21-1.3 Sensor Installation.
No ground tests are recommended for the sensor. Guidance relating to the interface between the sensor and the navigation system can be found in chapters 14 and 15.
21-1.4 Stand-Alone Navigation Equipment Installation.
a. Navigation parameters displayed on cockpit instruments such as HSI, CDI, distance display, electronic flight instrument system, moving maps, FMSs, etc. should be evaluated against the criteria described in chapters 12, 14, and 15 of this AC.
b. Failure modes and associated annunciations, such as loss of electrical power, loss of signal reception, GNSS equipment failure, autopilot/FD response to flags, etc., should be reviewed against the criteria described in chapters 12, 14, and 15 of this AC.
21-2. Flight Test - GPS, GPS/SBAS, and GPS/GBAS.
21-2.1 Equipment Installation.
a. Verify navigation data continuity during normal aircraft maneuvering for the navigation modes to be validated (e.g., bank angles of up to 30 degrees and pitch angles associated with take-off, departures, approaches, landing and missed approaches as applicable).
b. Verify the overall GNSS equipment operation to include at least the following:
(1) Hold at a designated waypoint;
(2) Intercept and track to or from a waypoint on a selected course;
(3) Turn anticipation;
(4) Waypoint sequencing;
(5) Selection of an approach;
(6) The general presentation of navigational data (depiction of the “TO” waypoint, distance to waypoint, estimated time of arrival, estimated time enroute, ground speed, etc.); and
(7) Evaluate the overall operation on all types of procedures or paths that the equipment supports (e.g., straight legs, DME arcs, and RF legs).
c. Evaluate displayed vertical navigation parameters on interfaced flight deck instruments such as an HSI, CDI, etc. Evaluate how distance to go, course, bearing, etc. are displayed on all flight deck presentations during approach procedures when step-down fixes are included in the navigation database (see paragraphs 12-8 and 18-2.b).
d. Verify that FTE can be maintained at less than 1.0 NM for enroute and approach transition operating modes, and less than 0.25 NM for non-precision approach, both with and 144
without autopilot and/or FD use, as applicable. This test may not be necessary if the FTE has been previously established for the aircraft. One acceptable way of assessing FTE is to monitor the measured cross-track deviation using the navigation display provided.
e. The following issues should be evaluated when the equipment is interfaced with a FGS. The objective of this paragraph is to ensure proper aircraft operation when the GNSS is interfaced with the aircraft’s FGS. If these issues cannot be addressed for a particular autopilot
(e.g., because the autopilot does not respond to flag indications), the GNSS equipment may still be installed, but either should not be connected to the autopilot, or have an appropriate AFMS/RFMS limitation that mitigates the issue.
(1) Evaluate steering response while the FD and/or autopilot is coupled to the GNSS equipment during a variety of different track and mode changes. This evaluation should include, as applicable, transition from enroute through the approach to missed approach modes and then back to enroute. Additionally, evaluate all available display sensitivities.
(2) Execute several fly-by turns with varying wind conditions for the FD and autopilot. Verify the equipment accomplishes the turn as a fly-by waypoint and discourages overshoot. Fly-by turns are turns where the equipment initiates the turning maneuver before sequencing the waypoint by an amount equal to the turn anticipation distance.
(3) Verify that the lateral maneuver anticipation supplied by the GNSS equipment is appropriate for the aircraft type. Verify that an appropriate annunciation of impending waypoint crossing is provided.
(4) Verify that execution of the Direct-To function with a resultant aircraft heading change does not overshoot and cause “S” turns. Re-initializing the Direct-To function after completion of most of the required track change may be an acceptable means of compliance for equipment which does not inherently account for the change in aircraft heading.
(5) Evaluate the autopilot response to a GNSS fault by simulating a representative fault consistent with the equipment architecture (e.g., pulling the circuit breaker) for the GNSS equipment. This test should be done in all of the GNSS enroute and approach modes.
