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Old 2nd Nov 2007, 15:07
  #17 (permalink)  
jonny dangerous
 
Join Date: Nov 2001
Location: FL 410
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Mr Towers, just out of curiosity---was that a wingletted 800 or not?

Our outfit had some probs when we started receiving the wingletted 800's and still following Boeing's step climb recommendation of climbing to 2000 feet above OPT ALT etc.

Our SOP for step climbing is now (no more than) 1000 feet above OPT ALT. The 800 seems to be much less happy climbing thusly, so I'll most times delay until within 500 feet of OPT.

Personally I find lots of colleagues wanting to get up there as soon as we can: i.e. the instant the OPT says 380, guys/gals will want 390. I have taken to pulling out pen and paper and recording the vitals prior to the climb (Wind Component, G/S, TAS, FF) and then comparing them to the new vitals at altitude.

It sometimes, actually often surprises these colleagues that SGR has actually decreased (depending on winds etc).

Most colleagues also surprised when doing the Step Climb evaluation via the FMC and the New Cruise Evaluation via the FMC. Sometimes they differ by half. Who knows what the variables are in the algorithms employed, but in either case, what is 0.1% savings exactly? Not accounting for rounding error, if 5T of fuel will be burned between present position and destination, saving 0.1% fuel looks to me like a savings of 5 kilos of fuel (if the modelling assumptions are correct: a dubious proposition IMHO). And this on engines burning 1000 kilos an hour, over the following two hours. That's quite a level of precision...

My take? No rush to step climb. If the ride's good, and unless there's a terrific wind differential, the savings might be marginal, or non-existant.

However, my outfit's mantra is pretty much follow the flight plan from dispatch. And with no structured educational program to highlight these issues, we're at 410 much more often than is warranted, I think.
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