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threshold crossing height. When coded in this way, approaches may be
used as an overlay for a LOC or NDB approach, for example, and the
need for this waypoint altitude constraint modification by the crew is
eliminated.
VNAV should be used only for approaches that have one of the following features:
• a published GP angle
• an RWxx waypoint coincident with the approach end of the runway
• a missed approach waypoint prior to the approach end of the runway (e.g.
MXxx).
These features permit construction of a normal glide path. An example of an
approach without these features is a VOR approach with a MAP beyond the
runway threshold. These approaches are gradually being re-coded to permit
VNAV path operation.
Note: Approaches designated for circling only are not VNAV compatible.
October 31, 2004
767 Flight Crew Training Manual
Approach and Missed Approach
Copyright © The Boeing Company. See title page for details.
FCT 767 (TM) 5.37
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.
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 leveloffs while descending in VNAV prior to the final
approach, reset the MCP altitude selector to the next lower constraint prior to
altitude capture when the altitude restriction is assured.
Use of Altitude Intervention (As installed) 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
the crew has failed to reset the MCP altitude to a lower altitude. If this occurs, set
the MCP altitude to the next lower altitude constraint or the DA(H) or MDA(H),
as appropriate, and select altitude intervention. When VNAV altitude intervention
is selected, VNAV path deviation indications on the map display disappear
momentarily while the path is recalculated, but should reappear.
If altitude intervention is selected when on-approach logic is active, typically after
the airplane has sequenced the first approach waypoint, level flight is commanded
until reaching the VNAV path, then the airplane captures the VNAV path.
Note: When a PROC HOLD is active, VNAV altitude intervention functions
normally by causing the next waypoint altitude constraint to be deleted and
a descent to be initiated.
October 31, 2004
767 Flight Crew Training Manual
Approach and Missed Approach
Copyright © The Boeing Company. See title page for details.
5.38 FCT 767 (TM)
Non - ILS Approach - One Engine Inoperative
Engine out maneuvering prior to and after the final approach fix with one engine
inoperative is the same as an all engine non-ILS approach.
Procedure Turn and Initial Approach
Cross the procedure turn fix at flaps 5 and flaps 5 maneuvering airspeed. If a
complete arrival procedure has been selected via the CDU, the initial approach
phase may be completed using LNAV and VNAV path, or other appropriate
modes.
Vertical Path Construction
This section describes typical final approach vertical profile (path) construction
criteria as they relate to flying instrument approaches using VNAV. This
information may also be useful to pilots who wish to fly the vertical path using
V/S.
Where there is a glide path (GP) angle coded in the navigation database, the FMC
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767机组训练手册Flight Crew Training Manual (FCTM)767(77)
