Appendix 2
commanding a bank angle up to 30 degrees above 400 feet above ground level (AGL) and up to 8 degrees below 400 feet AGL.
d. Upon initiating a go-around or m issed approach (through activation of take-off/go around (TOGA) or other means), the flight guidance mode should remain in LNAV.
Note: If the flight guidance does not remain in LNAV upon initiation of a go-around or missed approach, then the applicant and/or operator should define flight crew contingency procedures for maintaining compliance with the desired track and re-engaging LNAV as soon as possible. These contingency procedures should clearly address flight crew actions should a go-around or missed approach begin with the aircraft established on or having just completed an RF leg segment.
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 design assurance 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. The system design assurance 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 an approach.
Note 1: The AFM/RFM should document systems designed consistent with this effect. This documentation should describe the specific aircraft configurations or modes of operation achieving RNP values less than 0.3.
A2-14
Appendix 2
Meeting this requirem ent 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 paragraph A2-5.b 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:
(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.
Note: Since loss of GNSS is unlikely, one means of compliance for this requirement is to show when GNSS is lost (i.e., when annunciation of loss of RNP capability occurs prior to the aircraft reaching the DA):
1) The conditional probability the aircraft exits the final approach obstacle clearance volume should be less than
0.001 (one in a thousand). This will ensure that 999 times out of 1000 the aircraft can complete an RNP AR approach should a loss of GNSS occur; and
2) The conditional probability the aircraft exits the missed approach obstacle clearance volume should be 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 should a loss of GNSS occur. Since executing a missed approach is unlikely under normal weather conditions, this conditional A2-15
Appendix 2
probability is less s tringent than the requirement for the final approach segment.
A2-6. Requirements for Approaches with a Missed Approach Less Than RNP 1.
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. 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).
a. No single-point-of-failure can cause the loss of guidance compliant 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 design assurance must be consistent with at least a major failure condition for the loss of lateral guidance on an RNP AR approach when the missed approach procedure requires RNP less than 1.0 to avoid obstacles or terrain.
(2) For RNP AR missed approach operations requiring less than 1.0 to avoid obstacles or terrain, the loss of the lateral guidance display is a hazardous (severe-major) failure condition.
Note: The AFM/RFM 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 missed approach procedure. Meeting this requirement can substitute for the general requirement for dual equipment (described above).
b. 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 capability, 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.
c. After initiating a go-around or missed approach following loss of GNSS, the aircraft A2-16
Appendix 2
must automatically revert to another m eans of navigation that complies with the RNP value.
Public RNP AR Procedures Minimum Straight Segments between Turns and Decision Altitude Min Time = 10 s RF in final DA LTP DER Runway RF in miss 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 GS = Category Speed + 15 kt Min Time = 50 s Direction of Flight Figure 1. M inimum Straight Path Before DA
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A2-7. Navigation Data Validation Program.
The aircraft’s onboard navigation database defines the RNP AR procedure path and associated constraints, allowing for lateral and vertical guidance. In view of the reduced obstacle clearance associated with RNP AR proc edures, 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 8260-10, 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 A2-18
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the navig ation database for each parameter can be found at the FAA’s Performance Based Flight Systems Branch (AFS-470) website located at:
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 United States 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.
A2-19
Appendix 2
d. Data Suppliers.
As a m inimum, data suppliers must have an LOA for processing navigation data in accordance with AC 20-153. An LOA recognizes the data supplier as one whose data quality, integrity and quality management practices are consistent with the criteria of DO-200A. The aircraft operator’s supplier (e.g., FMS company) 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: If the manufacturer documents the modification has no effect on the navigation database or path computation, the operator need not perform this additional confirmation.
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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(2) Software Problem Reports.
Present clarification on how open software problem reports are resolved that exist within the aircraft or other equipment that could directly or indirectly affect the RNP approval.
Open software problems or changes that could effect 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 perform ance (e.g., autopilot engaged, FD or manual control with CDI or map display, including lateral and vertical modes A2-21
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A2-22 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).
(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 2-6 in RTCA/DO-283A. The FTE should be demonstrated in each phase of flight and each autopilot mode.
e. Interface to FGS.
Verify acceptable autopilot response to an RNP fault by 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.
Appendix 3
Appendix 3. RNP Advanced Features.
A3-1. Introductio
n.
This appendix provides guidance on the performance and functional requirements for RNP systems containing radius to fix capability. This appendix does not apply to RNP AR; see appendix 2 for all RNP AR guidance.
A3-2. Radius to Fix Leg Capability.
RF legs are an optional capability rather than a minimum requirement for RNP operations.
