1. UH-60 HYDRAULIC SYSTEM
BY: CW2 Ron Nelson

2. TERMINAL LEARNING OBJECTIVE
To develop the student Instructor Pilot’s understanding of the components and functions of the UH-60 Hydraulic System.
Ref: UH-60 Operator’s Manual (-10)
C Co d Flight Line Supplement
Hydraulics Systems Student Handout

3. OUTLINE of ELEMENTS System Components and Location
#1 Hydraulic system
#2 Hydraulic system
Back-up hydraulic system
Leak Detection Isolation (LDI) and Pressure Malfunctions

4. COMPONENTS and LOCATION
Hydraulic Systems Operational Diagram

5. #2 HYDRAULIC PUMP
MODULE

6. #1 HYDRAULIC SYSTEM CHARACTERISTICS
Supplies hydraulic pressure through the No 1 transfer module to the 1st stage primary servos and the 1st stage tail rotor servo
Pump - variable-delivery, pressure-compensated, piston-type component.
Pressure output is 3,050 psi (
Two filters with filter conditioning indicator buttons advise pilot when filter is contaminated
Extends at 70 psid (bypass at 100 (±10) psid on return filter

8. #2 HYDRAULIC SYSTEM CHARACTERISTICS
Supplies hydraulic pressure through the #2 transfer module to the 2nd stage primary servos and to all pilot assist servos.
Pump, interchangeable, same as #1 system and B/U pump.
No. 2 transfer module, like #1 has a pressure switch, shuttle/transfer valve, and two shut-off (hyd control) valves. (2nd stage servos and pilot assist module).

9. #2 HYDRAULIC SYSTEM CHARACTERISTICS
Components of pilot assist module:
Shut-off valves (3)
Boost and SAS valves (spring loaded, fail safe open)
Pitch/trim valve, deenergizes to closed position
Pressure reducer with relief valve (1,000 psi for PT) Relief valve opens above 1375 psi, 1300 psi.

10. ON
#2 HYDRAULIC PUMP
MODULE

11. BACKUP HYDRAULIC SYSTEM CHARACTERISTICS
Supplies hydraulic pressure through the utility module to the 2nd stage tail rotor and through the No. 1 and No. 2 transfer modules and to all servos supplied for both systems. Also, it supplies hydraulic charge to the APU accumulator for APU starts.
Motor: 115 volt AC, 3 phase, 12 3/4 Hp. An internal depressurization valve unloads the motor by reducing TQ requirement at low RPM. (0.5 sec/4 sec). The motor’s function is to drive the B/U pump.

13. HYD LEAK DETECTION/ISOLATION SYSTEM (LDI)
LDI prevents the further loss of fluid in case of a leak. LDI uses pressure switches and fluid level sensors for monitoring pump fluid level, pump pressure for primary and tail rotor servos, and pilot assist servos.
Logic modules operate shutoff valves to isolate leaks and to turn on the B/U pump when required.
Output of the logic modules will either turn on lights to the caution/advisory panel or turn off valves automatically, except when pilot action is required.

17. Transfer Modules
The No. 1 and No. 2 transfer modules connect hydraulic pressure from the pump modules to the flight control servos.
The modules are interchangeable
Each module is an integrated assembly of shutoff valves, pressure switches, check valves, and restrictors.
Transfer modules are spring-loaded to the open or normal position.

18. Transfer Modules
If hydraulic pressure is lost, the transfer valve automatically transfers backup pump pressure to the system that has lost pressure.
Each transfer module has a primary shutoff valve that allows the pilots to shut off pressure to the primary servos for the respective system.
The first stage tail rotor servo valve is located in the No. 1 transfer module.
The pilot assist shutoff valve is located in the No.2 transfer module.

19. Transfer Modules
Each transfer module has a pressure switch that activates the appropriate HYD PUMP (#1 or #2) caution light when #1 or #2 system pressure drops below 2000 psi.
This switch also sends a signal to LDI that the system has lost pressure.

