737 MAX Flight Crew Operations Manual
Flight Management, Navigation -
Flight Management System
Operation
MN-FLT-OH-201
11.31.9
Vertical Actual Navigation Performance (VANP)
Vertical Actual Navigation Performance (VANP) is the FMC’s estimate of the
quality of its altitude determination. It is shown on RNP PROGRESS page 4/5.
VANP represents the estimated maximum altitude error with 99.7% probability.
That is, the FMC is 99.7% certain that the airplane’s actual altitude lies within a
vertical band equal to plus or minus the ANP value. The lower the VANP value,
the more confident the FMC is of its altitude estimate.
Note:
VANP is calculated from the baro-corrected altitude provided by the Air
Data System. The pilot must set the baro setting reported by ATIS or
provided in the approach clearance for the 99.7% confidence level to be
valid.
Required Navigation Performance (RNP)
The FMC supplies a default required navigation performance (RNP) value for
oceanic, en route, terminal, and approach environments. RNP can also be supplied
by the Navigation Database or may be entered by the crew. Actual navigation
performance (ANP) should not exceed RNP.
If ANP exceeds the displayed RNP value, the UNABLE REQD NAV PERF–RNP
message will be displayed on the CDU scratchpad after the designated time to
alert has elapsed. An additional amber UNABLE REQD NAV PERF–RNP will be
displayed on the MAP. The amber FMC lights located on the main panel will also
illuminate with the annunciation of this message. RNP is shown on the POS
SHIFT, RNP PROGRESS 4/5 and the RTE LEGS pages.
March 1, 2021
