It is often considered a good idea to have the alternate some distance away
from the destination (e.g., 100 miles) so that bad weather is unlikely to close
both the destination and the alternate; distances of up to 600 miles (970 km)
are not unknown. In some cases the destination airport may be so remote
(e.g., a Pacific island) that there is no feasible alternate airport; in such a
situation an airline may instead include enough fuel to circle for 2 hours near
the destination, in the hope that the airport will become available again within
that time.
There is often more than one possible route between two airports. Subject to safety
requirements, commercial airlines generally wish to minimise costs by appropriate choice of
route, speed, and height.
Various names are given to weights associated with an aircraft and/or the total weight of the
aircraft at various stages.
•
Payload is the total weight of the passengers, their luggage, and any cargo. A
commercial airline makes its money by charging to carry payload.
•
Operating weight empty is the basic weight of the aircraft when ready for operation,
including crew but excluding any payload or usable fuel.
•
Zero fuel weight is the sum of operating weight empty and payload—that is, the laden
weight of an aircraft, excluding any usable fuel.
•
Ramp weight is the weight of an aircraft at the terminal building when ready for
departure. This includes the zero fuel weight and all required fuel.
•
Brake release weight is the weight of an aircraft at the start of a runway, just prior to
brake release for take-off. This is the ramp weight minus any fuel used for taxiing. Major
airports may have runways that are about 2 miles (3 km) long, so merely taxiing from
the terminal to the end of the runway might consume up to a ton of fuel. After taxiing,
the pilot lines up the aircraft with the runway and puts the brakes on. On receiving
take-off clearance, the pilot throttles up the engines and releases the brakes to start
accelerating along the runway in preparation for taking off.
•
Takeoff weight is the weight of an aircraft as it takes off partway along a runway. Few
flight planning systems calculate the actual takeoff weight; instead, the fuel used for
taking off is counted as part of the fuel used for climbing up to the normal cruise
height.
•
Landing weight is the weight of an aircraft as it lands at the destination. This is the
brake release weight minus the trip fuel burned. It includes the zero fuel weight,
unusable fuel, and all alternate, holding, and reserve fuel.
I
A - Z of Flight
July 2017
www.alliance-airways.net
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