曝光台 注意防骗
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into altitude acquire is by adaptive capture. That is, entry is controlled by
altitude rate. At higher altitude rates, capture occurs further from the
selected altitude.
D. Preparation for climb two ------ when ATC clearance is given to a
cruise altitude, the MCP altitude is set equal to the FMCS cruire altitude.
The A/P ALT HOLD and SPEED mode switches illuminate and ALT
HOLD and V/S (vertical speed) ARM for AFDS and MCP SPD for A/T
are annunciated. The A/S cursor now driven to MCP speed.
E. Climb two -------- climb is initiated by pressing the VNAV mode
switch on the MCP. The VNAV mode switch and N1 mode switch
illuminate and all others are off. The A/P now commands speed error
from the FMC, the A/T is controlling thrust to a climb N1 from the FMC.
F. Level off at FMCS cruise altitude -------- The A/P acquires and holds
the FMCS cruise altitude . The A/T follows FMCS guidance to transition
from climb N1 to cruise speed. When a new cruise altitude is desired, it
is selected on the MCP and on the FMCS CDU cruise page. Climb is
initiated by pressing EXEC key on the FMCS CDU.
G. Climb Three ------ The A/P changes to VNAV SPD guidance and the
A/T changes to climb N1 guidance. The airplane climb to the new
altitude under FMCS guidance.
[2] Figure 40-2 illustrates an example of the descent phase.
Fig. 40-2 VNAV descent
VNAV descent path are projected by FMC during cruise operation. The
FMC continually computes the top of descent and the end of descent
based on active flight plan and navigation and performace data bases.
VNAV descent is almost automatic and its goal is to get the airplane to
the glideslope capture point by the most economical means. LNAV must
remain valid to make a VNAV path descent.
A. Initial condition -------- with the A/P in CMD, VNAV engaged and
the MCP altitude set equal to the FMC cruise altitude, the A/P and A/T
are commanded to the FMC described vertical path. Prior to reaching the
top of descent( T/D), a lower altitude must be selected on the MCP.
B. Descent one ------ At T/D, the FMC provides guidance to the A/P and
A/T to command the VNAV descent path. In VNAV descent path, if 255
knots is exceeded below 10,000 feet, FMC sets LVL CHG (Level change)
reversion request.
C. Level off at BARON altitude ------- FMC direct A/P to command a
level off at the BARON (the last waypoint) altitude.
D. Descent Two ------ Preparation for a descent consists of selection of a
lower altitude on the MCP. At top of descend ( T/D) , the FMC provides
guidance to the A/P and A/T to command the VNAV descent path.
E. Level off at MCP altitude -------- Acquiring the MCP ALT causes the
A/P to command a level off at the MCP altitude even though this
deviates from the VNAV descent path.
F. Descent three -------- Selecting a new MCP ALT causes the VNAV
switch light to go out and the ALT HOLD and SPEED mode switches to
illuminate. A/T command and airspeed target are changed to MCP speed.
VNAV path descent is initiated by pressing the VNAV mode switch on
the MCP. FMC provides vertical speed guidance to the A/P and A/T to
recapture the VNAV path.
G. Level off at FMC approach altitude -------- FMC computed targets
direct the A/P to command altitude acquire and altitude hold at the FMC
approach altitude.
[3] Figure 40-3 illustrates an example of the autoland. After selecting
APP and engaging the second autopilot to CMD, an automatic transition
is made from ILS approach through autoland. The LNAV and VNAV are
still in control.
Fig. 40-3 autoland
A. Initial conditions -------- with LNAV and VNAN engaged, the FMC
provides guidance to the A/P and A/T to command approach altitude at
150 knots on a heading for localizer intercept.
B. Approach preparations -------- Tune both VHF NAV receivers to the
inbound ILS frequency. Select the inbound course on both course
displays. Press the APP mode switch on the MCP and engage the second
A/P to CMD.
C. Localizer mode -------- Mode logic in the A/P determines the optimum
capture point relative to the localizer beam. At localizer capture, LNAV
is disengaged and the LNAV mode switch extinguishes.
D. Glide slope mode ------ The glide slope capture point is approximately
0.5 dot of deviation. The A/P and F/D commands a descent to make a
smooth transition to glide slope.
E. Approach on course ------- Approach on course (AOC) occurs at 1500
feet radio altitude.
F. Approach on course plus ten seconds -------- Ten seconds after AOC,
the second A/P is engaged in both roll and pitch channels.
G. Radio altitude FCC internal discretes ------ The airplane should be
stabilized on the ILS in the landing configuration before reaching 800
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