Appendix 2 APPENDIX 2. AIRCRAFT QUALIFICATION
1. Introduction. This appendix describes the performance and functional criteria for aircraft to qualify for Required Navigation Performance (RNP) Authorization Required (AR) approaches.
Applicants may establish compliance with this appendix as part of a type certification or Supplemental Type Certification (STC) and document this in the Aircraft Flight Manual Supplement (AFMS). The type-certificate holder of a previously certified aircraft can document compliance with these aircraft qualification criteria without a new airworthiness project
(e.g., without an Aircraft Flight Manual (AFM) change), and should advise the appropriate Aircraft Certification Office (ACO) of any new performance not covered by the original airworthiness approval. The AFM or other aircraft qualification evidence should address:
the required modes of operation to fly an RNP AR approach; the normal and abnormal flightcrew operating procedures; responses to failure alerts and annunciations; and any other operating limitations. In addition to the specific RNP AR guidance in this document, the aircraft must comply with the current edition of Advisory Circular (AC) 20-138( ), Airworthiness Approval of Positioning and Navigation Systems.
2. Performance Requirements. This paragraph defines the general performance requirements for aircraft qualification. Paragraphs 3, 4, and 5 provide guidance material on an acceptable means of satisfying these requirements.
a. Path Definition. The published instrument approach procedure (IAP) and section 3.2 of RTCA/DO-236( ), Minimum Aviation System Performance Standards: Required Navigation Performance for Area Navigation, define the path the aircraft must use to evaluate performance.
The aircraft’s navigation system will also define all Vertical Paths (VPATH) in the Final Approach Segment (FAS) by a Flight Path Angle (FPA) (RTCA/DO-236( ), Section 3.2.8.4.3) as a trajectory to a fix and altitude.
b. Lateral Accuracy. The aircraft must comply with RTCA/DO-236( ), Section 2.1.1.
c. Vertical Accuracy. The vertical system error includes altimetry system error (ASE) (assuming the temperature and lapse rates of the International Standard Atmosphere (ISA)), the effect of Along-Track Error (ATE), system computation error, data resolution error, and Flight Technical Error (FTE). The 99.7 percent of system error in the vertical direction must be less than the following (in feet):
NOTE: Where θ is the vertical navigation (VNAV) path angle, h is the height of the local altimetry reporting station and ∆h is the height of the aircraft above the reporting station.
( )( )( ) ( ) ( )( ) ( )( )( ) 22 22 28 36076115 1 225 60 75 88 10 65 10 50. . tan tan . .RNP h h h hθθ ∆ ∆−−⋅ + + + − ⋅+ + ⋅+ +
Appendix 2
d. Airspace Containment. The Federal Aviation Administration (FAA) publishes RNP AR approaches as performance-based approaches. As such, they do not inherently require any specific technology or procedure but instead require a level of performance.
(1) Primary Means of Compliance. This AC provides a detailed acceptable means of compliance for aircraft using an Area Navigation (RNAV) system relying primarily on Global Navigation Satellite System (GNSS) and a VNAV system relying on barometric altimetry or Satellite-based Augmentation Systems (SBAS). Paragraphs 3, 4, and 5, in conjunction with guidance described in Appendices 3 and 4, describe an acceptable means of achieving the RNP.
Aircraft and operations complying with these paragraphs provide the requisite airspace containment.
(2) Other Systems or Alternative Method of Compliance (AMOC). For other systems or AMOC, the probability of the aircraft exiting the lateral and vertical extent of the obstacle clearance volume must not exceed 10-7 per approach, including the missed approach.
An operator may satisfy this requirement through an operational safety assessment applying:
appropriate quantitative, numerical methods; qualitative operational and procedural considerations and mitigations; or an appropriate combination of both quantitative and qualitative methods.
