Cfm56-7b

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Cfm56-7b

Postby raghav » 25 Aug 2012, 09:29

What is the meaning of -7b in cfm56-7b?
What is n1 trim ? How can we do n1 trimming?

Need to know more Abt this
raghav
 
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Re: Cfm56-7b

Postby sjap » 25 Aug 2012, 10:07

-7b is just the model number of this engine. -5 for example you find under A320.
-7 is the model number, the B is this variant of this model. The -7E is the enhanced version found under the newer 737's. (wikipedia)

N1 trim is the difference of the real N1 needed for the real thrust provided, determined on the testcell only.
The testcell measures the real produced thrust. Every engine is a bit different, so the N1 for each engine is different too for the same thrust. The N1 trim is there to make sure that, for example, at 100 % N1 (seen in the cockpit) the exact same thrust is produced for each engine, while the real RPM (not seen) may be slightly different.
The N1 trim must be programmed in the ID plug of the engine.
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Re: Cfm56-7b

Postby raghav » 25 Aug 2012, 18:13

Thanks for reply

But may I know how they achieve this trimming?
raghav
 
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Re: Cfm56-7b

Postby sjap » 25 Aug 2012, 19:06

The trimming is done by pinprogramming the rating plug on the EEC. So this way the EEC is programmed to get the correct RPM for the asked N1.
You can see the N1 trim level in the EEC bite from the CDU.
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Re: Cfm56-7b

Postby raghav » 26 Aug 2012, 09:07

Thanks sir

2day I checked out the engine nameplate n found under n1 trim column "3"
What's it mean?
raghav
 
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Re: Cfm56-7b

Postby sjap » 26 Aug 2012, 10:46

raghav wrote:Thanks sir

2day I checked out the engine nameplate n found under n1 trim column "3"
What's it mean?


Its just a number.
It does not mean 3 % N1 or 3 rpm, its just a trim factor. It just tells the EEC to correct the rpm a certain amount, but how much i do not know.
If i find out i'll let you know.
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Re: Cfm56-7b

Postby sjap » 19 Sep 2012, 11:48

Found, thanks to a colleague of mine:
Attachments
N1 trimlevel.jpg
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Re: Cfm56-7b

Postby raghav » 29 Sep 2012, 13:50

Thanks buddy
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