20. Utility Module
The utility module connects hydraulic pressure from the backup pump to the:
No. 1 and No.2 transfer modules
2nd stage of the tail rotor servo
APU accumulator
A pressure switch on the module senses the backup pump operating and turns on the BACK-UP PUMP ON advisory light.
If the flow rate through the module to the APU accumulator goes over 1-1/2 gpm, a vilocity fuse shuts off the flow.

21. Logic Modules
Two logic modules, one in the left relay panel and the other in the right relay panel, are used to control the operation of the hydraulic systems.
Inputs to the logic modules include:
pressure switches
fluid level switches on the pump modules
inputs received from control switches in the hydraulic system
Outputs from the logic modules include:
turn on lights on the caution/advisory panel
turn off one or more valves due to a system malfunction
All switching functions of the hydraulic logic modules are automatic except for moving of the servo off switches.

22. Pilot Assist Module
The pilot assist module connects hydraulic pressure to the four pilot-assist servos.
Pressure is reduced to 1000 psi for use by the pitch trim actuator.
A relief valve is incorporated with the pressure reducer, the relief valve opens above 1375 psi.
Three shutoff switches are built into the Pilot Assist Module; Trim, SAS, and Boost (Three Stupid Boxes)
A pressure switch on the front of the module lights the SAS caution light when pressure drops below 2000 psi.

23. PRACTICAL EXERCISE

24. MASTER CAUTION Leak in the #1 Hydraulic System
Partial loss of fluid sensed at #1 res level sensing switch
LDI turns off No. 1 TR servo
BACKUP pump turns ON
Turns on #2 TR Servo
#1 Resv Low caution Light ON
#1 TR Servo Caution Light ON
B/U Pump On Advisory Light ON
#2 TR Servo Advisory Light ON

25. MASTER CAUTION Leak in the #1 Hyd Sys CONTINUES
Complete loss of res fluid in #1 pump
Backup pump supplies No. 1 PRI servo and No. 1 TR servo (#1 TR servo back on)
If no other leak the leakage is upstream of the No. 1 transfer module
#1 HYD Caution Light ON
#1 PRI Servo Caution light may flicker Chapter 5 limitations?

26. MASTER CAUTION Leak in the #1 Hyd Sys CONTINUES!
Partial Loss of Backup reservoir fluid
Activation of B/U pump low level sensing switch
PILOT ACTION!
SVO OFF switch - 1st STG
LAND ASAP
Leakage in the #1 PRI servo stage
B/U pump RSVR LOW Light ON
WARNING
If the #2 PRI SERVO PRESS caution light illuminates, establish a landing attitude, minimize control inputs, and begin a descent
LIMITATIONS?

27. MASTER CAUTION Leak in the #2 Hydraulic System
Partial fluid loss sensed at #2 res low level sensing switch
LDI turns off PLT assist servos
If no other lights on leakage is in the Pilot Assist area
#2 Resv Low Caution Light ON
BOOST Servo OFF, Trim Fail, FPS, SAS OFF Caution Lights ON
Note increased pedal and collective loads

28. MASTER CAUTION Leak in the #2 Hyd Sys CONTINUES!
Complete loss of No. 2 resv fluid
BACKUP PUMP ON
Pilot Assist servos turned on
If no other lights, leak is upstream of the transfer module
#2 Hyd Pump caution Light ON
B/U Pump ON Adv
Boost Servo Off/SAS Off caution Light OFF
#2 Resv Low, #2 HYD Pump, and B/U Pump On advisory lights

29. MASTER CAUTION Leak in the #2 Hyd Sys CONTINUES!
Partial Loss of B/U Pump Resv fluid
PILOT ACTION!
SVO OFF switch - 2nd STG
LAND ASAP
B/U Pump Resv Low caution light ON
WARNING
If the #1 PRI SERVO PRESS caution light illuminates, establish a landing attitude, minimize control inputs, and begin a descent

30. SUMMARY
We discussed the components of the #1 and #2 and Backup Hydraulic Systems.
We outlined the functions and capabilities of the Leak Detection/Isolation System
We applied through our practical exercise systems malfunctions analysis and both aircraft and pilot reactions and limitations of all three systems.

31. QUESTIONS?