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. Equipment Performance - RNP (General).
7-1. Introduction.
a. The intent of the RNP chapters 7-10 and 17 along with appendix 2 and 3 is to provide the airworthiness guidance manufacturers need for implementing RNP capability when used in conjunction with the performance and installation chapters in this AC applicable to the equipment. The airworthiness information in this AC supersedes the airworthiness guidance in all revisions of ACs 90-101 and 90-105. Applicants should not base their new RNP AR or RNP airworthiness applications on the 90-series ACs because that guidance is not complete for airworthiness purposes. However, previous airworthiness approvals based on those ACs remain valid.
b. RTCA/DO-236C, Chg 1, Minimum Aviation System Performance Standards:
Required Navigation Performance for Area Navigation, dated June 19, 2013, and RTCA/DO 283B are closely linked to provide coherent RNP standards at both the aircraft level and RNP equipment level respectively.
(1) Aircraft manufacturers that use the type certificate process for all design, production and airworthiness approval of RNP capability may use RTCA/DO-236C, Chg 1 as the compliance standard at the aircraft level. While the RNP equipment is included as part of the type certificate, it should comply with RTCA/DO-283B (as modified by TSO-C115d) although requirements trade-offs are possible as long as the aircraft performance meets the requirements of RTCA/DO-236C, Chg 1.
(2) RNP equipment manufacturers building equipment for later installations (i.e., not associated with an aircraft OEM type certificate) cannot anticipate the installed RNP airworthiness capability at the aircraft level. These projects should use the standards in RTCA/DO-283B, as modified by TSO-C115d, for their RNP equipment.
Note: TSO-C115d includes significant modifications to the standards in RTCA/DO-283B. Manufacturers choosing to use the standards in RTCA/DO-283B must incorporate the TSO C115d modifications.
c. A database is an essential component necessary for RNP equipment to perform its intended function. RNP equipment operational approval for IFR use is based upon a database assurance process through a type 2 LOA. A type 2 LOA provides database objective evidence of integrity consistent with the monitoring and alerting requirement for RNP systems.
d. Chapter 8 is specific to the equipment performance considerations for RNP approach (RNP APCH) procedures; chapter 9 is specific to the equipment performance considerations for RNP enroute and terminal operations; and chapter 10 is specific to the equipment performance considerations for oceanic RNP. Chapter 17 describes installation considerations for RNP. Airworthiness guidance for RNP AR, including installation considerations, is addressed in appendix 2 of this AC while appendix 3 of this AC describes advanced RNP functions. Appendix 7 contains templates t o demonstrate RF leg capability.
RNP AR and RNP operational approval guidance can be found in the latest revisions of ACs 53
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.
e. A foundation for RNP operations in the U.S. NAS relies on the ability to perform RNP 2.0, RNP 1.0, and RNP APCH operations (excluding RNP AR operations) to the LNAV line of minima. It is important to understand that RNP is an aircraft- level capability comprising the sensor, navigation computer, database, display systems, and flight guidance integration; not just an FMS function or TSO label. In general, aircraft with properly installed GNSS systems qualify for RNP 2.0, RNP 1.0, and RNP APCH to LNAV minima, but there are some additional considerations (see chapters 8 and 9 for specific guidance).
f. Aircraft may have additional RNP capabilities such as RNP APCH to LNAV/VNAV or LPV line of minima, or advanced RNP functions.
(1) GPS/SBAS and FMS equipment manufacturers should provide a statement in the RNP capabilities document for these additional RNP capabilities provided the equipment is installed according to the installation instructions/manual. Reference paragraphs 12-7.b and A5-2 for more information regarding the RNP capabilities document. The statement of RNP capabilities should be part of the installation instructions/manual.
(2) These additional capabilities have aircraft integration dependencies that must be considered during the airworthiness approval before the RNP capability can be approved at the aircraft-level.
g. TSO-C129(AR) equipment may not support all foundational RNP operations due to the minimum requirements in those TSOs. See chapters 8 and 9 for specific guidance on aircraft with TSO-C129(AR) equipment.
h. GPS/SBAS and GPS/GBAS sensors can be approved on aircraft without baro- VNAV to provide vertical path guidance for RNP 0.3 operations and RNP AR operations as low as RNP 0.1. However, all aircraft and FMS requirements for RNP and RNP AR operations still apply. Refer to chapters 15 and 17 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 RTCA/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 for RNP 2.0, RNP 1.0 and RNP APCH to LNAV minima.
Class 2 and Class 3 equipment provide vertical guidance for RNP approaches when operating within GPS/SBAS coverage.
i. 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 provider’s coverage area to use GPS/SBAS or GPS/GBAS for RNP and RNP AR operations.
