docum ents). The GNSS/inertial hybrid outputs of the INS/IRU must meet the equipment requirements of appendix R. However, appendix R is not invoked by any TSO. It is acceptable for tightly coupled INS/IRU – GNSS hybrid sensors meeting appendix R to be integrated with FMS or multi-mode receivers for operational use under instrument flight rules on RNAV or RNP instrument routes or procedures.
c. The FAA assumes that GPS/inertial position data is limited to enroute through LNAV approach horizontal positioning. Using this position data for operations requiring higher precision would require other integrity and accuracy enhancements such as GPS/SBAS, GPS/GBAS, or other integrity/accuracy monitor function. Since hybrid vertical position and integrity has not been addressed by appendix R, any use should be identified and resolved as part of the appendix R approval process.
(1) No exclusion is intended for previously certified equipment meeting the requirements of RTCA/DO-229C, appendix R. It is acceptable to use previously certified GNSS sensors integrated with INS/IRU systems meeting the requirements specified in RTCA/DO-229C, appendix R. However, RTCA/DO-229C, appendix R assumed selective availability was ‘on’, so it may not adequately describe system performance if the applicant wishes to take credit for selective availability being ‘off.’
(2) Aircraft with GPS/inertial installations approved for LNAV approaches can also include a baro-VNAV installation to provide the vertical guidance deviations acceptable for LNAV/VNAV approaches. Chapters 10, 17, and 22 describe baro-VNAV performance and installation considerations.
d. Tightly coupled INS/IRU systems integrated with GNSS sensors outputting PVT that is the same as GNSS may be demonstrated to be equivalent to either TSO-C145c, or TSO- C196a and receive a GNSS TSOA/LODA. Any discrepancies should be identified and resolved as part of the TSO approval, but appendix R will take precedence. It may be necessary to conduct further evaluation during any follow-on approval since the characteristics and performance required for the inertial integration are closely linked to aircraft architecture, integration method, and GNSS failure modes.
(1) TSO-C129a has been cancelled so no new approvals to that standard are possible.
(2) Tightly coupled INS/IRU systems with an existing TSO-C129(AR) TSOA/LODA may still be produced and integrated with GNSS sensors that have an existing TSO-C129(AR) TSOA/LODA.
(3) Applicants requesting a TSO-C196a or TSO-C145c TSOA/LODA for their tightly coupled INS/IRU systems will need to include part number differentiation and installation instructions limiting integration to GNSS sensors approved to the same TSO.
e. When demonstrating RAIM or RAIM equivalency, the GPS signal-in-space failure modes to be used for the demonstration should be proposed and agreed upon as part of the TSO approval. For example, the applicant should address the correlated effects of multiple erroneous pseudoranges due to ionospheric activity. After exclusion of a faulty satellite, show 41
that the position solu tion is valid and the inertial states/models are not corrupted by the faulty GPS data prior to its detection and exclusion.
f. All attitude and heading data output by the integrated system must comply with the relevant regulations under all foreseeable operating conditions. This includes during GPS signal-in-space failures (including prior to detection and after exclusion).
g. In the absence of any GPS input, the attitude and heading data output by the integrated system must comply with the relevant regulations, including those conditions addressed in the aircraft functional hazard assessment (FHA).
Note: It may be necessary to revise the FHA to address failure conditions unique to the GPS/inertial system.
h. If the system sustains integrity coasting capability, the INS/IRU equipment manufacturer must document the coasting performance and limitations. That is, document the coasting time while sustaining performance at the desired navigation performance level, horizontal alert limit (HAL) or RNP. This documentation must be consistent with the alerting algorithms for the aircraft (e.g., RNP). The coasting performance should consider factors that could influence coasting times (e.g., inertial sensor accuracy, gyro misalignment, inertial parameter calibration accuracy prior to loss of GPS signals, aircraft maneuvers prior to and during the coasting period, and aircraft speed).
