S 864-014

 (5)  
Remove the circuit breaker locks and close these circuit breakers on the overhead panel, P11:

 S 434-013
 (a) 11D26, HYDRAULIC RAT CONT OR HYDRAULIC RAT AUTO CONT
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757 MAINTENANCE MANUAL
 (b)  11D27, HYDRAULIC RAT AUTO, or HYDRAULIC RAT AUTO PWR
 (6)  S 864-016Remove the lock set for the circuit breakers and close these circuit breakers on the main power distribution panel, P6: (a) 6F1, RAT MAN, or RAT MAN PWR (b) 6F2, RAT MAN CONT
 (7)  S 794-027Do the leakage test for the auxiliary pitot system No. 2 and the alternate static system (AMM 34-11-00/501).
 (8)  S 714-028Do the test for the RAT auto deployment system (AMM 29-21-00/501).

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757 MAINTENANCE MANUAL
 HYDRAULIC POWER TRANSFER UNIT (PTU) SYSTEM - DESCRIPTION AND OPERATION
______________________________________________________________________
 1.  General_______
 A.  The power transfer unit (PTU) system provides an alternative power source for the left hydraulic system if left engine power or left EDP pressure is lost.
 B.  The PTU uses right system pressure to provide left system pressure without transfering fluid between the two systems. The PTU contains in one housing a hydraulic motor and a hydraulic pump joined by a driveshaft.
 C.  The PTU system supplies power only to the following systems:
 (1)  
TE flaps

 (2)  
LE slats

 (3)  
Landing gear

 (4)  
Nose gear steering

 (5)  
ON AIRPLANES WITH HYDRAULIC MOTOR-DRIVEN GENERATOR;
 hydraulic motor-driven generator

 D.  The left engine-out relay No. 2 turns the PTU on if power is lost in the left engine.
 E.  The PTU is also turned on by the left EDP pressure switch if left EDP pressure falls below approximately 1275 psi.
 F.  The PTU can be turned on with the PTU manual control switch on right side panel P61.
 2.  Component Details (Fig. 1)_________________
 A.  Power Transfer Unit (PTU) (Fig. 2)
 (1)  
The power transfer unit consists of a hydraulic motor and a hydraulic pump in one housing. The motor and pump are joined by a driveshaft inside the housing. The hydraulic motor uses 28 gpm at 3000 psi to provide a pump output of 22.5 gpm at 2175 psi. As pump output pressure increases, pump delivery flow decreases until flow is near zero at 2600 psi. The PTU is on the inboard wall of the left main wheel well.

 (2)  
The hydraulic motor is a fixed displacement piston type. Fluid enters the motor through a hydraulic fuse and a flow regulator. The flow regulator controls motor speed by limiting the fluid flow to the motor to about 28 gpm. The hydraulic fuse prevents overspeed of the motor if the regulator fails. If the supply flow exceeds about 35 gpm, the fuse closes to shutoff all flow to the motor. The fuse reopens when inlet pressure drops to about 100 psi. The motor moves fluid through the motor case to lubricate and cool the motor. The case drain fluid flows into the right system return line.
　
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