PMDG747-400X cruise setting very high

[flyboycjs 1]

Hi,Have a problem that i can't fix. It seems to me that when im in stable cruise at FL320 mach .82 my N1 seems to be at about 90% all the time. Should this not be around 70%. All weights are correct in FMC from load manager.Any help would be appreciated.

[michal 44]

If you are flying at altitude which is too high for your current weight or if your outside air temperature is way above normal (seriously degrading engine performance) - this is exactly what could happen. You may search this forum since there was a lot of discussion on these topics.

[flyboycjs 1]

Still have the same problem. No matter what ALT im at N1 will stay at around 90% at cruise. Have tried sorting it with minimal fuel and weight but still no joy. Cost index does change cruise speed but N1 still at 90%. Please help

[downscc 1,327]

The N1 of around 90% sounds about right for speed/altitude. You should remember that the much thinner air is resulting in much less thrust at a given N1... for example, look at the fuel flow figures. These are much lower at FL320 than at 10,000 ft at same N1.

[flyboycjs 1]

I was lead to believe that an N1 setting of around 70% was around normal opp at cruise. I learned this from a 747-400 pilot.

[FLEX1978 373]

As Dan says this is perfectly normal, I would be more worried seeing 70% N1 in Criuse.Rob

[flyboycjs 1]

So are you saying that 90% is fine. Seem very close to take off thrust say of around 103%

[michal 44]

So are you saying that 90% is fine. Seem very close to take off thrust say of around 103%[/font]

Actually it is nowhere near the takeoff thrust. Look at your fuel flow - fuel consumption will tell you how "normal" is this setting. N1 by itself is not indicative of the thrust, there are many factors in play here and thin air is one of them.

[FLEX1978 373]

If your interested, spare a little time to read about the basics of high bypass turbofans engines and it will make sense. Ever wondered why these aircraft wanna Cruise as high as possible?Rob

[falcon999 24]

There were many experts on the team throughout every phase of the development and testing process. The engine performance model was scrutinized closely. I would be very surprised if there was a signifcant problem with the engine performance model.

[KCA9304 0]

So are you saying that 90% is fine. Seem very close to take off thrust say of around 103%

Nameless,Be informed that the 747-400 HAS a Manual on Cruise Performance as well.In your case it will provide you even with more accurate data than some friend flying a 747-400.Consult the section Cruise- and Fuel Planning and find the required N1 yourself.(to help a little: page 2-14)Regards,Harry

[flyboycjs 1]

Thanks for all the help every one. The manual help me out with this problem :(