6-8. INS/IRU - DME/DME Integration.
a. Paragraph 6-8 defines a m inimum DME/DME/IRU (D/D/I) RNAV system baseline performance capable of supporting RNAV 1 and RNAV 2 routes, as well as RNAV 1 DPs and STARs. For routes and procedures designed using this performance standard, the FAA will decide if adequate DME coverage is available using FAA computer modeling and flight inspection assets. This assessment of DME coverage will also determine if an expanded service volume is necessary for select DME facilities.
b. The minimum DME/DME requirements of paragraph 6-4 apply and are not repeated here, except where additional performance is required. The performance confirmation process in paragraph 6-4.2 also applies to paragraph 6-8.
c. There is no requirement to use VOR, NDB, LOC, or AHRS during normal operation of the DME/DME/IRU RNAV system.
d. The 95% position estimation error must be better than or equal to the value obtained using the equation referenced in paragraph 6-4.f note 2 given any two DME facilities satisfying the criteria in paragraphs 6-4.b thru 6-4.d, and any combination of other valid DME facilities not meeting that criteria.
Note: Based on an evaluation of IRU performance, the growth in position error after reverting to IRU can be expected to be less than 2 NM per 15 minutes.
e. Inertial system performance must satisfy the criteria in paragraph 6-6.
f. Additional required FMS capabilities are:
(1) Automatic position updating from the DME/DME solution.
Note: Equipment manufacturers or airworthiness applicants should note in the appropriate documentation for the flight crew if any inertial coasting annunciation is suppressed following loss of radio updating.
(2) Accepting a position update immediately prior to takeoff.
(3) Excluding VORs greater than 40 NM from the aircraft.
g. The total system error (TSE) must be less than or equal to 1.0 NM (95%) throughout the route. To maximize the amount of IRU coasting allowed, the flight technical error for D/D/I aircraft on terminal procedures should be limited to 0.5 NM (95%).
Note: The FAA assures that systems meeting the D/D/I RNAV minimum performance standard satisfy this requirement on all identified routes and procedures, and these RNAV systems do not require further evaluation.
Systems seeking approval using different RNAV system characteristics or performance must demonstrate this performance for each published route or procedure.
Chapter 7. Equipmen t Performance - RNP (General).
7-1. Introduction.
a. The intent of the RNP c hapters 7-9 and 16 along with appendix 2 and 3 is to provide the airworthiness information found in AC 90-101A and AC 90-105 in this AC. The information is taken directly from AC 90-101A and AC 90-105, but contains some necessary minor changes due to formatting and grammar considerations. The information from AC 90-101A and AC 90-105 has not changed other than to recognize TSO-C196(AR) equipment and, in some places, add minor clarification information or correct mistakes. This is a necessary first step to consolidate all the positioning and navigation equipment airworthiness guidance and RNP airworthiness guidance into one AC. The plan is for future AC 90-101 and AC 90-105 revisions to remove the airworthiness guidance. Information on special characteristics of RNP operations and advantages of GPS/SBAS and GPS/GBAS for RNP operations incorporating vertical guidance is provided below.
b. Chapter 8 is specific to the equipment performance considerations for RNP approach procedures, and chapter 9 is specific to the equipment performance considerations for RNP terminal operations. Airworthiness guidance for RNP AR, including installation considerations, is addressed in appendix 2 of this AC while appendix 3 of this AC describes advanced features (radius to fix (RF) leg types) for RNP systems. Chapter 16 describes installation considerations for RNP. RNP AR and RNP operational approval guidance can be found in the latest revisions of ACs 90-101 and 90-105, respectively.
Note: RNP AR was previously named RNP SAAAR. The name has been changed to RNP AR for international harmonization.
c. GPS/SBAS and GPS/GBAS sensors can be approved on FMS-equipped aircraft without baro-VNAV to provide vertical path guidance for RNP 0.3 operations and RNP AR operations as low as RNP 0.1 with no change to existing RNP criteria, GPS/SBAS, or GPS/GBAS performance standards. However, all aircraft and FMS requirements for RNP and RNP AR operations still apply. Refer to chapters 14 and 16 of this AC (appendix 2 for RNP AR) for airworthiness guidance, and the latest revisions of AC 90-101, and AC 90-105 for operational guidance.
