach transitions for the selected airport and runway.
(9) Means to Retrieve and Display Navigation Data.
The navigation system must provide the ability for the flight crew to verify the procedure to be flown through review of the data stored in the onboard navigation database.
This includes the ability to review the data for individual waypoints and for navigation aids.
(10) Magnetic Variation.
For paths defined by a course (CF and FA path terminators), the navigation system must use the magnetic variation value for the procedure in the navigation database. The navigation database must accurately represent the procedure as promulgated by the procedure designer, including the magnetic variation used in the procedure design.
Note: The above guidance is for using magnetic variation in the navigation computer for path generation.
(11) Changes in RNP Value.
RNP changes to lower RNP values must be complete by the first fix defining the leg with the lower RNP value. Any operational procedures necessary to meet this requirement must be identified.
Note: One acceptable means to meet this requirement may A2-11
--- Appendix 2 be to require the flight crew to manually set the lowest RNP value the RNP AR procedure uses before commencing the procedure (i.e., prior to the initial approach fix).
(12) Automatic Leg Sequencing.
The navigation system must provide the capability to automatically sequence to the next leg and display the sequencing to the flight crew in a readily visible manner.
(13) Altitude Restriction Display.
A display of the altitude restrictions associated with flight plan fixes must be available to the pilot. If there is an RNP AR procedure with a flight path angle associated with any flight plan leg, the equipment must display the flight path angle for that leg.
d. Flight Technical Error.
The applicant must confirm ability to maintain FTE (95 percent of the flying time) during straight and curved path segments (see paragraph 17-2).
e. Displays.
(1) Continuous Display of Deviation.
(a) The navigation system must provide the capability to continuously display to the pilot flying, on the primary flight instruments for navigation of the aircraft, the aircraft position relative to the RNAV defined path (both lateral and vertical deviation). The display must allow the pilot to readily distinguish if the cross-track deviation exceeds the RNP value (or a smaller value) or if the vertical deviation exceeds 75 feet (or a smaller value).
(b) The aircraft should have an appropriately-scaled, non-numeric deviation display (i.e., lateral deviation indicator and vertical deviation indicator) in the pilot’s primary optimum field of view. A fixed-scale CDI is acceptable as long as the CDI demonstrates appropriate scaling and sensitivity for the intended RNP value and operation. With a scalable CDI, the scale should derive from the selection of RNP, and should not require the separate selection of a CDI scale. Alerting and annunciation limits must also match the scaling values.
If the equipment uses default RNP values to describe the operational mode (e.g., enroute, terminal area and approach), then displaying the operational mode is an acceptable means from which the flight crew may derive the CDI scale sensitivity.
(c) In lieu of appropriately scaled lateral and vertical deviation indicators in the pilot’s primary optimum field of view, a numeric display of deviation may be acceptable depending on the flight crew workload and the numeric display characteristics.
A2-12
Appendix 2
(2) Identification of the Active (TO) Waypoint.
The navigation system must provide a display identifying the active waypoint either in the pilot’s primary optimum field of view, or on a readily accessible and visible display to the flight crew.
(3) Display of Distance and Bearing.
The navigation system must provide a display of distance and bearing to the active (TO) waypoint in the pilot’s primary optimum field of view. Where not viable, a readily accessible page on a control display unit, readily visible to the flight crew, may display the data.
(4) Display of Groundspeed and Time.
The navigation system must provide the display of groundspeed and time to the active (TO) waypoint in the pilot’s primary optimum field of view. Where not viable, a readily accessible page on a control display unit, readily visible to the flight crew, may display the data.
(5) Display of TO/FROM the active waypoint.
The navigation system must provide a TO/FROM display in the pilot’s primary optimum field of view.
Note: See paragraph 8-3.g(2) for TO/TO navigation computer displays.
(6) Desired Track Display.
The navigation system must have the capability to continuously display to the pilot flying the aircraft the RNAV desired track. This display must be on the primary flight instruments for aircraft navigation.
(7) Display of Aircraft Track.
The navigation system must provide a display of the actual aircraft track (or track angle error) either in the pilot’s primary optimum field of view or on a readily accessible and visible display to the flight crew.
(8) Failure Annunciation.
The aircraft must provide a means to annunciate failures of any aircraft component of the RNAV system, including the navigation sensors. The annunciation must be visible to the pilot and located in the primary optimum field of view.
A2-13
Appendix 2
(9) Slaved Course Selector.
The navigation system must provide a course selector automatically slaved to the RNAV computed path.
(10) RNAV Path Display.
Where the minimum flight crew is two pilots, the navigation system must provide a readily visible means for the pilot monitoring to verify the aircraft’s RNAV defined path and the aircraft’s position relative to the desired path.
(11) Display of Distance to Go.
The navigation system must provide the ability to display distance to go to any waypoint selected by the flight crew.
(12) Display of Distance Between Flight Plan Waypoints.
The navigation system must provide the ability to display the distance between flight plan waypoints.
(13) Display of Deviation.
The navigation system must provide a numeric display of the vertical deviation with a resolution of 10 feet or less, and the lateral deviation with a resolution of 0.01 NM or less.
