Airbus Top-of-Descent calculations with configuration
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Airbus Top-of-Descent calculations with configuration
I have been trying to find whether or not the Airbus top of descent calculation takes into account any existing configuration .
This is only in a scenario with any slats or flaps locked and a flight which continues to its intended destination assuming a short flight
Please do not bother with the specifics as to why a flight would continue to its destination with any slats , flaps locked . I just need to know if the fmgs takes into account the existing configuration for calculating the top of descent
This is only in a scenario with any slats or flaps locked and a flight which continues to its intended destination assuming a short flight
Please do not bother with the specifics as to why a flight would continue to its destination with any slats , flaps locked . I just need to know if the fmgs takes into account the existing configuration for calculating the top of descent
Only half a speed-brake
I do not think so, seems beyond the engineereing logic behind FMS.
FCTM
FCOM
FCTM
Note: The FMS predictions do not take into account the slat or flap failures. Since fuel consumption is increased, these predictions are not valid.
FMS PRED UNRELIABLE
Disregard FMS fuel predictions and refer to QRH/PER-B Fuel Penalty Factors Tables in order to find the applicable Fuel Penalty Factor.
Disregard FMS fuel predictions and refer to QRH/PER-B Fuel Penalty Factors Tables in order to find the applicable Fuel Penalty Factor.
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flightdetent thank you for your reply.
The slat / flap failure and any subsequent flight planning with this failure prompted me to investigate this further. The FMS fuel predictions are not correct and in general you would use a fuel penalty factor . This penalty factor is a rather conservative one and if you only had a slat jamming at position one , then with some realistic calculations you could consider continuing to your destination if it's a rather short flight .
Realistic calculations are : Establish fuel required from level flight to top of descent using actual fuel flow . Establish fuel required from top of descent to touch down . The key is to find the right top of descent point with the existing configuration.
The slat / flap failure and any subsequent flight planning with this failure prompted me to investigate this further. The FMS fuel predictions are not correct and in general you would use a fuel penalty factor . This penalty factor is a rather conservative one and if you only had a slat jamming at position one , then with some realistic calculations you could consider continuing to your destination if it's a rather short flight .
Realistic calculations are : Establish fuel required from level flight to top of descent using actual fuel flow . Establish fuel required from top of descent to touch down . The key is to find the right top of descent point with the existing configuration.
Only half a speed-brake
Ar you trying to determine TOD due to descent requirement or fuel planning? Both ways, VNAV and DES predictions of no use.
FD.
FD.
Last edited by FlightDetent; 8th Jan 2016 at 14:00.