Note: TSO-C146(AR) invokes either DO-229 revision ‘C’ or ‘D’, section 2.2 for Class Gamma GPS/SBAS equipment. The navigation computer requirements in section 2.2 invoked by TSO-C146(AR) are a specific method of complying with the RNP requirements in DO-283A when using GPS/SBAS. Class 2 and Class 3 equipment do not require baro-VNAV for RNP approaches with vertical guidance when operating within GPS/SBAS coverage.
d. GPS/SBAS and GPS/GBAS used for RNP and RNP AR do not require the baro-VNAV temperature mitigations; however, the aircraft must be within the service 44
provider’s coverage area to use GPS/SBAS or GPS/GBAS for RNP and RNP AR oper ations.
The following are performance advantages for GPS/SBAS or GPS/GBAS compared to baro-VNAV for RNP and RNP AR:
(1) An accurate and repeatable vertical flight path with consistent alignment of the glide path angle (GPA) with visual landing cues and landing aids (e.g., visual approach slope indicator (VASI) or precision approach path indicator (PAPI)).
(2) No temperature restrictions on using the procedure.
(3) GPS/SBAS and GPS/GBAS can meet the RNP 0.1 vertical performance contours without independent system monitoring.
(4) The flight path is not affected by manual or Automated Traffic Information System (ATIS) altimeter setting errors.
7-2. Special Characteristics of RNP Instrument Approaches.
a. GPS is the prim ary navigation system to support RNP approach procedures. The missed approach segment may be based upon a conventional NAVAID (e.g., VOR, DME, NDB).
b. Unique Features and Requirements of RNP Approaches.
(1) RNP approaches normally include at least two lines of minima: LNAV and LNAV/VNAV. The LNAV/VNAV minima are based on using systems meeting the performance criteria for baro-VNAV systems in chapter 15.
(2) RF legs are discussed in appendix 3, RNP Advanced Features.
(3) Unless the pilot has in sight the visual references required to continue the approach, the procedure must be discontinued if any of the following conditions occur:
(a) The navigation display is flagged invalid.
(b) Loss of integrity alerting function.
(c) The integrity alerting function is activated before passing the FAF.
Note: Discontinuing the procedure may not be necessary for a GNSS fail-down condition to LNAV only, or for a multi-sensor RNP system that includes demonstrated RNP capability without GPS. Aircraft and/or equipment manufacturer documentation should be examined against functional and performance requirements to determine the extent the system may be used in such a configuration.
7-3. Special Characteristics of RNP 1 Operations.
a. Operation on RNP obstacle departure procedures (ODPs), standard instrum ent departures (SIDs), and STARs.
(1) Pilots are not required to monitor ground-based navigation facilities used in position updating unless required by the AFMS/RFMS.
(2) The navigation performance needed to fly RNP 1 procedures must be clearly designated on all appropriate charts.
b. Requirements for Navigation Infrastructure.
(1) If DME is used, the DME navigation infrastructure supporting the design of a procedure must be assessed and validated by the FAA or an FAA authorized third-party service provider. This includes a computer model assessment and an analysis by FAA flight inspection assets. DME coverage may use expanded service volume for select DME facilities so there is no requirement to use VOR, LOC, NDB, or AHRS during normal operation of the DME/DME RNP system. Expanded service volume facilities require a satisfactory flight inspection prior to use.
(2) DME signals must meet signal-in-space accuracy tolerances everywhere the signals are received in that procedure.
(3) For DME-based RNP operations where reliance is placed upon the IRU/Inertial Reference System (IRS), some aircraft systems revert to VOR/DME-based navigation before reverting to inertial coasting. When the VOR is within 40 NM from the procedure and there is insufficient DME/DME navigation infrastructure, the impact of VOR radial accuracy must be evaluated by the FAA and determined to not affect aircraft position accuracy.
(4) The FAA must monitor the navigation infrastructure and issue timely warnings of outages (NOTAM).
(5) All RNP 1 procedures must be flown by aircraft meeting the performance requirements in this AC using DME/DME/IRU and/or GPS.
