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.
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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:
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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.
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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.
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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
Appendix 2 associated constraints, allowing for lateral and vertical guidance. In view of the reduced obstacle clearance associated with RNP AR procedures, the associated navigation database information warrants special attention and consideration. This paragraph provides guidance for validating RNP AR instrument approach data contained in aircraft navigation databases. The guidance in this paragraph applies in full to aircraft operators performing RNP AR instrument approach procedures, as well as to any other entity with which an operator may contract to provide navigation database validation services.
Note 1: Although an aircraft operator may contract with an outside entity to perform navigation database validation services, the operator is responsible for ensuring the aircraft navigation database contains RNP AR instrument approach procedures validated in accordance with this appendix.
Note 2: An aircraft operator’s application to conduct RNP AR procedures should specifically describe the extent and nature of the services provided by an outside entity contracted to perform navigation database validation services.
a. Database Management Process.
The operator must identify in writing the individual responsible for managing the overall onboard navigation database process. The process and procedures for accepting, verifying and loading navigation data into the aircraft must be established in writing and maintained under configuration control (e.g., formal control of revisions and updates to the process). The operator may not contract out this responsibility to a third party.
b. RNP AR Procedure Data Validation.
The operator must ensure an RNP AR instrument approach procedure contained in its database has been validated before flying that approach procedure in IMC. The validation process ensures the RNP AR procedure contained in the navigation database accurately reflects the intended procedure design parameters. Proper data validation includes the following:
(1) Accuracy Check.
Compare the RNP AR procedure in the navigation database with the government source data. The FAA Form 8260-series, specifically form 8260-3 and 8260-10, and other government source data defining the procedure, are available at the FAA Aviation System Standards website. Data for international procedures is available via the respective country’s aeronautical information publication (AIP). Any differences between the database and source data must be investigated. A list of the specific procedure data parameters that must be examined during this accuracy check, as well as the allowable differences between source data and that contained in the navigation database for each parameter can be found at the FAA’s Performance Based Flight Systems Branch (AFS-470) website located at:
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Appendix 2 http://www.faa.gov/about/office_org/headquarters_offices/avs/offices/afs/afs400/afs470/rnp/
(2) Flyability Check.
An initial flyability check is required for all non-part 97 U.S. RNP AR procedures, as well as all foreign RNP AR procedures the operator is authorized to fly. Validate the RNP AR instrument approach procedures in the navigation database to ensure they match the published instrument approach procedures using: the actual aircraft in visual meteorological conditions; a flight simulation training device (FSTD) approved for RNP AR; or an appropriately configured desktop/laptop computer. An FSTD or desktop/laptop computer must use software identical to that used by the aircraft (i.e., FMS software) and use an aerodynamic model of the aircraft's flight characteristics. A map display must be used in the aircraft, FSTD or computer to compare the database procedure with that published. This validation process requires flying the entire procedure and should confirm the path is flyable, does not contain any lateral or vertical discontinuities, and is consistent with the published procedure.
c. Data Updates.
(1) Before using an updated navigation database (e.g., 28 day update), the operator must ensure the RNP AR approach data contained in that update remains within the tolerances prescribed in paragraph A2-7.b(1) of this appendix, when compared to the government source data. If a data parameter is found to exceed prescribed tolerances , the operator should consult with the appropriate navigation data supplier to resolve the discrepancy prior to using the approach procedure. Discrepancies may be resolved by correcting the error within the current cycle, removal of the procedure from the database, or potentially through operational mitigations approved by the FAA until the procedure data can be corrected.
(2) The method by which an operator conducts this recurring data comparison is optional, subject to the approval of the principle operations inspector or flight standards district office. One acceptable method is to establish a reference database, sometimes referred to as a “golden database,” containing known validated approach data, and comparing data from subsequent navigation updates against this reference data. Some FMS suppliers provide automated tools that enable a quick comparison of data parameters between databases and alert to any changes or differences. Operators may also choose to compare the navigation data contained in the updated database directly against the government source data. Regardless of the method used, operators must assure the integrity of the validated navigation data at each update cycle.
Note: An operator should be particularly attentive to potential discrepancies when database updates coincide with a change to the data supplier’s packing software. This packing software is used to format the navigation data into code readable by aircraft avionics.
d. Data Suppliers.