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 AR 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. GNSS is the primary navigation system to support RNP approach procedures. The missed approach segment may be based upon a conventional NAVAID (e.g., VOR, DME, NDB), but DME/DME-based systems are not acceptable for RNP APCH.
b. Tightly-coupled GPS/IRU or GPS/SBAS/IRU systems can provide a coasting capability in the event GPS positioning is not available.
7-3. Special Characteristics of RNP 1.0 and RNP 2.0 Operations.
a. RNP 1.0 is used on the initial, intermediate and missed approach segments of instrument approaches along with obstacle departure procedures (ODPs), standard instrument departures (SIDs), and STARs. DME/DME/IRU and/or GNSS are the primary navigation systems supporting RNP 1.0 operations.
b. RNP 2.0 routes are intended for operations in oceanic and remote areas. GNSS is the primary navigation system to support RNP 2.0 operations.
Chapter 8. Equipment Performance - RNP Approach.
8-1. Introduction.
This chapter provides guidance on the performance and functional criteria 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 11. B aro-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 Criteria.
a. Aircraft with the following avionics equipment that meet the applicable installation chapters in this AC automatically qualify for RNP APCH to LNAV minima capability without further documentation by virtue of the avionics TSO and airworthiness approval:
• TSO-C115c (or later revision) FMS with a TSO-C129(AR) Class B1 or C1, TSO C145(AR), or TSO-C196(AR) sensor;
Note: See paragraph 8-3.g(2) for “TO/TO” navigation computers.
• TSO-C146 Class Gamma equipment;
• TSO-C129(AR), Class A1 equipment; or,
• Aircraft with an RNP AR approval.
b. A TSO-C115b FMS using a TSO-C129(AR) Class B1/C1, TSO-C145(AR), or TSO C196(AR) sensor with documented compliance to the RNP requirements in RTCA/DO-236 (revision ‘B’ or later) or RTCA/DO-283 (revision ‘A’ or later) as part of the approval basis also provides RNP APCH to LNAV minima capability without further evaluation.
Note: See paragraph 8-3.g(2) for “TO/TO” navigation computers.
c. Avionics or aircraft manufacturers may provide a service bulletin for a pilot or equipment operating handbook entry, or other notification stating aircraft with the equipment in paragraphs 8-2.a and 8-2.b, and an appropriate airworthiness approval, has RNP APCH to LNAV line of minima capability.
Note 1: Aircraft with RNP APCH to LNAV minima capability based on TSO-C129(AR) and TSO-C196(AR) GNSS have limitations requiring operators to perform pre-departure RAIM checks.
Note 2: TSO-C129a has been cancelled so it is not possible to receive a new TSO-C129a TSOA. But equipment with an existing TSO-C129a TSOA may still be produced and installed.
Note 3: New airworthiness approval applicants should consider including RNP APCH to LNAV minima as part of their application and document the capability in the AFM(S)/RFM(S). Doing so could benefit customers seeking operational approvals.
d. Multi-sensor systems that use DME/DME or DME/DME/IRU as the only means of RNP compliance are not authorized to conduct RNP APCH to LNAV minima. However, operators still retain the option to develop special RNP approaches using these systems.
8-3. Performance and Functional Criteria for RNP Systems.
a. Accuracy.
(1) During operations on the initial and intermediate segments and for the missed approach of a RNP APCH 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.
(2) 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.
(3) Table 9 in chapter 17 indicates allowable “FTE credit” for various RNP operations when using autopilot, flight director, or manual flight control. Applicants may use these FTE values toward meeting TSE for the desired RNP operation without further demonstration or evaluation. Applicants may use different FTE values provided they demonstrate the aircraft complies with the appropriate TSE specified for the operation in paragraphs 8-3.a(2) and 8-3.a(3).
Note: Applicants may use 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. It is acceptable to use smaller deviation scaling, such as 0.3 NM full-scale deflection for the initial, intermediate, and final approach segment.
However, the final approach segment scaling must not be smaller than 0.3 NM (not applicable to RNP AR, LP/LPV, GLS, or when using RTCA/DO-229() angular scaling).
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 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. Path Definition.
Aircraft performance is evaluated around the path defined by the published RNP APCH procedure. RNP equipment should provide lateral guidance so aircraft remain within the lateral boundaries of the defined RNP APCH procedure. Aircraft performance should comply with RTCA/DO-236C, Chg 1. Additionally, when constructing the descent path for the final approach segment of an RNP instrument approach procedure, the RNP equipment must always use the procedure-defined flight path angle.
Note: RNP instrument approach procedures may have a final approach fix with an ‘AT’ altitude constraint. The intent of the guidance in paragraph 8-3.e is to use the published flight path angle for descent path construction.
This is to ensure geometric point-to-point between two ‘AT’ constraints is not used for the final approach segment.
f. Signal in Space.
