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////////////////////////A / PW4000 SERIES /747-400 / ENGINES /MAINTENANCE MANUAL ////////////////////////
SEE  B 
SEE  A  FLANGE T FLANGE S  FLANGE P  FLANGE P  FLANGE S FLANGE T 
(4 LOCATIONS) PROBE THERMOCOUPLE EGT (TT4.95)  EPR (PT4.95) PROBE SEE D 
TURBINE EXHAUST CASE  TURBINE EXHAUST CASE 
EPR (PT4.95) SEE C PROBE 

A FWD  B FWD
Engine Pressure Ratio (PT4.95) Probe Inspection Figure 601 (Sheet 1)
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PRESSURE PORT
WIDTH 0.160 INCH
L-AO724

Engine Pressure Ratio (PT4.95) Probe Inspection
Figure 601 (Sheet 2)

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////////////////////////A / PW4000 SERIES /747-400 / ENGINES/MAINTENANCE MANUAL ////////////////////////
D.  Do a check of the EPR probe (Fig. 601).
 S 026-002-N00
 (1)  
Remove the EPR (PT4.95) probe (AMM 77-11-01/401).

 S 216-003-N00

 (2)  
Examine the EPR probe for nicks, dents, cracks, and damage from heat.

 (a)  
Nicks and dents are permitted.

 (b)  
Damage (due to heat) is permitted if you can install the EPR probe or the EGT thermocouple probe.

 (c)  
Cracks are not permitted.

 1)  If you find cracks, replace the EPR probe (AMM 77-11-01/401).
 S 216-004-N00
 (3)  Examine the average pressure port of the EPR probe for damage to the threads.
 (a)  If the threads are damaged, do the repair of the threads with a thread chaser die.
 S 216-005-N00
 (4)  Examine the temperature sampling inlet tubes and the discharge slots in the casting of the EPR probe for blockage.
 (a)  Make sure you can see through the ports on the leading and the trailing edges (respectively) of the EPR probe. 1) The view (line of sight) through the EPR probe must be 80%
 free of blockage (minimum).
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 (5)  AIRPLANES WITH PW SB77-16; Examine the four pressure sampling ports on the leading edge of the EPR probe for minimum opening dimensions (Fig. 601).
 (a)  You can use a 0.0635 inch (1.613 mm) diameter hand-held drill to remove the unwanted material.
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S 226-016-N00
 (6)  AIRPLANES WITHOUT PW SB77-16; Examine the six pressure sampling ports on the leading edge of the EPR probe for minimum opening dimensions. (a) You can use a 0.030 inch (0.762 mm) diameter hand-held drill to remove the unwanted material.
 (b) (c)  Connect the EPR probe to the ground pressure cart.Blow air at a maximum pressure of 125 PSIG (861.8 KPaG) through the tube fittings.
 NOTE:____ If you hold a piece of paper up to the pressure sampling ports while the air flows, it should move about the same distance away from each port.
 (d) (e)  Disconnect the EPR probe from the ground pneumatic cart.If you cannot repair the EPR probe to the minimum necessary dimensions, replace the EPR (PT4.95) probe (AMM 77-11-01/401).
　
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