MSO-C129b.pdf

Subject: MSO-C129b, AIRBORNE SUPPLEMENTAL NAVIGATION

EQUIPMENT USING THE GLOBAL POSITIONING SYSTEM

(GPS) / PRECISE POSITIONING SERVICE (PPS)

DISTRIBUTION: SMC/GP (5 cys); AFFSA; NAWCAD; ESC/GA; SPAWAR Code 30;

CECOM; PMA/PMW-187

Department of Defense GPS Joint Program Office User Systems Engineering

Los Angeles AFB, CA

MSO-C129b

Date: 13 October 2005

Military Standard Order

(a) Applicability.

(1) Minimum Performance Standard. This Military Standard Order (MSO) prescribes the minimum performance standard that airborne supplemental area navigation equipment using Global Positioning System (GPS) / Precise Positioning Service (PPS) must meet in order to be identified with the applicable MSO marking. Airborne supplemental area navigation equipment using GPS that are to be so identified and that are manufactured on or after the date of this MSO must meet the minimum performance standard of Section 2, RTCA, Inc.

Document No. DO-208, “Minimum Operational Performance Standards for Airborne Supplemental Navigation Equipment Using Global Positioning System (GPS),” dated July 1991, except as specified herein. The similarity of this MSO with Technical Standard Order (TSO) C129a, "Airborne Supplemental Navigation Equipment using the Global Positioning System (GPS)", is intentional.

(2) Substitution. Airborne supplemental navigation equipment identified with the MSO-C129b marking are acceptable substitutes for airborne supplemental navigation equipment identified with a TSO-C129a marking in Required Navigation Performance (RNP) airspace for RNP-20 through RNP-0.3 operations.

(3) Equipment Classes. Equipment approved under this MSO shall be identified with the applicable equipment class as follows:

(i) Class A( ). Equipment incorporating both the GPS/PPS sensor and navigation capability. This equipment shall incorporate Receiver Autonomous Integrity Monitoring (RAIM) as defined by paragraph (a)(5)(xii) of this MSO.

1. Class A1. En route, terminal, and non-precision approach (except localizer, localizer directional aid (LDA), and simplified directional facility (SDF)) navigation capability.

2. Class A2. En route and terminal navigation capability only.

MSO-C129b 13 October 2005

(ii) Class B( ). Equipment consisting of a GPS/PPS sensor that provides data to an integrated navigation system (i.e., flight management system, multi-sensor navigation system, etc.). The equipment consisting of a GPS/PPS sensor must meet all of the Class B( ) requirements specified in this MSO in order to be identified with a Class B( ) marking.

1. Class B1. En route, terminal, and non-precision approach (except localizer, LDA, and SDF) capability. This equipment provides RAIM capability as specified in paragraph (a)(6)(iv) of this MSO.

2. Class B2. En route and terminal capability only. This equipment provides RAIM capability as specified in paragraph (a)(6)(iv) of this MSO.

3. Class B3. En route, terminal, and non-precision approach (except localizer, LDA, and SDF) capability. This equipment requires the integrated navigation system to provide a level of GPS integrity equivalent to that provided by RAIM as specified in paragraph (a)(6)(iv) of this MSO.

4. Class B4. En route and terminal capability only. This equipment requires the integrated navigation system to provide a level of GPS integrity equivalent to that provided by RAIM as specified in paragraph (a)(6)(iv) of this MSO.

NOTE 1: Limitations on equipment installations that require the integrated navigation system with which the GPS/PPS sensor is interfaced to provide a level of GPS integrity equivalent to that provided by RAIM should be included in the installation instructions.

NOTE 2: Systems utilizing Tactical Air Navigation (TACAN), Very High Frequency Omni-directional Ranging (VOR) and/or Distance Measuring Equipment (DME) for integrity monitoring may require modification in the future as changes to the National Airspace System occur.

(iii) Class C( ). Equipment consisting of a GPS/PPS sensor that provides data to an integrated navigation system (i.e., flight management system, multi-sensor navigation system, etc.) which provides enhanced guidance to an autopilot or flight director in order to reduce flight technical error. Class C equipment is limited to installations in Air Transport category aircraft or equivalent. (It is intended that this class of equipment need not meet the display requirements applicable to the other equipment classes of this MSO.) The equipment consisting of a GPS/PPS sensor must meet all of the Class C( ) requirements specified in this MSO in order to be identified with a Class C( ) marking.

1. Class C1. En route, terminal, and non-precision approach (except localizer, LDA, and SDF) capability. This equipment provides RAIM capability as specified in paragraph (a)(7)(iv) of this MSO.

13 October 2005 MSO-C129b

2. Class C2. En route and terminal capability only. This equipment provides RAIM capability as specified in paragraph (a)(7)(iv) of this MSO.

3. Class C3. En route, terminal, and non-precision approach (except localizer, LDA, and SDF) capability. This equipment requires the integrated navigation system to provide a level of GPS integrity equivalent to that provided by RAIM as specified in paragraph (a)(7)(iv) of this MSO.

4. Class C4. En route and terminal capability only. This equipment requires the integrated navigation system to provide a level of GPS integrity equivalent to that provided by RAIM as specified in paragraph (a)(7)(iv) of this MSO.

NOTE 1: Limitations on equipment installations that require the integrated navigation system with which the GPS/PPS sensor is interfaced to provide a level of GPS integrity equivalent to that provided by RAIM should be included in the installation instructions.

NOTE 2: Systems utilizing TACAN, VOR and/or DME for integrity monitoring may require modification in the future as changes to the National Airspace System occur.

