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engwerda

Is this typical of the 744?

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I am just taking a short flight from Melbourne to Sydney. Gross weight at take off was 223 tons with 43,000 kgs of fuel on board. Even with CLB-2 selected and showing on the display it still climbs at over 3,000fpm up to FL300. Is this typical? The aircraft is on Autopilot and has VNAV, LNAV and THR REF engaged and showing all that on the PFD. Below FL200, once it had acquired the target speed set by VNAV, it ws occasionally reaching 5000fpm. I certainly can't remember ever being on a 744 that reached altitude that quickly but then the shortest leg I have ever flown on real 744 has been 8 hours. Just curious - am I missing something here or do they all climb like a rocket? Ideally what sort of fuel levels should I be landing with anyway?Gerry

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>I am just taking a short flight from Melbourne to Sydney.>Gross weight at take off was 223 tons with 43,000 kgs of fuel>on board. Even with CLB-2 selected and showing on the display>it still climbs at over 3,000fpm up to FL300. Is this typical?>The aircraft is on Autopilot and has VNAV, LNAV and THR REF>engaged and showing all that on the PFD. Below FL200, once it>had acquired the target speed set by VNAV, it ws occasionally>reaching 5000fpm. I certainly can't remember ever being on a>744 that reached altitude that quickly but then the shortest>leg I have ever flown on real 744 has been 8 hours. Just>curious - am I missing something here or do they all climb>like a rocket? Ideally what sort of fuel levels should I be>landing with anyway?>>GerryHi Gerry,If I calculated the weight correctly from metrix to english, your gross weight is 491,192lbs. If I have that correct, your climb rate is correct. The real 747 will climb fairly quickly at this light weight, especially if you're using maximum thrusts from the engines. But since you're so light, you don't need maximum thrust unless the runway is short and you need that thrust to accelerate to the required take-off speeds. If the runway is long enough, you can select a derated thrust on the thrust limit page of the FMC, such as 15% or use an assumed temperature to derate the engines, and the airplane won't climb so quickly. I usually make short distance flights and my gross weight at take-off is around 620,000lbs. At this weight, my climb rate is from 2500 to 3000 fpm. I also use climb 2 on the thrust limit page of the FMC. When flying in VNAV and you have thrust REF, the auto throttles will use the demanded N1 thrust that's indicated in green on the upper EICAS and will use whatever pitch required to maintain the climb speed that's commaned by the FMC. So what the airplane is doing is flying the speed that's commaned by the FMC. Pilots will sometimes switch to speed/vertical speed to reduce the rate of climb, especiallly around congested airports and to prevent TCAS traffic alerts. Ken.

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Guest capntom

We did a little flight ATL-MIA this morning and climbed up to FL410 in very little time, at about the weight you show. Note that despite any takeoff or climb derates entered, above about 15,000' the plane will use full rated climb thrust.At light weights, the thrust to weight ration is very good, initial climb rates of 6000 fpm are not uncommon.Cheers: Tom

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Ken and Tom,Many thanks for your valuable advice. I take Ken's point that to avoid ATC problems it is better to handle this manually with the VS. It is great to get such good advice in this forum and thanks to you both for passing on your expertise.

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Guest matey

With some 491.200 lbs gross weight the 747-400 is very very light! The climb rate is perfectly normal. My average gross weight is arround 600.000 lb and the plane achieves 3500-4500 ft/min at CLB-1 derrate. Over 15.000 ft the climb rate slows a little but CLB-1 changes to CLB so it again reaches good climb speed.Think other way: if for example at 491.200 lbs the maximum climb rate was 2500ft/min, what would happen if the plane takes off at the maximum gross weight of 875.000 lbs? climb at 100ft/min ;-), and if an engine fails seconds after take off???Use the load manager to increase the weight (in my case I use 2/3 pax load that would give me arround 600.000-650.000 lbs GW). Or try a take off at the maximum GW and see how the once rocket becomes a turtle :-)

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