As a minimum, data suppliers must have an LOA for processing navigation data in A2-22
Appendix 2 accordance with AC 20-153(latest revision). An LOA recognizes the data supplier as one whose data quality, integrity, and quality management practices are consistent with an acceptable process. The aircraft operator’s supplier (e.g., FMS manufacturer) must have a Type 2 LOA. Those entities providing data to the aircraft operator’s supplier likewise must possess either a Type 1 or Type 2 LOA.
e. Aircraft Modifications.
If a manufacturer modifies an aircraft system required for RNP AR operations
(e.g., software or hardware change), the operator must, before flying any RNP AR procedures in IMC, confirm the aircraft’s ability to fly RNP AR procedures as published, with the modified aircraft system(s). The operator should examine a number of RNP AR procedures in its navigation database for this flyability check. The criteria described in paragraph A2-7.b(2) of this appendix should be used to perform this check.
Note: The operator does not need to perform this additional confirmation if the manufacturer documents the modification has no effect on the navigation database, or path computation.
f. Recurrent Audits.
The processes identified in this paragraph for validating and updating RNP AR instrument approaches in navigation databases are subject to recurrent FAA audits. The operator’s processes, as well as those performed by any outside entity contracted to provide navigation database services, are subject to audit by the FAA. Additionally, operators are expected to conduct their own recurrent audits of entities with whom they contract to provide navigation database services described in this appendix.
A2-8. Installation Considerations for RNP AR.
a. Detailed Rationale.
The applicant should provide:
(1) RNP Certification Plan.
Provide detailed rationale in the RNP certification plan (or project specific certification plan) for the use of RNP. This rationale should include a detailed explanation as to how the assigned levels support the system safety assessment, as well as a detailed explanation of the system architecture, including any means used to mitigate hazards and failure conditions resulting from the use of RNP. Additionally, include a detailed explanation of the interfaces between the FD, the autopilot and other sensors, and avionics hardware/software required, as it relates to the computed commands used for RNP.
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Appendix 2
(2) Software Problem Reports.
Present clarification on how existing open software problem reports are resolved within the aircraft or other equipment that could directly or indirectly affect the RNP approval.
Open software problems or changes that could affect RNP operations should be addressed.
b. Failure Modes/Annunciation.
Identify any failure modes potentially affecting RNP capability. Verify annunciation of RNP failure modes exists. This verification should be compatible during manual flight and with the aircraft’s FGS to ensure unambiguous flight crew action(s). Verify that following failure modes, any pilot selected entries are retained or their cancellations annunciated (e.g., manual entry of RNP type, blackballed navaid, etc.). Typical failure modes include loss of electrical power, loss of signal reception, and RNP equipment failure (including degradation of navigation performance resulting in a loss of RNP containment integrity). The aircraft manufacturer should also verify that a visual alert within the flight crew’s primary field of view occurs with a loss of navigation capability and/or loss of RNP containment integrity.
An aural alert should accompany the visual alert.
c. Aircraft Manufacturer Installation Guidelines.
The aircraft manufacturer should comply with the following installation guidelines. Avionics manufacturers should note the following guidance to ensure their positioning and navigation equipment can support RNP operations.
(1) Each installation of RNP equipment requires an airplane flight manual containing the limitations and operating procedures applicable to the installed equipment. In addition, an RNP capabilities document for the system should be developed and submitted for FAA approval. The RNP capabilities document should be referenced in the airplane flight manual and made available to the operator upon request. The document will provide a description of the system, including assumed operating environment, the interface of the navigation function to the flight crew, the specific navigation capabilities of the system and potential application.
The intended use of the document will be to facilitate operational approval of the navigation capability for RNP operations. The flight manual or referenced capabilities document should contain at least the following information:
(a) A statement indicating the aircraft meets the requirements for RNP and demonstrated the established minimum RNP capabilities. This documentation should include:
the phase of flight (e.g., oceanic, enroute, terminal area, approach), mode of flight (e.g., manual, FD on or off, and/or autopilot on or off, and applicable lateral and vertical modes), minimum demonstrated RNP value, and sensor limitations, if any (e.g., GPS required). The phase of flight description should indicate what procedure design criteria the navigation performance is designed to support, as applicable.
(b) Any conditions or constraints on path steering performance (e.g., autopilot engaged, FD or manual control with CDI or map display, including lateral and vertical modes A2-24
Appendix 2 and/or CDI/map scaling requirements).
(c) The criteria used for the demonstration of the system, acceptable normal and non-normal procedures, the demonstrated configurations, type of facilities used, and any constraints or limitations necessary for safe operation.
