(4) A valid DME f acility:
(a) Broadcasts an accurate facility identifier signal;
(b) Satisfies the minimum field strength requirements; and
(c) Is protected from other interfering DME signals according to the co-channel and adjacent channel requirements.
e. There is no requirement to use VOR, LOC, NDB, IRU or attitude heading reference system (AHRS) during normal operation of the DME/DME RNAV system.
f. When the RNAV system is using a minimum of two DME facilities that satisfy the criteria in paragraph 6-4, and any other valid DME facilities not meeting that criteria, the 95% position estimation error must be better than or equal to 1.75 NM. A flight technical error (FTE) contribution not exceeding 1.0 NM (95%) may be assumed for RNAV 2 operations.
Note 1: This performance requirement is met for any navigation system that uses two DME stations simultaneously, limits the DME inclusion angle to between 30 and 150 and uses DME sensors that meet the accuracy requirements of TSO-C66c. If the RNAV system uses DME facilities outside the range identified above, the DME signal-in-space error can be assumed to be 0.1 NM 95%.
Note 2: When using a minimum of two DME facilities satisfying the criteria above, the 95% position estimation error must be better than or equal to the following equation:
) sin( )2 2( )2 2(22 , 2, 2, 1, 1/ sisairsisairDMEDME
Single facility reference, where:
sis = 0.05 NM
air is MAX {(0.085 NM, (0.125% of distance)}
= inclusion angle (30o to 150o)
g. The RNAV system must ensure co-channel DME facilities do not cause erroneous guidance. This could be accomplished by including VOR reasonableness checking when initially tuning a DME facility, or excluding a DME facility when there is a co-channel DME within line-of-sight. See paragraph 6-4.1 for guidance on testing reasonableness checks.
Note: The DME assessm ent cannot use a DME facility when there is a co-channel DME facility within line-of-sight.
h. The RNAV system must use operational DME facilities. DME facilities listed by NOTAM as unavailable (for example, under test or other maintenance) could still reply to an airborne interrogation. Therefore, non-operational facilities must not be used. An RNAV system may exclude non-operational facilities by checking the identification or inhibiting the use of facilities identified as not operational.
i. Operational mitigations defined to qualify equipment with this AC will not require pilot action during critical phases of flight, pilot monitoring of the RNAV system’s navigation updating source(s), or time intensive programming/ blackballing of multiple DME stations prior to executing a procedure.
Note 1: Blackballing single facilities listed by NOTAM as out-of-service and/or programming route/procedure-defined “critical” DME is acceptable when this mitigation requires no pilot action during a critical phase of flight. A programming requirement also does not imply the pilot should complete manual entry of DME facilities not in the navigation database. Instead, this allows RNAV systems to tune a critical DME, as appropriate to a specific route or procedure.
Note 2: The critical phase of flight is normally from the final approach fix on an approach procedure through missed approach, or from field elevation to 2,500 ft above airport elevation on a departure.
6-4.1 Reasonableness Checks.
a. Many FMSs perform a reasonableness check to verify valid DME measurements.
Reasonableness checks are very effective against database errors or erroneous system acquisition (such as co-channel facilities), and typically fall into two classes:
(1) Those the FMS uses after it acquires a new DME. The FMS compares the aircraft’s position before using the DME to the aircraft’s range to the DME; and
(2) Those the FMS continuously uses, based on redundant information (for example, extra DME signals or IRU data).
b. The reasonableness checks are intended to prevent navigation aids from being used for navigation update in areas where the data can lead to radio position fixing errors due to co-channel interference, multipath, and direct signal screening. In lieu of using radio navigation aid published service volume, the navigation system should provide checks, which preclude use of duplicate frequency navigation aids (NAVAIDs) within range, over-the-horizon 31
NAVAIDs, and use of NAVAIDs with poor geom etry.
c. Under certain conditions, reasonableness checks can be invalid.
(1) Do not assume a DME signal remains valid just because it was valid when acquired.