(6) If any critical DME facilities exist, they must be identified within the relevant United States Flight Information Publications. All DME ground stations used to define the availability of these ODPs, SIDs, and STARs must comply with applicable ICAO standards.
Chapter 8. Equipmen t Performance - RNP Approach.
8-1. Introduction.
This chapter provides guidance on the perform ance and functional requirements for systems used to conduct RNP approach operations, which are designated under part 97 as RNAV (GPS) or GPS and categorized as RNP APCH in ICAO. The baro-VNAV equipment performance applicable to RNP approaches is specified in chapter 10. Baro-VNAV systems are optional capabilities that are not a minimum requirement to fly RNAV (GPS) or GPS approaches using the LNAV line of minima.
8-2. Aircraft and System Requirements.
The notes below apply to the entire paragraph.
a. Aircraft with approval to conduct R NAV (GPS) or GPS approaches meet the performance and functional requirements in this AC for RNP instrument approaches without RF legs.
b. Aircraft with a statement of compliance with the criteria in this AC in their airplane flight manual (AFM)/rotorcraft flight manual, AFMS/RFMS, pilot operating handbook (POH), or the operating manual for their avionics meet the performance and functional requirements for RNP instrument approaches. This presumes compliance with the operational guidance in AC
90-105.
c. Aircraft with a statement from the manufacturer documenting compliance with the criteria in this AC meet the performance and functional requirements for RNP instrument approaches. These statements should include the airworthiness basis for compliance.
Compliance with the sensor requirements will have to be determined by the equipment or aircraft manufacturer while compliance with the functional requirements in this chapter and chapter 14 may be determined by the manufacturer or by inspection by the operator, but must presume compliance with operational guidance in AC 90-105.
d. GPS stand-alone systems should be approved in accordance with TSO-C146(AR) Class 1, 2, or 3 or have an existing TSO-C129(AR) Class A1 approval (see 8-2.f note 2) and meet the applicable functionality and performance requirements of chapter 5, this chapter, and chapter 9. These systems should be installed for instrument flight rules (IFR) use in accordance with this AC.
e. GPS sensors used in multi-sensor system equipment (e.g., FMS) should be approved in accordance with TSO-C196(AR), or TSO-C145(AR) Class 1, 2, or 3 or have an existing TSO-C129(AR) Class B1, C1, B3, C3 approval (see 8-2.f note 2) and meet the performance and functionality requirements of chapter 5, this chapter, and chapter 9. These systems should be installed for IFR use in accordance with this AC.
f. Multi-sensor systems should be approved in accordance with TSO-C115b (or later revision), but may also have incomplete system TSO-C146(AR) Class Gamma approval (see paragraph 3-2.e) or an existing incomplete system TSO-C129(AR) Class A approval (see note 47
2). Those system s using GPS equipment should comply with the applicable GPS equipment chapters and chapters 6, 11-13, 15, 18-19, and 21 of this AC. These systems should also meet the performance and functionality requirements in this chapter.
Note 1: GPS equipment approved to TSO-C129(AR) must meet the system functions specified in this chapter. In addition, integrity should be provided by RAIM. It is recommended that GPS receivers include the pseudo-range step detection and health word checking functions if those functions were not specifically required for TSO approval (see appendix 1 for additional information).
Note 2: TSO-C129a has been cancelled so it is not possible to receive a new incomplete system TSO-C129a TSOA. But equipment with an existing TSO-C129a TSOA may still be produced and installed.
Note 3: Multi-sensor systems that use DME/DME or DME/DME/IRU as the only means of RNP compliance are not authorized to conduct RNP approaches. However, operators still retain the option to develop special RNP approaches using these systems.
8-3. Performance and Functional Requirements for RNP Systems.
a. Accuracy.
(1) The aircraft must com ply with RTCA/DO-236B, Minimum Aviation System Performance Standards: Required Navigation Performance for Area Navigation, dated October 28, 2003, paragraph 2.1.1.