21-2.2 LP/LPV, LPV and GLS.
a. For installations where the autopilot has not been modified and the GNSS equipment provides ILS-like deviations, conduct several approaches while flying raw data, FD and coupled to the autopilot, as applicable. The objective of this test is to ensure that the GNSS equipment interface is compatible with the aircraft; the objective is not to verify approach performance.
b. For installations where the autopilot has been modified, the autopilot lateral/vertical control channel performance has not been assessed, or non-standard deviations are provided (not ILS-like), then the approach performance will need to be evaluated per the latest revision of AC 23-17, AC 25.1329-1, AC 27.1329 contained in AC 27-1, or AC 29.1329 contained in AC 29-2 (or equivalent means).
c. For manual control to the approach flight path, the appropriate flight display(s) must provide sufficient information to maintain the approach path and make alignment with the runway or go-around without excessive reference to other cockpit displays.
d. Evaluate full-scale deflection while on approach to ensure the system operates properly.
e. Evaluate the FGS approach functionality to ensure compatibility with the gain scheduling employed by some FGSs during approaches. For example, some FGSs depend upon a radio altimeter, or, middle marker beacon passage inputs to enable a "glideslope extension" function to reduce "porpoising" or aerodynamic instability when coupled to a glideslope signal during the final approach phase. But WAAS LPV approaches do not have middle marker beacons so FGS response needs to be evaluated when incorporating LPV capability.
f. No additional testing is needed to verify LP capability if LPV has been satisfactorily demonstrated. Confirm the cockpit annunciation scheme will provide a clear, unambiguous annunciation of LP service when selected by the pilot. Verify through analysis or previous testing the FGS is able to support horizontal-only approach guidance inputs.
g. Verify/assess all switching and transfer functions, including electrical bus switching, pertaining to the GNSS installation. Evaluate the aircraft system response during switches to all alternate navigation sources and ensure that the switch is accomplished as expected, that it is clearly annunciated, and that the switching itself does not induce any inaccurate guidance.
Verify any air data and inertial source select switches are appropriately reflected in the positioning and navigation equipment.
h. Review and verify, where appropriate, various failure modes and associated annunciations, such as loss of electrical power, loss of signal reception, GNSS equipment failure, FGS response to GNSS flags, etc. Verify that a warning associated with loss of navigation is accompanied by a visual indication within the pilot’s primary field of view.
i. A crew workload analysis when operating the GNSS equipment in association with other piloting requirements should be conducted during all phases of flight and found to be acceptable, including those non-normal procedures that can be evaluated in flight.
21-2.3 GPS/GBAS VDB Receiver Installation.
a. To verify non-interference (electromagnetic compatibility) between the VDB and VHF communications equipment, a flight test should be accomplished using the highest available VDB broadcast frequency, and transmitting VHF communication at 100 kHz above the VDB channel. Use 118.000 MHz for VHF communications equipment that ca nnot transmit below 118.000 MHz.
b. VDB receiving capability should be demonstrated in flight. Unlike ILS, where the ILS facility is always located in front of the aircraft on approach, a GPS/GBAS facility could be located anywhere with respect to the approach path. Therefore, the flight test should verify VDB signal reception at all angles relative to the airframe.
--- Chapter 22. Installed Performance - Test (RNAV Multi-Sensor Equipment).
22-1. Ground Test.
Refer to TSO-C115b/RTCA/DO-187, TSO-C115c/RTCA/DO-283A, or TSO-C115d/RTCA/DO-283B as appropriate, for RNAV multi-sensor equipment ground test information.
22-2. Flight Test.
