Note: It is also acceptable for the navigation system to automatically load all route waypoints from the database by selecting the route name.
i. Flight Director/Autopilot.
For all rotorcraft enroute RNP 0.3 operations, the use of an autopilot and/or FD is an acceptable means of complying with the FTE assumption in paragraph 9-5.3.a(1). Any alternate means of FTE bounding, other than autopilot and/or FD, may require FTE substantiation through an airworthiness demonstration.
Note: Some rotorcraft may need a stability augmentation system to achieve 0.25 NM FTE during manual flight.
j. Database Integrity.
The navigation database suppliers must comply with AC 20-153(latest revision).
The GPS/SBAS TSOA provides sufficient evidence for compliance to AC 20-153(latest revision), but GNSS operational approval for IFR use is based upon a database assurance process through a type 2 LOA (see paragraph 19-8).
9-5.4 Approval for Rotorcraft RNP 0.3 Operations.
a. The GPS/SBAS-enabled navigation system equipment manufacturer should provide an RNP capability statement that the equipment meets the performance and functional criteria in paragraph 9-5.3 for rotorcraft enroute RNP 0.3 operations. If provided, an RNP capability statement must include a description of the equipment procedures for pilots to select the rotorcraft enroute RNP 0.3 capability. The equipment manufacturer may provide the RNP capability statement through a service bulletin or equivalent document and list the GPS/SBAS equipment model(s) that meet the criteria in section 9-5 and are eligible for rotorcraft enroute RNP 0.3 operations.
b. The GPS/SBAS equipment must be installed according to a TC, ATC, or STC and any rotorcraft limitations required for IFR operations also apply to rotorcraft enroute RNP 0.3 capability. As an example to illustrate the point, a single-pilot rotorcraft could have a limitation to use an autopilot when conducting IFR operations. This limitation would also apply to rotorcraft enroute RNP 0.3 capability.
c. Applicants for new GPS/SBAS approvals should consider including rotorcraft enroute RNP 0.3 capability as part of their application and document the capability in the RFM(S). Doing so could benefit customers seeking operational approvals.
Chapter 10. Equipment Performance – RNP Oceanic
10-1. Introduction.
a. This chapter provides guidance for RNP 10 and RNP 4.0 equipment approvals in oceanic areas. RNP 10 supports 50 NM lateral and 50 NM longitudinal separations in oceanic or remote areas without reliance on ground-based navigation aids. Paragraph 10-2 describes the performance and system criteria equipment must meet for RNP 10 and reflects the criteria in the ICAO Performance-based Navigation (PBN) Manual.
b. RNP 4.0 supports 30 NM lateral and 30 NM longitudinal separations in oceanic areas. GNSS is the primary navigation sensor supporting RNP 4.0 operations either as a stand alone system or part of a multi-sensor system. Paragraph 10-3 describes the performance and functional criteria equipment must meet for RNP 4.0 and reflects the criteria in the ICAO PBN Manual.
10-2. Aircraft and System Criteria for RNP 10.
Operational implementation of RNP 10 is an application of RNAV supporting 50 NM lateral and 50 NM longitudinal distance-based aircraft separation minima in oceanic or remote airspace. As an RNAV application, there is no requirement for onboard performance monitoring and alerting. Aircraft operating in RNP 10 oceanic and remote areas must be equipped with at least two independent and serviceable long-range navigation systems using INS/IRU and/or GNSS.
10-2.1 Performance Criteria.
a. Accuracy.
(1) During operations in airspace or on routes designated as RNP 10, the lateral TSE must be within ±10 NM for at least 95 per cent of the total flight time. The along-track error must also be within ±10 NM for at least 95 per cent of the total flight time.
(2) The navigational positioning error is the dominant contributor to cross-track and along-track error for aircraft capable of coupling the navigation system to the flight director or autopilot. A manufacturer or operator may consider FTE, path definition error, and display errors insignificant when obtaining an RNP 10 operations approval.
b. Integrity.
Malfunction of the aircraft’s long-range navigation equipment without annunciation is a major failure condition (i.e., the probability of a malfunction with no annunciation must be less than 10-5 per hour).
c. Continuity.
Loss of function of the long-range navigation equipment is a major failure condition for oceanic and remote operations. Dual independent long- range navigation system equipage 75
may satisfy the continuity criteria (excluding signal-in-space criteria).
d. Signal-In-Space.