NOTE: If the aircraft does not remain within the obstacle clearance volume after annunciating the system’s failure, then this requirement applies to the total probability of excursion outside the obstacle clearance volume. This includes events caused by latent conditions (integrity) and by detected conditions (continuity). When ensuring the aircraft does not exit the obstacle clearance volume, an analysis of the aircraft performance should consider the monitor limit of the alert, the latency of the alert, the crew reaction time, and any aircraft response to the alert. The requirement applies to a single approach, considering the exposure time of the operation and the Navigational Aid (NAVAID) geometry and navigation performance available for each published approach.
NOTE: This containment requirement derives from the operational requirement. This requirement is notably different from the containment requirement specified in RTCA/DO-236( ). The requirement in RTCA/DO-236( ) facilitates airspace design and does not directly equate to obstacle clearance.
e. System Monitoring. The critical components of RNP AR approach procedure implementation are the RNP requirements of the approach and the ability of the aircraft navigation system to both monitor navigation performance and alert the pilot when RNP requirements are not being met.
3. RNP AR General Requirements.
NOTE: RTCA/DO-236( ) provides additional information concerning many of the required functions for RNP AR aircraft qualification.
Appendix 2
a. Position Estimation. The navigation system must estimate the aircraft’s position. This section identifies unique issues for the navigation sensors within the context of RNP AR instrument approaches.
(1) GNSS.
(a) The GNSS sensor must comply with the guidelines in AC 20-138( ). The total system accuracy analysis may use the following sensor accuracies without additional substantiation: GNSS sensor accuracy better than 36 meters (95 percent), and augmented GNSS (Ground Based Augmentation Systems (GBAS) or SBAS) sensor accuracy is better than 2 meters (95 percent).
(b) In the event of a latent GNSS satellite failure and marginal GNSS satellite geometry (e.g., Horizontal Integrity Limit (HIL) equal to the horizontal alert limit), the probability that the Total System Error (TSE) remains within the procedure design obstacle clearance volume must be greater than 95 percent (both laterally and vertically).
NOTE: GNSS-based sensors output an HIL, also known as a horizontal protection level (HPL) (refer to AC 20-138( ), Appendix 1, and RTCA/DO-229( ), Minimum Operational Performance Standards for Global Positioning System/Wide Area Augmentation System Airborne Equipment, for an explanation of these terms). HIL is a measure of the position estimation error assuming a latent failure is present. In lieu of a detailed analysis of the effects of latent failures on the TSE, an AMOC for GNSS- based systems is to ensure HIL remains less than twice the RNP value, minus the FTE 95 percent, during the RNP AR approach operation.
(2) Inertial Reference Unit (IRU). An IRU must satisfy the criteria of Title 14 of the Code of Federal Regulations (14 CFR) part 121 appendix G. While appendix G defines the requirement for a drift rate of 2 nautical miles (NM) per hour for flights up to 10 hours, this rate does not apply to an RNAV system after loss of position updating. A manufacturer may assume an IRU demonstrating compliance with part 121 appendix G experiences an initial drift rate of 4 NMs for the first 30 minutes (95 percent) without further substantiation. Aircraft manufacturers and applicants can demonstrate improved inertial performance in accordance with the methods described in Appendix A or B of the current edition of FAA Order 8400.12( ), Required Navigation Performance 10 (RNP 10) Operational Approval.
NOTE: Integrated GNSS/IRU position solutions reduce the rate of degradation after loss of position updating. For “tightly coupled” GNSS/IRUs, RTCA/DO-229( ), Appendix R, provides additional guidance.
(3) Distance Measuring Equipment (DME). GNSS-updating is the basis for initiating all RNP AR approach procedures. The aircraft may use DME/DME-updating as a reversionary navigation mode during an RNP AR approach or missed approach when the navigation system continues to comply with the required RNP value. The manufacturer should also identify any requirements for the DME infrastructure and/or any necessary operational procedures and
Appendix 2 limitations for conduct of an RNP AR approach procedure through the use of DME/DME-updating of the aircraft’s position.