(2) Do not assume extra DME signals are available. The intent of this baseline is to support operations where the infrastructure is minimal (for example, when only two DMEs are available for parts of the procedure).
d. When an FMS manufacturer uses a reasonableness check to satisfy any criteria in this AC, they must test the effectiveness of the check under stressing conditions. An example of this condition is a DME signal that is valid at acquisition and “ramps off” during the test (similar to what a facility under test might do), when there is only one other supporting DME or two signals of equal strength. A “ramp off” rate would be significantly higher or slower than the normal range of groundspeed.
6-4.2 Performance Confirmation.
a. New systems m ay demonstrate compliance with these criteria as part of the airworthiness approval. For existing systems, the applicant should determine compliance with the equipment and aircraft criteria in this chapter.
b. Aircraft manufacturers (TC holders) incorporating FMS and DME/DME positioning should review the available data for the integrated navigation system, and obtain additional data as appropriate, to determine compliance with the criteria in this AC.
c. Equipment manufacturers (typically DME and FMS TSOA/LODA holders) need to consider DME accuracy. DME sensors have been demonstrated to a variety of performance requirements per TSO-C66. TSO-C66 performance standards have evolved as follows:
(1) TSO-C66: (Aug 1960) RTCA/DO-99.
(2) TSO-C66a: (Sep 1965) RTCA/DO-151, accuracy requirement as total error with 0.1 NM attributed to ground facility, airborne equipment accuracy of 0.5 NM or 3% of distance, whichever is greater, with a maximum of 3 NM.
(3) TSO-C66b: (Nov 1978) RTCA/DO-151a, accuracy requirement as total error with 0.1 NM attributed to ground facility, airborne equipment accuracy of 0.5 NM or 1% of distance, whichever is greater, with a maximum of 3 NM.
(4) TSO-C66c: (Sept 1985) RTCA/DO-189, accuracy requirement as total error for the airborne equipment of 0.17 NM or 0.25% of distance, whichever is greater.
d. The accuracy required by TSO-C66c is adequate to support the criteria in this AC.
DME equipment approved under revision ‘c’ does not require further evaluation for RNAV 1 and RNAV 2 operations. Applicants with equipment built to earlier TSO revisions may use the 32
following process to establish m ore accurate performance than originally credited to support RNAV 1 and RNAV 2 operations.
(1) Rather than relying on original demonstrated performance, the applicant may elect to review the original TSO or TC/STC test data to determine the demonstrated accuracy and/or make any appropriate changes to qualification tests to determine achieved accuracy.
Note: When conducting accuracy analysis, the DME signal-in-space error can be assumed to be 0.1 NM 95% (both inside and outside the published service volume). If demonstrating accuracy under bench or flight test conditions, the actual accuracy of the bench equipment or ground facility should be considered.
(2) New testing should be performed under the same conditions used to demonstrate compliance with the original TSO-C66 standard.
(3) Applicants who have demonstrated more accurate DME performance should state the demonstrated accuracy in a letter to their customers.
6-4.3 Multi-Sensor System FMS.
a. The FMS or aircraft m anufacturer should review the available data for the integrated navigation system, and obtain additional data as appropriate, to determine compliance with the criteria in paragraph 6-4. Applicants who have determined compliance should state such in the operating instructions or AFMS/RFMS, along with any limitations (for example, if the pilot is expected to manually inhibit the use of facilities that are listed by NOTAM as unavailable).
The applicant’s certification may limit the compliance to specific DME systems, or may reference any DME qualified to the accuracy requirements of TSO-C66c.
b. FMS accuracy is dependent on a number of factors, including: latency effects, the selection of DME facilities, the method of combining information from multiple DMEs, and the effects of other sensors used to determine a position. For FMSs using two (or more) DMEs at the same time and limiting the DME include angle to between 30 and 150, the accuracy requirement can be met if the DME sensors meet the accuracy requirements of TSO-C66c. For FMSs without these characteristics, the accuracy should be evaluated under poor DME geometry scenarios and should consider the demonstrated DME sensor accuracy. Poor geometry scenarios may include angles at the limits specified earlier, with or without additional DME facilities available outside those conditions.
c. Identify those conditions that would result in failure to meet the accuracy requirement, and the means to preclude those identified conditions.
