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.
Chapter 11. Equipment Performance - Baro-VNAV.
11-1. General Limitations for Operations under IFR.
a. A baro-VNAV system may be approved for enroute, terminal, and approach use within the contiguous U.S., Alaska, and Hawaii. VNAV equipment may be used to provide advisory vertical path guidance to aid in more efficient and precise operation of the aircraft.
However, unless compensated for temperature, baro-VNAV equipment can only be used within the limitations for temperature published on approach procedure charts. The barometric altimeter must always be the primary altitude reference for all flight operations (see paragraphs 12-7, 18-2.b and 23-3.1).
b. Systems providing automatic temperature compensation to the baro-VNAV guidance must comply with RTCA/DO-283B, appendix H. This enables baro-VNAV operations outside of the temperature limits published on approach procedure charts.
(1) Equipment manufacturers may include compensation for temperatures above and below the limits published on approach charts.
Note: Any equipment limitations must be documented in the installation manual.
(2) Temperature compensation may be provided on segments other than the final approach and missed approach (i.e., the segments prescribed by RTCA/DO-283B, appendix H) if the equipment includes a method for the flight crew to inhibit the compensation function.
Equipment manufacturers providing baro-VNAV temperature compensation on other segments must specify language in the installation instructions/manual for an AFM(S)/RFM(S) caution that the flight crew/pilot must coordinate use of temperature compensation with ATC prior to employing this function. The reason for an AFM(S)/RFM(S) caution is to ensure there is no loss of separation between an aircraft employing temperature compensation and an aircraft not employing this function.
Note: Aviation authorities in different countries may or may not authorize temperature compensation outside the final approach segment.
c. Procedures for manual altitude corrections must be established for systems that do not provide automatic temperature compensation. A pilot workload evaluation must be performed for all segments in the approach, including the missed approach holding waypoint.
d. Baro-VNAV equipment may also be used to provide advisory vertical guidance to aid in more efficient and precise operation of the aircraft for enroute, terminal, and/or approach operations (see chapter 4). The primary barometric altimeter will be the primary altitude reference for all flight operations.
e. Baro-VNAV performance is not adequate for vertical guidance on LPV or GLS approaches.
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11-2. Baro-VNAV Equipment Performance for Operations under IFR.
a. The initial certification of a baro-VNAV system requires an engineering evaluation because of the need to verify performance, failure indications, environmental qualifications, etc.
Subsequent installations of the same baro-VNAV equipment system in other aircraft may require additional engineering evaluation, depending upon the degree of integration with other aircraft systems, in particular autopilot and FD systems.
b. For enroute, terminal, and approach IFR operations, the airborne baro-VNAV system must have TSE components in the vertical direction that are less than those shown in Table 6 below, 99.7 % of the flying time (reference RTCA/DO-283B, paragraph 2.2.2.6.1).
Misleading guidance during LNAV/VNAV approach operations is considered a major failure condition (see Table 8). A baro-VNAV system providing vertical guidance during the final approach segment of an LNAV/VNAV approach operation must meet the design error and failure mode probability requirements that satisfy a major failure condition (see paragraph 12-2).
Note 1: Baro-VNAV vertical guidance is independent from the lateral guidance. Loss of baro -VNAV guidance during an LNAV/VNAV approach results in a fail-down to LNAV or a missed approach. Therefore, loss of navigation for baro-VNAV is considered a minor failure condition.
Note 2: Baro-VNAV systems certified before 11/20/1989 may have been certified to a lesser standard that is not consistent with a major failure condition. Operators of these aircraft should apply the final approach segment step-down fix to the LNAV/VNAV line of minima and should use the primary barometric altimeter to ensure meeting the step-down fix altitude constraint.
(1) Baro-VNAV TSE includes all errors (except horizontal coupling error and the effects of temperature) resulting from the vertical guidance equipment installation. This includes altimeter system errors.
(2) During the final approach segment only (i.e., from the final approach fix to the missed approach point) baro-VNAV TSE must also include horizontal coupling error.