During GNSS 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 GNSS operations on the final approach segment, the aircraft navigation equipment must provide an alert if the probability of signal-in-space errors causing a lateral position 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.
g. Functional Criteria for Navigation Displays.
(1) The RNP system must have the following navigation displays and functions installed in accordance with this AC. 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 criteria 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. However, TO/TO RNP systems must accommodate route discontinuities and continue providing navigation information.
(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 must 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. It is also acceptable for the scaling to be more conservative than the TSE; for example, ±0.3 NM for the initial, intermediate, and missed approach segments.
(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 and be located in the primary field of view.
(4) It is not necessary for navigation displays, particularly primary flight displays, to include an actual navigation performance (ANP) or RNP accuracy value. The displays only need to provide an alert if the RNP criteria for the operation cannot be met.
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 flight crew 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 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 databas e, 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) Active navigation sensor type;
(d) The identification of the active (To) waypoint;
(e) The ground speed or time to the active (To) waypoint; and
(f) 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 documents DO-236C Chg 1, DO 283B (as modified by TSO-C115d), and RTCA/ DO-201A, Standards for Aeronautical Information, dated April 19, 2000.
Note 2: Numeric values (e.g., RNP values) for procedures must be automatically loaded from the RNP system database.
(11) The capability to display an indication of the RNP system failure in the pilot’s primary field of view.
(12) The capability to indicate to the crew when the NSE alert limit is exceeded (alert provided by the “onboard performance monitoring and alerting function”).
i. Flight Director/Autopilot.
It is recommended that the flight director (FD) and/or autopilot remain coupled for RNP approaches. If the lateral TSE cannot be demonstrated without these systems, then coupling becomes mandatory. In this instance, operating guidance must indicate that coupling to the FD and/or autopilot from the RNP system is mandatory for approaches.
j. Database Integrity.
The navigation database suppliers must comply with AC 20-153(latest revision). A Type 2 LOA, issued by the appropriate regulatory authority, demonstrates compliance with this requirement. Type 2 LOAs issued prior to this AC are considered compliant.
8-4. System Eligibility and Approval for RNP APCH Operations.
a. Introduction.
The original equipment manufacturer (OEM) or the holder of installation approval for the aircraft (e.g., STC holder), must demonstrate compliance with the appropriate provisions of this AC to the FAA and the approval can be documented in manufacturer documentation
(e.g., Service Letters, etc.). AFM/RFM entries are not required provided the FAA accepts the manufacturer’s documentation.
b. Eligibility for RNP Instrument Approach Operations.
Systems meeting the criteria in paragraphs 8-2 and 8-3 are eligible for RNP instrument approach operations.
Chapter 9. Equipment Performance - RNP Enroute and Terminal.
9-1. Introduction.
This chapter provides guidance on the performance and functional criteria for RNP 2.0 operations in remote/oceanic enroute areas and RNP 1.0 operations in terminal areas. RNP 1.0 can be used to conduct RNP instrument departure procedures (including RNP ODPs and SIDs) and RNP STARs within the U.S. NAS where domestic air traffic control procedures are applied. Paragraph 9-5 provides guidance on the performance and functional criteria for rotorcraft enroute RNP 0.3 in terminal/enroute and offshore areas.
Note: There is no intent to use RNP 2.0 for domestic enroute operations in the U.S.
9-2. Aircraft and System Criteria for RNP 2.0 and RNP 1.0.
a. Aircraft with the following avionics equipment automatically qualify for RNP 2.0 and RNP 1.0 capability without further documentation by virtue of the avionics TSO and airworthiness approval:
• TSO-C115c (or later revision) with a TSO-C129(AR) Class B1 or C1, TSO-C145(AR), or TSO-C196(AR) sensor.
Note: See paragraph 8-3.g(2) for “TO/TO” navigation computers.
• TSO-C146(AR) Class Gamma equipment;
• Aircraft with an RNP AR approval.
b. A TSO-C115b FMS using a TSO-C129(AR) Class B1/C1, TSO-C145(AR), or TSO-C196(AR) sensor with documented compliance to the RNP requirements in RTCA/DO-283A as part of the approval basis also provides RNP 2.0 and RNP 1.0 capability without further evaluation.
Note: See paragraph 8-3.g(2) for “TO/TO” navigation computers.
c. Avionics or aircraft manufacturers may provide a service bulletin for a pilot or equipment operating handbook entry, or other notification stating aircraft with the equipment in paragraphs 9-2.a and 9-2.b, and an appropriate airworthiness approval, has RNP 2.0 and 1.0 capability.
Note 1: The pilot or operating handbook entry must describe the steps necessary to access the capability.
Note 2: New airworthiness approval applicants should consider including RNP 2.0 and 1.0 as part of their 63