If using GNSS, the aircraft long-range navigation equipment must provide an alert if the probability of signal-in-space errors causing a lateral position error greater than 20 NM exceeds 10-7 per hour.
10-2.2 System Criteria.
a. Aircraft Incorporating Two or More GNSSs.
(1) Paragraph 10-2.2.a provides an acceptable means of complying with RNP 10 criteria for aircraft using a GNSS-only installation; that is, no integration with other navigation sensors.
(2) Aircraft approved to use GNSS for oceanic and remote operations without reliance on other long-range navigation systems meet the RNP 10 criteria without the time limitations associated with INS/IRU equipment. However, using GNSS depends upon using an FDE availability prediction (see paragraph 10-2.2.a(3)).
(3) Dual GNSS installations with a TSOA qualify for RNP 10 when the operator uses an approved dispatch GNSS FDE availability prediction. The AFM(S) should also indicate if a particular GNSS installation meets the appropriate FAA criteria for oceanic and remote operations.
(a) When conducting GNSS pre-departure dispatch FDE predictions, the maximum allowable time for a predicted loss of GNSS FDE capability is 34 minutes. The 34 minute time limit must be a condition of the RNP 10 operations approval.
Note 1: If a GNSS FDE prediction indicates a loss of FDE capability exceeding 34 minutes, the performance criteria for the intended RNP 10 operation cannot be met. The operator must reschedule the RNP 10 operation to a period when predicted FDE is available; or, select another route where predicted FDE capability is available.
Note 2: The FAA’s SAPT prediction program does not provide FDE predictions for oceanic operations.
(b) TSO-C145/TSO-C146(AR) and TSO-C196(AR) GNSS equipment supports oceanic and remote operation by virtue of the TSOA when used in conjunction with an approved GNSS FDE prediction program. No further evaluation is needed for TSO-C145/C146/C196 equipment.
(c) TSO-C129(AR) GPS equipment might not support oceanic and remote operations. Appendix 1 describes additional criteria defining an acceptable means of compliance for TSO-C129(AR) GPS equipment to support an operations approval for oceanic 76
and remote operations. The AFM(S) should also indicate if a particular TSO-C129a GNSS installation meets the appendix 1 criteria for oceanic and remote operations.
(4) Multi-sensor navigation systems (i.e., FMSs) meet the RNP 10 criteria when integrating dual GNSS with FDE, and approved using the guidance contained in this AC.
b. Aircraft Incorporating a Single INS/IRU and a Single GNSS.
(1) Aircraft approved to use a single INS/IRU and a single GNSS for oceanic and remote operations meet the RNP 10 criteria without time limitations.
(2) The INS/IRU equipment must meet the standards of paragraph 10-2.1 and 10
2.2.c, but aircraft qualification only requires one INS/IRU.
(3) The GNSS equipment must meet the standards of paragraph 10-2.1 and
10-2.2.a, but aircraft qualification only requires one GNSS.
Note: If a GNSS FDE prediction indicates FDE unavailability exceeding 34 minutes, the performance criteria for the intended RNP 10 operation cannot be met using GNSS. The operator must predicate their RNP 10 operations on an INS/IRU for that portion of the flight.
c. Aircraft Incorporating a Single INS/IRU or a Single GNSS.
(1) Aircraft equipped with a single INS/IRU or a single GNSS are qualified for oceanic and remote navigation in the Houston oceanic control area/flight information region, the Gulf of Mexico portion of the Miami oceanic control area/flight information region, the Monterrey control area, and the Merida High control area within the Mexico flight information region/upper control area. Aircraft equipped with a single GNSS meet the RNP 10 performance criteria in this airspace without time limitations.
Note: Aircraft qualification in these regions is predicated on the air traffic surveillance provided in the Gulf of Mexico. Therefore, RNP 10 authorizations approved solely in accordance with this paragraph must clearly limit the RNP 10 operational approval to the Gulf of Mexico.
(2) The INS/IRU equipment must meet the standards of paragraph 10-2.1 and 10
2.2.c, but only one INS/IRU is required.
(3) The GNSS equipment must meet the standards of paragraph 10-2.1 and
10-2.2.a, but only one GNSS is required.
d. Aircraft Incorporating Two or more INS/IRUs – Standard Time Limit.
