OPERATOR’S MANUAL
CMA-9000 FLIGHT MANAGEMENT SYSTEM
GPS NAVIGATION
The GPS sensor uses independent channels and can track any combination of GPS satellites. The GPS sensor
computes and outputs three-dimensional position and velocity components, time, ground speed, and track.
Both code and carrier phase tracking are used. Carrier phase tracking greatly reduces position and velocity
errors under highly dynamic aircraft manoeuvres.
The GPS sensor continuously monitors satellite health. All unhealthy satellites are dropped from the position
solution. In addition, all GPS signals-in-space used in the position solution are checked for failure by a Receiver
Autonomous Integrity Monitor (RAIM). It is understood that satellite failures are unannounced and can occur at
any instant. The RAIM continuously calculates the horizontal (HIL) and vertical integrity limits. The integrity limit
gives the radius in the horizontal plane and vertical direction within which the worst-case radial position error will
stay 99.99999% of the time without a satellite failure, and 99.9% of the time in the presence of a satellite failure.
The HIL is compared in the FMS to the value required for the phase of flight (alert limit), and an alert is
generated when the integrity value exceeds the alert limit. Alert limits are described in Section 15, RNP
Capability Modification.
The RAIM function maximises the availability of the oceanic, en-route, terminal, non-precision approach while
guaranteeing the integrity as described above.
When GPS is the sensor used for navigation and the HIL (Horizontal Integrity Limit) is within the phase of flight
limit, the GPS HIL is displayed as the Actual Navigation Performance (ANP) value on the PROGRESS 1/4 page.
The HIL is also displayed on the GPS STATUS 2/2 page.
The combination of a GPS INT annunciator as well as an alert message GPS NAV LOST provides an indication
between the loss of FDE (Failure Detection and Exclusion) availability and the loss of navigation.
The GPS sensor requires a minimum of four satellites for navigation, five satellites to allow integrity monitoring
and the detection of a failed satellite, and six or more satellites to identify and exclude (isolate) the failed satellite
from the navigation solution. No operator action is required to accomplish satellite failure detection and
exclusion (FDE) as these functions are automatic. Provided adequate signal-to-noise levels exist, any satellite
with an elevation angle of 2° or more above the antenna's local horizon can be acquired, and once acquired, it
will be tracked to an elevation angle of 0° above the horizon.
Typical time-to-first-fix (TTFF) values are 55 seconds (initialized) and 120 seconds (un-initialized, e.g. search-
the-sky mode). Satellite re-acquisition after signal loss is typically 5 seconds. When a sufficient number of
satellites that has been acquired, the GPS sensor enters navigation mode and outputs the required data to the
FMS.
Page 12-2
August 17, 2010
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