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thrust usage

crosscheck9 Guest

Hi,
I just took off from Bahrain's International Airport with a 777, bound for Gatwick, but I was climbing at 2800 fpm, with the autothrottle set for 260 kts above 10,000ft, but I noticed that it was taking 90% N1. How can I fix this, and what am I doing wrong. Supposedly, it should only require 55%

5 Responses

Pro Member Chief Captain
Alex (Fire_Emblem_Master) Chief Captain

55%!!! No. There's not a plane i can think of that doesnt require more than 88% N1 over 10,000 to maintain a 2800FPM climb rate. And, you usually dont climb at 2800FPM over 10,000. too much strain on the engines. Above 10,000. climb out at 15-1700FPM.

However, if i dont point this out, someone will, and may still yet point out, the default 777's engines seem a tad underpowered. Most 777's these days have over 90,000lb thrust, if not over 100,000lb.

Pro Member First Officer
leadfoot First Officer

I reset my 777 engines from 84000lbs thrust to 95000lbs thrust. I use the TO/GA setting for my takeoff and entire climb. It usually sets the engines at 88-90% N1. You should try to get to alt reasonably quick, the sooner you get there the better. the engines are more efficient up there. If you were to set thrust to maintain 15-1700' fpm and 260 kts, you would have to constantly add power as you climb. In the 777, I set up for a 280-290kt climb profile after 10000' then maintain speed by adjusting climb rate. At N1 90%, I can still climb 2000-2500fpm throught the mid 20s. By the time I'm at alt. My speed is within 20kts of cruise.

crosscheck9 Guest

Hi,
Are the 777's really supposed to climb at near full thrust. That just sounds crazy but it may be true. I have no idea. The sound of the loud engines made me nervous, for in reality, after takeoff, you dont find the engines to be really loud. Thanks

Pro Member Chief Captain
Alex (Fire_Emblem_Master) Chief Captain

Actually, you don't use the volume of the engine noise, its fuel flow. Because at 33,000FT, the 777, while operating at 88% N1, has a fuel flow, IF i remember right, of around 7-8500PPM. Whereas, at the same 88% at ground level equates to over 12,000PPH.

(PPH= Pounds Per Hour)

It's all got to do with the density of the air and all that good stuff 😀

Pro Member First Officer
leadfoot First Officer

The 737 at cruise speed the engines are set to around 74-76% N1. That gets me Mach .8 or .81 The 777 however is from the box rather weak, like N1 90-92% just to maintain .8 mach. I don't think that is right. So I reset the engine thrust in the config files from 84000lbs to 95000lbs thrust. I figure I hit the target just right though, because now when I cruise the 777 the N1#s are right around 75%, and I can cruise at book figures-- .84 mach.

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