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optimum if altitude changes are difficult to obtain on specific routes. This
minimizes the possibility of being held at a low altitude/high fuel consumption
condition for long periods of time. The requested/accepted initial cruise altitude
should be compared to the thrust limited or the maneuver margin limited altitudes.
Remember, a cruise thrust limited altitude is dependent upon the cruise level
temperature. If the cruise level temperature increases above the chart value for
gross weight, maximum cruise thrust will not maintain desired cruise speed.
Step altitudes can be planned at waypoints or they can be optimum step points
calculated by the FMC. Optimum step points are a function of the route length,
flight conditions, speed mode, present airplane altitude, STEP TO altitude (or
adjacent STEP TO altitudes) and gross weight. The FMC computed step point
provides for minimum trip cost for the flight, including allowances for climb fuel.
Initiate a cruise climb to the new altitude as close as practicable to the step climb
point.
Note: FMC default values for the step climb may not be appropriate for RVSM
or metric airspace. Manually enter the appropriate step climb values as
needed.
Fuel for Enroute Climb
777-200 - 777-300ER
The additional fuel required for a 4,000 foot enroute climb varies from 300 to
1,000 lbs (225 to 450 kgs) depending on the airplane gross weight, initial altitude,
air temperature, and climb speed. The fuel increment is largest for high gross
weights and low initial altitudes. Additional fuel burn is offset by fuel savings in
the descent. It is usually beneficial to climb to a higher altitude if recommended
by the FMC or the flight plan, provided the wind information used is reliable.
October 31, 2006
777/787 Flight Crew Training Manual
Climb, Cruise, Descent and
Holding
Copyright © The Boeing Company. See title page for details.
4.10 FCT 777/787 Preliminary (TM)
787-8
The additional fuel required for a 4,000 foot enroute climb varies from TBD to
TBD lbs (TBD to TBD kgs) depending on the airplane gross weight, initial
altitude, air temperature, and climb speed. The fuel increment is largest for high
gross weights and low initial altitudes. Additional fuel burn is offset by fuel
savings in the descent. It is usually beneficial to climb to a higher altitude if
recommended by the FMC or the flight plan, provided the wind information used
is reliable.
Cruise Using HUD System
787-8
The HUD may be used at any altitude but above 25,000 feet the horizon line
appears above the visible horizon.
Low Fuel Temperature
Fuel temperature changes relative to total air temperature. For example, extended
operation at high cruise altitudes tends to reduce fuel temperature. In some cases
the fuel temperature may approach the minimum fuel temperature limit.
Fuel freezing point should not be confused with fuel ice formation caused by
frozen water particles. The fuel freezing point is the temperature at which the
formation of wax crystals appears in the fuel. The Jet A fuel specification limits
the freezing point to -40°C maximum, while the Jet A-1 limit is -47°C maximum.
In the Former Soviet Union, the fuel is TS-1 or RT, which has a maximum freezing
point of -50°C, which can be lower in some geographical regions. The actual
uplifted freezing point for jet fuels varies by the geographical region in which the
fuel is refined.
Unless the operator measures the actual freezing point of the loaded fuel at the
dispatch station, the maximum specification freezing point must be used. At most
airports, the measured fuel freezing point can yield a lower freezing point than the
specification maximum freezing point. The actual delivered freezing temperature
can be used if it is known. Pilots should keep in mind that some airports store fuel
above ground and, in extremely low temperature conditions, the fuel may already
be close to the minimum allowable temperature before being loaded.
For blends of fuels, use the most conservative freezing point of the fuel on board
as the freezing point of the fuel mixture. This procedure should be used until 3
consecutive refuelings with a lower freezing point fuel have been completed. Then
the lower freezing point may be used. If fuel freezing point is projected to be
critical for the next flight segment, wing tank fuel should be transferred to the
center wing tank before refueling. The freezing point of the fuel being loaded can
then be used for that flight segment.
October 31, 2006
777/787 Flight Crew Training Manual
Climb, Cruise, Descent and
Holding
Copyright © The Boeing Company. See title page for details.
　
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