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
-- application and document the capability in the AFM(S)/RFM(S). Doing so could benefit customers seeking operational approvals.
d. TSO-C129(AR) Class A1 equipment typically supports RNP 1.0 operations associated with instrument approach and departure procedures, but might not support other operations requiring RNP 2.0 or RNP 1.0. TSO-C129(AR) avionics manufacturers should provide an RNP capabilities document stating compliance with the RNP criteria in this chapter for RNP 2.0 and RNP 1.0 capability. Avionics or aircraft manufacturers may provide a service bulletin for a pilot or equipment operating handbook entry, or other notification stating aircraft with this equipment has RNP 2.0 and RNP 1.0 capability based on the avionics manufacturer’s statement of compliance.
Note 1: If the equipment supports RNP 2.0 and RNP 1.0 capability, equipment manufacturers can use their AC 90 100A reference as an acceptable RNP statement of compliance.
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.
e. Multi-sensor systems that use DME/DME/IRU as the only means of RNP compliance must document the equipment meets the performance and functional criteria in paragraph 9-3. RNP 2.0 approvals are based on GNSS, including GNSS/IRU, due to implementation in remote/oceanic areas. Therefore DME/DME/IRU should not be the basis for any RNP 2.0 approvals.
f. RNP aircraft with P-RNAV approval based on GPS capability meet the functional criteria of this AC for RNP 1.0 operations, such as RNP DPs, RNP SIDs, and RNP STARS.
Note 1: RNP 1.0 operations are based on GPS positioning or DME/DME/IRU if adequate DME coverage is available.
Positioning data from other types of navigation sensors may be integrated with the GPS data provided it does not cause position errors exceeding the TSE budget.
Otherwise, means should be provided to deselect the other navigation sensor types.
Note 2: RNP 2.0 for remote/oceanic operations must meet the continuity requirements associated with a major failure condition.
9-3. Performance and Functional Criteria.
a. Accuracy.
(1) During terminal operations in airspace or on routes designated as RNP 1.0, the lateral TSE must be within ±1 NM for at least 95 percent of the total flight time. The alongtrack error must also be within ±1 NM for at least 95 percent of the total flight time.
(2) 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.
Note: Using a lateral deviation indicator with 1 NM full-scale deflection is an acceptable means of compliance for maintaining TSE. An autopilot or FD may also be used for maintaining TSE, but roll stabilization systems do not qualify.
(3) During enroute operations in airspace or on routes designated as RNP 2.0, the lateral TSE must be within ±2 NM for at least 95 percent of the total flight time. The alongtrack error must also be within ±2 NM for at least 95 percent of the total flight time.
(4) 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.
Note: Using a lateral deviation indicator with 2 NM full-scale deflection is an acceptable means of compliance for maintaining TSE. An autopilot or FD may also be used for maintaining TSE, but roll stabilization systems do not qualify.
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 for RNP 1.0 if the operator can revert to a different navigation system and proceed to a suitable airport. For RNP 2.0 remote/oceanic airspace applications, loss of function is a major failure condition.
d. Performance Monitoring and Alerting.
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:
(1) 2 NM is greater than 10-5 for RNP 1.0 operations; or,
(2) 4 NM is greater than 10-5 for RNP 2.0 operations.
e. Path Definition.
RNP equipment should provide lateral guidance so aircraft remain within the lateral boundaries of the defined RNP route. Aircraft performance should comply with RTCA/DO-236C, Chg 1.
f. Signal-in-Space.
If using GNSS, the aircraft navigation equipment must provide an alert if the probability of signal-in-space errors causing a lateral position error greater than:
(1) 2 NM exceeds 10-7 per hour for RNP 1.0 operations; or,
(2) 4 NM exceeds 10-7 per hour for RNP 2.0 operations.
g. Functional Criteria of Navigation Data Displays.
(1) The RNP system must have the following navigation displays and functions installed in accordance with this AC.
(2) Navigation data, including a TO/FROM indication and a failure indicator, must be displayed on a lateral deviation display (CDI, 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. 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 when looking forward along the flight path.
(b) The lateral deviation display scaling must agree with any alerting and annunciation limits.
(c) The lateral deviation display must have a full-scale deflection suitable for the current phase of flight and must be based on the required total system accuracy. Scaling of 66
±1 NM for RNP 1.0 and ±2 NM for RNP 2.0 is acceptable. It is also acceptable for the scaling to be more conservative; for example, ±1.0 NM for an RNP 2.0 route.
(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.
(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 may be used. The navigation map display must give 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 criteria and be located in the primary field of view.
(3) 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 are the minimum system capabilities needed in RNP 1.0 or RNP 2.0 equipment:
(1) The capability to continuously display to the pilot flying, on the primary flight instruments for navigation of the aircraft (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 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 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 validity period of the navigation data to the pilot.
(4) The means to retrieve and display data stored in the navigation database relating to individual waypoints and navigation aids, so the pilot can verify the route to be flown.