Actual RB211 RPM
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Actual RB211 RPM
I remember seeing some time ago a thread about what RPM engines such as the RB211 actually spin at. Unfortunately the 4 character minimum in the search function doesn't lend itself to finding a lot of topics in this TLA full industry and I can't find it.
So i'm interested in either finding that thread, or alternatively, could someone tell me what sort of RPM each spool is spinning at at 100%?
Thanks
So i'm interested in either finding that thread, or alternatively, could someone tell me what sort of RPM each spool is spinning at at 100%?
Thanks
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RB211-524GT
All figures at 100%
N1 3900 RPM
N2 7000 RPM
N3 10611 RPM
Interesting to see that only the fan speed changes. Wouldn't have guessed that, considering the size difference of the engines.
Trent 900 figures anyone?
All figures at 100%
N1 3900 RPM
N2 7000 RPM
N3 10611 RPM
Interesting to see that only the fan speed changes. Wouldn't have guessed that, considering the size difference of the engines.
Trent 900 figures anyone?
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I'll wager that these are merely 100% gage calibration points. On a cold day N1% will certainly be lower than on ISA day. (Because of increasing air density).
At moderately higher OAT N1 will increase, but once above the flat-rate limit, N1 falls off again (for EGT protection).
At moderately higher OAT N1 will increase, but once above the flat-rate limit, N1 falls off again (for EGT protection).
Last edited by barit1; 8th Feb 2008 at 02:19.
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You're right, the N1 gage knows nothing of OAT - but the ENGINE does.
To reach a given EPR, the engine doesn't have to turn as fast on a cold day (high density = high mass flow at a given N1). This is the whole concept behind using N1 for power management (eg a GE or CFM engine); You can't know what N1 to set until you know OAT (and also pressure altitude...)
To reach a given EPR, the engine doesn't have to turn as fast on a cold day (high density = high mass flow at a given N1). This is the whole concept behind using N1 for power management (eg a GE or CFM engine); You can't know what N1 to set until you know OAT (and also pressure altitude...)
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spannersatKL - No, I understand fully the RR/PW EPR (IEPR) scheme.
I'm merely saying if you set EPR on a warm day and note the N1, then set the same EPR on a cold day and note the N1, you will come to the conclusion I stated: When the air is more dense, it takes less fan rpm to achieve a given EPR.
The air doesn't care who makes the fan.
I'm merely saying if you set EPR on a warm day and note the N1, then set the same EPR on a cold day and note the N1, you will come to the conclusion I stated: When the air is more dense, it takes less fan rpm to achieve a given EPR.
The air doesn't care who makes the fan.
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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.
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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barit1,
what confused me was that you didn't mention EPR/N1 relationship in your first post:
Of course you will have a different N1% on a cold day over a hot day, as you will be setting a different EPR, not because the indicated N1 % changes due to temp.
Hopefully you can see where there was confusion....
Sincerely,
N1 Vibes
what confused me was that you didn't mention EPR/N1 relationship in your first post:
I'll wager that these are merely 100% gage calibration points. On a cold day N1% will certainly be lower than on ISA day. (Because of increasing air density).
Hopefully you can see where there was confusion....
Sincerely,
N1 Vibes