(2) During operations on the initial and intermediate segments and for the missed approach of a RNP approach procedure, the lateral TSE must be within ±1 NM for at least 95 percent of the total flight time. The along-track error must also be within ±1 NM for at least 95 percent of the total flight time.
(3) During operations on the final approach segment, the lateral TSE must be within ±0.3 NM for at least 95 percent of the total flight time. The along-track error must also be within ±0.3 NM for at least 95 percent of the total flight time.
(4) To satisfy the accuracy requirement, the FTE should not exceed 0.5 NM on the initial, intermediate and missed approach segments of an RNP approach procedure. The FTE should not exceed 0.25 NM on the final approach segment of the approach.
Note 1: This requirement is considered satisfied as long as the TSE for each segment is not exceeded where the navigation system provides for RNP performance monitoring and alerting and where the integration of 48
operational modes and configuration s account for accuracy and FTE.
Note 2: Using a deviation indicator with 1 NM full-scale deflection on the initial, intermediate and missed approach segments and 0.3 NM full-scale deflection on the final approach segment is an acceptable means of compliance.
b. Integrity.
Malfunction of the aircraft navigation equipment that causes the TSE to exceed 2 times the RNP value without annunciation is classified as a Major failure condition under airworthiness regulations (i.e., 10-5 per hour).
c. Continuity.
Loss of function is classified as a minor failure condition if the operator can revert to a different navigation system and safely proceed to a suitable airport.
d. Performance Monitoring and Alerting.
During operations on the initial, intermediate, and the missed approach segments, the RNP System or the RNP system and pilot in combination must provide an alert if the accuracy requirement is not met or if the probability that the lateral TSE exceeds 2 NM is greater than 10-5. During operations on the final approach segment, the RNP system or the RNP system and pilot in combination must provide an alert if the accuracy requirement is not met or if the probability that the lateral TSE exceeds 0.6 NM is greater than 10-5.
e. Signal in Space.
During operations on the initial, intermediate, and missed approach segments, the aircraft navigation equipment must provide an alert if the probability of signal-in-space errors causing a lateral position error greater than 2 NM exceeds 10-7 per hour. During operations on the final approach segment, the aircraft navigation equipment must provide an alert if the probability of signal-in-space errors causing a navigation system error greater than 0.6 NM exceeds 10-7 per hour.
Note: There are no RNP requirements for the missed approach if it is based on conventional means (VOR, DME, and NDB) or on dead reckoning.
f. Path Definition.
Aircraft performance is evaluated around the path defined by the published procedure and RTCA/DO-236B, paragraph 3.2.5.4.1.
Note: The guidance in this paragraph provides equivalent performance to the intent in AC 90-105 for basic RNP 49
approach. AC 90-105 references R TCA/DO-236B, paragraph 3.2.5.4.2, Fixed-Radius Transitions, which is more closely associated with RNP Advanced Features in appendix 3.
g. Functional Requirements for Navigation Displays.
(1) The following navigation displays and functions are required, as installed in accordance with this AC or equivalent system installation advisory material. Navigation data, including a TO/FROM indication and a failure indicator, must be displayed on a lateral deviation display (course deviation indicator (CDI), electronic horizontal situation indicator (EHSI)) and/or a navigation map display. These must be used as primary flight instruments for aircraft navigation, for maneuver anticipation, and for failure/status/integrity indication.
Note: Unlike traditional, ground-based instrument procedures, some navigation computers construct RNP procedures by navigating to each procedure defined waypoint. This is referred to as “TO/TO navigation”. See paragraph 8-3.g(2) for guidance on RNP systems with navigation computers using TO/TO navigation algorithms.
(2) RNP systems using TO/TO navigation algorithms do not require a navigation display with a TO/FROM indication during RNP instrument procedures. Displays supporting TO/TO navigation computers can fully comply with all RNP-related requirements in this AC without a TO/FROM indication. At a minimum, the navigation display supporting a TO/TO RNP system should display the active waypoint and active waypoint name.