(4) Exceptions to RTCA/DO-208 for all Classes of Equipment:

(i) Precedence. In the event of a conflict between the performance requirements or conditions imposed by the prime item specification for the GPS/PPS navigation sensor and the performance requirements or conditions imposed by this MSO through the invocation of RTCA/DO-208, the precedence of the performance requirements or conditions shall be as follows. Unless otherwise explicitly specified in this MSO, if the performance requirements or conditions imposed by the prime item specification are more rigorous or stringent than the requirements or conditions imposed by this MSO, then the performance requirements or conditions imposed by the prime item specification shall take precedence.

However, if the prime item specification performance requirements or conditions do take precedence, those performance requirements or conditions do not necessarily need to be met in order to be identified with the applicable MSO marking (see paragraph (c)(1)(xii)).

(ii) System Characteristics. Add the following to paragraph 1.2 of RTCA/DO-208: GPS provides two defined levels of positioning service: (1) the PPS, and (2) the Standard Positioning Service (SPS). When employed as described herein, the PPS is sufficient to serve as a guidance source for navigation in Required Navigation Performance (RNP) airspace for RNP-20 through RNP-0.3 operations. In the event that the PPS cannot be accessed, either because the GPS/PPS equipment lacks the requisite cryptographic keys ("PPS keys") or because of an operator-commanded PPS lock out (see paragraph 2.2.3.5), the SPS can serve as a substitute guidance source for navigation in RNP airspace for RNP-20 through RNP-

0.3 operations subject to local Air Traffic Control (ATC) regulation.

(iii) GPS Signal Characteristics. Add the following to paragraph 1.2.7 of RTCA/DO-208: Detailed PPS signal information is provided in the GPS PPS Performance Standard. Detailed SPS signal information is provided in the GPS SPS Performance Standard.

GPS signal-in-space technical details, for both the PPS and the SPS, are provided in IS-GPS- 200.

(iv) Time and Velocity. In lieu of paragraph 1.3.7 of RTCA/DO-208, substitute the following statement: The GPS equipment is capable of providing accurate position, velocity, and time (PVT) information. There may be future requirements for Universal Time Coordinated (UTC) and ground speed for other applications such as Automatic Dependent Surveillance (ADS) and Combat Identification.

(v) GPS Error Budgets. Add the following statement to paragraph 1.4.2 of RTCA/DO-208: For the PPS error budget, see the GPS PPS Performance Standard.

(vi) Operation of Controls. Add the following requirements to paragraph

2.1.4. of RTCA/DO-208: Controls shall be designed to maximize operational suitability and minimize pilot workload. Reliance on pilot memory for operational procedures shall be minimized.

(vii) Accessibility of Controls. Add the following requirements to paragraph 2.1.5 of RTCA/DO-208: Controls that are normally adjusted in flight shall be readily accessible and properly labeled as to their function. Controls for switching between the GPS signal processing modes shall be readily accessible and properly labeled as to their function.

(viii) Sensor Interfaces. In lieu of paragraph 2.1.6 of RTCA/DO-208, substitute the following requirement: The interfaces with other aircraft equipment must be designed such that normal or abnormal RNAV equipment operation shall not adversely affect the operation of other equipment nor shall normal or abnormal operation of other equipment adversely affect the RNAV equipment operation. The normal or abnormal operation of the GPS signal processing modes, defined in paragraph 2.2.3.5, shall not adversely affect the operation of other aircraft equipment.

(ix) Control/Display Capability. Add the following requirement to paragraph 2.1.7 of RTCA/DO-208: It shall be possible for the operator to manually switch to any of the GPS signal processing modes, defined in paragraph 2.2.3.5, at any time without loss of the navigation function.

(x) Effects of Test. Add the following requirement to paragraph 2.1.9 of RTCA/DO-208: The design of the GPS signal processing modes, defined in paragraph 2.2.3.5, shall be such that the application of the specified test procedures shall not produce a condition detrimental to the performance of the equipment.

(xi) GPS Signal Processing Mode Requirements. Add the following requirements to paragraph 2.2.3 of RTCA/DO-208 thereby producing an entirely new subsection:

“2.2.3.5 GPS Signal Processing Mode Requirements GPS/PPS equipment shall be designed to process the GPS signals and necessary data described in the GPS PPS Performance Standard under interference conditions described in paragraph 2.2.3.2 for the GPS/PPS navigation sensor and under the minimum signal conditions defined in paragraph 2.2.3.1. GPS/PPS equipment shall also be designed to process the GPS signals and necessary data described in the GPS SPS Performance Standard under the minimum signal conditions defined in paragraph 2.2.3.1. If dual-frequency ionospheric corrections are not applied to a pseudorange, then the equipment shall decode the ionospheric coefficients in the GPS navigation message and apply the ionospheric corrections described in IS-GPS-200. If dual-frequency ionospheric corrections are applied to a pseudorange, then the GPS ionospheric model shall not be used for that satellite. A tropospheric correction shall be applied.

"GPS satellite navigation data shall be continuously decoded. New ephemeris data (subframes 1, 2, 3 of the GPS navigation message) shall not be used for other than initial acquisition purposes until the data is verified by reception of a second message containing the same data. Ionospheric data (subframe 4) shall not be used until the data is verified by reception of a second message, potentially from a second satellite, containing the same data.

"The GPS/PPS equipment shall be designed to operate in at least the following three GPS signal processing modes. GPS/PPS equipment which is unable to operate in the second mode may still be eligible for identification with the applicable MSO marking provided a deviation or waiver authorizing the omission is granted; see paragraph (c)(1)(xii) of this

MSO.

a) Normal keyed PPS mode;

b) Operator-commanded PPS lock out mode; and

c) Unkeyed PPS mode.