Flight tests are conducted to verify proper operation and accuracy of the multi-sensor equipment as installed in the aircraft (except for GNSS accuracy, see paragraph 21-2). Flight tests should include at least the following:
Note: Required flight evaluations for the first-time airworthiness approval of multi-sensor equipment are accomplished by the cognizant ACO unless specific tests are delegated by the ACO to a flight test pilot designated engineering representative (DER).
a. Evaluation to determine satisfactory EMC between the multi-sensor equipment installation and other onboard equipment (this test may be partially accomplished as a ground test).
b. Validate multi-sensor equipment navigational accuracy in each operating mode. In addition to overall system navigation performance, particular test requirements for navigational accuracy will vary depending upon the particular sensors integrated in the multi-sensor equipment and whether sensor accuracy performance data has previously been obtained. The performance of each navigation sensor should be evaluated separately and in combination with other sensors as applicable.
c. Initial certification for systems including a VOR/DME or multiple (scanning) DME sensor that has not been previously certified must be based upon a demonstration of system accuracy by recording (at not greater than 15 minute intervals) the VOR/DME and/or DME/DME sensor position and comparing it to the actual position during evaluation flights.
The latest revisions of AC 25-7 and AC 23-8 provide guidance on test distances from VOR and DME navigation aids. Recorded data should include sufficient signal parameters and sensor performance data to provide a clear indication of satisfactory sensor performance. The particular flight paths should be selected based upon an analysis of critical signal characteristics, station geometry, signal coverage (including limited station availability with acceptable range), aircraft movement, etc. The system should demonstrate its ability to detect poor signal conditions, inadequate navigation capability, recovery from in-flight power failure, etc. The auto-tune logic should be reviewed and tested to verify that ground stations are identified and tuned correctly.
d. Inertial systems that satisfy the criteria in 14 CFR part 121, appendix G and comply with Table 10 below do not need further evaluation. Based on an evaluation of INS/IRU performance, the growth in position error after reverting to INS/IRU can be expected to be less 147
than 2 NM per 15 minutes. Applicants that desire certification credit for better performance should coordinate with their ACO for the requirements to demonstrate and document the performance.
Time Since Radio Updating (T) (hr) IRS/IRU 95% Error (NM)
0.0 to 0.5 hr 8*T
0.5 to 1.5 hr 4 Table 10. INS/IRU Accuracy After Loss of Radio Updating
e. Verify navigation data continuity during normal aircraft maneuvering for the navigation modes to be validated (e.g., bank angles of up to 30 degrees and pitch angles associated with approaches, missed approaches and departures).
f. Verify the overall operation of the multi-sensor equipment to include at least the following: the ability to create and modify a flight plan, hold at a designated waypoint, intercept and track to or from a waypoint on a selected course (Course to Fix leg), turn anticipation, waypoint sequencing, selection of an approach and the general presentation of navigational data (depiction of the “TO” waypoint, distance to waypoint, estimated time of arrival, estimated time enroute, ground speed, etc.). Evaluate displayed vertical navigation parameters on interfaced flight deck instruments such as an HSI, CDI, etc. Evaluate how distance to go, course, bearing, etc. are displayed on all flight deck presentations during approach procedures when step-down fixes are included in the navigation database (see paragraphs 12-8 and 18-2.b).
g. Verify that FTE does not exceed 1.0 NM for enroute, 0.5 NM for approach transition and missed approach operating modes, and 0.25 NM for non-precision approach, both with and without autopilot and/or FD use, as applicable. This test may not be necessary if the FTE has been previously established for the aircraft. One acceptable way of assessing FTE is to monitor the measured cross-track deviation while either flying under autopilot control or flying manually using the navigation display provided.
h. If the equipment uses barometric input, verify that the equipment properly interprets the barometer reading. Special consideration should be given to manually entering a barometric correction.
i. Verify/assess all switching and transfer functions, including electrical bus switching, pertaining to the multi-sensor installation. The aircraft system response during any switch over to alternate navigation sources must be evaluated. Particular attention should be given to mode switching and transition requirements associated with the approach mode for equipment incorporating GNSS sensors.
j. Review and verify, where appropriate, various failure modes and associated annunciations, such as loss of electrical power, loss of signal reception, multi-sensor equipment failure, FGS response to GNSS flags, etc. Verify that a warning associated with loss of navigation is accompanied by a visible indication within the pilot’s primary field of view.
