S 715-245-N00
(7)
Slowly move the thrust lever rearward to the idle position.
(a) Let the engine become stable for 5 minutes.
S 975-103-N00
(8) Make sure the results of the pressure ratio for the turbine cooling air are in the permitted limits.
(a)
Calculate the observed N2 (rpm):
Observed N2 rpm = %N2 X 99.00 rpm
(b)
Calculate the pressure ratio for the turbine cooling air:
= PS4I = 0.97 X PS4I
--------PT3 PS3
(c)
Make a graph of the pressure ratio and the N2 speed on the check curve for the turbine cooling air (Fig. 506).
(d)
Make sure the point on the graph point is in the permitted limits.
NOTE: If the pressure ratio is less than the minimum limit,
____ then there is not a sufficient flow of turbine cooling air. If the pressure ratio is more than the maximum limit, then there is too much flow of the turbine cooling air. Too much flow can cause the engine performance to decrease and a possible bearing skid can occur from a change in the bearing thrust loads.
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0.70
0.69
0.68
0.67
PS4I/PT3
OR 0.97 (PS4I/PS3)
0.66
0.65
0.64
0.63
0.62
0.61
0
60 110
NOTES: THE PERMITTED BAND IS NOT APPLICABLE TO THE IDLE POWER CONDITIONS.
THIS CURVE IS FOR ENGINES PRE-PW-SB 72-514
AND ENGINES PRE-PW-SB 72-662 WITH TOBI DUCT
PN's 50K120, 50K178-01 OR 50K363-01.
(PW4052, PW4056, PW4060, PW4060A, PW4060C AND ALL (-1C) INTERMIX MODELS WHICH INCLUDES PW4062-1C)
L-A5162
Turbine Cooling Air Ratio Check Limits
Figure 506 (Sheet 1)
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////////////////////////A / PW4000 SERIES /747-400 / ENGINES /MAINTENANCE MANUAL ////////////////////////
0.73
0.72
0.71
0.70
0.69
0.68
0.67
0.66
0.65
0.64
0
PS4I/PT3
OR 0.97 (PS4I/PS3)
AND ENGINES PRE-PW-SB 72-662 WITH TOBI DUCT THIS CURVE IS FOR ENGINES POST-PW-SB 72-514 NOTES: THE PERMITTED BAND IS NOT APPLICABLE_____ PN's 50K178-001, 50K363-001, OR 50K542-01. TO THE IDLE POWER CONDITIONS.
(-1C) INTERMIX MODELS WHICH INCLUDES PW4062-1C) (PW4052, PW4056, PW4060, PW4060A, PW4060C AND ALL
1296 L-B4510
Figure 506 (Sheet 2) Turbine Cooling Air Ratio Check Limits
H93297
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0.76
0.75
0.74
0.73
0.72
0.71
0.70
0.69
0.68
0.67
0.66
PS4I/PT3
OR 0.97 (PS4I/PS3)
AND ENGINES POST-PW-SB 72-662 WITH TOBI DUCT THIS CURVE IS FOR ENGINES POST-PW-SB 72-514 NOTES: THE PERMITTED BAND IS NOT APPLICABLE_____ PN 50K136-01. TO THE IDLE POWER CONDITIONS. 中国航空网 www.aero.cn 航空翻译 www.aviation.cn 本文链接地址：747-400 AMM 飞机维护手册 动力装置 POWER PLANT 1(71)
