The CMA-9000 can be configured to one of two distinct modes: the civil mode and the military mode. Integrity monitoring and resulting consequences as required by TSO-C115b, AC20-130A, and DO-236A are the main differences between the two options.
When in the military navigation configuration option, the sensor navigation solutions will be assumed to have integrity unless proven otherwise. The navigation modes selection logic is geared to accuracy performance and the FMS will not necessarily force mode transitions based on integrity. Some integrity monitoring is nevertheless performed to raise alarms. The pilot is expected to consider navigation mode alarms and force navigation sensor selections if judged necessary. When in the civil navigation configuration option, the sensor navigation solutions will be assumed not to have integrity unless proven otherwise. The navigation modes selection logic is geared to safety (integrity) and the FMS may force mode transitions to remain in a navigation mode with integrity, thereby also preventing unnecessary alarms from being raised. This configuration option is intended to fully comply with TSO-C115, AC20-130A, and the integrity requirements of DO-236A. The CMA-9000 has several navigation modes. In sequence of priority, they are: Hybrid INS/GPS (military), GPS (civil), DME (civil), VOR/DME (civil) /TCN (military), Hybrid INS/DVS (military), Inertial (military), DVS (military), Kalman (civil) and Dead Reckoning (DR) (civil and military modes).
While in operation the CMA-9000 continuously computes the independent sensor positions. Each sensor output is monitored and compared against validity criteria. Any sensor which is declared as failed or has degraded sufficiently will automatically be deselected and will be restored to inventory only when restored to its criteria levels.
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Page May 10, 20075 (1) Global Positioning System (GPS) (Option)GPS is the highest priority navigation mode of the FMS, and will be used when sufficient satellite coverage exists in the Phase Of Flight (POF) for which it is approved. The sensor continuously monitors the integrity of the satellites by using a Receiver Autonomous Integrity Monitor (RAIM).
The GPS will remain selected for navigation when it’s RAIM function computes a Horizontal Integrity Limit (HIL) value that is less than the GPS Integrity alert limit, which is a function of the current POF and Required Navigation Performance (RNP). When the HIL exceeds the alert limit, or if the GPS loses it’s RAIM function then the first secondary mode is selected. (2) Hybrid INS/GPS (EGI)
When an EGI is configured and the hybrid solution is available and valid, it will have priority over a non-certified GPS. When the hybrid solution becomes invalid but the GPS solution remains valid, the GPS solution will be used. When both the hybrid and GPS solutions become invalid but the INS solution is valid, it will not be used. The INS solution will only be used if any radio (DME/VOR) solution fails.
(3) DME/DME
DME is the secondary navigation mode and will be used in areas with sufficient DME coverage and for which the appropriate navigation database is installed. In this mode the FMS automatically tunes the on-board DME equipment to acquire distance data from up to six DME ground stations to determine aircraft position. The position is updated once every 10 seconds from measured sensor data. In addition a velocity rate and heading based update is computed at least once every second.
For DME sensors, the raw information received is compared with the predicted position and signals rejected if a discrepancy between the predicted position and DME slant range information exceeds the applicable tolerances.
(4) VOR/DME or VOR/DME/TACAN (if TACAN installed)
VOR/DME or VOR/DME/TACAN navigation is a reversionary navigation mode which is used in areas with sparse DME coverage where there are two or less VOR/DME/TACAN stations. This mode combines co-located DME distances and VOR bearing to determine position. The position is updated once every 10 seconds.
For VOR, DME or TACAN sensors, the raw information received is compared with the predicted position. Signals will be rejected if the discrepancy between the predicted position and DME/VOR or TACAN information exceeds the applicable tolerances.
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Page May 10, 20076 (5) Hybrid INS/DVSWhen a SAGEM SIGMA50H EGI is configured and the hybrid INS/DVS position and velocities provided by the EGI are available and valid, a hybrid INS/DVS navigation becomes available.