6-5. VOR/DME.
a. Multi-sensor equipm ent may incorporate VOR/DME updating and must meet the performance for the route to be flown. However, terminal and enroute RNAV implementation in the United States does not require using VOR, so any use of VOR must include 33
reasonab leness checking and demonstrate that positional accuracy from an erroneous VOR signal-in-space will not exceed 1.75 nm for RNAV 2 and 0.87 nm for RNAV 1 (reference AC 90-100A, appendix 1, paragraph 2.h). This could be accomplished by not using VOR signals when DME/DME will be available or weighting and/or monitoring the VOR signal with DME/DME to ensure it does not mislead position results (for example, through reasonableness checks). See paragraph 6-4.1 for guidance on testing reasonableness checks.
b. For times when the multi-sensor equipment is using data from only a single collocated VOR/DME (such as during an RNAV (VOR/DME) approach), the total maximum position fixing error of the airborne multi-sensor equipment must be equal to or less than that shown in Table 4. To find the cross track (xtk) and along track (atk) error at this point, enter the table with the tangent distance in nautical miles and distance along track in nautical miles from the tangent point.
Along-Track Distance (NM) 0 5 10 15 20 25 30 35 40 50 60 70 80 90 100 110 120 130 0 xtk 0.6 0.8 1.1 1.4 1.7 2.0 2.3 2.6 3.2 3.9 4.5 5.2 5.8 6.4 7.1 7.7 8.4 atk 0.6 0.6 0.6 0.6 0.7 0.7 0.8 0.8 0.9 1.0 1.0 1.1 1.2 1.3 1.4 1.5 1.6 5 xtk 0.6 0.6 0.8 1.1 1.4 1.7 2.0 2.3 2.6 3.3 3.9 4.5 5.2 5.8 6.4 7.1 7.7 8.4 atk 0.6 0.6 0.7 0.7 0.7 0.8 0.8 0.8 0.9 0.9 1.0 1.1 1.2 1.3 1.4 1.5 1.6 1.7 10 xtk 0.6 0.7 0.9 1.1 1.4 1.7 2.0 2.3 2.6 3.3 3.9 4.5 5.2 5.8 6.5 7.1 7.7 8.4 atk 0.8 0.8 0.8 0.8 0.9 0.9 0.9 1.0 1.0 1.1 1.2 1.2 1.3 1.4 1.5 1.6 1.7 1.8 15 xtk 0.6 0.7 0.9 1.1 1.4 1.7 2.0 2.3 2.6 3.3 3.9 4.5 5.2 5.8 6.5 7.1 7.7 8.4 atk 1.0 1.0 1.0 1.1 1.1 1.1 1.2 1.2 1.2 1.3 1.4 1.4 1.5 1.6 1.7 1.7 1.8 1.9 20 xtk 0.6 0.7 0.9 1.2 1.4 1.7 2.0 2.3 2.7 3.3 3.9 4.6 5.2 5.8 6.5 7.1 7.7 8.4 atk 1.3 1.3 1.3 1.3 1.3 1.4 1.4 1.4 1.4 1.5 1.6 1.6 1.7 1.8 1.9 1.9 2.0 2.1 25 xtk 0.7 0.8 1.0 1.2 1.5 1.8 2.1 2.4 2.7 3.3 3.9 4.6 5.2 5.8 6.5 7.1 7.8 8.4 atk 1.5 1.5 1.6 