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Old 8th February 2008 | 15:18
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Sootikin
 
Joined: Jul 2004
Posts: 17
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From: Home for bewildered engineers
Shaft Speeds in G/H/-T

It's even more confusing than some might think.

The percentage / shaft speeds relations quoted previously are purely reference numbers, and are not the actual operating limits. (I believe that these RPMs were the originally predicted operating speeds for the RB211-22B. Actual engine data showed that the operating limits would be different, but for convenience, the limits are quoted as percentages.)

So, for the RB211-524G/H/-T
Reference Speeds
100% HP = 10,611 rpm
100% IP = 7,000 rpm
100% LP= 3,900 rpm

MTO Operating Limits
HP Speed = 99.2%
IP Speed = 107.7%
LP Speed = 110.5% (i.e. 1.105 x 3900 = 4309.5 rpm)

(There are also Max Continuous and Max Overspeed / Overtemp limits, but lets not add to the confusion.)

The equivalent Trent 900 data you should find in the TCDS on the EASA site.

Hope This Helps.
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