(4) Very High Frequency (VHF) Omni-Directional Range Station (VOR).
The aircraft’s RNAV system may not use VOR-updating during public RNP AR instrument approach procedures (IAP). The manufacturer should identify any flightcrew procedures or techniques for a given aircraft to comply with this requirement.
NOTE: The aircraft need not have a direct means of inhibiting VOR updating. The operator may meet the requirement of this paragraph by providing operational procedures enabling flightcrews to inhibit VOR-updating or procedures requiring a missed approach upon annunciation of reversion to VOR-updating.
(5) Multi-Sensor Systems. There must be automatic reversion to an alternate RNAV sensor if the primary RNAV sensor fails. However, there need not be automatic reversion from one multi-sensor system to another multi-sensor system.
(6) ASE. The 99.7 percent aircraft ASE for each aircraft (assuming the temperature and lapse rates of the ISA) must be less than or equal to the following with the aircraft in the approach configuration:
(ft) (where H is the true altitude of the aircraft)
(7) Temperature Compensation Systems. Temperature compensation systems with an airworthiness approval providing corrections to the barometric vertical navigation (baro-VNAV) guidance must comply with RTCA/DO-236( ), Appendix H.2. This requirement applies to the FAS. Manufacturers should document compliance to this standard to allow the operator to conduct RNP AR approaches when the actual temperature exceeds the temperature limits published on the RNP AR approach chart.
b. Path Definition and Flight Planning.
(1) Maintaining Track and Leg Transitions. The aircraft must have the capability to execute leg transitions and maintain tracks consistent with the following paths:
(a) A geodesic line between two fixes;
(b) A direct path to a fix;
(c) A specified Track to Fix (TF), defined by a course; and
(d) A specified track to an altitude.
NOTE: You can find the industry standards for these paths in RTCA/DO-236( ) and ARINC Specification 424, which refer to them as TF, Direct to Fix (DF), Course to a Fix (CF), and fix to an altitude (FA) path terminators. Also, certain procedures require RF legs as described in 82 388 10 65 10 50..ASE H H−−= − ⋅⋅ + ⋅⋅ +
Appendix 2 paragraph 4 of this appendix. European Organization for Civil Aviation Equipment (EUROCAE) ED-75( ), RTCA/DO-236( ) and ED-77/DO-201( ) describe the application of these paths in more detail.
NOTE: The navigation system may accommodate other ARINC 424 path terminators (e.g., VM) and the Missed Approach Procedure (MAP) may use these types of paths when there is no requirement for RNP containment.
(2) Flyby and Flyover Turns. The aircraft must have the capability to execute flyby and flyover turns. For flyby turns, the navigation system must limit the path definition within the theoretical transition area defined in RTCA/DO-236( ) under the wind conditions identified in Order 8260.58( ). Since the flyover turn is not compatible with RNP flight tracks, RNP AR procedure design will use a flyover turn at a fix only when there is no requirement for RNP containment.
(3) Waypoint Resolution Error. The Navigation System Database (NDB) 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 construction of flight plan waypoints. The NDB must contain vertical angles (Flight Path Angles (FPA)) 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 flightcrew can activate at any time. This function must be available to any fix. The system must also be capable of generating a geodesic path to the designated “To” fix, without “S-turning” and without undue delay.
NOTE: The manufacturer should identify any limitations associated with the operational use of the aircraft navigation system’s “Direct-To” function.
For example, if there are limitations associated with intercepting an RF leg segment, the AFM or aircraft qualification guidance should identify those limitations.
(5) Capability to Define a VPATH. The navigation system must be capable of defining a VPATH by an FPA to a fix. The system must also be capable of specifying a VPATH between altitude constraints at two fixes in the flight plan. The navigation system must also define fixed altitude constraints as one of the following:
(a) An “AT or ABOVE” altitude constraint (e.g., 2400A may be appropriate for situations where bounding the VPATH is not a requirement);
(b) An “AT or BELOW” altitude constraint (e.g., 4800B may be appropriate for situations where bounding the VPATH is not a requirement);
(c) An “AT” altitude constraint (e.g., 5200); or
(d) A “WINDOW” constraint (e.g., 2400A3400B).