(1) Aircraft Equipped with Two or More INSs or IRUs Approved in Accordance with Part 121 Appendix G. Inertial systems approved in accordance with part 121 appendix G 77
meet RNP 10 performance criteria for up to 6.2 hours of flight time. This time starts when the flight crew places the INS/IRU system in the inertial navigation mode.
(a) If the flight crew updates the INS/IRU systems en route (through manual or automatic means), the flight crew must adjust the 6.2 hour RNP 10 time limit to account for the update’s accuracy. The flight crew must base any adjustments to the time limit on the demonstrated capability of the updates stated in the aircraft’s airworthiness approval documentation (i.e. the AFMS(S)).
(b) INS/IRU accuracy, reliability, training, and maintenance issues required by an airworthiness approval in compliance with part 121 appendix G are applicable to an RNP 10 operation, including any associated oceanic/remote navigation procedures. Except as authorized by the FAA Administrator, and in accordance with the applicable section of 14 CFR, RNP 10 operations based solely IRS/IRU requires at least dual equipage (i.e. two or more inertial systems). Refer to 14 CFR § 121.351, § 125.203, and § 135.165.
Note 1: The long-term inertial drift rate of 2.0 NM/hour (a 95 percent radial position error rate (circular error rate)) is the performance basis for the 6.2 hour time limit. This drift rate is statistically equivalent to an individual 95 percent cross-track and an individual 95 percent along-track position error rates (orthogonal error rates) of 1.6015 NM/hour each; and, a 95 percent cross-track and a 95 percent along-track position error limit of 10 NM each
(e.g., 10 NM/1.6015 NM/hour=6.2 hours).
Note 2: The FAA has adopted the ICAO term
“oceanic/remote” instead of Class II.
(2) Aircraft approved for North Atlantic minimum navigation performance specification operations or for RNAV operations in Australia meet RNP 10 criteria for up to 6.2 hours after the flight crew places the long-range navigation system in the inertial navigation mode.
e. Aircraft Incorporating Two or more INS/IRUs – Extended Time Limit.
The 6.2 hour time limit is the baseline for RNP 10 inertial systems performance, and the time limit begins when the flight crew places the long-range navigation system in the inertial navigation mode. However, this time limit may be extended by one of the following methods:
(1) Establishing an extended time limit during a formal RNP 10 airworthiness approval process (e.g., a new TC, ATC, or STC project).
(2) An existing airworthiness approval holder requests an extension for the installed inertial navigation system from the appropriate ACO based on justifying engineering data.
(3) An airworthiness applicant or existing airworthiness approval holder requests an extended time limit by showing how multiple navigation sensors that mix or average navigation position error justifies an extension (e.g., triple-mixed INSs). If the applicant requests an extended time limit based on mixing, then the availability of the mixing capability is a limitation for flight on RNP 10 routes. If the mixing or averaging function is not available, the operator must use a time limit that does not depend on mixing.
10-2.3 System Eligibility and Approval for RNP 10 Operations.
RNP 10 is an RNAV operational application supporting 50 NM lateral and 50 NM longitudinal distance-based aircraft separation minima in oceanic or remote airspace. As an RNAV application, there is no requirement for onboard performance monitoring and alerting.
There are two methods to recognize aircraft and system eligibility for RNP 10 operations: 1) RNP 10 certification; and, 2) prior navigation system certification. In both cases, the aircraft must be equipped with at least two independent and serviceable long-range navigation systems using GNSS and/or INS/IRU.
RNP 10 Aircraft Certification.
a. RNP 10 aircraft qualification is typically documented in the AFM(S) for aircraft with a formal airworthiness approval for RNP operations. RNP operations approval is not typically limited to just RNP 10. The AFM(S) should document the demonstrated RNP accuracy values the aircraft supports along with any limitations (e.g., navigation aid sensor requirements for present position updating). Implementing States may base operational approval on the stated performance in the AFM(S).
Note: Aircraft qualified for RNP 4.0 operations
automatically qualify for RNP 10 operations.
b. An applicant may obtain an airworthiness approval specific to RNP 10 aircraft qualification. The following example AFM(S) wording (or equivalent) is used when RNP 10 is granted for a change in, or new demonstration of, the INS/IRU certified performance:
“The <insert name> navigation system meets the aircraft qualification criteria of AC 20-138 <insert latest revision> as a primary means of navigation for flights up to XXX hours in duration without present position updating. Determining the flight duration starts when the flight crew places the long-range navigation system in the inertial navigation mode.”