The FMS is computing an INS/DVS Navigation solution if all of the following are true:
a) The FMS receives valid INS status, INS/DVS position, velocity, and Quality Factor data (e.g. navigation labels are received with SSM NORMAL and values are within the required range) from the EGI sensor.
b) The INS status indicates Navigation mode. c) The INS is not declared Fail.
(6) Inertial
An Inertial navigation becomes available when an EGI is configured. In the INS navigation mode, the FMS is using the raw INS position and velocities provided by the EGI for navigation.
(7) Kalman Filter (Optional)
The CMA-9000 uses the Attitude and Heading Reference System (AHRS), and the GPS to provide a Kalman Filter navigation mode. In this mode, the primary navigation sensor is a GPS receiver. The AHRS is made into a dead-reckoning navigation system by emulating an INS navigator with a Kalman filter performing closed-loop GPS correction and alignment. Each sensor has specific performance characteristics and behavior which when combined provide for continuous navigation. The GPS receiver has bounded but noisy positioning and velocity errors and the GPS navigation solution is subject to the availability of the GPS satellite constellation. The AHRS exhibits steady error growth which when converted to a dead-reckoning system will yield steady error growth in the position and velocity navigation solution. However, the AHRS-based inertial navigation solution is always available.
The Kalman Filter provides the means to combine both navigation modes so that accurate navigation can continue for some time after the GPS is lost. The GPS and the AHRS are integrated via a Kalman Filter to continuously correct and align the AHRS-based inertial navigation solution, as if the inertial navigation solution were static at a known position point. The inertial navigation solution based on the AHRS measurements offer short-term navigation when the GPS or other approved navigation sensor cannot provide navigation data. The inertial navigator uses measurements from the AHRS and corrections from the Kalman Filter when GPS is available. Once GPS is lost, the AHRS inertial navigation solution is provided until its error bounds have been exceeded. The CMA-9000 calculates these drift errors and makes the navigation solution unavailable when this error exceeds a limit. When exceeding the error the number will be 300 m 95% of the time which is equivalent to 400 m 99% of the time. The Kalman navigation mode typically lasts about 3-4 minutes. The GPS LOST discrete output is activated as soon as GPS data is not available and the Master Caution discrete output is activated when the 300 meter limit is exceeded.
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Page May 10, 20077 (8) DVSThe navigation mode based solely on Doppler is the less accurate FMS navigation mode based on sensor. It has priority over the Dead Reckoning mode only.
When a RDN85 or ANV353 DVS is configured, the CMA-9000 can compute a navigation solution if all of the following criteria is verified:
a) The FMS receives valid Doppler velocities and mode indication (e.g. labels are received with SSM NORMAL and values are within the required range) from the DVS;
b) The Doppler mode is LAND, SEA or CALM SEA for the RDN85 or in OPER for the ANV353 DVS;
c) The FMS receives valid heading data (e.g. labels are received with SSM NORMAL and values are within the required range) from an external sensor (refer to Section Heading Sources for possible heading inputs and selection logic).
The navigation solution computed by the CMA-9000 is based on the following data: • Doppler velocities (longitudinal, lateral and vertical)
• FMS System Selected Attitude (pitch and roll) • FMS System Selected Heading
(9) Dead Reckoning (DR)
When the external sensor data inputs become insufficient to maintain the normal navigation modes, the FMS reverts to the dead reckoning mode of navigation. The FMS must now rely on the last known aircraft position, combined with heading and TAS inputs, and the last valid computed wind, for its aircraft position calculation. Prolonged DR operation will result in decreased position accuracy. Alerts are provided when the estimated position accuracy exceeds the requirements for each phase of flight.
The FMS will automatically recover its normal modes of operation and position accuracy upon restoration of the external sensor inputs.
F. Annunciators and Keys
The FMS contains a full alphanumeric keyboard with special function keys. There are six line select keys (LSK) on each side of the display area. The functions of the LSKs are specific to each screen page. Figure 2A thru 2D describes the annunciators and FMS keys.
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