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note reflects that an obstacle assessment has been completed for the
visual segment of the approach and that descent below the MDA
during execution of a missed approach is allowed.
Currently the only approach plates publishing a DA are RNAV approaches
under the column titled LNAV/VNAV. To use this DA requires display of a
gradient path on the LEGS page and display of the path deviation indicator
(PDI) on the Map.
RNAV approach plates also list MDA minima under the column titled LNAV.
This MDA will be used, and a DDA created, when a gradient path will not
display or a PDI is not available. In this event use V/S at a constant rate from
the FAF to minimums.
RADIO ALTIMETER
Radio altimeter setting will be 250 ft. for non-precision approaches. This is
consistent with Flight Manual guidance and is the result of research to minimize
CFIT encounters / accidents. Setting the radio altimeter to 250 ft. may provide
additional terrain awareness should descent below minimums occur without
adequate visual cues or if descent relationship to the runway, with visual cues, is
not proper.
737 Sec. 3 Page 219
Flight Manual Continental Rev. 11/15/02 #41
RNP / ACTUAL (ANP)
Required Navigation Performance (RNP) criteria is the defined accuracy
(mileage) requirement for phases of enroute and terminal flight and various
approaches when the FMC is used as the sole means of navigation.
RNP value is controlling for RNAV, GPS, and BCD NDB. It is also
controlling for BCD VOR approaches where raw data is not available or
is not monitored.
When RNP is controlling for an approach, the ACTUAL (ANP) performance
value must remain smaller than the RNP from the FAF inbound to the runway.
ANP is an FMC measure of the current navigation system performance (think of
this value as an FMC prediction of system accuracy).
If the ANP exceeds the RNP inside the FAF, messaging must indicate the
exceedance clearly within the field-of-view and the message treated as a goaround
signal. The message we receive with an RNP exceedance is UNABLE
REQD NAV PERF – RNP and it appears on the Map.
To enable this message on the Map the RNP must be manually entered, even if
the value is the same as the approach phase default of .5nm. To enter the
required RNP, type it into the scratchpad and then line select it to the RNP field
at 6L on the LEGS page. Manual entry of RNP is not required when raw data is
controlling.
Refer to the RNP REQUIREMENTS table in the QRH for the appropriate
setting when raw data is not controlling.
Note: When raw data is monitored and is controlling for an approach, if ANP
exceeds RNP outside of the FAF, LNAV and/or VNAV can be used if
ANP proves to be at .5nm or better (this can be evaluated by
comparison to raw data sources). If in doubt, or if the error proves
excessive, it is recommended that VORLOC or HDG SEL be used in
lieu of LNAV, and V/S in lieu of VNAV. Use V/S a rate determined
from the approach plate or Vertical Speed Reference table. Raw data
should be used to help determine the FAF. If ANP exceeds RNP after
passing the FAF continuing the approach with use of LNAV and/or
VNAV requires that on-course parameters and a stable descent, as
referenced on raw data, be maintained. If ever uncertain about the
aircraft position and/or accuracy while on final approach a go-around
should be initiated.
Sec. 3 Page 220 737
Rev. 11/15/02 #41 Continental Flight Manual
APPROACH SELECTION
· An approach procedure is selected from the CDU DEP/ARR page(s).
· At-or-above waypoint altitudes at the FAF, or outside the FAF and on the
approach, should be changed to hard altitudes (i.e., change 3000A to 3000)
to make descent in VNAV more predictable.
After approach selection, and modification if necessary, it is important to match
the LEGS page display to your circumstances. For example: if you select an
approach and extend the centerline from a given fix that has an altitude
constraint, if ATC descends you below that altitude before reaching the fix,
either remove the altitude constraint at the waypoint or extend the centerline
from a closer-in waypoint compatible with the altitude clearance you receive.
APPROACHES WITHOUT REFERENCE TO RAW DATA
RNAV, GPS and BCD NDB approaches do not have reference to raw
data. It is, therefore, a requirement that these approaches must be selectable
from the FMC database and that the final approach segment waypoints and
altitudes not be modified. Verify that approach selection, setup and appropriate
RNP entry is accurate.
APPROACHES WITH REFERENCE TO RAW DATA
Approaches flown with reference to raw data for primary course compliance
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