"2.2.3.5.1 Normal Keyed PPS Mode The normal GPS/PPS equipment operating mode shall be the keyed PPS mode. Whenever the equipment has been keyed with valid PPS keys, the equipment shall operate in the keyed PPS mode unless otherwise commanded by the operator. In the keyed PPS mode, all GPS related information shall be derived exclusively from the PPS signals as described in the GPS PPS Performance Standard, except during acquisition or reacquisition. If MSO Approved GFE/GFI Parts List (MAGPL) items are incorporated and the GPS/PPS equipment is operating in keyed-PPS mode, unless at least one Y-code signal is tracked, no data from the GFE/GFI, pertinent to PPS URA, dither, and epsilon calculations shall be used to generate the solution of position, velocity, time, or integrity.

"2.2.3.5.2 Operator-Commanded PPS Lock Out (PPS-LO) Mode

When specifically commanded by the operator, GPS/PPS equipment operating in the keyed mode shall transition to operating in the operator-commanded PPS-LO mode. In the PPS- LO mode, all GPS related information shall be derived exclusively from the SPS signals as described in the GPS SPS Performance Standard. Commanding the PPS-LO mode differs from commanding the zeroization of the PPS keys since the PPS keys shall not be zeroized in response to the PPS-LO mode command. The PPS keys shall be retained in the PPS-LO mode and the equipment shall continue to function as a PPS receiver with all required capabilities enabled except for deriving all position related information exclusively from the SPS signals (i.e., no classified selective availability (SA) processing applied and no classified anti-spoofing (A-S) techniques employed). The use of classified SA processing and/or classified A-S techniques for functions other than deriving the output position related information is not precluded. When the PPS-LO mode is de-commanded by the operator, the equipment shall revert back to operating in the keyed PPS mode. The transitions from keyed PPS mode to PPS-LO mode, and from PPS-LO mode to keyed PPS mode, shall be accomplished within 8 seconds of operator command or de-command. The mode transition shall be accomplished without loss of navigation function. GPS/PPS equipment which is unable to operate in the PPS-LO mode pursuant to a deviation or waiver (see paragraph (c)(1)(xii) of this MSO) may incur operational restrictions that preclude access to certain airspace. If MSO Approved GFE/GFI Parts List (MAGPL) items are installed and the GPS/PPS equipment is operating in PPS-LO mode, no data from the GFE/GFI, pertinent to PPS URA, dither, and epsilon calculations shall be used to generate the solution of position, velocity, time, or integrity.

"2.2.3.5.3 Unkeyed PPS Mode The back-up GPS/PPS equipment operating mode shall be the unkeyed PPS mode.

Whenever the equipment has not been keyed with valid PPS keys, or the equipment has been zeroized, the equipment shall operate in the unkeyed PPS mode.

“Note: This mode is not the SPS mode. If a satellite is transmitting P-code or C/A-code on

L2, the GPS/PPS equipment operating in unkeyed PPS mode should have the capability to track these codes.”

(xii) Sensitivity and Dynamic Range. Add the following requirements to paragraph 2.2.3.1 of RTCA/DO-208: Antenna elevation mask angles below 7.5 degrees may be utilized provided the applicant develops acceptable test conditions and supporting analysis to substantiate use of the desired mask angle in the unkeyed PPS and PPS-LO modes. For the Normal Keyed PPS mode the antenna elevation mask angle shall be no greater than 5 degrees.

The equipment shall meet 2D accuracy requirements and dynamic tracking requirements with an input L1 P(Y)-code signal between -133 dBmic and -125 dBmic and an input L2 P(Y)-code signal between -136 dBmic and -128 dBmic incident on the antenna, with a noise density of -178 dBm/Hz (Tsky = 115 degrees K). Manufacturers are encouraged, but are not required, to design the GPS/PPS equipment to be interoperable with one or more of the standard GPS antennas as specified in MSO-C144.

"Note: The equipment should indicate in the installation instructions what type(s) of antenna the equipment is interoperable with and the maximum and minimum tolerable losses for installation with that type of antenna."

(xiii) Continuous Wave Interference (CWI). In lieu of paragraph 2.2.3.2 of RTCA/DO-208, substitute the following requirement: The equipment shall meet the requirements in paragraph 2.2.3 in the presence of interfering CW signals as specified in RTCA Document No. DO-229, “MOPS for GPS/Wide Area Augmentation System Airborne Equipment”, dated January 16, 1996, Appendix C for L1 operation. For L2 operation, the interfering CW signals are the same as for L1, but offset in frequency by -347.82 MHz.

(xiv) Dynamic Tracking. Add the following requirement to paragraph

2.2.3.4 of RTCA/DO-208: The equipment shall meet the applicable GPS position integrity performance requirements of Table 2-1 within the specified times stated in subparagraphs a and b.

(xv) Definitions of Terms and Conditions of Tests. Add the following requirements to paragraph 2.5.1 of RTCA/DO-208, thereby producing an entirely new subparagraph:

“i. GPS Signal Processing Modes The equipment shall be tested in all three GPS signal processing modes (Normal Keyed PPS Mode, PPS-LO Mode, and Unkeyed PPS Mode). To avoid unnecessary duplication, it shall be permissible to use analysis to satisfy the testing requirements by similarity for those functional and accuracy criteria which do not vary between the different GPS signal processing modes. For tests to verify that altitude measurement is properly incorporated, the Unkeyed PPS Mode and PPS-LO Mode shall only be subject to the test described in paragraph 2.5.2.5.3.8, the Normal Keyed PPS Mode shall only be subject to the test described in paragraph 2.5.2.5.3.9.”

