B787 and TPR
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B787 and TPR
Hi,
Can someone explain a bit on the TPR thrust unit that the B787 uses?
What and how exactly does it measure thrust?
To give you an idea of the numbers we are talking about, here is from the FCOM.
At max takeoff N1 (ISA);
N1 is 92,2%
TPR is 82,8
Is it some kind of value for the amount of AVAILABLE thrust used?
Meaning in the example that you have 17,2% of thrust still available.
(apologies if this has been discussed already)
Cheers,
XPM
Can someone explain a bit on the TPR thrust unit that the B787 uses?
What and how exactly does it measure thrust?
To give you an idea of the numbers we are talking about, here is from the FCOM.
At max takeoff N1 (ISA);
N1 is 92,2%
TPR is 82,8
Is it some kind of value for the amount of AVAILABLE thrust used?
Meaning in the example that you have 17,2% of thrust still available.
(apologies if this has been discussed already)
Cheers,
XPM
Join Date: Jul 2000
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It appears to stand for either Turbofan Power Ratio or Turbine Pressure Ratio depending on where it's found.
I think it's going to be Turbofan Power Ratio on the 787.
From what I've read on the net, it appears to basically display thrust as a percentage of maximum available in each mode ie TO, CLB, GA, and can even be used in reverse.
So you can now set say 85% of Take off power or Climb power or have 85% reverse thrust and the TPR will read 85.
Looks like it'll be possible to takeoff with 100%TPR get airborne call for "climb thrust" and still have 100%TPR but now in CLB thrust mode, CLB 1 will always be 90% and CLB 2 80% initially until it is blended out towards 100% again during the climb.
Somewhere in the change from TO to CLB the TPR will have to read either less than 100% TO or greater than 100% CLB though. Probably greater that 100% climb, at least it'll appear correctly as reducing thrust towards 100% climb thrust.
I think it's going to be Turbofan Power Ratio on the 787.
From what I've read on the net, it appears to basically display thrust as a percentage of maximum available in each mode ie TO, CLB, GA, and can even be used in reverse.
So you can now set say 85% of Take off power or Climb power or have 85% reverse thrust and the TPR will read 85.
Looks like it'll be possible to takeoff with 100%TPR get airborne call for "climb thrust" and still have 100%TPR but now in CLB thrust mode, CLB 1 will always be 90% and CLB 2 80% initially until it is blended out towards 100% again during the climb.
Somewhere in the change from TO to CLB the TPR will have to read either less than 100% TO or greater than 100% CLB though. Probably greater that 100% climb, at least it'll appear correctly as reducing thrust towards 100% climb thrust.
Join Date: May 2005
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Definetely Turbofan Power Ratio.
From the RR Trent training notes,
"TPR actual is derived from the P20, P30, T20 and EGT parameters."
Calculated in the following manner;
.
. P3.0 x √ EGT
_____________ = TPR
. P2.0 x √T2.0 .
.
P2.0 = Engine Inlet airpressure
P3.0 = HP Compressor Discharge Pressure
T2.0 = Engine Inlet Temperature
EGT = Exhaust Gas Temperature
.
.
From the RR Trent training notes,
"TPR actual is derived from the P20, P30, T20 and EGT parameters."
Calculated in the following manner;
.
. P3.0 x √ EGT
_____________ = TPR
. P2.0 x √T2.0 .
.
P2.0 = Engine Inlet airpressure
P3.0 = HP Compressor Discharge Pressure
T2.0 = Engine Inlet Temperature
EGT = Exhaust Gas Temperature
.
.