(14) Display of Barometric Altitude.
The aircraft must display barometric altitude from two independent altimetry sources, one in each pilots’ primary optimum field of view to support an operational cross check of altitude sources.
Note 1: If the aircraft includes the ability to automatically compare the output of the independent altitude sources, including independent aircraft static air pressure systems, and the aircraft can provide an alert in the pilot’s primary optimum field of view when deviations between the sources exceed ±100 feet, then the applicant should document this comparator monitoring function in the AFM/RFM or aircraft qualification guidance.
Note 2: As stated in paragraph A2-3.b(1)(c) note 3 of this appendix, using GPS/SBAS vertical guidance precludes the need for independent monitoring as prescribed by AC 90-101 (latest revision), appendix 4, paragraph 3.h.
A2-14
Appendix 2
(15) Display of Active Sensors.
(a) The aircraft must display the current navigation sensor(s) in use. The aircraft should provide this display in the primary optimum field of view.
Note: Flight crew procedures may mitigate the need for this display if the applicant and/or operator can demonstrate the flight crew workload is acceptable.
(b) In-service aircraft that do not display the current navigation sensor in use may still be eligible for RNP AR approach operations. To be eligible, the aircraft manufacturer must demonstrate continued RNP AR approach performance when GNSS is lost (for example, through inertial navigation) and continue to monitor/annunciate loss of RNP capability (i.e., annunciating “Unable RNP”). Since the loss of GNSS is unlikely:
(i) The aircraft performance must show the conditional probability the aircraft exits the final approach obstacle clearance volume is less than 0.001 (one in a thousand). This ensures that 999 times out of 1000 the aircraft can complete an RNP AR approach when a loss of GNSS occurs.
(ii) To support execution of the missed approach procedure, the aircraft performance must show the conditional probability the aircraft exits the missed approach obstacle clearance volume is less than 0.01 (one in a hundred). This will ensure that 99 times out of 100 the aircraft can complete a missed approach procedure from the lowest minimums following loss of GNSS.
Note 1: Executing a missed approach is unlikely given the weather condition requirements to begin an RNP AR approach procedure. Therefore, the conditional probability requirement for the procedure’s missed approach is less stringent than the performance requirement for the procedure’s final approach segment.
Note 2: The aircraft manufacturer may conduct the aircraft performance demonstration through laboratory and simulation analysis. Flight test data collection and demonstration in the actual aircraft is not required.
f. Hazard Affects.
(1) The system must be consistent with at least a major failure condition for the display of misleading lateral or vertical guidance on an RNP AR approach.
(2) The system must be consistent with at least a major failure condition for the loss of lateral guidance and a minor failure condition for loss of vertical guidance on an RNP AR A2-15
Appendix 2 approach.
Note 1: Loss of vertical guidance is considered a minor failure condition because the pilot can take action to stop descending or climb when guidance is lost.
Note 2: The guidance in paragraph A2-3.f of this appendix is consistent with the intent of AC 90-101A. However, AC 90-101A contains an editorial error that could cause confusion among RNP AR 0.3 and less than 0.3 for misleading guidance versus loss of guidance.
g. Navigation Database.
The aircraft navigation system must use an on-board navigation database that can:
• Receive updates in accordance with the AIRAC cycle; and
• Allow retrieval and loading of RNP AR procedures into the RNAV system.
h. Database Protection.
(1) The aircraft's navigation system must not permit the flight crew to modify the stored data in the onboard navigation database.
Note: When the flight crew selects and loads a procedure from the onboard navigation database, the RNAV system must execute the procedure as published. This does not preclude the flight crew from having the means to modify a procedure or route already loaded into the RNAV system.
However, no modification of the procedures stored in the onboard navigation database may occur, and the procedures must remain intact within the onboard navigation database for future use and reference.
(2) The aircraft must provide a means to display the validity period for the onboard navigation database to the flight crew.
A2-4. Requirements for RNP AR Approaches with RF Legs.
RNP AR procedures may have RF legs intercept the final approach segment of approaches inside the final approach fix and the RNP value of the RF legs can be less than 1.0. RNP AR applicants including RF leg capability must ensure the aircraft systems will support these features. See appendix 3 for detailed RF leg guidance. The AFM(S)/RFM(S) or aircraft qualification guidance should identify whether or not RF leg capability is provided.
A2-16
Appendix 2 A2-5. Requirements for RNP AR Approach values less than 0.3.
The AFM/RFM or aircraft qualification documentation should identify if the aircraft is capable of using lines of minima associated with RNP less than 0.3, and which equipment configuration is required to achieve this capability (e.g., dual autopilots may achieve a smaller RNP capability than dual FDs).
a. No single-point-of-failure can cause the loss of guidance compliant with the RNP value associated with the approach. Typically, the aircraft must have at least the following equipment: dual GNSS sensors, dual FMSs, dual air data systems, dual autopilots, and a single inertial reference unit (IRU).
b. The system must be consistent with at least a hazardous (severe-major) failure condition for the display of misleading lateral or vertical guidance on an RNP AR approach where the procedure requires RNP less than 0.3 while executing an approach.
