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777/787 Flight Crew Training Manual
Approach and Missed Approach
Copyright © The Boeing Company. See title page for details.
5.34 FCT 777/787 Preliminary (TM)
A vertical path suitable for use of VNAV is one that approximates 3° and crosses
the runway threshold at approximately 50 feet. To obtain such a VNAV path,
maximum use of the navigation database is recommended. For approaches where
an RNP is specified, or approaches where a DA(H) is used, the waypoints in the
navigation database from the FAF onward may not be modified except to add a
cold temperature correction, when appropriate, to the waypoint altitude
constraints. With respect to the construction of a suitable final approach path,
there are two types of approaches in the navigation database:
• approaches with a glide path (GP) angle displayed on the final approach
segment of the LEGS page. The final approach segment is completely
compatible with VNAV and complies with final approach step down
altitudes (minimum altitude constraints).
• approaches where no GP angle is published and where the approach end
of the runway is defined by a runway waypoint (RWxx) or a missed
approach point fix (MXxx or a named waypoint) exists. Normally these
waypoints display an approximate 50 foot threshold crossing altitude
constraint and may be used “as is” for VNAV. If the RWxx waypoint
altitude constraint does not coincide with approximately 50 feet, this
waypoint may be modified with a threshold crossing altitude of
approximately 50 feet.
Note: Threshold crossing altitude normally require entry of a four-digit
number. Example: enter 80 feet as 0080.
VNAV may be used for approaches modified in this way; however, the
approach should be flown by constant reference to raw data (VOR, NDB,
DME, etc.) and compliance with each minimum altitude constraint is
required. Use of a DA(H) is not appropriate when the final approach is
manually constructed in this manner.
ILS approaches coded with the appropriate threshold crossing height may
be used as an overlay for other approaches such as LOC or NDB.
VNAV should be used only for approaches that have one of the following features:
• a published GP angle on the LEGS page for the final approach segment
• an RWxx waypoint coincident with the approach end of the runway
• a missed approach waypoint before the approach end of the runway, (e.g.,
MXxx).
These features permit construction of a normal glide path. VOR approaches with
the missed approach point on the LEGS page beyond the runway threshold and
circling only approaches do not have these features.
With the autopilot engaged, the EICAS alert message AUTOPILOT and VNAV
mode fail indications are available to alert the flight crew of potential problems
with the flight path.
October 31, 2006
777/787 Flight Crew Training Manual
Approach and Missed Approach
Copyright © The Boeing Company. See title page for details.
FCT 777/787 Preliminary (TM) 5.35
When appropriate, crews should make cold temperature altitude corrections by
applying a correction from an approved table to the waypoint altitude constraints.
The FMC obtains the GP angle displayed on the LEGS page from the navigation
database. This GP angle is based on the standard atmosphere and is used by the
FMC to calculate the VNAV path which is flown using a barometric reference.
When OAT is lower than standard, true altitudes are lower than indicated altitudes.
Therefore, if cold temperature altitude corrections are not made, the effective GP
angle is lower than the value displayed on the LEGS page. When cold temperature
altitude corrections are made, VNAV PTH operation and procedure tuning
function normally; however, the airplane follows the higher of the glide path angle
associated with the approach (if available) or the geometric path defined by the
waypoint altitude constraints.
When on final approach, VNAV should be used with speed intervention active to
reduce workload. Adding speed constraints to the final approach waypoints is not
recommended because of the extra workload, no safety benefit, and reduced
ability to make last minute approach changes.
To prevent unnecessary level offs while descending in VNAV before the final
approach, reset the MCP altitude selector to the next lower constraint before
altitude capture, when compliance with the altitude restriction is assured.
Use of Altitude Intervention during Approaches using VNAV
Altitude intervention is appropriate during approaches only if the AFDS enters
VNAV ALT mode above the approach path and descent must be continued.
Entering VNAV ALT mode can occur if passing a waypoint on the approach and
　
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