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This is because the true airspeed of the airplane is lower than would be the case if
the actual temperature were equal to the assumed temperature.
Do not use the ATM if conditions that affect braking such as a runway
contaminated by slush, snow, standing water, or ice exist, or if potential windshear
conditions exist. ATM procedures are allowed on a wet runway if suitable
performance accountability is made for the increased stopping distance on a wet
surface.
Fixed Derate (As Installed)
This method uses a takeoff thrust less than maximum takeoff thrust for which
complete and independent performance data are provided in the AFM. Derated
thrust is obtained by selection of TO l or TO 2.
The fixed derate is considered a limitation for takeoff. Thrust levers should not be
advanced beyond the fixed derate limit unless conditions are encountered during
the takeoff where additional thrust is needed on both engines, such as windshear.
A thrust increase following an engine failure could result in a loss of directional
control.
Note: Although fixed derate takeoffs are permitted on wet or contaminated
runways, provided takeoff performance accounts for runway surface
conditions, they are not recommended if potential windshear conditions
exist.
Combination Fixed Derate (As Installed) and ATM
This method uses a takeoff thrust less than the fixed derate takeoff thrust by first
selecting a fixed derate of TO l or TO 2. This derate takeoff thrust is then further
reduced by assuming a temperature that is higher than the actual temperature. In
this case, the thrust reduction authorized by most regulatory agencies is limited to
25% below the derated takeoff thrust.
Improved Climb Performance Takeoff
When not field length limited, an increased climb limit weight is achieved by
using the excess field length to accelerate to higher takeoff and climb speeds. This
improves the climb gradient, thereby raising the climb limit and obstacle limited
weights. V1, VR and V2 are increased to maintain consistent performance
relationships. V1, VR and V2 must be obtained from dispatch or the airport
analysis.
October 31, 2006
777/787 Flight Crew Training Manual
Takeoff and Initial Climb
Copyright © The Boeing Company. See title page for details.
3.20 FCT 777/787 Preliminary (TM)
Low Visibility Takeoff
Low visibility takeoff operations, below landing minima, may require a takeoff
alternate. When selecting a takeoff alternate, consideration should be given to
unexpected events such as an engine failure or other non-normal situation that
could affect landing minima at the takeoff alternate. Operators, who have
authorization for engine inoperative Category II/III operations, may be authorized
lower alternate minima.
With proper crew training and appropriate runway lighting, takeoffs with visibility
as low as 500ft/150m RVR may be authorized (FAA). With takeoff guidance
systems and centerline lighting that meets FAA or ICAO criteria for Category III
operations, takeoffs with visibility as low as 300ft/75m RVR may be authorized.
Regulatory agencies may impose takeoff crosswind limits specifically for low
visibility takeoffs.
All RVR readings must be equal to or greater than required takeoff minima. If the
touchdown or rollout RVR system is inoperative, the mid RVR may be substituted
for the inoperative system. When the touchdown zone RVR is inoperative, pilot
estimation of RVR may be authorized by regulatory agencies.
Adverse Runway Conditions
Slush, standing water, or deep snow reduces the airplane takeoff performance
because of increased rolling resistance and the reduction in tire-to-ground friction.
Most operators specify weight reductions to the AFM field length and/or obstacle
limited takeoff weight based upon the depth of powdery snow, slush, wet snow or
standing water and a maximum depth where the takeoff should not be attempted.
Slush or standing water may cause damage to the airplane. The recommended
maximum depth for slush, standing water, or wet snow is 0.5 inch (12.7 mm) on
the runway. For dry snow the maximum depth is 4 inches (102 mm).
A slippery runway (wet, compact snow, ice) also increases stopping distance
during a rejected takeoff. Takeoff performance and critical takeoff data are
adjusted to fit the existing conditions. Check the airport analysis or the PI section
of the QRH for takeoff performance changes with adverse runway conditions.
Note: If there is an element of uncertainty concerning the safety of an operation
with adverse runway conditions, do not takeoff until the element of
uncertainty is removed.
During wet runway or slippery conditions, the PM must give special attention to
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787机组训练手册Flight Crew Training Manual 787(39)