Appendix 2
(6) Altitudes and/or Speeds. The navigation system must extract from the onboard NDB the altitudes and/or speeds defined in published terminal procedures.
(7) Path Construction. The navigation system must be able to construct a path to provide guidance from current position to a vertically constrained fix.
(8) Capability to Load Procedures from the NDB. The navigation system must have the capability to load the entire flight procedure into the RNAV system from the onboard NDB.
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 means for the flightcrew to verify the flight procedure through review of the data stored in the onboard NDB. This includes the ability to review the data for individual waypoints and for NAVAIDs.
(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 NDB.
(11) Changes in RNP Value. Changes to lower RNP values must be complete by the first fix defining the leg with the lower value. The manufacturer must identify any operational procedures necessary to meet this requirement.
NOTE: One acceptable means to meet this requirement may be manually setting the lowest RNP value contained within the RNP AR procedure, prior to commencing the approach.
(12) Automatic Leg Sequencing. The navigation system must provide the capability to automatically sequence to the next leg and display the sequencing to the flightcrew in a readily visible manner.
(13) Altitude Restrictions. A display of the altitude restrictions associated with flight plan fixes must be available to the pilot. The equipment must display the FPA associated with any flight plan leg of an RNP AR procedure.
c. Demonstration of Path Steering Performance. When a demonstration of RNP capability includes a demonstration of the aircraft’s path steering performance (i.e., FTE), you must conduct that demonstration in accordance with AC 120-29( ), paragraphs 5.19.2.2 and 5.19.3.1.
d. Displays.
(1) Continuous Display of Deviation. 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).
Appendix 2
(a) The aircraft should have an appropriately-scaled, non-numeric deviation display
(i.e., lateral deviation indicator (LDI) and vertical deviation indicator (VDI)) in the pilot’s primary optimum field of view (FOV). A fixed-scale course deviation indicator (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 the RNP value, 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., en route, terminal area, and approach), then displaying the operational mode is an acceptable means from which the flightcrew may derive the CDI scale sensitivity.
(b) In lieu of appropriately scaled LDIs and VDIs in the pilot’s primary optimum FOV, a numeric display of deviation may be acceptable depending on the flightcrew workload and the numeric display characteristics.
(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 FOV, or on a readily accessible and visible display to the flightcrew.
(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 FOV. Where not viable, a readily accessible page on a control display unit (CDU), readily visible to the flightcrew, may display the data.
(4) Display of Groundspeed (GS) and Time. The navigation system must provide the display of GS and time to the active (To) waypoint in the pilot’s primary optimum FOV. Where not viable, a readily accessible page on a CDU, readily visible to the flightcrew, may display the data.
(5) Display of To/From the Active Fix. The navigation system must provide a To/From display in the pilot’s primary optimum FOV.
(6) Desired Track Display. The navigation system must have the capability to continuously display to the pilot flying the desired RNAV track. This display must be on the primary flight instruments for navigation of the aircraft.
(7) Display of Aircraft Track. The navigation system must provide a display of the actual aircraft track (or track angle error (TKE)) either in the pilot’s primary optimum FOV, or on a readily accessible and visible display to the flightcrew.
(8) Failure Annunciation. The aircraft must provide a means to annunciate failures of any component of the RNAV system, including the navigation sensors. The annunciation must be visible to the pilot and located in the primary optimum FOV.
(9) Slaved Course Selector. The navigation system must provide a course selector automatically slaved to the RNAV computed path.
Appendix 2
(10) RNAV Path Display. Where the minimum flightcrew 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 flightcrew.
(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 FOV, to support an operational cross check of altitude sources.
