Copyright D.P. Browne 2011

Wind Profile And Optimum Flight Level

The FMGC predictions depend upon the wind data entered by the fight crew. During the flight plan construction, using the MCDU, the flight crew may enter the wind speeds and directions for the Climb, Cruise and Descent phase of the flight. These wind speeds are either entered manually or uploaded via an ACARS link.

The wind speeds and directions are displayed on the Flight Plan B page.

These forecast wind speeds are used to determine fuel and time predictions for the waypoints in the flight plan.

During the flight the FMGC updates the wind speed forecasts using actual wind speeds measured via the ADIRU. Usually the flight crew enter only the climb and cruise winds speeds before flight and then enter the descent wind speeds during the flight closer to the descent phase

Wind Profile

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Optimum Flight Level

The optimum flight level is displayed on the Progress page and indicates the most economic flight level for a given Cost Index (CI).

Descent Profile

The FMGC computes a descent path to minimize the fuel burn, while satisfying the various altitude constraints that may exist in the flight plan. The decent profile starts at the flight cruise level and ends at VAPP speed 1000 feet above the runway.

Cost Index

The flight crew enter a Cost Index on the INIT A page, or it is entered as part of a company route. The Cost Index is used to determine the econ speeds for Climb and cruise and descent. The Cost Index range from 0 to 999

0

Corresponds to minimum fuel consumption  ( Max Range)

999

Corresponds to minimum time