22-2.1 Interface to FGS.
a. Evaluate steering response while the FD and/or autopilot is coupled to the multi-sensor equipment during a variety of different track and mode changes. This evaluation should include, as applicable, transition from enroute through the approach to missed approach modes and then back to enroute. Additionally, evaluate all available display sensitivities.
b. Several fly-by turns should be accomplished with varying wind conditions for FD and autopilot. Verify the equipment accomplishes the turn as a fly-by waypoint and discourages overshoot. Fly-by turns are defined as turns where the equipment initiates the turning maneuver prior to sequencing the waypoint by an amount equal to the turn anticipation distance.
c. Verify that the lateral maneuver anticipation supplied by the multi-sensor equipment is appropriate for the aircraft type. Verify that if the multi-sensor equipment is coupled to an autopilot or on approach, an appropriate annunciation of impending waypoint crossing is provided.
d. Verify that execution of the Direct-To function with a resultant aircraft heading change does not overshoot and cause “S” turns that exceed the lateral path tracking FTE requirements.
e. Evaluate the autopilot response to a multi-sensor equipment fault by simulating a representative fault consistent with the equipment architecture (e.g., pulling the circuit breaker) for the equipment. This test should be done in each of the sensor modes, if applicable.
22-2.2 GNSS Precision Approach.
a. For equipment that provides GNSS precision approach capability, or for equipment with non-standard navigation displays, conduct several approaches while flying raw data, FD only and coupled to the autopilot, as applicable. The objective of the test is to ensure that the multi-sensor equipment interface is compatible with the aircraft and is not a verification of approach performance. This objective is valid only for installations with existing and proven performance (e.g., GNSS providing ILS like deviations to replace or supplement an existing ILS). For installations where the autopilot has been modified or the autopilot lateral/vertical control channel performance has not been assessed, then the approach performance will need to be evaluated per the latest revision of ACs 23-17 or 25.1329-1, or equivalent means.
b. For manual control to the approach flight path, the appropriate flight display(s) must provide sufficient information without excessive reference to other cockpit displays, to enable a suitably trained pilot to maintain the approach path, make alignment with the runway or go-around.
Chapter 23. Installed Performance - Test (Baro-VNAV).
23-1. Introduction.
Paragraphs 23-2 and 23-3 describe the installed performance test considerations for an initial approval. Subsequent installations are addressed in paragraph 23-4. An initial approval refers to the very first time an applicant presents a particular model of baro-VNAV equipment for FAA certification and airworthiness installation approval for an IFR navigation system.
Any new models of baro-VNAV equipment by the same manufacturer should undergo the same approval process as the original equipment unless it can be shown by analysis and test that the new model will function as well or better than the approved equipment.
23-2. Ground Test.
23-2.1 Lab/Bench Tests and Equipment Data Evaluation.
Normally the baro-VNAV equipment manufacturer will accomplish these actions for a certification design approval. This phase consists of the following:
a. Analysis of the manufacturer’s procedures for verification and validation of software and review of supporting documentation in accordance with the guidelines of RTCA/DO-178B or ‘C’.
b. Verification of compliance with appropriate environmental qualification standards such as RTCA/DO-160F.
Note: Previously certified baro-VNAV systems may have used an earlier RTCA/DO-160 revision. This equipment may still be installed within the provisions of its original certification.
c. Examination of the equipment’s display capabilities with emphasis on warning, caution, and advisory annunciations.
d. Analysis of failure modes.
e. Review of reliability data to establish that all probable failures are detected.
f. Evaluate the controls, displays, annunciations, and system behavior from a human performance perspective.
g. Review of installation and maintenance manuals.
h. Evaluation of operator's manual (pilot’s guide).
23-2.2 Aircraft Installation Data Evaluation.