1.6 1.6 1.6 1.6 1.7 1.7 1.7 1.8 1.9 1.9 2.0 2.1 2.1 2.2 2.3 30 xtk 0.7 0.8 1.0 1.2 1.5 1.8 2.1 2.4 2.7 3.3 3.9 4.6 5.2 5.9 6.5 7.1 7.8 8.4 atk 1.8 1.8 1.8 1.8 1.9 1.9 1.9 1.9 2.0 2.0 2.1 2.1 2.2 2.2 2.3 2.4 2.4 2.5 35 xtk 0.8 0.8 1.0 1.3 1.5 1.8 2.1 2.4 2.7 3.3 4.0 4.6 5.2 5.9 6.5 7.1 7.8 8.4 atk 2.1 2.1 2.1 2.1 2.1 2.2 2.2 2.2 2.2 2.3 2.3 2.4 2.4 2.5 2.5 2.6 2.7 2.7 40 xtk 0.8 0.9 1.1 1.3 1.5 1.8 2.1 2.4 2.7 3.3 4.0 4.6 5.2 5.9 6.5 7.1 7.8 8.4 atk 2.4 2.4 2.4 2.4 2.4 2.4 2.4 2.5 2.5 2.5 2.6 2.6 2.7 2.7 2.8 2.9 2.9 3.0 50 xtk 0.9 1.0 1.1 1.3 1.6 1.9 2.2 2.5 2.8 3.4 4.0 4.6 5.3 5.9 6.5 7.2 7.8 8.4 atk 2.9 2.9 3.0 3.0 3.0 3.0 3.0 3.0 3.0 3.1 3.1 3.2 3.2 3.3 3.3 3.4 3.4 3.5 60 xtk 1.0 1.0 1.2 1.4 1.7 1.9 2.2 2.5 2.8 3.4 4.0 4.7 5.3 5.9 6.6 7.2 7.8 8.5 atk 3.5 3.5 3.5 3.5 3.5 3.6 3.6 3.6 3.6 3.6 3.7 3.7 3.8 3.8 3.8 3.9 3.9 4.0 70 xtk 1.0 1.1 1.3 1.5 1.7 2.0 2.3 2.6 2.9 3.5 4.1 4.7 5.3 6.0 6.6 7.2 7.9 8.5 atk 4.1 4.1 4.1 4.1 4.1 4.1 4.1 4.2 4.2 4.2 4.2 4.3 4.3 4.4 4.4 4.4 4.5 4.5 80 xtk 1.1 1.2 1.4 1.6 1.8 2.1 2.3 2.6 2.9 3.5 4.1 4.7 5.4 6.0 6.6 7.3 7.9 8.5 atk 4.6 4.7 4.7 4.7 4.7 4.7. 4.7 4.7 4.7 4.8 4.8 4.8 4.9 4.9 5.0 5.0 5.0 5.1 90 xtk 1.2 1.3 1.4 1.6 1.9 2.1 2.4 2.7 3.0 3.5 4.2 4.8 5.4 6.0 6.7 7.3 7.9 8.6 atk 5.2 5.2 5.2 5.2 5.2 5.3 5.3 5.3 5.3 5.3 5.4 5.4 5.4 5.5 5.5 5.5 5.6 5.6 100 xtk 1.3 1.4 1.5 1.7 1.9 2.2 2.4 2.7 3.0 3.6 4.2 4.8 5.4 6.1 6.7 7.3 7.9 8.6 atk 5.8 5.8 5.8 5.8 5.8 5.8 5.9 5.9 5.9 5.9 5.9 6.0 6.0 6.0 6.1 6.1 6.1 6.2 110 xtk 1.4 1.5 1.6 1.8 2.0 2.3 2.5 2.8 3.1 3.6 4.2 4.9 5.5 6.1 6.7 7.3 8.0 8.6 atk 6.4 6.4 6.4 6.4 6.4 6.4 6.4 6.4 6.5 6.5 6.5 6.5 6.6 6.6 6.6 6.7 6.7 6.7 120 xtk 1.5 1.6 1.7 1.9 2.1 2.3 2.6 2.8 3.1 3.7 4.3 4.9 5.5 6.1 6.8 7.4 8.0 8.6 atk 6.9 7.0 7.0 7.0 7.0 7.0 7.0 7.0 7.0 7.1 7.1 7.1 7.1 7.2 7.2 7.2 7.3 7.3 130 xtk 1.6 1.7 1.8 2.0 2.2 2.4 2.6 2.9 3.2 3.7 4.3 4.9 5.6 6.2 6.8 7.4 8.0 8.7 atk 7.5 7.5 7.5 7.6 7.6 7.6 7.6 7.6 7.6 7.6 7.7 7.7 7.7 7.7 7.8 7.8 7.8 7.9 T a n g e n t
D i s t a n c e
N M Table 4. 2D Accuracy Requirements for Equipment Using a Single Co-located VOR/DME
Note 1: Equipment error assumes a waypoint input resolution of 0.01 minute, and output resolution of 0.01 minute for approach and 0.1 minute otherwise.