NOTE: If the aircraft can automatically compare the output of the independent altitude sources, including independent static air pressure systems, and can provide an alert in the pilot’s primary optimum FOV when deviations between the sources exceed ±100 feet, manufacturers should document this comparator-monitoring function in the AFM or aircraft qualification guidance.
(15) Display of Active Sensors. The aircraft must display the current navigation sensor(s) in use. The aircraft should provide this display in the primary optimum FOV.
NOTE: The flightcrew can use this display for operational contingency procedures. Flightcrew procedures may mitigate the need for this display if the manufacturer and/or operator can demonstrate that the flightcrew workload is acceptable.
e. Design Assurance.
(1) The System Design Assurance (SDA) 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 SDA 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 a RNP AR approach.
NOTE: 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.
Appendix 2
f. NDB.
(1) NDB. The aircraft navigation system must use an onboard NDB which can:
(a) Receive updates in accordance with the Aeronautical Information Regulation and Control (AIRAC) cycle; and
(b) Allow retrieval and loading of RNP AR procedures into the RNAV system.
(2) Database Protection. The aircraft’s navigation system must not permit the flightcrew to modify the stored data in the onboard NDB.
NOTE: When the flightcrew selects and loads a procedure from the onboard NDB, the RNAV system must execute the procedure as published. This does not preclude the flightcrew 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 NDB may occur, and the procedures must remain intact within the onboard NDB for future use and reference.
(3) Validity Period. The aircraft must provide a means to display to the flightcrew the validity period for the onboard NDB.
4. Requirements for RNP AR Approaches with RF Legs. This section defines additional requirements to conduct approaches with RF legs. The AFM or aircraft qualification guidance should identify whether this is a provided capability.
a. Capability. The navigation system must have the capability to execute leg transitions and maintain tracks consistent with an RF leg between two fixes.
NOTE: If the aircraft cannot proceed “Direct-To” the initial fix defining an RF leg segment, or “Direct-To” an intermediate segment of an RF leg segment, the AFM or aircraft qualification guidance should document these limitations.
b. Electronic Map. The aircraft must have an electronic map display of the selected procedure.
c. Commanding a Bank Angle. The flight management computer (FMC), the flight director (FD) system, and autopilot must be capable of commanding a bank angle up to 25 degrees above 400 feet above ground level (AGL) and up to 8 degrees below 400 feet AGL.
d. Flight Guidance Mode. Upon initiating a go-around or missed approach (through activation of takeoff/go-around (TOGA) or other means), the flight guidance mode should remain in lateral navigation (LNAV).
NOTE: If the flight guidance does not remain in LNAV upon initiation of a go-around or missed approach, then the manufacturer and/or operator should define flightcrew contingency procedures for maintaining compliance
Appendix 2 with the desired track and re-engaging LNAV as soon as possible. These contingency procedures should clearly address flightcrew actions should a go-around or missed approach begin with the aircraft established on or having just completed an RF leg segment.
5. Requirements for Using Lines of Minima Less Than RNP 0.3. The AFM or aircraft qualification documentation should identify if the aircraft is capable of using lines of minima associated with RNP less than 0.3, and the required equipment configuration to achieve this capability. For example, dual autopilots may achieve a smaller RNP capability than dual FDs.
a. Loss of Guidance. 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 flight management systems (FMS), dual air data systems (ADS), dual autopilots, and a single IRU.
b. Design Assurance/Misleading Guidance. The SDA 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 to avoid obstacles or terrain while executing an approach.
NOTE: The applicant should document systems designed consistent with this effect, and this documentation may eliminate the need for application of operational mitigations for the aircraft.
c. Design Assurance/Loss of Guidance. The SDA 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 to avoid obstacles or terrain while executing the approach.
NOTE: The AFM/Rotorcraft Flight Manual (RFM) should document systems designed consistent with the effect. This documentation should describe the specific aircraft configurations or modes of operation achieving RNP values less than 0.3. Meeting this requirement can substitute for the general requirement for dual equipment (described above).
