Hydraulic

Question 1

Components

Answer 1

3 interchangeable pumps, 2 transfer modules, one utility module, 3 dual-stage primary servos, tail rotor servos, pilot-assist servo assembly, APU accumulator and rescue hoist

Question 2

Pressurization

Answer 2

With exception of pitch and roll trim actuators in pilot-assist servo assembly (1000 psi), all components receive 3000 psi

Question 3

HYD Warning

Answer 3

Illuminates when the hydraulic system is severely degraded as a result of several compound malfunctions involving No 1/2 and backup hydraulic systems

Question 4

Hydraulic Pumps / Components

Answer 4

Combination pump/reservoir mounted on and driven by accessory module

Incorporates pressure relief valve, bleed valve, pressure filter, return filter, and auto low level sensing switch

Pressure relief and bleed valves protect from overpressurization

Pressure filter has no bypass to preclude unfiltered fluid from entering primary servos

Auto low-level sensing switch, mounted on top of pump, closes when fluid is low (#1 RSVR LOW)

Question 5

No 1 Transfer Module

Answer 5

Routes hydraulic fluid to primary servos and first stage tail rotor

Transfer module automatically routes fluid from the backup pump if pressure is lost via the transfer/shuttle valve

Pressure switch illuminates #1 HYD PUMP and sendings signal to the LDI when No 1 pressure drops below prescribed limits

Question 6

No 2 Transfer Module

Answer 6

Same as No 1 except, routes hydraulic fluid to primary servos and pilot-assist servo

Pressure to pitch and roll trim actuators secured by depressing TRIM button; boost servos and SAS secured by depressing SAS/BOOST pushbutton

Question 7

Primary Servo Shutoff

Answer 7

With either 1st or 2nd OFF selected, servo shutoff valve energized closed and pressure to respective stage is secured

Electrical interlock prevents securing of hydraulic pressure to both stages simultaneously; also prevents inadvertent securing of pressure to operable stage if the other is malfunctioning

Question 8

Backup System

Answer 8

Provides pressure to No 1/2 systems prior to rotor engagement, rescue hoist system, and recharges APU accumulator

Supplies emergency pressure to No 1/2 system and 2nd stage tail rotor servo when pressure loss occurs

When supplying pressure to 2nd stage tail rotor servo, priority valve may secure hydraulic pressure to the rescue hoist due to low system pressure

• CAUTION* If the BACKUP PUMP PWR circuit breaker is out and a condition exists that requires the backup pump to operate, then either the hydraulic system must be configured so that the backup pump will not activate upon resetting the cb or ac power must be secured prior to resetting the cb. Damage to the current limiters may occur and will be indicated by a loss of all loads on No 1 AC PRI
• NOTE* FLIR failure may occur if the backup hydraulic pump is turned on with FLIR operating

Question 9

Backup Hydraulic Pump

Answer 9

Identical to No 1/2 except powered by ac electric motor

Internal depressurizing valve reduces pressure to aid startup of electric motor; when power supplied, valve closes and pump supplies 3000 psi to system

Energizes after 4 seconds o APU or external power or 0.5 seconds with either main generator on

Question 10

Backup Pump Switchology (WOW/no WOW)

Answer 10

WOW activated:
OFF - remains off

ON - with No 1/2 pumps operating normally, recirculates fluid to and from each transfer module and maintains pressure in APU accumulator and rescue hoist systems

AUTO - automatically maintains pressure to No 1/2 systems including 2nd stage tail rotor servo

WOW not activated:
OFF or AUTO - automatically maintains pressure to No 1/2 systems including 2nd stage tail rotor servo (as required for pressure and/or fluid loss detected by LDI); also maintains pressure in 2nd stage tail rotor when TAIL SERVO switch placed to BACKUP

ON - same as WOW

NOTE When the APU accumulator pressure is low and the backup pump is activated, the backup pump will run for at least 90 seconds (180 with winterization kit), regardless of BACKUP HYD PUMP switch position

