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altitude with “Slope and Wind Corrected Field Length” determined above
and airport OAT to obtain Field Limit Weight. Also read Climb Limit
Weight for the same OAT. Intermediate altitudes may be interpolated or
use next higher altitude.
Obstacle Limit Weight
This table provides obstacle limit weights for reference airport conditions
based on obstacle height above the runway surface and distance from brake
release. Enter the correction tables to correct the reference Obstacle Limit
Weight for the effects of OAT, pressure altitude and wind as indicated. In
the case of multiple obstacles, enter the tables successively with each
obstacle and determine the most limiting weight.
787 Flight Crew Operations Manual
Performance Dispatch
Text
FAA
Category A Brakes
PD.14.2 Boeing Proprietary
Brake Energy Limits VMBE
Tables are presented to determine the Maximum Brake Energy Speed
VMBE. Compliance with this limitation is required to ensure that the
brakes have enough capacity to execute a maximum effort stop from V1
without the use of thrust reversers. Enter the upper table with pressure
altitude and OAT to determine the reference VMBE. Then enter the lower
table with the reference VMBE and brake release weight to determine
VMBE for a specific takeoff. Adjust for slope, wind and deactivated brakes
as described below the table. The resulting VMBE must be greater than or
equal to V1. If VMBE is less than V1, brake release weight must be
decreased by the amount shown below the table.
Takeoff Speeds
The speeds presented in the Takeoff Speeds table as well as FMC
computed takeoff speeds can be used for all performance conditions except
where adjustments must be made to V1 for clearway, stopway, brake
deactivation, improved climb, contaminated runway situations,
unbalanced for brake energy, or obstacle clearance with unbalanced V1.
These speeds may be used for weights less than or equal to the performance
limited weight.
The FMC will protect for minimum control speeds by increasing V1, VR
and V2 as required. However, the FMC will not compute takeoff speeds
for weights where the required speed increase exceeds the maximum
certified speed increase. This typically occurs at full rated thrust and light
weights. In this case, the message "V SPEEDS UNAVAILABLE" will
appear on the FMC scratchpad and the takeoff speed entries will be blank.
Takeoff is not permitted in this condition as certified limits have been
exceeded. The options are to select a smaller flap setting, select derate
thrust and/or add weight (fuel). Selecting derate thrust is the preferred
method as this will reduce the minimum control speeds. Note that the
assumed temperature method may not help this condition as the minimum
control speeds are determined at the actual temperature and therefore are
not reduced.
Normal takeoff speeds, V1, VR, and V2 are read from the table by entering
with takeoff flap setting and brake release weight. Use the tables provided
to correct takeoff speeds for altitude and actual temperature or assumed
temperature for reduced thrust takeoffs. Slope and wind corrections to V1
are obtained by entering the Slope and Wind V1 Adjustment Table.
787 Flight Crew Operations Manual
Performance Dispatch
Text
FAA
Category A Brakes
Boeing Proprietary PD.14.3
Minimum Control Speeds
Regulations prohibit scheduling takeoff with a V1 less than minimum V1
for control on the ground, V1(MCG), and VR less than minimum VR,
(1.05) VMCA. It is therefore necessary to compare the adjusted V1 and
VR to V1(MCG) and Minimum VR respectively. To find V1(MCG) and
Minimum VR, enter the V1(MCG), Minimum VR table with the airport
pressure altitude and actual OAT. If the adjusted V1 is less than
V1(MCG), set V1 equal to V1(MCG). If the adjusted VR is less than Min
VR, set VR equal to Min VR and determine a new V2 by adding the
difference between the normal VR and Min VR to the normal V2. No
takeoff weight adjustment is necessary provided that the field length
available exceeds the minimum field length shown in the Field and Climb
Limit Weight table.
Brakes Deactivated
When operating with brakes deactivated, the field and brake energy limit
weights and the V1 and VMBE must be reduced to allow for reduced
braking capability. A simplified method which conservatively accounts
for the reduced braking capability of one brake deactivated is to reduce the
normal runway limited weight by 7700 lb and the V1 associated with the
reduced weight by one knot. With two brakes deactivated, reduce the
normal runway limited weight by 16100 lb and the V1 associated with the
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787机组操作手册Flight Crew Operations Manual 1(53)