(xvi) Standard Test Signals. In lieu of paragraph 2.5.1.c of RTCA/DO- 208, substitute the following requirements: The GPS/PPS equipment shall be able to operate on the L1 (1575.42 MHz) and L2 (1227.6 MHz) frequencies. The GPS/PPS equipment shall be able to operate with the C/A-code (1.023 MHz chipping rate) and P-code (10.23 MHz chipping rate) signals described in Navstar GPS Interface Specification (IS-GPS-200). The GPS/PPS equipment shall also be able to operate with the Y-code (10.23 MHz chipping rate) signals as described in the Navstar GPS Interface Control Documents (ICD-GPS-203 and/or in ICD-GPS 224 and/or in ICD-GPS-225).

(xviii) Test Procedures. Add the following requirements to paragraph

2.5.2 of RTCA/DO-208, thereby producing an entirely new subparagraph:

“e. Differences for the GPS Signal Processing Modes The Unkeyed PPS and PPS-LO mode test procedures are described in this section of RTCA/DO-208. For testing in the Normal Keyed PPS mode, the following changes must be made to the test procedures described in Section 2.5.2 of RTCA/DO-208:

a. A satellite will be considered “in view” if the elevation angle at the beginning of the run is 5 degrees or more.

b. The PPS signal-in-space accuracy shall be assumed to be 6m rms.

c. PPS Mode 2D accuracy tests as described in 2.5.2.6 of DO-208 shall be conducted under the conditions of Table 2-5, with the following exceptions: (1) at L1 the signal levels shall be –133 and –125 dBmic, respectively, rather than –130 and –123 dBmic; (2) at L2 the signal levels shall be –136 and –128 dBmic, respectively, rather than –130 and –123 dBmic, and the frequencies of the CWI shall be offset to the corresponding L2 band.

(xix) Government Furnished Equipment/Government Furnished Information (GFE/GFI). Items residing on the MSO Approved GFE/GFI Parts List (MAGPL) may be integrated into the GPS/PPS equipment without modification.

(5) Exceptions to RTCA/DO-208 for Class A( ) Equipment:

(i) Control/Display Readability. In lieu of paragraph 2.1.8 of RTCA/DO- 208, substitute the following requirement: The equipment shall be designed so that all displays and controls shall be readable under all normal cockpit conditions and expected ambient light conditions (total darkness to bright reflected sunlight). All displays and controls shall be arranged to facilitate equipment usage. The distinction between the different signal processing modes of GPS shall be readable under normal cockpit conditions and ambient light conditions.

The controls/displays for the different signal processing modes of GPS shall be arranged to facilitate equipment usage.

NOTE: Limitations on equipment installations to ensure display readability should be included in the installation instructions.

(ii) Maneuver Anticipation. Add the following requirement to paragraph

2.1.10 of RTCA/DO-208: For systems approved for non precision approaches (Class A1 equipment), maneuver anticipation (turning prior to the “to” waypoint) shall not be implemented at the missed approach fix or the missed approach holding fix.

(iii) Update Rate. In lieu of paragraph 2.1.11 of RTCA/DO-208, substitute the following requirement: Navigation information used for display shall be updated at an interval of 1.0 second or less.

(iv) Numeric Display Information. In lieu of paragraph 2.2.1.1.1 of RTCA/DO-208, substitute the following requirement:

1. Equipment certified to Class A2 shall continuously provide either a display or electrical output with the following requirements:

a. The display shall be as accurate as the resolution required for the displayed full scale range, referenced to a centered CDI display (see table in paragraph (a)(5)(v)).

b. The equipment shall provide a numeric display or electrical output of cross-track deviation to at least + 20 nm (left and right). A minimum resolution of 0.1 nm up to 9.9 nm and 1.0 nm beyond shall be provided. The display may be pilot selectable.

2. Equipment certified to Class A1, shall, in addition to the requirements for Class A2:

a. Provide a numeric (digital) display or electrical output of cross-track deviation to a resolution of 0.01 nm for deviations less than 1.0 nm.

b. Compute and display Track Angle Error (TAE) to the nearest one degree. Track angle error is the difference between desired track and actual track (magnetic or true). In lieu of providing a numeric display of track angle error, non-numeric TAE may be displayed in conjunction with the non-numeric cross-track deviation, provided the display provides equivalent situational awareness.

NOTE 1: While the numeric display need not be located with the non-numeric cross-track display (subparagraph 2.2.1.1.2) or in the pilot's primary field of view, Flight Technical Error (FTE) can be reduced when the numeric display is integrated with the non-numeric display or is located within the pilot's primary field of view. Both digital cross track and TAE have been shown to reduce FTE. This information should be displayed together (either within the CDU or remotely displayed near the non-numeric display) for better tracking performance.

NOTE 2: The use of non-numeric cross track data integrated with non-numeric track angle error data into one display may provide the optimum of situation and control information for the best overall tracking performance.

(v) Non-Numeric Display Information. In lieu of paragraph 2.2.1.1.2 of RTCA/DO-208, substitute the following requirements:

1. The equipment shall continuously provide either a display or electrical output with the following requirements:

En route Terminal Non-Precision Approach Full-Scale Deflection (+ nm) 5.0 1.0 0.3 Readability (Display only, nm) ≤1.0 ≤0.1 ≤0.03 Minimum Discernible Movement (Display only, nm)

≤0.1

≤0.01

≤0.01

Resolution of Electrical Output Percentage of Full Scale (+)

1%

Accuracy of Centered Display (+ nm) 0.2 0.1 0.01 Linearity of Display or Electrical Output (+) 20% 20% 20%

2. The applicable non-numeric display information shall be automatically presented upon activation of the appropriate operating mode and the conditions outlined in paragraph (a)(5)(ix).

