SPEED CONSIDERATIONS The cruise speed may be either: • Managed • Selected MANAGED When the cruise altitude is reached, the A/THR operates in SPEED/MACH mode. The optimum cruise Mach number is automatically targeted. Its value depends on: • CI • Cruise flight level • Temperature deviation • Weight • Headwind component . The crew should be aware that the optimum Mach number will vary according to the above mentioned parameters, e.g. it will increase with an increasing headwind, e.g. +50 kt head wind equates to M +0.01. Should ATC require a specific time over a waypoint, the crew can perform a vertical revision on that waypoint and enter a time constraint. The managed Mach number would be modified accordingly to achieve this constraint. If the constraint can be met within a tolerance, a magenta asterix will be displayed on the MCDU; if the constraint cannot be met, an amber asterix will be displayed. Once the constrained waypoint is sequenced, the ECON Mach is resumed.
Posted on: Wed, 11 Sep 2013 23:00:01 +0000