Normally the baro-VNAV equipment manufacturer will provide an aircraft as a test 150
bed for a first-time installation approval. The first-time installation approval will serve as a basis for subsequent installation approvals on the same type of aircraft incorporating the same autopilot/FD system and for other aircraft installations not incorporating autopilot/FD interface with the baro-VNAV equipment. The following assessments must be made:
a. Review the installation drawings, wiring diagram, and descriptive wiring routing.
b. Examine the installed equipment cockpit layout with emphasis on equipment controls, applicable circuit breakers (labels and accessibility), switching arrangement and related indicators, displays, annunciators, etc.
c. Analyze the data flow diagram to review which equipment transmits what data to which other equipment.
d. Review the equipment installation structural analysis to ascertain whether all system components are satisfactorily attached to the basic aircraft structure.
e. Examine the electrical load analysis to verify that the system installation’s added electrical power requirements will not cause overloading of the aircraft’s electrical generating capacity.
f. Evaluate the integration with the associated lateral navigation equipment.
23-3. Flight Test.
23-3.1 Functional Flight Test.
a. Evaluate all baro-VNAV equipment operating modes.
b. Examine the interface (function) of other equipment connected to the baro-VNAV system.
c. Review various failure modes and associated annunciations, such as loss-of electrical power, loss of lateral navigation signals, baro-VNAV equipment failures, etc.
d. Evaluate steering response while the autopilot is coupled to the baro-VNAV equipment during a variety of lateral and vertical track changes including selection of baro-VNAV modes while operating at the maximum and minimum speeds approved for baro-VNAV use.
e. Evaluate displayed baro-VNAV navigation parameters on interfaced flight deck instruments such as an HSI, CDI, etc. E valuate how distance to go, course, bearing, etc. are displayed on all flight deck presentations during approach procedures when step-down fixes are included in the navigation database (see paragraphs 12-8 and 18-2.b).
f. If equipped, when temperature compensation is enabled ensure that the display of corrected altitude(s) is consistent on all displays in the cockpit.
g. Assess all switching and transfer functions pertaining to the baro-VNAV equipment including high-power electrical loads and electrical bus switching.
h. Evaluate whether magnetic or radio frequency interference exists between the baro-VNAV equipment installation and other onboard equipment, or vice versa.
i. Evaluate the accessibility of all controls pertaining to the baro-VNAV system installation.
j. Evaluate the display(s) and annunciator(s) visibility pertaining to the baro-VNAV system installation during day and night lighting conditions. No distracting cockpit glare or reflections may be introduced.
k. Analyze crew workload and determine acceptability when operating the baro- VNAV equipment.
23-3.2 Navigation Error Flight Test.
a. The initial certification of each baro-VNAV system to be used for IFR approach operations should be based on a system performance demonstration by recording the baro-VNAV equipment vertical guidance and comparing it to the actual aircraft position along a pre-established vertical flight path. This evaluation can be made by using the actual coded path and appropriate path definition.
b. Data should be gathered using a variety of descent rates, angles, and lateral navigation source inputs available to the baro-VNAV system.
Note 1: GPS/SBAS LNAV/VNAV most closely emulates baro-VNAV performance. See paragraph 18-5 for a description of GPS/SBAS versus baro-VNAV differences.
Note 2: Some baro-VNAV implementations may provide ascent guidance as well for the missed approach segment or for applications other than approach operations. Data should also be gathered for ascent guidance if the equipment provides that capability.
c. The data should demonstrate that the appropriate accuracy criteria of paragraph
11-2.b are met on a 99.7% probability basis.
d. Flights should verify proper operation of caution indications and lateral navigation interface.
e. Normal flight maneuvers should not cause loss of system sensor inputs and the system dynamic response should be confirmed.
f. Evaluate any unusual flight technical errors or errors from using the autopilot and FD.
23-4. Follow-on Approval.
The applicant or installing agency requesting a follow-on baro-VNAV system installation using FAA Form 337 field approval should:
a. Contact either the manufacturer or organization responsible for obtaining the first-time airworthiness approval to:
(1) Obtain a sample AFMS/RFMS (or supplemental flight manual, as appropriate).