(d) Define all the assumptions on systems external to the aircraft (e.g., signal in space performance, coverage, and survey accuracy). This includes GNSS-based limitations in the AFM(S)/RFM(S) for RNP AR APCH availability predictions at the destination, or checking NOTAMs. These predictions are consistent with the equipment performance described in chapter 5.
(i) A pre-departure RAIM prediction (FD or FDE as appropriate) is acceptable for GPS-based RNP AR operations that are limited to RNP AR 0.3 accuracy.
(ii) GPS/SBAS provides improved availability and enhanced accuracy during RNP AR operations. An RNP AR operation that is limited to RNP AR 0.3 accuracy based on GPS/SBAS only needs to confirm via NOTAM that there is no GPS/SBAS outage.
(iii) A pre-departure FDE RAIM prediction is acceptable for RNP AR operations limited to RNP AR 0.3 accuracy when outside of the GPS/SBAS coverage area or during a GPS/SBAS outage.
(iv) A pre-departure RNP prediction must be conducted prior to dispatch for accuracy values below RNP AR 0.3 (i.e., RNP AR < 0.3). If no RNP prediction capability is available (either external to the aircraft or within the navigation system), then the operator must not plan to use RNP AR < 0.3. Instead, the operator must plan to use RNP AR 0.3 if that line of minima exists for the procedure.
Note: The guidance on RNP prediction only applies to RNP AR operations conducted in the U.S. national airspace system. This does not apply to RNP AR operations in other ICAO States. When operating in another State’s airspace, operators must follow the RNP AR operational requirements for that State.
(2) If compliance to the continuity requirements has been shown through a combination of navigation sensors, the AFMS/RFMS should contain a statement that “Continuity of RNP navigation has been demonstrated only where the operational environment supports all of the following types of sensors: <insert type of sensors for which credit is being sought>.
d. Flight Technical Error (FTE).
The aircraft manufacturer should verify maintenance of FTE (95% of the flying time) during straight and curved path segments per Table 9. The FTE should be demonstrated in each phase of flight and each autopilot mode.
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Appendix 2
e. Interface to FGS.
Verify acceptable autopilot response to an RNP fault by simulating a representative fault consistent with the equipment architecture (e.g., pulling the circuit breaker) for the RNP equipment. The aircraft manufacturer should complete this test in each of the RNP and autopilot modes, as applicable.
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Appendix 3 Appendix 3. Advanced RNP Functions.
A3-1. Introduction.
a. ICAO document 9613 Performance Based Navigation (PBN) Manual, fourth edition, 2013 lists six advanced RNP functions. The six functions are:
• RF legs
• Parallel offsets
• Scalable RNP
• RNAV holding
• Fixed radius transitions (FRT)
• Time of arrival control (TOAC) Note: The PBN Manual includes Higher Continuity as an advanced RNP function. Higher continuity is not really a function, but a result of the hazard level associated with advance RNP functions affecting aircraft equipage (see paragraph A3-1.e).
b. The equipment must include RF legs, Parallel offsets, Scalable RNP, RNAV holding, and FRTs for advanced RNP recognition. The rationale for including all of these functions is for international harmonization. To include advanced RNP recognition, t he equipment, at a minimum, must meet the performance and functional criteria for RNP 2.0, RNP
1.0 and RNP APCH to LNAV minima.
(1) TSO-C115d implements RTCA/DO-283B which provides acceptable methods of implementing advanced RNP functions in RNP equipment consistent with the aircraft performance requirements found in RTCA/DO-236C, Chg 1.
(2) At present, the U.S. intends to implement only RF legs, Parallel offsets, and Scalable RNP which constitutes the U.S. definition of advanced RNP. RNAV holding, FRT, and TOAC are presently considered optional advanced RNP functions in the U.S.
(3) Other States may choose to implement a different subset of functions, or all six functions for their advanced RNP definition.
(4) At present, TOAC is a function for longer-term implementation and remains optional for all equipment due to uncertain equipment requirements and airspace implementation.
c. Equipment manufacturers may decide to only implement a select set of advanced RNP functions rather than implementing all functions for “advanced RNP” recognition.
Implementing selected functions means the equipment will have limitations for the functions not implemented. That is, aircraft using equipment with a reduced set of functions will not receive “advanced RNP” recognition. These aircraft will be restricted from airspace that requires functions not implemented in the equipment, or that requires “advanced RNP” A3-1