Note: The “XXX hours” specified in the AFM(S) for INS/IRU systems do not include credit for present position updating.
(1) For long-range navigation systems capable of updating the aircraft’s present position while airborne, the airworthiness approval must address the impact present position updating has on position accuracy and any impact on time limits for RNP 10 operations. The approval should clarify the role of ground-based navigation facilities in present position 79
updating (if any), clarify the role of GNSS present position updating (if equipped), and define any requisite flight crew procedures necessary to initiate and terminate present position updating. The credit received for present position updating can be applied to the “XXX hours” specified in the AFM(S) for INS/IRU systems.
(2) Demonstration of aircraft performance in accordance with this AC does not constitute operations approval to conduct RNP operations.
(3) The demonstration of inertial performance to FAA Aircraft Certification Service (AIR) forms the basis for the suggested AFM(S) wording above, but is only one element of the approval process. Aircraft that have this wording in their flight manual will be eligible for operational approval through issuance of OpSpecs/MSpecs or an LOA (as applicable) when the operator and aircraft meet all other RNP 10 qualification criteria.
Prior Navigation System Certification.
Manufacturers and operators may use their prior navigation system certification to recognize an aircraft whose performance under criteria of another RNP specification equates to or exceeds the RNP 10 performance criteria listed in this AC. Manufacturers and operators may also use other navigation specifications standards when they are sufficient to ensure compliance with RNP 10 performance criteria.
10-3. Aircraft and System Criteria for RNP 4.0.
Aircraft operating in RNP 4.0 oceanic and remote areas must be equipped with at least two independent and serviceable long-range navigation systems. GNSS must be used as either a stand-alone navigation system, as one of the sensors in a multi-sensor system, or as part of an integrated GNSS/inertial system.
10-3.1 Performance and Functional Criteria for RNP 4.0.
a. Accuracy.
(1) The lateral TSE must be within ±4 NM for at least 95 per cent of the total flight time. The along-track error must also be within ±4 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.
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 major failure condition for oceanic and remote navigation. The continuity criteria is satisfied by the carriage of dual independent long-range navigation systems (excluding SIS).
d. Performance Monitoring and Alerting.
(1) The RNP system must provide an alert if the accuracy criteria is not met, or if the probability that the lateral TSE exceeds 8 NM is greater than 10-5 .
(2) On-board performance monitoring and alerting compliance does not imply an automatic monitor of FTE. The on-board monitoring and alerting function should at least consist of an NSE monitoring and alerting algorithm and a lateral deviation display enabling the crew to monitor the FTE.
(3) Path definition error is considered negligible.
e. Signal-in-Space.
When using GNSS, the aircraft navigation system must provide an alert if the probability of signal-in-space errors causing a lateral position error greater than 8 NM exceeds 10-7 per hour.
f. 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. The display scaling may be set automatically by default logic or set to a value obtained from the navigation database.
(c) The lateral deviation display must be automatically slaved to the RNP computed path and must have a full-scale deflection suitable for the current phase of flight. 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.
(3) 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.
(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 for the operation cannot be met.
g. System Capabilities.
The following are the minimum system capabilities needed in RNP 4.0 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.
(5) A means for the crew to create, review, and activate a flight plan. The system must incorporate a means for the crew to verify flight plan entries or changes before they are activated. The guidance output must not be affected until the flight plan or flight plan changes are activated.
(6) The capability to automatically sequence fixes.
(7) The means to display the following items, either in the pilot’s primary field of view, or on a readily accessible display page:
(a) The active navigation sensor type;
(b) The identification of the active (To) waypoint;
(c) The ground speed or time to the active (To) waypoint; and
(d) The distance and bearing to the active (To) waypoint.
(8) The capability to execute a “Direct to” function.
(9) The capability for automatic leg sequencing with display to the pilots.
(10) The system must have the capability to automatically execute leg transitions and maintain tracks consistent with the following ARINC 424 path terminators:
(a) Course to fix (CF);
(b) Direct to fix (DF); and
(c) Track to fix (TF).
Note: 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 and DO-201A.