Note 2: Equipment error assumes the maximum allowable difference between the displayed cross-track deviation and the computed cross-track deviation.
Note 3: Multi-sensor equipment accuracy shown in the above table does not necessarily satisfy accuracy requirements for operation in certain airspace. For 35
exam ple, navigation on published J and V routes requires a distance along-track from the tangent point to VOR/DME to be less than approximately 50 NM to meet airway width criteria.
Note 4: The above table is a result of the root-sum-square combination of the error elements shown below in Table 5.
The accuracy table is computed assuming the waypoint is always at the tangent point and the aircraft is at the along-track distance measured from the same tangent point.
This is important in the test procedures because the resulting cross-track error from the course setting is a function of the distance to waypoint.
GROUND EQUIPMENT ERROR AIRBORNE EQUIPMENT ERROR VOR 1.4 degrees VOR 3.0 degrees DME 0.1 nm DME 0.2 nm + 1% Course Setting Error 1.6 degrees Computation Error 0.5 nm Table 5. Error Elements
6-6. INS/IRU.
An INS/IRU insta llation is an acceptable lateral positioning source during a significant portion of the flight provided it meets the requirements described in 14 CFR part 121, appendix G while in inertial mode.
Note: Paragraph 6-6 applies to both “stand-alone” and loosely coupled integrations.
6-7. INS/IRU – GNSS Integration.
a. The guidance in paragraph 6-7 is applicable for tightly coupled integrations; and, is in addition to the guidance in paragraph 6-6.
b. For GNSS s ensors, RTCA/DO-229D, appendix R, provides INS/IRU – GNSS integration requirements. The GNSS/inertial hybrid outputs of the IRU should meet the equipment requirements of RTCA/DO-229D, appendix R.
c. The FAA assumes that there is a limitation on the use of the GPS/inertial position data output to support enroute through LNAV approach only. Using this data for operations requiring higher precision would require other integrity and accuracy enhancements such as GPS/SBAS or GPS/GBAS. Since hybrid vertical position and integrity has not been addressed by RTCA/DO-229D, any use should be identified and resolved as part of the non-TSO function 36
approval process.
Note 1: RTCA/DO-316, appendix R contains the same information found in RTCA/DO-229D, appendix R.
Note 2: No exclusion is intended for previously certified equipment meeting the requirements of RTCA/DO-229C, appendix R. It is acceptable to use previously certified GNSS sensors integrated with INS/IRU systems meeting the requirements specified in RTCA/DO-229C, appendix R. However, RTCA/DO-229C, appendix R assumed selective availability was ‘on’, so it may not adequately describe system performance if the applicant wishes to take credit for selective availability being ‘off.’
