Loss of SBAS
Refer to the current, pertinent flight manual for additional information regarding crew responses for loss of SBAS and approach downgrade procedures
Due to the high level of precision required by some approach service levels, losing SBAS may require the pilot to acknowledge a downgrade of approach service level, or to abort the approach. See the following table for approach degradation behavior:
|
Approach |
SBAS Becomes Unavailable |
Description |
Action Required |
Downgrade |
|---|---|---|---|---|
|
LNAV |
Approach phase not specified |
SBAS not required. The approach is continued. |
None |
N/A |
|
LNAV+V |
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|
LNAV/VNAV |
Before the FAF |
HSI displays approach service level in amber; VDI displays ‘NO GP’.2 |
Acknowledge message to redisplay CDI with LNAV 1 |
LNAV1 |
|
At/After the FAF |
HSI displays downgraded approach service level in magenta; VDI displays ‘NO GP’. |
None |
LNAV1 |
|
|
LP |
More than one minute to the FAF |
HSI displays approach service level in amber; |
None |
N/A |
|
Within one minute to the FAF |
HSI displays downgraded approach service level in magenta CDI is removed.2 |
Acknowledge message to redisplay CDI with LNAV 1 |
LNAV 1 |
|
|
At/After the FAF |
CDI is removed.2 |
Acknowledge ABORT APR message to redisplay CDI |
N/A |
|
|
LP+V |
More than one minute to the FAF |
HSI displays approach service level in amber; VDI displays ‘NO GP’. |
None |
N/A |
|
Within one minute to the FAF |
HSI displays downgraded approach service level in amber; CDI is removed. VDI displays ‘NO GP’. 2 |
Acknowledge message to redisplay CDI with LNAV+V 1 Glidepath |
LNAV+V 1 |
|
|
At/After the FAF |
CDI is removed. VDI displays ‘NO GP’. 2 |
Acknowledge ABORT APR message to redisplay CDI |
N/A |
|
|
LPV |
More than one minute to the FAF |
HSI displays downgraded approach service level in amber; |
None |
N/A |
|
Within one minute to the FAF |
HSI displays downgraded approach service level in amber VDI displays ‘NO GP’. 2 |
None |
LNAV/VNAV1 |
|
|
At/After the FAF |
HSI displays downgraded approach service level in magenta; VDI displays ‘NO GP’. |
None |
LNAV1 |
|
|
1 Some approaches may not publish minimums for the downgrade given as an example in this table. The system will select the appropriate downgrade, if available, for each published approach as it is derived from the database. If an appropriate downgrade is not available, the approach should be aborted. |
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2 System message is generated. |
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