(2) Obtain verification of the equipment approval status, including the software program identification and lateral navigation equipment that may be interfaced with the system.
(3) Discuss any problem areas and seek assistance in their solution.
b. Conduct a similar data evaluation as outlined in the paragraph 23-2.2 for baro-VNAV initial approval.
c. Conduct flight evaluations similar to the flight tests outlined in paragraph 23-3.1 for baro-VNAV initial approval.
d. Verify that the maximum expected groundspeed of the aircraft is less than the maximum operating speed for which the baro-VNAV equipment is qualified.
e. Spot check baro-VNAV approach performance by conducting an evaluation flight incorporating at least three ILS approaches comparing baro-VNAV vertical guidance to that provided by the ILS glideslope and three non-precision approaches that normally don’t include vertical guidance (such as LNAV) to a specified minimum descent altitude (not a descent angle).
Note: It is also acceptable to compare baro-VNAV performance to GPS/SBAS LPV, GPS/SBAS LNAV/VNAV or GPS/GBAS GLS vertical guidance in lieu of ILS. GPS/SBAS LNAV/VNAV most closely emulates the baro-VNAV performance.
f. Accuracy should be verified by comparison to the ILS glideslope indication and altimeter reading.
g. The purpose of this evaluation flight is not to validate baro-VNAV navigation error values, but rather to verify that, in the course of this installation, nothing was done to compromise the accuracy of the system as determined by the initial approval.
h. Significant differences between the vertical path data provided by the ILS glideslope and/or altimeter and baro-VNAV equipment must be evaluated to determine possible causes. If 153
a logical explanation is not available, additional flight test data points should be collected. If such error(s) persist, installation approval must be withheld.
Appendix 1 Appendix 1. GPS Oceanic/Remote Navigation.
A1-1. GPS Oceanic/Remote Navigation.
a. The following criteria define an acceptable means of compliance for approval of TSO-C129(AR) GPS equipment intended for oceanic and remote operation without reliance on other long-range navigation systems. This approval is granted as a non-TSO function according to existing policy. Equipment that previously demonstrated compliance to Notice 8110.60 or previous revisions of AC 20-138, appendix 1 are still eligible for oceanic and remote operation and do not need re-evaluation.
Note 1: TSO-C129a has been cancelled but equipment with an existing TSO-C129a TSOA may receive approval for oceanic/remote operation without reliance on other long range navigation systems.
Note 2: The FAA has adopted the ICAO term
“oceanic/remote” instead of Class II.
b. TSO-C196(AR) and TSO-C145/C146(AR) equipment are inherently capable of supporting this operation without further evaluation if the operator obtains an FDE prediction program (see paragraph 5-2.3). Equipment manufacturers may choose to provide further robustness for oceanic and remote area operations by including barometric aiding in their FDE algorithms. Appendix G of RTCA/DO-316 and RTCA/DO-229D, Change 1 provide an acceptable barometric aiding implementation method for TSO-C196(AR) and TSO-C145/C146(AR) equipment respectively.
Note: Barometric aiding enables the equipment to continue providing integrity when only four satellites are available for use in the position solution. Appendix G of RTCA/DO-229C for TSO-C145a/C146a equipment is identical to appendix G in RTCA/DO-229D, Change 1.
A1-2. Approval Process
a. TSO Authorization.
The criteria in this appendix are in addition to the TSO-C129(AR) requirements and approved as a non-TSO function. The ACO should issue a separate letter of design approval stating that the equipment (including part number) and software prediction program (including revision number) meet the criteria in this appendix. The applicant should be able to substantiate equivalent performance between the FDE prediction program and the airborne receiver algorithm. See paragraph 5-2.3 for information on FDE prediction program performance.
b. Installation Approval.
(1) The applicant obtains the GPS navigation equipment installation approval.
A1-1