(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
(i.e., the alert provided by the “onboard performance monitoring and alerting function”).
(13) The capability to fly parallel tracks at a selected offset distance. When executing a parallel offset, the navigation accuracy and all performance criteria of the original route in the active flight plan must be applicable to the offset route.
(a) The system must provide for entry of offset distances in increments of 1 NM, left or right of course. The system must be capable of offsets of at least 20 NM.
(b) System offset mode operation must be clearly indicated to the pilot. When in offset mode, the system must provide reference parameters (e.g. cross-track deviation, distance-to-go, time-to-go) relative to the offset path and offset reference points.
(c) An offset must not be propagated through route discontinuities, unreasonable path geometries, or beyond the ÍAF.
(d) The system must annunciation prior to the end of the offset path, with sufficient time to return to the original path.
(e) Once a parallel offset is activated, the offset must remain active for all flight plan route segments until removed automatically, until the pilot enters a direct-to routing, or until pilot (manual) cancellation.
(f) The parallel offset function must be available for en-route TF and the geodesic portion of DF leg types.
Note 1: Systems compliant with parallel offset requirements in RTCA/DO-236B (or later revision) and RTCA/DO-283A (or later revision) meet the parallel offset criteria for RNP 4.0.
Note 2: RTCA/DO-236C and RTCA/DO-283B require increments of 0.1 nm to support parallel offsets in terminal areas. Using these smaller increments is also acceptable for RNP 4.0 operations.
(14) The system must have the capability to perform fly-by transitions.
(a) Fly-by transitions must be the default when a transition type is not specified.
(b) Navigation systems should be designed to keep aircraft within the theoretical transition area.
(c) Fly-by theoretical transition areas are based upon the following assumptions:
• Course changes do not exceed 120 degrees for low altitude transitions (aircraft barometric altitude is less than FL 195); and,
• Course changes do not exceed 70 degrees for high altitude transitions (aircraft barometric altitude is equal to or greater than FL 195).
Note: Systems compliant with the fly-by transition requirements in RTCA/DO-236B (or later revision), RTCA/DO-283A (or later revision) and RTCA/DO-229C (or later revision) meet the fly-by transition criteria for RNP 4.0.
10-3.2 System Eligibility and Approval for RNP 4.0 Operations.
There are two methods to recognize aircraft and system eligibility for RNP 4.0 operations:
1) RNP certification; and, 2) prior navigation system certification. In both cases, the aircraft must be equipped with at least two independent and serviceable long-range navigation systems;
at least one of which must be GNSS.
a. RNP Certification.
RNP certification is typically documented in the AFM(S) for aircraft that have been formally certificated and approved for RNP operations and typically is not limited to RNP 4.0.
The AFM(S) addresses RNP levels that have been demonstrated to meet the certification criteria and any related provisions applicable to their use (e.g., navigation aid sensor requirements). Operational approval is based upon the performance stated in the AFM(S). This method also applies in cases where certification is received through an STC issued to retrofit equipment, such as GNSS receivers, to enable the aircraft to meet RNP 4.0 performance criteria in oceanic and remote area airspace.
b. Prior Navigation System Certification.
(1) This method is used to approve aircraft whose level of performance under previous standards equates to the RNP 4.0 criteria listed in this AC. The AFM(S) must indicate the aircraft is equipped with GNSS approved as a long-range navigation system for oceanic and remote airspace operations.
(2) RNP 4.0 operations using only GNSS is based upon a pre-departure FDE availability prediction program. 25 minutes is the maximum allowable time for which FDE capability is projected to be unavailable on any one event. This maximum outage time must be included as a condition of the RNP 4.0 operational approval. If predictions indicate that the maximum allowable FDE outage will be exceeded, the operation must be rescheduled to a time when FDE is available.
Note: The FAA’s SAPT prediction program does not provide FDE predictions for oceanic operations.
(a) Aircraft with TSO-C129(AR) equipment must also document the equipment is approval for oceanic operations according to appendix 1 in this AC.
(b) TSO-C115b (or later revision) is acceptable for multi-sensor systems incorporating GNSS sensors.
(3) Multi-sensor systems incorporating an approved INS/IRU can extend the maximum FDE unavailability time based upon the amount of time the system can maintain RNP 4.0 coasting performance without a position update. The approval must indicate the maximum GNSS FDE unavailability time.