UH-60 HYDRAULIC SYSTEM

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. 1-223d 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 • #1 Hydraulic system • #2 Hydraulic system • Back-up hydraulic system

4. COMPONENTS and LOCATION Hydraulic Systems Operational Diagram

5. #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

6. #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).

7. #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, resets @ 1300 psi.

8. 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.

9. 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.

10. PRACTICAL EXERCISE

11. 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 MASTER CAUTIONLeak in the #1 Hydraulic System

12. 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? MASTER CAUTIONLeak in the #1 Hyd Sys CONTINUES

13. 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? MASTER CAUTIONLeak in the #1 Hyd Sys CONTINUES!

14. 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 MASTER CAUTIONLeak in the #2 Hydraulic System

15. 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 MASTER CAUTIONLeak in the #2 Hyd Sys CONTINUES!

16. 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 MASTER CAUTIONLeak in the #2 Hyd Sys CONTINUES!

17. 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.

18. QUESTIONS?