3. A means shall be provided for manual selection of the applicable display sensitivities in paragraph (a)(5)(v)1. Additionally, the equipment shall display the non-numeric scale sensitivity, or provide an electrical output to display this information on an external display.

4. For Class A1 equipment, manual selection of a different scale sensitivity shall result in deselection of the approach mode. A proper indication must be provided.

5. In lieu of a linear lateral deviation scale for the final approach segment (final approach fix to missed approach point), an angular deviation display that emulates the nominal ILS localizer/MLS azimuth display resolution may be used, beginning with a full scale cross-track deflection of +0.3 nm at the final approach fix decreasing to +0.0576 nm (plus or minus 350 feet) at the runway threshold.

(vi) Waypoint Entry. In lieu of paragraphs 2.2.1.5 and 2.2.1.9 of RTCA/DO-208, substitute the following requirements:

1. Equipment certified to Class A2 shall at least provide the capability to manually enter and display (prior to its utilization in the flight plan) the coordinates of a waypoint in terms of latitude and longitude with a resolution of 0.1 minute or better. If the equipment provides the ability to enter a waypoint as a range and bearing from another waypoint, the waypoint input resolution shall be 0.1 nm and 1 degree or better.

2. Equipment certified to Class A1 shall at least provide the capability to manually enter and display (prior to its utilization in the flight plan) the coordinates of a waypoint in terms of latitude and longitude with a resolution of 0.01 minute or better. If the equipment provides the ability to enter a waypoint as a range and bearing from another waypoint, the waypoint input resolution shall be 0.1 nm and 0.1 degree or better.

(vii) Waypoint Storage. In lieu of paragraph 2.2.1.6 of RTCA/DO-208, substitute the following requirements:

1. The equipment shall provide an appropriately updateable navigation data base containing at least the following location information in terms of latitude and longitude with a resolution of 0.01 minute or better for the area(s) in which IFR operations are to be approved: all airports, VORs (and VOR/TACAN stations (VORTACs)), Non- Directional Beacons (NDBs), and all named waypoints and intersections shown on en route and terminal area charts, Standard Instrument Departures (SIDs) and Standard Terminal Arrival Routes (STARs).

NOTE: Manual entry/update of navigation database data shall not be possible.

(This requirement does not preclude the storage of “user defined data” within the equipment.)

2. Equipment certified to Class A1, in addition to the requirements of paragraph (a)(5)(vii)1, shall provide the following:

a. The equipment navigation database shall also include all waypoints and intersections included in published non-precision instrument approach (except localizer, LDA, and SDF) procedures.

b. The equipment shall store all waypoints, intersections, and/or navigation aids and present them in the correct order for a selected approach as depicted on published non-precision instrument approach procedure charts. The sequence of waypoints shall consist of at least the following: selected Initial Approach Fix (IAF), intermediate approach fix(es) (when applicable), final approach fix, missed approach point, and missed approach holding point. For procedures with multiple IAFs, the system shall present all IAFs and provide the capability for pilot selection of the desired IAF. Selection of the desired IAF shall automatically insert the remaining waypoints in the approach procedure in the proper sequence.

c. Waypoints utilized as a final approach fix or missed approach point in a non-precision approach procedure shall be uniquely identified as such to provide proper approach mode operation.

d. Modification of data associated with published instrument approach procedures by the user shall not be possible.

e. Waypoint data utilized in non-precision approach procedures shall be in terms of latitude and longitude and cannot be designated in terms of bearing (radial) and distance to/from a reference location.

f. When in the approach mode, except for holding patterns and procedure turns, the equipment must establish the desired flight path in terms of the path between defined endpoints up to the missed approach point.

3. The equipment shall provide the capability for entering, storing, and designating as part of the active flight plan a minimum of 9 discrete waypoints (including the active waypoint). In addition, for Class A1 equipment, it shall store and designate as part of the active flight plan the complete sequence of waypoints from the navigation data base necessary to complete the selected approach including the missed approach.

4. Waypoints shall be coded in the navigation database to identify them as “fly by” (turn anticipation permitted) or “fly over” (turn anticipation not permitted) as required by the instrument approach procedure, SID, or STAR. Waypoints which define the missed approach point and missed approach holding point in instrument approach procedures shall be coded as “fly over”.

5. Navigation databases shall meet the standards specified in Sections 3, 4, and 5 of RTCA Document No. DO-200, “Preparation, Verification and Distribution of User Selectable Navigation Data Bases,” dated November 28, 1988, and Sections 2 through 7 of RTCA Document No. DO-201, “User Recommendations for Aeronautical Information Services,” dated November 28, 1988.

(viii) Waypoint or Leg Sequencing. Add the following requirement to paragraph 2.2.1.7 of RTCA/DO-208:

1. The equipment shall provide the capability to fly from the present position direct to any designated waypoint. Access to this feature shall be by means of a single action by the pilot. Selection of the desired “TO” waypoint may require additional actions.

2. The equipment shall provide the capability for accomplishment of holding patterns and procedure turns. Activation of this function shall at least:

a. Change automatic waypoint sequencing to manual.

b. Permit the pilot to readily designate a waypoint and select a desired course (by means of a numerical keypad entry, HSI course pointer, CDI omni-bearing selector, etc.) to or from the designated waypoint (TO/FROM mode operation is acceptable).

c. Retain all subsequent waypoints in the active flight plan in the same sequence.

d. Permit the pilot to readily return to automatic waypoint sequencing at any time prior to the designated fix (“TO” waypoint) and continue with the existing flight plan.