Note 3: Aircraft with GPS/inertial installations approved for LNAV approaches can also include a baro-VNAV installation to provide the vertical guidance deviations acceptable for LNAV/VNAV approaches. Chapters 10, 17, and 22 describe baro-VNAV performance and installation considerations.
d. Tightly coupled equipment must be demonstrated to be equivalent to either TSO-C129(AR), TSO-C196, or TSO-C145(AR) as described in chapter 3. Any discrepancies should be identified and resolved as part of the TSO approval. It may be necessary to conduct further evaluation during any follow-on approval since the characteristics and performance required for the inertial integration are closely linked to aircraft architecture, integration method, and GNSS failure modes.
e. When demonstrating RAIM or RAIM equivalency, the GPS signal-in-space failure modes to be used for the demonstration should be proposed and agreed upon as part of the TSO approval. For example, the applicant should address the correlated effects of multiple erroneous pseudoranges due to ionospheric activity. After exclusion of a faulty satellite, show that the position solution is valid and the inertial states/models are not corrupted by the faulty GPS data prior to its detection and exclusion.
f. All attitude and heading data output by the integrated system must comply with the relevant regulations under all foreseeable operating conditions. This includes during GPS signal-in-space failures (including prior to detection and after exclusion).
g. In the absence of any GPS input, the attitude and heading data output by the integrated system must comply with the relevant regulations, including those conditions addressed in the aircraft functional hazard assessment (FHA).
Note: It may be necessary to revise the FHA to address failure conditions unique to the GPS/inertial system.
h. If the system sustains integrity coasting capability, the INS/IRU equipment 37
m anufacturer must document the coasting performance and limitations. That is, document the coasting time while sustaining performance at the desired navigation performance level, horizontal alert limit (HAL) or RNP. This documentation must be consistent with the alerting algorithms for the aircraft (e.g., RNP). The coasting performance should consider factors that could influence coasting times (e.g., inertial sensor accuracy, gyro misalignment, inertial parameter calibration accuracy prior to loss of GPS signals, aircraft maneuvers prior to and during the coasting period, and aircraft speed).
6-8. INS/IRU - DME/DME Integration.
a. Paragraph 6-8 defines a m inimum DME/DME/IRU (D/D/I) RNAV system baseline performance capable of supporting RNAV 1 and RNAV 2 routes, as well as RNAV 1 DPs and STARs. For routes and procedures designed using this performance standard, the FAA will decide if adequate DME coverage is available using FAA computer modeling and flight inspection assets. This assessment of DME coverage will also determine if an expanded service volume (ESV) is necessary for select DME facilities.
b. The minimum DME/DME requirements of paragraph 6-4 apply and are not repeated here, except where additional performance is required. The performance confirmation process in paragraph 6-4.2 also applies to paragraph 6-8.
c. There is no requirement to use VOR, NDB, LOC, or AHRS during normal operation of the DME/DME/IRU RNAV system.
d. The 95% position estimation error must be better than or equal to the value obtained using the equation referenced in paragraph 6-4.f note 2 given any two DME facilities satisfying the criteria in paragraphs 6-4.b thru 6-4.d, and any combination of other valid DME facilities not meeting that criteria,.
Note: Based on an evaluation of IRU performance, the growth in position error after reverting to IRU can be expected to be less than 2 NM per 15 minutes.
e. Inertial system performance must satisfy the criteria in paragraph 6-6.
f. Additional required FMS capabilities are:
(1) Automatic position updating from the DME/DME solution.
Note: Equipment manufacturers or airworthiness applicants should note in the appropriate documentation for the flight crew if any inertial coasting annunciation is suppressed following loss of radio updating.
(2) Accepting a position update immediately prior to takeoff.
(3) Excluding VORs greater than 40 NM from the aircraft.
g. The total system error (TSE) must be less than or equal to 1.0 NM (95%) throughout the route. To maximize the amount of IRU coasting allowed, the flight technical error for D/D/I aircraft on terminal procedures should be limited to 0.5 NM (95%).
Note: The FAA assures that systems meeting the D/D/I RNAV minimum performance standard satisfy this requirement on all identified routes and procedures, and these RNAV systems do not require further evaluation.
Systems seeking approval using different RNAV system characteristics or performance must demonstrate this performance for each published route or procedure.
