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CDL Enroute Performance Weight Penalties

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CDL Enroute Performance Weight Penalties

Old 31st Jan 2019, 19:57
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CDL Enroute Performance Weight Penalties

Hi everybody,
Just looking for any reference to my daily practice:
As we all are aware, In some CDL performance penalties state:

En route Performance Limiting weight is reduced by XXXX kg

For AIB Flysmart, there is no information about Enroute phase.
So practically I do not rely on FMGES (MCDU) MAX REC ALT or OPT ALT. As a solution I either:
Refer to QRH with an apparent weight equals to Actual weight +XXXX
or
temporarily overwrite Actual ZFW or GW on MCDU as increased by XXXX to see what the recalculated MAX REC ALT or OPT ALT is.

These are my intuitive practical solutions, not written in any technical document though.
Do you have a better idea or any solutions mentioned by any reference (either Boeing Airbus etc.)
Thanks.

Last edited by JABBARA; 1st Feb 2019 at 00:43. Reason: Topography
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Old 31st Jan 2019, 22:18
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If you have access to the Drift Down graphs in either the AFM or FCOM, they should do the job.
Irrelevant !

Last edited by JABBARA; 1st Feb 2019 at 00:40. Reason: editorial
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Old 1st Feb 2019, 10:01
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For the 777, the penalties are in the MEL/CDL.
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Old 1st Feb 2019, 12:47
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As I read it I think the OP is aware of that, I think the question being asked is what do you do with the numbers having extracted them from the CDL..

FWIW our 777 DDG/ CDL is surprisingly silent on this issue but I was taught to consider adding en-route penalties (temporarily) to the ZFW in the FMC if you are being asked to climb, the CDL penalties are significant and you are getting close the edge of the envelope

.

Last edited by wiggy; 1st Feb 2019 at 16:57.
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Old 1st Feb 2019, 16:49
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I never got a good answer to this question either other that if the MEL CDL is in the OFP its catered for driftdown-wise and any fuel penalties. Its the CDL Enroute Diversion Speed​ Effects thats has me baffled
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Old 1st Feb 2019, 20:30
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Again, for 777.
in the introduction part of the MEL/CDL, you have a chapter called Enroute Fuel Mileage Effects. « ... increase in flight planning fuel of 0.25% per 454kg of enroute climb weight penalty... »
another: Weight Reductions « ...for each missing item ... reduce the takeoff, landing and enroute climb limits by 46 kg... »

So I guess tou can treat it as the same weight in fuel. I don’t think you’ll find a SOP for that but probably have a rule of thumb for x kg equates y ft on Rec Max (on the T7 it’s something like 100ft for a tonne).

Last edited by airseb; 1st Feb 2019 at 20:41.
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