3. Class A1 equipment, unless incorporating or interfaced with an appropriate situational awareness display (i.e., an electronic map), shall be designed to prevent automatic waypoint sequencing from the missed approach waypoint to the missed approach holding waypoint. Except for equipment with an approved electronic map display, course guidance shall display an extension of the inbound track and distance from the missed approach waypoint until manual selection of the next desired waypoint. Manual sequencing to the next waypoint after the MAP shall be accomplished by means of no more than two actions by the pilot (e.g., acknowledgment of next waypoint and activate DIRECT TO).

(ix) Approach Mode Selection and Sequencing. Add the following requirement to RTCA/DO-208:

1. For accomplishment of non-precision approaches, when an approach is included in the active flight plan, Class A1 equipment shall provide the following:

a. At a radial distance of 30 nm from the destination airport (not distance along the flight plan route), the equipment shall immediately transition to terminal integrity performance as specified in Table 2-1 of RTCA/DO-208:

b. The equipment can enable the approach either manually or automatically.

i. If the approach is enabled manually, the equipment shall provide an approach enable alert at a radial distance of 30 nm from the destination airport. After display of this alert, a means shall be provided to enable the approach mode with a single action by the pilot. Concurrent with the approach enable alert, a suitable means to alert the pilot of the need to manually insert the barometric pressure setting shall be provided (unless the automatic altitude input utilizes barometric corrected altitude data).

ii. If the approach is enabled automatically, the equipment shall activate the approach mode prior to a distance of 3 nm inbound to the final approach fix. The approach should not be enabled automatically more than 30 nm from the destination airport. An indication that the approach has been enabled shall be provided.

Concurrent with this indication, a suitable means to alert the pilot of the need to manually insert the barometric pressure setting shall be provided (unless the automatic altitude input utilizes barometric corrected altitude data).

c. When the approach is enabled (either manually or automatically), the equipment shall provide a smooth transition from 5 nm non-numeric display sensitivity to 1 nm sensitivity. No unique indication of the sensitivity change is required.

d. At a distance of 3 nm inbound to the final approach fix, the equipment shall provide an annunciation indicating an automatic non-numeric display sensitivity change will occur. If the approach was not previously enabled, the approach enable alert shall be repeated (manual systems only).

e. At a distance of 2 nm inbound to the final approach fix, if the approach has been enabled, the equipment shall automatically verify that satellite vehicle geometry will be suitable during the approach. This must be done using the RAIM prediction function defined in paragraph (a)(5)(xii)4a, including the final approach fix (FAF) and the MAP.

If the RAIM function is predicted to be available, the equipment shall switch to approach mode and:

i. Immediately transition from terminal integrity performance to approach integrity performance as specified in Table 2-1 of RTCA/DO-208.

ii. Provide a smooth transition from 1 nm non-numeric display sensitivity to 0.3 nm sensitivity at the final approach fix.

f. If the RAIM function is not predicted to be available during the approach, or if the approach has not been enabled at a distance of 2 nm inbound to the final approach fix, the equipment shall provide an indication that approach navigation is not provided. This indication must be sufficient to ensure that the pilot will not inadvertently conduct an approach using terminal area scale sensitivity.

2. If the pilot manually sequences to the missed approach holding point, the equipment shall:

a. Transition from approach integrity performance to terminal integrity performance as specified in Table 2-1 of RTCA/DO-208.

b. Provide a smooth transition from 0.3 nm non-numeric display sensitivity to 1 nm sensitivity.

3. A means shall be provided for deselection of the approach mode with a single action by the pilot, e.g. single button push. Deselection of the approach mode shall:

a. Transition from RNAV (non-precision) approach integrity performance to terminal integrity performance as specified in Table 2-1 of RTCA/DO- 208.

b. Provide a smooth transition from 0.3 nm non-numeric display sensitivity to 1 nm sensitivity.

4. If the ability to perform DME arcs is provided, the equipment shall permit the pilot to readily accomplish such procedures in accordance with published non-precision approach procedures utilizing piloting techniques similar to those applicable to use of the reference DME facility.

(x) Failure/Status Indications. In lieu of paragraph 2.2.1.10 of RTCA/DO-208, substitute the following requirement: The equipment shall indicate, independent of any operator action, the following:

1. By means of a navigation warning flag on the navigation display:

a. The absence of power required for the navigation function.

b. Any probable equipment malfunction or failure affecting the navigation function.

c. Loss of navigation function.

d. For equipment certified to Class A1, inadequate or invalid navigation data in the approach mode detected in accordance with RTCA DO-208 paragraph 2.2.1.13, Table 2-1, and paragraph (a)(5)(xii) of this MSO.

e. For equipment certified to Class A1, loss of the RAIM detection function in the approach mode, after passing the final approach fix. However, the navigation warning flag may be delayed until the RAIM detection function is lost for more than 5 minutes.

2. By means of an appropriately located annunciator:

a. When RAIM is not available, inadequate navigation data due to poor space vehicle geometry such that the probability that navigation error exceeds the position integrity performance requirements in RTCA/DO-208 (Table 2-1) is greater than or equal to 0.05.

b. The RAIM function detects a position error that exceeds the GPS position integrity performance requirements in RTCA/DO-208 (Table 2-1).

c. Loss of the RAIM function. Display of the integrity annunciation may be delayed for a period of time consistent with the requirements of paragraph (a)(5)(xi)2 of this MSO.

d. For equipment certified to Class A1, the loss of the RAIM detection function in the approach mode at or before the final approach fix, including the predicted unavailability of RAIM as described in paragraph (a)(5)(ix)1.f.

e. For equipment certified to Class A1, failure to enable the approach as described in paragraph (a)(5)(ix)1.d.

f. For equipment certified to Class A1, when operating in the approach mode without RAIM and navigation performance is degraded because Horizontal Dilution of Precision (HDOP) exceeds 4.0.