Chapter 7. Equipmen t Performance - RNP (General).
7-1. Introduction.
a. The intent of the RNP c hapters 7-9 and 16 along with appendix 2 and 3 is to provide the airworthiness information found in AC 90-101A and AC 90-105 in this AC. The information is taken directly from AC 90-101A and AC 90-105, but contains some necessary minor changes due to formatting and grammar considerations. The information from AC 90-101A and AC 90-105 has not changed other than to recognize TSO-C196 equipment and, in some places, add minor clarification information or correct mistakes. This is a necessary first step to consolidate all the positioning and navigation equipment airworthiness guidance and RNP airworthiness guidance into one AC. The plan is for future AC 90-101 and AC 90-105 revisions to remove the airworthiness guidance. Information on special characteristics of RNP operations and advantages of GPS/SBAS and GPS/GBAS for RNP operations incorporating vertical guidance is provided below.
b. Chapter 8 is specific to the equipment performance considerations for RNP approach procedures; and, chapter 9 is specific to the equipment performance considerations for RNP terminal operations. Airworthiness guidance for RNP (AR), including installation considerations, is addressed in appendix 2 of this AC while appendix 3 of this AC describes advanced features (radius to fix (RF) leg types) for RNP systems. Chapter 16 describes installation considerations for RNP. RNP AR and RNP operational approval guidance can be found in the latest revisions of ACs 90-101 and 90-105, respectively.
Note: RNP AR was previously named RNP SAAAR. The name has been changed to RNP AR for international harmonization.
c. GPS/SBAS and GPS/GBAS sensors can be approved on FMS-equipped aircraft without baro-VNAV to provide vertical path guidance for RNP 0.3 operations and RNP AR operations as low as RNP 0.1 with no change to existing RNP criteria, GPS/SBAS, or GPS/GBAS performance standards. However, all aircraft and FMS requirements for RNP and RNP AR operations still apply. Refer to chapters 14 and 16 of this AC (appendix 2 for RNP AR) for airworthiness guidance, and the latest revisions of AC 90-101, and AC 90-105 for operational guidance.
d. GPS/SBAS and GPS/GBAS used for RNP and RNP AR do not require the baro-VNAV temperature mitigations; however, the aircraft must be within the service 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 m eet the RNP 0.1 vertical performance contours without independent system monitoring.
(4) The flight path is not affected by manual or Automated Traffic Information System (ATIS) altimeter setting errors.
7-2. Special Characteristics of RNP Instrument Approaches.
a. GPS is the prim ary navigation system to support RNP approach procedures. The missed approach segment may be based upon a conventional NAVAID (e.g., VOR, DME, NDB).
b. Unique Features and Requirements of RNP Approaches.
(1) RNP approaches normally include at least two lines of minima: LNAV and LNAV/VNAV. The LNAV/VNAV minima are based on using systems meeting the performance criteria for baro-VNAV systems in chapter 15.
(2) RF legs are discussed in Advanced Features, appendix 3.
(3) Unless the pilot has in sight the visual references required to continue the approach, the procedure must be discontinued if any of the following conditions occur:
(a) The navigation display is flagged invalid.
(b) Loss of integrity alerting function.
(c) The integrity alerting function is activated before passing the FAF.
Note: Discontinuing the procedure may not be necessary for a GNSS fail-down condition to LNAV only; or, for a multi-sensor RNP system that includes demonstrated RNP capability without GPS. Aircraft and/or equipment manufacturer documentation should be examined against functional and performance requirements to determine the extent the system may be used in such a configuration.
7-3. Special Characteristics of RNP 1 Operations.
a. Operation on RNP obstacle departure procedures (ODPs), standard instrum ent departures (SIDs), and STARs.
(1) Pilots are not required to monitor ground-based navigation facilities used in position updating unless required by the AFMS/RFMS.
(2) The navigation performance needed to fly RNP 1 procedures must be clearly designated on all appropriate charts.