B737 power settings

[Golden Flyer]

Think it'd be better if you post this in the Westjet forum.

[youngflier]

ya the same this happens in my husky.

[looproll]

after takeoff there is usually the call "SET CLIMB THRUST"



here's a nifty site: http://www.b737.org.uk/pilotnotes.htm

[grammar boy]

Regarding the B737-700 series (and/or all NG37s, I suppose), a question about the power settings: Is there a reduction in power from initial climb to cruise, or are they left the same throughout the climb? (I ask the question based on my experience on WJ flights only.)

Our FMCs are defaulted to set climb thrust at 1500' AAE. It may sound like there is no thrust reduction because we use de-rated takeoff thrust and climb power settings, and then further reduce the takeoff thrust by applying an assumed temperature. We do this (as do most airlines) in order to save engine wear. We only use enough thrust to meet the performance criteria for a specific runway on a specific day.

For the -700:
TO (full rated takeoff thrust) is 24,000lbs per side
TO-1 is 22k
TO-2 is 20k

we then have CLB (full), CLB-1, CLB-2

The FMC decides on an appropriate CLB thrust based on the TO thrust used, so that you don't get a huge kick in the pants at 1500' if you are light and go to full climb thrust. (i.e. doing a TO-2 takeoff, with a high assumed temp and then going to full CLB thrust, you will actually get a pretty big power INCREASE when climb thrust is set).

It's usually not too much of a change at 1500', which is why you probably can't tell in the back. At 15000 feet we are at full climb thrust, but by then CLB-2, CLB-1 and CLB are the same N1, so all you see is a mode change from CLB-2 to CLB for example, with no N1 change.

Quick and dirty, hope that answers it. I could go into much more detail, but it would probably bore the crap out of you and my fingers would get tired.

Cheers

[Krashman]

Do you not need to set a specific EPR (exhaust pressure ratio) specific to the pressure alt?

[grammar boy]

The -200 had EPR, and we would get a CLB thrust setting off the charts, or in some of the aircraft, a TAT/EPR guage on the panel.

On the NG, the FMC figures it all out, in combination with the EEC (Electronic Engine Control) and a whole bunch of other systems that probably have input as well.

Also, N1 is the primary power setting reference on the NG. EPR does not exist. on the aircraft.