User manual

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A high cost index is used when operating costs are more expensive than
fuel or to avoid additional costs due to delay (e.g. passengers missing
connecting flights). The aircraft would then fly faster to reduce flight
time, but would normally burn more fuel.
A control interval of zero results in maximum range airspeed and mini-
mum trip fuel burn. Conversely, a maximum value results in the mini-
mum time speed and ignores the cost of fuel.
Redispatch Planning
Designed to conserve fuel, the intent of redispatch is to lower the con-
tingency fuel on board at the planned destination airport, thereby mini-
mising the release fuel loaded at the departure airport.
Fuel is a major cost element for all airlines, representing around ⅓ of total
op-erational costs. A reduction of 1% in fuel usage per year can save
from $US 15.000 to $US135.000 per aircraft.
Contingency fuel planning is a function of trip length or trip fuel burn.
It was originally implemented to cover errors in navigation and weather
forecasting. These techniques have improved, though, decreasing the
chance that contin-gency fuel will actually be burnt.
Contingency fuel can be minimised by careful selection of a redispatch
fix.
Redispatch fix
Redispatch works because a flight can be planned between the depar-
ture airport and a short release destination airport (nearer the departure
airport than the planned destination) by inserting a redispatch fix along
the route by which a decision is made whether to:
• continue to the short release destination airport or,
• if possible within the fuel rules, to continue the flight onwards
to the planned destination airport.