Note: GPS/SBAS Class 2 and Class 3 as well as GPS/GBAS vertical positioning performance exceeds the accuracy requirements of a barometric sensor used for final approach VNAV. The GPS/SBAS 50m Vertical Alert Limit (VAL) used for LNAV/VNAV is consistent with baro-VNAV and may also be used to comply with RNP approach.
c. Table 6 is a means to identify the degradation in altimeter performance as altitude increases. But Table 6 is not intended as an exact representation of expected performance 87
characteristics with distinct steps. Instead, altimeter performance degradation is curvilinear as altitude increases. Therefore, to qualify a baro-VNAV system, the 99.7% aircraft altimetry system error for the aircraft (assuming International Standard Atmosphere temperature and lapse rates) must be less than or equal to the following:
𝐴𝐴𝐴 = −8.8 ∗ 10−8 ∗ 𝐻2 + 6.5 ∗ 10−3 ∗ 𝐻 + 50 (ft) where H is the true altitude of the aircraft.
Altitude Region (MSL) Level Flight Segments Flight Along Specified Vertical Profile At or below 5000 ft.
150 ft. 160 ft.
5000 ft. to 10000 ft 200 ft. 210 ft.
10000 ft. to 29,000 ft 200 ft. 210 ft.
Above 29,000 ft to 41,000 ft 200 ft.
(See Notes 1 and 2) 260 ft.
Table 6. Vertical Path Performance Limit for Baro-VNAV Note 1: These requirements are based upon airborne altimetry and avionics systems that provide performance consistent with reduced vertical separation minimums (RVSM) requirements. Aircraft meeting RVSM requirements provide acceptable vertical total system error in level flight for the last row in table 6. No additional demonstration or compliance evaluation is required.
However, the altimetry system error cannot be extrapolated to the other altitude blocks.
Note 2: For aircraft type designs prior to April 9, 1997, the value is 200 ft in the cruise flight envelope and is not to exceed 250 ft over the full aircraft operating envelope.
Basic height-keeping parameters for 1000 ft. vertical separation minimum between flight levels 290 and 410 are in ICAO Document 9574, Manual on Implementation of 1000 ft. Vertical Separation Minimum between FL 290-FL410 Inclusive.
Note 3: Table 6 does not address altitudes above FL 410 because current altimetry and baro-VNAV systems are adequate for the 2,000 ft air traffic control vertical separation criteria.
d. Flight crew Inputs.
(1) The altitude associated with the active waypoint should be to the nearest 100 feet for enroute and terminal flight phases, and nearest 10 feet for the approach phase. If provided, waypoint horizontal position should be in increments not greater than 0.1 nautical miles.
(2) The ascent or decent angle should be to at least the nearest 0.1 degree for equipment that specifies gradient angles.
(3) The station elevation, if necessary for equipment employing slant range error correction, should be at least to the nearest 1,000 feet for enroute and terminal flight phases, and to the nearest 100 feet for the approach phase.
(4) For terminal and approach operations, the ability to enter the altitude associated with at least eight (for TO-FROM equipment) or nine (for TO-TO equipment) successive waypoints.
(5) A means to confirm input data correctness prior to the system using the new data.
e. System Displays.
(1) There should be a continuous display of vertical path deviation with the performance indicated in Table 7 below.
Enroute/Terminal (feet) Approach (feet) Full-Scale Deflection (see note 1) ≤ 500 150 (see note 2) Readability ≤ 100 ≤ 30 Minimum Discernable Movement ≤ 10 ≤ 5 Table 7. Vertical Path Deviations Note 1: This is the minimum standard for vertical deviation display scaling and does not preclude using a scale of other than the values listed (e.g. large PFD display) provided that the scaling is suitable to control the aircraft on the intended path.
Note 2: Other values of full-scale deflection for approach may be acceptable provided the proposed value is found satisfactory by an engineering evaluation.