Note: AC 20-174, Development of Civil Aircraft and Systems, provides an acceptable method for establishing design assurance levels and may be used to show compliance with this requirement. This guidance provides an acceptable method for establishing a design assurance process by taking into account the overall aircraft operating environment and the independent functions of the aircraft’s systems.
c. The system must be consistent with at least a hazardous (severe-major) failure condition for the loss of lateral guidance and a minor failure condition for the loss of vertical guidance on an RNP AR approach where the procedure requires RNP less than 0.3 while executing an approach.
Note 1: Directly meeting this requirement can substitute for the general requirement for dual equipment (described above).
Note 2: Loss of vertical guidance is considered a minor failure condition because the pilot can take action to stop descending or climb when guidance is lost.
Note 3: The guidance in paragraphs A2-5.b and A2-5.c of this appendix is consistent with the intent of AC 90-101A.
However, AC 90-101A contains an editorial error that could cause confusion among RNP AR 0.3 and less than
0.3 for misleading guidance versus loss of guidance.
d. Upon initiating a go-around or missed approach (through activation of TOGA or other means), the flight guidance mode should remain in LNAV. If the aircraft does not provide the ability to remain in LNAV, then the following requirements apply:
A2-17
Appendix 2
(1) If the aircraft supports RF legs, the lateral path guidance after initiating a go-around (given a minimum 50-second straight segment between the RF end point and the DA) must be within 1 degree (1°) of the track defined by the straight segment through the DA point (see Figure 1). The prior turn can be of arbitrary angular extent and radius as small as 1 NM, with speeds commensurate with the approach environment and the radius of the turn.
(2) The flight crew must be able to couple the autopilot or FD to the RNAV system (engage LNAV) by 400 feet AGL.
e. After initiating a go-around or missed approach following loss of GNSS, the aircraft must automatically revert to another means of navigation that complies with the RNP value.
A2-6. Requirements for Approaches with a Missed Approach Segment Less Than RNP 1.0.
a. The AFM/RFM or aircraft qualification guidance should identify whether or not the aircraft can achieve less than RNP 1.0 when executing a missed approach procedure segment.
The AFM/RFM or aircraft qualification guidance should also specify the aircraft configurations or modes of operation necessary to achieve RNP values less than 1.0 (e.g., dual autopilots may achieve a smaller RNP capability than dual FD).
b. No single-point-of-failure can cause the loss of guidance or loss of lateral guidance display with the RNP value associated with a missed approach procedure. Typically, the aircraft must have at least the following equipment: dual GNSS sensors, dual FMSs, dual air data systems, dual autopilots, and a single IRU.
(1) The system must be consistent with at least a major failure condition for the loss of lateral guidance compliant with the RNP value on an RNP AR missed approach segment that requires RNP less than 1.0.
Note: What this means is, lateral guidance may still be available even though the RNP value cannot be maintained.
As an example, an UNABLE RNP annunciation represents a loss of lateral guidance compliant with the RNP value.
However, aircraft navigation remains available because lateral guidance is not lost; there is simply a loss of confidence and integrity in the lateral guidance.
(2) For RNP AR missed approach segment operations requiring less than 1.0, the total loss of display of lateral guidance to the flightcrew is a hazardous (severe-major) failure condition.
(3) The system must be consistent with at least a hazardous (severe-major) failure condition for the display of misleading lateral guidance where the RNP AR missed approach segment requires RNP less than 1.0.
A2-18
Appendix 2 Note: It may be possible to obtain approval for navigation functions that have hazardous level effects with FMS software developed to DO-178B or ‘C’ level C criteria.
AC 20-174 provides an acceptable method for establishing design assurance levels. This guidance may be helpful for navigation architectures containing independent functions.
c. Upon initiating a go-around or missed approach (through activation of TOGA or other means), the flight guidance mode should remain in LNAV to enable continuous track guidance, particularly during an RF leg. If the aircraft does not provide this capa bility, the following requirements apply:
(1) If the aircraft supports RF legs, the lateral path after initiating a go-around (TOGA) (given a minimum 50 second straight segment between the RF end point and the DA) must be within 1 degree of the track defined by the straight segment through the DA point (see Figure 1). The prior turn can be of arbitrary angular extent and radius as small as 1 NM, with speeds commensurate with the approach environment and the radius of the turn.
(2) The flight crew must be able to couple the autopilot or FD to the RNAV system (engage LNAV) by 400 feet AGL.
d. After initiating a go-around or missed approach following loss of GNSS, the aircraft must automatically revert to another means of navigation that complies with the RNP value.
A2-19
T
Appendix 2
Public RNP AR Procedures Minimum Straight Segments between Turns and Decision Altitude GS = Category Speed + 15 kt Figure 3. Minimum Straight Path Before DA A2-7. Navigation Data Validation Program.
The aircraft’s onboard navigation database defines the RNP AR procedure path and RF in final DA Direction of Flight If there is a turn before or after the DA , Distance before or after DA computed from Distance ( NM ) = GS ( KT ) * T ( SEC )/ 3600 where Runway DER LTP Min Time = 50 s RF in miss Min Time = 10 s A2-20