(a) If an aircraft’s sensor suite intends to support traditional navigation using ground-based navigation aids (such as executing a VOR-DME instrument approach procedure), then the aircraft and avionics manufacturers must ensure the aircraft installation properly accommodates these traditional, ground-based instrument flight procedures. A TO/FROM indication is essential to qualify the aircraft for these traditional procedures because they may rely on navigation to and from a navigation aid, an ad hoc fix assigned by air traffic control, or a defined fix.
(b) Additionally, a TO/FROM indication is necessary when the RNP system uses GNSS substitution for the ground-based navigation aid(s) defining a traditional instrument procedure.
(3) A non-numeric lateral deviation display (for example, CDI, EHSI), with a TO/FROM indication and a failure annunciation, used as primary flight instruments for aircraft navigation, for maneuver anticipation, and for failure/status/integrity indication, should have the following attributes:
Note: see paragraph 8-3.g(2) for TO/TO navigation computer displays.
(a) The displays m ust be visible to the pilot and located in the primary field of view.
(b) The lateral deviation display scaling should agree with any alerting and annunciation limits, if implemented.
(c) The lateral deviation display must have a full-scale deflection suitable for the current phase of flight and must be based on the TSE requirement. Scaling of ± 1 NM for the initial, intermediate, and missed approach segments and ±0.3 NM for the final segment is acceptable.
(d) The display scaling may be set automatically by default logic or set to a value obtained from a navigation database. The full-scale deflection value must be known or must be available for display to the pilot commensurate with approach values.
(e) The lateral deviation display must be automatically slaved to the RNP computed path. It is recommended that the course selector of the deviation display be automatically slewed to the RNP computed path.
Note: This does not apply for installations where an electronic map display contains a graphical display of the flight path and path deviation.
(f) As an alternate means, a navigation map display must provide equivalent functionality to a lateral deviation display with appropriate map scales (scaling may be set manually by the pilot). To be approved as an alternative means, the navigation map display must be shown to meet the TSE requirements and be located in the primary field of view.
h. System Capabilities.
The following system capabilities are required as a minimum:
(1) The capability to continuously display to the pilot flying, on the primary flight instruments for aircraft navigation (primary navigation display), the RNP computed desired path and aircraft position relative to the path. For operations where the required minimum flightcrew is two pilots, a means for the pilot not flying (pilot monitoring) must also be provided to verify the desired path and the aircraft position relative to the path.
(2) A navigation database, containing current navigation data officially promulgated for civil aviation, which can be updated in accordance with the aeronautical information regulation and control (AIRAC) cycle. The stored resolution of the data must be sufficient to achieve the required track keeping accuracy. The database must be protected against pilot modification of the stored data.
(3) The means to display the navigation data validity period to the pilot.
(4) The means to retrieve and display data stored in the navigation database relating to individual waypoints and navigation aids, to enable the pilot to verify the route to be 51
flown.
(5) Capability to load from the database into the RNP system the whole approach to be flown. The approach must be loaded from the database, into the RNP system, by its name.
(6) The means to display the following items, either in the pilot’s primary field of view, or on a readily accessible display page:
(a) Distance between flight plan waypoints;
(b) Distance to go to the waypoint selected by the pilot;
(c) Along track distances between waypoints;
(d) Active navigation sensor type;
(e) The identification of the active (To) waypoint;
(f) The ground speed or time to the active (To) waypoint; and
(g) The distance and bearing to the active (To) waypoint.
(7) The capability to execute a “Direct to” function.
(8) The capability for automatic leg sequencing with display to the pilots.
(9) The capability to execute RNP instrument approach procedures extracted from the onboard database including the capability to execute fly-over and fly-by turns.
(10) The capability to automatically execute leg transitions and maintain tracks consistent with the following ARINC 424 path terminators, or their equivalent:
(a) Initial Fix (IF).
(b) Track to Fix (TF).
(c) Direct to Fix (DF).
Note 1: Path terminators are defined in ARINC Specification 424, and their application is described in more detail in RTCA/DO-236B and RTCA/ DO-201A, Standards for Aeronautical Information, dated April 19, 2000.
Note 2: Numeric values for tracks must be automatically loaded from the RNP system database.