NOTE: 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.
d. Flight Guidance Mode. Upon initiating a go-around or missed approach (through the 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, the following requirements apply:
(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 decision altitude (DA)), must be within 1 degree of the track defined by the straight segment through the DA point (refer to Figure 1, Minimum Straight Path Before Decision Altitude). The prior turn
Appendix 2 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 flightcrew must be able to couple the autopilot or FD to the RNAV system (engage LNAV) by 400 feet AGL.
e. Other Means of Navigation. 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.
NOTE: Since loss of GNSS is unlikely, one means of compliance with this requirement is to show that in the event GNSS is lost (i.e., when annunciation of the loss of RNP capability occurs prior to the aircraft reaching the DA), the conditional probability of the aircraft exiting the final approach obstacle clearance volume should be less than 0.001 (one in a thousand). This will ensure that 999 times out of 1,000 the aircraft can complete an RNP AR approach should a loss of GNSS occur. Additionally, the conditional probability of the aircraft exiting the missed approach obstacle clearance volume should be less than 0.01 (one in one hundred). This will ensure that 99 times out of 100 the aircraft can complete a MAP from the lowest minimums should a loss of GNSS occur. Since executing a missed approach is unlikely under normal weather conditions, this conditional probability is less stringent than the requirement for the FAS.
6. Requirements for Approaches with a Missed Approach Requiring RNP Less Than 1.0.
The AFM or aircraft qualification documentation should identify if the aircraft is capable of achieving less than RNP 1.0 when executing a MAP and the required equipment to achieve this capability. For example, dual autopilots may achieve a smaller RNP capability than dual FDs.
a. Loss of Guidance. No single point of failure can cause the loss of guidance compliant with the RNP value associated with a MAP. Typically, the aircraft must have at least the following equipment: dual GNSS sensors, dual FMSs, dual ADSs, dual autopilots, and a single IRU.
b. Design Assurance. The SDA must be consistent with at least a major failure condition for the loss of lateral or vertical guidance on an RNP AR approach when the MAP requires RNP less than 1.0 to avoid obstacles or terrain.
NOTE: For RNP AR missed approach operations requiring less than 1.0 to avoid obstacles or terrain, the loss of display of lateral guidance is a hazardous (severe/major) failure condition. The AFM should document systems designs consistent with this effect. This documentation should describe the specific aircraft configurations or modes of operation achieving RNP values less than 1.0 during a MAP. Meeting this requirement can substitute for the general requirement for dual equipment (described above).
Appendix 2
c. Flight Guidance Mode. Upon initiating a go-around or missed approach (through the 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 capability, the following requirements apply:
(1) If the aircraft supports RF legs, the lateral path 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 of the track defined by the straight segment through the DA point (refer to 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 flightcrew must be able to couple the autopilot or FD to the RNAV system (engage LNAV) by 400 feet AGL.
d. Other Means of Navigation. After initiating a go-around or missed approach following the loss of GNSS, the aircraft must automatically revert to another means of navigation that complies with the RNP value.
NOTE: Since loss of GNSS is unlikely, one means of compliance with this requirement is to show that in the event GNSS is lost (i.e., when annunciation of the loss of RNP capability occurs prior to the aircraft reaching the DA) the conditional probability of the aircraft exiting the final approach obstacle clearance volume should be less than 0.001 (one in a thousand). This will ensure that 999 times out of 1,000 the aircraft can complete an RNP AR approach should a loss of GNSS occur. Additionally, the conditional probability of the aircraft exiting the missed approach obstacle clearance volume should be less than 0.01 (one in one hundred). This will ensure that 99 times out of 100 the aircraft can complete a MAP from the lowest minimums should a loss of GNSS occur. Since executing a missed approach is unlikely under normal weather conditions, this conditional probability is less stringent than the requirement for the FAS.