3. Additional navigation data (such as distance to waypoint, time to waypoint, ground speed, etc.) shall be removed or flagged when the adequacy of navigation information upon which this data is based cannot be assured.

NOTE: Presentation of a failure/status annunciation does not require removal of navigation information from the navigation display. Consideration should be given to continued display of navigation information concurrent with the failure/status annunciation when conditions warrant. The removal of navigation information from the navigation display is not necessary when switching between the different GPS signal processing modes.

NOTE: It is impractical for the operator to monitor, unaided, the changing parameters that affect accuracy. Therefore, the equipment should monitor those parameters for degraded performance that may result from propagation, reception, geometry, SA or other effects to the extent possible and be capable of automatic compensation, deselection, or manual deselection following annunciation of degraded performance consistent with paragraph (a)(4)(xi) of this MSO.

4. Approach mode status/annunciations. Equipment certified to Class A1 shall provide:

a. An annunciation, suitable indication or message that the approach mode is enabled.

b. An annunciation that the system is in the approach mode (RAIM in RNAV (non-precision) approach integrity performance and non-numeric display in approach sensitivity).

c. An annunciation of impending automatic non-numeric display sensitivity change to approach sensitivity.

d. An annunciation to alert the pilot of the need to manually insert the barometric pressure (unless automatic altitude input utilizing barometric corrected altitude data is available).

e. An annunciation to alert the pilot to enable the approach mode.

(xi) Annunciation of Integrity Alarm.

1. Delete the second sentence of the opening paragraph 2.2.1.13.2 of RTCA/DO-208 and replace with: “A separate and distinctive indication shall be raised in each of the following two circumstances.”

2. Add the following requirement to paragraph 2.2.1.13.2 of RTCA/DO-208: In order to minimize nuisance integrity alarms when system navigation accuracy is otherwise not in doubt, properly substantiated compensating features (such as clock coasting, inertial data, other sensors, etc.) may be incorporated into the system. The alarm under these conditions may be delayed for a period of time consistent with the worst cases of undetected clock drift or other failures that would cause the position error to exceed the accuracy required for that phase of flight. The applicant must develop appropriate test procedures to demonstrate the proposed compensating features provide the required level of navigation accuracy and integrity.

(xii) RAIM Implementation. Any algorithm which verifies the integrity of the position output using GPS measurements and barometric aiding is considered a RAIM algorithm. An algorithm which uses additional information (e.g., multi-sensor system) to verify the integrity of the position output may be acceptable as a RAIM-equivalent. Note that if RAIM is not incorporated in the GPS sensor, the sensor is only eligible for Class B3, B4, C3, and C4 certification. For sensors that provide RAIM, add the following requirements to paragraph

2.2.1.13.3 of RTCA/DO-208:

1. The RAIM function shall provide a worldwide availability of at least 95% given the optimal 21 GPS constellation (evaluated at a maximum resolution of 3 degrees in latitude, 180 nm in longitude, every 5 minutes). Barometric altitude aiding may be necessary to achieve this availability. RAIM-equivalent functions must also demonstrate an availability of at least 95%. If the equipment incorporates altitude aiding, appropriate requirements can be found in paragraph (a)(5)(xvii).

2. The RAIM function shall provide terminal integrity performance as specified in Table 2-1 of RTCA/DO-208 within 30 nm of the departure and destination points. In addition, approach mode (Class A1 equipment) integrity performance shall be provided from 2 nm prior to the final approach fix to the missed approach point. En route integrity performance shall be provided during other conditions.

3. The equipment shall automatically select the RAIM integrity performance requirements applicable to phase of flight.

4. Equipment certified to Class A1 shall provide a RAIM prediction function:

a. This function must automatically predict the availability of RAIM at the final approach fix and missed approach point of an active approach when 2 nm inbound to the final approach fix.

b. This function shall provide the pilot, upon request, a means to determine if RAIM will be available at the planned destination at the estimated time of arrival (ETA) (within at least ±15 minutes computed and displayed in intervals of 5 minutes or less). Once complete almanac data has been received, this capability shall be available at any time after the destination point and estimated time of arrival at that point are established. The availability of corrected barometric altitude (either by automatic or manual altimeter setting input) may be assumed for this purpose. (For the purpose of this calculation an acceptable value of the standard deviation of pressure altitude error is 50 meters.) A means to manually identify a satellite that is expected to be unavailable at the destination (for scheduled maintenance as identified in a GPS Notice Advisory to Navstar User (NANU) or an FAA Notice to Airmen

(NOTAM)) shall be provided. Identification of such a satellite for RAIM prediction purposes should not affect the satellite selection process or deselect that satellite from use in the navigation solution.

c. This function shall display, upon request, RAIM availability at the ETA and over an interval of at least ±15 minutes computed in intervals of 5 minutes or less about the ETA.

5. The GPS equipment shall detect a pseudorange step error greater than 1,000 meters, including steps which cause loss of lock for less than 10 seconds. A pseudorange step is defined to be a sudden change in the measured distance to a satellite. If a pseudorange step is detected for a satellite, that satellite shall be excluded from use in the navigation algorithm until its integrity can be verified through fault detection (RAIM). The manufacturer is free to choose any method to calculate the predicted pseudorange or to detect a step. However, any method used should properly take into account satellite movement and aircraft dynamics up to a groundspeed of 750 knots and accelerations up to 14.7 meters/second/second.

