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MCDU PROG page and keypad


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I can ask but as I stated its irrelevant the FP as it hap[pens on any plan we do to any location. long short high low. the opt starts at say 370 and towards the end starts showing a reducing value.

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OK well maybe its me not understanding since it didn't happen in the old airbuses. Should the OPT on the PROG page reduce towards the end of the flight? for instance the flight im on now currently OPT is FL385 but as I get closer to the end of the cruise it will reduce slowly to more like FL250. I mean I ignore it and dont decent until T/D but its just bugging me that either I dont understand or its not normal.

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  • Deputy Sheriffs

What I can tell you is this from FCOM:

The optimum flight level (OPT FL) indicates the most economic flight level for a given cost index,
weight, weather data. It is continuously updated in flight. It requires a 5 min minimum cruise time,
at a minimum cruise flight level of FL 100.

The OPT FL is a compromise between fuel and time saving. As a result, the flight crew may
observe jumps in OPT FL due to GW, ISA, or wind changes
. The computation of the OPT FL takes
into account the wind entries made by the flight crew, as well as the winds propagated by the FMS
from previously entered winds.
Note: For simplification purposes, the FCOM/QRH gives the OPT FL at a given Mach number.
It does not consider the cost index, therefore the FMGS and the FCOM/QRH values are
different.

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  • Deputy Sheriffs

It will be looked at. Unfortunately the devs have a long list of items. It may take some time. Currently we are collecting additional RW data.

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