what is the standard or do other factors like weight and fuel change the speed.
Thanks.
Chris, the short answer is that ALL other factors have to be borne in mind - you have to keep weight, power, rate of climb, airspeed etc. in balance.
However, that's simpler than it sounds; and it's also part of the fun in FS. The key instrument to watch is the N1 gauge at the top of the engine instruments panel. N1 actually shows turbine speed as a percentage of the maximum rate - but it also corresponds to 'fuel demand.'
So first of all set the right airspeed. 250-275 knots is fine up to say 20,000 feet, then I usually switch to Mach. speed (I usually use 0.65 in the early stages of the climb). Then keep an eye on N1, which should be showing say 60-65%.
Above say 25,000 feet you may well see N1 creeping up. This is because the engines are having to work harder and harder to maintain both the speed and the set rate of climb. Best technique from then on is to moderate (that is, reduce) the rate of climb as necessary to keep N1 at a reasonable level (say below 70%).
Others may say that you can safely increase the airspeeds I've quoted, and also maintain 1,800 fps most of the way up; and they'll be right, you can! But I tend to use conservative settings because I like long trips, and therefore try to economise on fuel consumption in the climb. You'd be surprised how much extra fuel an airliner can use up in just the first few minutes if you climb flat out!
In any case, when you get really high - say up towards 35,000 feet - you may see N1 pushing up to 90%-plus if you're still trying to hold both a high airspeed and 1,800 fpm; it's even possible to stall the aeroplane if you overdo both speed and rate of climb in the thinner air high up.
So watch the instruments, develop an 'ascent plan' that suits you, and then stick to it. My own technique in the 737 is to set airspeed at 0.65 Mach from 20,000, increasing to Mach 0.70 above 25,000, and then seek to maintain N1 at or about 62%. If it gets above that I moderate the rate of climb to get N1 back to the target figure.
Hope all that helps.
Posted: Mon Mar 31, 2008 7:37 am
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