(xiii) 2D Accuracy Requirements (95 percent probability). In lieu of paragraph 2.2.2 of RTCA/DO-208, substitute the following requirement: The total of error contributions of the airborne equipment shall not exceed either error value listed in this paragraph. The reference spheroid shall use latitude/longitude values corresponding to the WGS-84 ellipsoid (see Appendix B of RTCA/DO-208). Since FTE factors are beyond the control of the equipment manufacturer or installer, these error sources are not included in this paragraph. The GPS Joint Program Office (JPO) PPS Equipment Certification Office (PECO) has determined that equipment meeting the display characteristics requirements contained in this MSO provide for acceptable values of FTE when properly installed in an aircraft.

GPS RNAV 2D Accuracy Requirements (95% Confidence)

Oceanic Error Type

(nm) En Route (random or

J/V routes) (nm) Terminal

(nm) Non-Precision Approach (nm)

Position fixing error* 0.124 0.124 0.124 0.056 CDI Centering** 0.2 0.2 0.2 0.01

* Equipment error assumes an average HDOP of 1.5, GPS equipment waypoint input and output resolution of 0.01 minute for approach/0.1 minute otherwise. Position fixing errors are static values

** The maximum difference between the displayed cross-track deviation and the computed cross-track deviation.

(xiv) (VNAV) Functional and Accuracy Requirements-Standard Conditions. Add the following requirement to paragraph 2.3 of RTCA/DO-208: If the vertical navigation (VNAV) option is provided by the equipment, the equipment must meet the requirements of paragraphs 2.3 and 2.5.3 of RTCA/DO-208.

(xv) Altitude Measurement Tests in the Unkeyed PPS and PPS-LO Modes. In addition to RTCA/DO 208, the following requirements and tests apply to equipment which uses altitude-aiding in the Unkeyed PPS and PPS-LO Modes. If alternative algorithms or test procedures are to be used, the manufacturer shall establish a set of tests acceptable to and approved by the PECO and demonstrate equivalent performance with those tests. Add the following requirements to section 2.5.2.5.3 of RTCA/DO-208, thereby producing an entirely new subsection:

1. “2.5.2.5.3.8. Tests to Verify that Altitude Measurement is Properly Incorporated in the Unkeyed PPS and PPS-LO Modes.

a. “As stated in paragraph 2.5.2.5.1, all tests described in paragraph 2.5.2.5 apply to equipment operating in the Unkeyed PPS and PPS-LO modes that employs a snapshot-type RAIM integrity algorithm that uses pseudorange measurements from GPS satellites either singly or in conjunction with an altitude input. The following on-line tests shall be performed to verify that the altitude measurement is properly incorporated. Tests should start early enough for the receiver to settle before each of the specified test periods begins.

b. All tests shall be conducted using the Optimal 21 constellation as described in Appendix I of RTCA/DO-208 for July 1, 1990. Test times are with respect to the GPS epoch time described in the same appendix. Note that the angle from the vernal equinox to the Greenwich meridian at GPS time 0:00 on July 1, 1990 is 278.8°, which must be taken into account when determining the position of satellites in an earth-centered, earth-fixed coordinate system.

i. For equipment which uses pressure altitude with local barometric correction as an optional input for GPS navigation and RAIM, conduct static tests with initial conditions as follows:

Test No.

Location (Lat/Long)

Geometric Altitude (Feet)*

Integrity Alarm Limit

(nm)

Initial Space Vehicle (SV) Pseudorange Error

(Meters)**

Failed

SV

Initial Altitude Error

(Meters)***

1 42°N/87.5°W 18,000 2.0 SV12 & SV16: -33

SV14 & SV20: +33

SV3 -477

2 42°N/87.5°W 18,000 2.0 SV9, SV14 & SV20: +33

SV12, SV16: -33

SV3 0

3 34°N/118°W 10,000 1.0 SV5, SV10 & SV15: +33

SV7: -33

SV4 -290

4 34°N/118°W 10,000 1.0 SV5, SV10 & SV15: +33

SV7 & SV12: -33

SV4 0

5 33°N/97°W 1,000 0.3 SV3, SV10 & SV21: +33

SV5: -33

SV2 -34

6 33°N/97°W 1,000 0.3 SV3, SV10 & SV21: +33

SV5 & SV15: -33

SV2 0

7 30°N/90°W 200 0.3 SV5, SV10 & SV17: +33

SV12: -33

SV15 -12

8 30°N/90°W 200 0.3 SV5, SV10 & SV17: +33

SV7 & SV12: -33

SV15 0

* Geometric altitude is the highest above the surface of the WGS-84 ellipsoid at the present position (latitude and longitude).

** A positive SV error causes an observed pseudorange which is smaller than the actual distance from the receiver to the SV.

*** A positive altitude error causes a barometric altitude which is higher than the geometric altitude.

ii. For these tests, the receiver is fixed at the geometric location and altitude specified and the Space Vehicles (SVs) change their orbital positions. The “Failed SV” for each test must not provide any signals to the receiver for the duration of the test. If an initial error is not specified for a SV pseudorange measurement, the error for the test for those SVs should be set to zero.

iii. Data should be recorded for each test during the specified “Period of Test” to determine the time at which the RAIM integrity limit alarm is activated. For a successful test, this alarm must not occur during the time from the start of the test to the time identified as the “Earliest Alarm Time”, but must occur between the time identified as "Earliest Alarm Time" and the “Latest Alarm Time”. As shown below, a positive error rate in meters per minute is induced in either the identified SV pseudorange value or the barometric altimeter input beginning at the “Start Time of Ramp Error” and continuing throughout the test. The magnitude of the error rate is specified by the “Error Rate”.

Test No.

Period of Test Error Source Start Time of Ramp…