First off, my first post here, and thanks to all for some great forums. Quick intro, I'm a recently-instrument-rated CPL who will be shortly studying intently for my ATPL exams and will hopefully move into full-time professional flying in the near future. I love any and all tech discussion on aircraft (to the dismay of many of my friends), so this forum is golden.
I've done a ridiculous amount of long haul travel in previous jobs, and am wondering about the normal procedures and considerations for the selection of step climb levels during long sectors. For instance, I've flown LAX-MEL numerous times with Qantas, which is always flown on the 744ER, departing many times at MTOW (Captain has announced this) - it is standard for the initial cruise level out of LAX to be either FL280 or FL300. In some instances, the aircraft remains at this initial level for some time before it's stepped up to FL340 (skipping FL320). It's then generally stepped by 2000ft at a time, and in my experience normally arrives at TOD at FL380.
I have read somewhere that a 4000ft step is preferable than a 2000ft step for fuel burn reasons, but this does not seem logical to me, since surely the preference is to climb the 2nd block of 2000ft at a lower weight. I have also read in some manuals/textbooks that being above optimum altitude normally results in lower fuel burn than being below optimum altitude by the same amount. With this in mind, what are the reasons for selecting 4000ft steps, and not simply bracketing with a 2000ft climb every step? I imagine it's a combination of ATC requirements during Pacific ops, no RVSM available, favourable winds etc. etc.
Any answers would be great! Thanks again, cheers all.