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Step Climbs & Fuel Consumption -- PS1 & PMDG 747-400

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My greetings to all Captains,Today I've read an article on fuel planning for PS 1 (Precision Simulations) B744. Particularly, its part on step climbs during LRCs (long-range cruises) seems to be very useful 'cause guarantees wise fuel consumption which I'm going to test all way down from KJFK to LTBA (Ataturk Intl, Istanbul, Turkey) using real Delta (DAL72) flight plan. I think the whole article would be of some help for those of us who would not dismiss additional info on fuel planning as extra to what PMDG 747 AOM provides. Ok, to wrap up I include here an excerpt from this article (it's quite long but it worths reading :):"The object is to climb as high as feasible after takeoff to reach an altitude, where fuel consumption is minimal (optimum altitude). Under normal circumstances, 4000 feet step-climbs are utilized to save fuel over long distance flights. The normal procedure to accomplish this is to first climb to an altitude, which is slightly above (1000 to 2000 feet) the optimum altitude at takeoff. Then maintain this cruising altitude, until the optimum altitude has drifted upwards to an altitude approximately 2000 feet above your present altitude. This process takes approximately 3 hours (required time to burn off the necessary fuel weight). The aircraft is then climbed 4000 feet, to again be higher than the optimum altitude (this procedure is known as bracketing). This allows the aircraft to straddle the optimum altitude, while minimizing the number of en-route step climbs (burn per step-climb is approximately 1200 KG of fuel). If the step-climb altitude cannot be sustained for at least 200 nm prior to the top of descent point, the fuel benefits are negated. Following the above procedure will save approximately 5-10% fuel, when compared to flying at one constant altitude over the entire trip."BTW, PMDG Team, does the Queen uses the same logic for fuel consumption? Thank you!P.S.: Sorry if you, Captains, have already been using this procedure in your flights :) It was quite new for me, however.Regards,Rustam


Victor Quebec

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ATC is always the bad guy in these deals, IRL. Sometime you just can't get the altitudes you need for a crossing! Most of the long haul airspace is now RVSM, allowing 2000' steps, and sometimes 1000' steps. Check on your V-NAV page 2 before takeoff and see what the optimum and max altiudes are for your weight. For a 5-6 hour flight (a shortie) a typical optimum alt might be FL330. Is is generally permissable to climb as much as 2000' above the optimum if required by ATC. Wind trade is an important issue here, if you will get more or less head or tailwind etc. Page 2 will also give a reccomended time to climb to the next step altitude (it will be sooner with 2000' instead of ICAO).Tom

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BTW, PMDG Team, does the Queen uses the same logic for fuel consumption? Yeap :)Vangelis===================================== E. M. Vaos Precision Manuals Development Group www.precisionmanuals.com=====================================



Precision Manuals Development Group


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