This capability can be used in the initial, intermediate, and missed approach segments of instrument approaches, RNP DPs and RNP STARS. Additional information on RF legs may be found in the Aeronautical Information Manual. For RNP systems incorporating RF Leg capability, the systems must comply with the criteria in chapter 8 for RNP Approach, and chapter 9 for RNP 1 (terminal).
Note: RF legs will not be used in the final approach segment of an RNP approach.
a. System Requirements.
(1) Path Definition.
The RNP lateral accuracy requirement is evaluated around the path defined by the published procedure and RTCA/DO-236B, paragraph 3.2.3.3.
Note 1: Industry standards for paths can be found in RTCA/DO-236B.
Note 2: The guidance in this paragraph clarifies the intent in AC 90-105 for RNP Advanced Features. AC 90-105 mistakenly references RTCA/DO-236B paragraphs
3.2.5.4.1, Fly-By Transitions, and 3.2.5.4.2, Fixed-Radius Transitions, rather than paragraph 3.2.3.3, RF legs.
(2) Demonstration of Path Steering Performance.
The navigation system must have the capability to execute leg transitions and maintain tracks consistent with an RF leg between two fixes. There is no requirement for the aircraft to include a redundant navigation capability to perform RF legs should a loss of navigation occur during the RF leg. However, TC or STC applicants for RNP approval that include RF legs are encouraged to provide a redundant navigation capability on the aircraft that can maintain the RF leg track.
Note: The AFM/RFM or aircraft qualification guidance should document limitations if: 1) the aircraft cannot A3-1
Appendix 3
proceed “Direct-To” the initial fix defining an RF leg segm ent, 2) the aircraft cannot accept a radar vector (a heading assigned by ATC) to the middle of an RF leg segment for intercepting and completing the RF leg segment from that point while sustaining the desired level of performance.
(3) Flight Technical Error (FTE).
System documentation should support maintenance of FTE (95 percent of the flying time) during straight and curved path segments, for each phase of flight and each autopilot and/or FD mode requested. If using FTE values other than those listed in RTCA/DO-283A, the applicant must complete the demonstration in accordance with AC 120-29A, paragraphs 5.19.2.2 and 5.19.3.1.
Note: The applicant may use AC 120-29A, paragraphs
5.19.2.2 and 5.19.3.1 to compute accepted FTE values.
(4) Interface to FGS.
An acceptable autopilot and/or FD response to an RNP system failure or loss must be verified in each autopilot and FD mode, as applicable.
Note: If autopilot malfunction testing was performed for worst case failures, no further validation is required. In this case, the aircraft or equipment manufacturer must provide a statement of confirmation.
(5) Failure Modes/Annunciation.
System documentation should identify any failure modes potentially affecting RNP system RF Leg capability. Failure modes may include loss of electrical power, loss of signal reception, and RNP equipment failure, including navigation performance degradation, resulting in a loss of RNP containment integrity. The applicant should verify that a visible alert occurs within the flightcrew’s primary field of view when loss of navigation capability and/or loss of integrity are experienced.
b. Functional Requirements.
(1) Autopilot and Flight Director.
RNP procedures with RF legs require using an autopilot or FD with at least “roll-steering” capability that is driven by the RNP system. The autopilot/FD must operate with suitable accuracy to track the lateral and, as appropriate, vertical paths required by a specific RNP procedure.
A3-2
Appendix 3
A3-3
(2) Bank Angle.
The flight management computer, the FD system, and the autopilot must be capable of commanding a bank angle up to 25 degrees above 400 feet AGL.
(3) Electronic Map Display.
The aircraft must have an electronic map display depicting the RNP computed path of the selected procedure including RF legs.
(4) Maintaining LNAV in Missed Approach.
If abandoning a procedure while on an RF Leg or initiating a go-around or missed approach (through activation of TOGA or other means), the flight guidance mode should remain in LNAV to enable deviation and positive course guidance display during an RF leg. If the aircraft does not provide this capability, crew procedures must be used that assure the aircraft will adhere to the specified flight path during the RF Leg segment.
Note: For missed approaches with an RF Leg, the flightcrew must be able to couple the autopilot or FD to the RNP system (engage LNAV) by 500 feet AGL.
c. System Approval - Eligibility Airworthiness Documents.
The flight manual or referenced document should contain the following information:
(1) A statement indicating the aircraft meets the requirements for RNP operations with RF legs and has demonstrated the established minimum capabilities for these operations. This documentation should include the phase of flight, mode of flight (e.g., 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.
(2) Any conditions or constraints on path steering performance should be identified
(e.g., autopilot engaged, FD with map display, including lateral and vertical modes, and/or CDI/map scaling requirements). Use of manual control with CDI only is not allowed on RF legs.
(3) The applicant should identify the criteria used for the system demonstration, acceptable normal and non-normal procedures, the demonstrated configurations, type of facilities used, and any constraints or limitations necessary for safe operation.