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EN ROUTE 3.41 nm
TERMINAL 2.07 nm
APPROACH VOR/DME 0.61 nm
OTHER CASES 0.36 nm
When one FMGC changes the NAV accuracy from LOW to HIGH (or HIGH to LOW), the MCDU and
the ND display the "NAV ACCUR UPGRAD" (or DOWNGRAD) message.
A318/A319/A320/A321 FLIGHT CREW
OPERATING MANUAL
AIRCRAFT SYSTEMS
AUTO FLIGHT - FLIGHT MANAGEMENT
NAVIGATION - EVALUATION OF POSITION ACCURACY
A318/A319/A320/A321 FLEET DSC-22_20-20-20 P 5/16
FCOM 19 AUG 10
These messages are inhibited when the navigation mode is IRS/GPS.
When in IRS/GPS mode, the GPS PRIMARY status is related to integrity criterion: This is the
capability to detect a failure and provide appropriate warning of it. This criterion indicates the
confidence that the flight crew can have in the FMS position.
If the GPS PRIMARY status complies with this criterion, the "GPS PRIMARY" message is displayed
on the MCDU (PROG page, [5R] field and scratchpad) and temporarily on the ND. If the GPS
PRIMARY status no longer complies with this criterion (integrity lost), the GPS PRIMARY status is
lost and the MCDU and the ND display the "GPS PRIMARY LOST" message. It is possible to clear
the scratchpad message on the MCDU, but not on the ND. During a non-ILS approach, a triple-click
aural warning is also triggered.
Note: When the position computation uses IRS/GPS mode (FOM < 0.28 nm), the EPU is always
smaller than any value required by airworthiness authorities (whose minimum, in approach,
is 0.36 nm). As a result, accuracy is always at HIGH when in IRS/GPS mode, and so when
in GPS PRIMARY.
CAUTION "HIGH" or "LOW" on the PROG page indicates the FM position accuracy, based
on estimated uncertainty. When GPS PRIMARY mode is lost, the flight crew must
periodically check this position accuracy (although in GPS PRIMARY mode, the
position accuracy is always at HIGH).
A318/A319/A320/A321 FLIGHT CREW
OPERATING MANUAL
AIRCRAFT SYSTEMS
AUTO FLIGHT - FLIGHT MANAGEMENT
NAVIGATION - EVALUATION OF POSITION ACCURACY
A318/A319/A320/A321 FLEET DSC-22_20-20-20 P 6/16
FCOM 19 AUG 10
When the GPS is manually deselected, the "GPS IS DESELECTED" message is displayed on the
MCDU, 80 nm before the T/D or at approach phase transition.
ESTIMATED POSITION UNCERTAINTY
Applicable to:
,
,
MSN,,,,
The FMS displays the EPU to the flight crew and compares it with the Required Navigation
Performance (RNP):
If the EPU does ‐ not exceed the RNP, accuracy is HIGH
‐ If the EPU exceeds the RNP, accuracy is LOW.
The RNP is displayed in the REQUIRED field of the PROG page. The displayed RNP is (in a
decreasing order of priority):
‐ The value that the flight crew entered
‐ The navigation database procedure value
‐ The system’s default value.
When a flight crew enters an RNP that is higher than the published value, one of the following
messages is displayed : "PROCEDURE RNP IS XX.XX", or "AREA RNP IS XX.XX". When this
occurs, the flight crew should verify the RNP value that was manually entered in the REQUIRED field
of the PROG page, and clear or modify it if necessary.
The "AREA RNP IS XX.XX" message is also displayed at the change of flight area if the new RNP
(default value) is smaller than the displayed RNP (manually entered).
The RNP value should be in accordance with the specified RNP values of the navigation/approach
charts (if charts specify the RNP).
A318/A319/A320/A321 FLIGHT CREW
OPERATING MANUAL
AIRCRAFT SYSTEMS
AUTO FLIGHT - FLIGHT MANAGEMENT
NAVIGATION - EVALUATION OF POSITION ACCURACY
A318/A319/A320/A321 FLEET DSC-22_20-20-20 P 7/16
FCOM 19 AUG 10
DEFAULT AREA RNP VALUES
EN ROUTE 2.0 nm
TERMINAL 1.0 nm
APPROACH GPS 0.3 nm
OTHER CASES 0.5 nm
When one FMGC changes the NAV accuracy from LOW to HIGH (or HIGH to LOW), the MCDU and
the ND display the "NAV ACCUR UPGRAD" (or DOWNGRAD) message.
These messages are inhibited when the navigation mode is IRS/GPS.
When in IRS/GPS mode, the GPS PRIMARY status combines two different criteria:
‐ The accuracy criterion previously described (HIGH/LOW accuracy)
‐ An integrity criterion: This is the capability to detect a failure and provide appropriate warning of it.
This criterion indicates the confidence that the flight crew can have in the FMS position.
If the GPS PRIMARY status complies with both criteria, "GPS PRIMARY" is displayed on the MCDU
(PROG page, [5R] field and scratchpad) and temporarily on the ND.
If the GPS PRIMARY status no longer complies with one of these criteria (Navigation downgraded
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A320机组操作手册FLIGHT CREW OPERATING MANUAL 1(63)