Question 11

Automatic Backup Pump Intiation

Answer 11

1. No 1 HYD PUMP
2. No 2 HYD PUMP
3. # 1 RSVR LOW
4. # 1 TAIL RTR SERVO

Question 12

Utility Module

Answer 12

Routes fluid to No 1/2 transfer modules, 2nd stage tail rotor servo, rescue hoist, and APU accumulator

Pressure switch triggers BACKUP PUMP ON when above a prescribed limit

Priority valve (between utility module and rescue hoist) restricts fluid to hoist if backup pressure too low

Velocity fuse secures fluid flow to APU accumulator if flow rate exceeds prescribed limit

Question 13

Hydraulic Leak Test (BRAAW)

Answer 13

Requires:

1. BACKUP HYD PUMP switch in AUTO
2. Rotors engaged
3. Ac power
4. All hydraulic reservoirs full
5. Weight on Wheels (WOW)

Indications:

1. # 1 RSVR LOW
2. # 2 RSVR LOW
3. BACKUP RSVR LOW
4. SAS
5. BOOST SERVO OFF
6. AFCS DEGRADED
7. # 1 TAIL RTR SERVO
8. # 2 TAIL RTR SERVO
9. BACKUP PUMP ON
10. MASTER CAUTION

Question 14

Leak Detection/Isolation (LDI) #1

Answer 14

Actuation of No 1 Reservoir low level sensing switch = #1 RSVR LOW

> No 1 tail rotor servo turned off = #1 TAIL RTR SERVO

> Backup pump turned on = BACKUP PUMP ON

> Open No 2 tail rotor servo shutoff valve = #2 TAIL RTR SERVO ON

> DOES LEAK STOP?

• • YES? = leakage in No 1 tail rotor servo supply system =
    1. No 1 pump continues to supply No 1 primary servo
    2. Backup pump powers No 2 tail rotor servo
    3. CAUTIONS = #1 RSVR LOW, #1 TAIL RTR SERVO
    4. ADVISORIES = BACKUP PUMP ON, #2 TAIL RTR SERVO ON

** NO?

> Complete loss of No 1 reservoir hydraulic fluid = #1 HYD PUMP [#1 PRI SERVO may flicker]

> Backup pump supplies No 1 primary servo and No 1 tail rotor servo = #2 TAIL RTR SERVO ON goes out

> PILOT ACTION?

• • YES (PRI SERVO switch 1ST OFF) =
    1. Loss of No 1 primary servos
    2. Backup pump supplies No 1 tail rotor servo
    3. CAUTIONS: #1 HYD PUMP, #1 PRI SERVO, #1 RSVR LOW
    4. ADVISORIES: BACKUP PUMP ON

**NO

> DOES LEAK STOP?

• *YES = leak upstream of No 1 transfer module
  1. Backup pump supplies No 1 primary servos and No 1 tail rotor servo
  2. CAUTIONS = #1 RSVR LOW, #1 HYD PUMP
  3. ADVISORY = BACKUP PUMP ON

**NO > leak in primary servo No 1 stage

> Partial loss of backup reservoir fluid = BACKUP RSVR LOW

> Total loss of backup reservoir fluid = BACKUP PUMP ON turns off =

1. Loss of No 1 primary servo and No 1/2 tail rotor servos
2. CAUTIONS = #1 HYD PUMP, #1 PRI SERVO PRESS, #1 TAIL RTR SERVO, #1 RSVR LOW, BACKUP RSVR LOW
3. No advisories

Question 15

Leak Detection/Isolation (LDI) #2

Answer 15

Actuation of No 2 Reservoir low level sensing switch = #2 RSVR LOW

> Pilot assist servos turned off = BOOST SERVO OFF, SAS, AFCS DEGRADED (increased pedal and collective loads)

> DOES LEAK STOP?

• • YES? = leakage leak in pilot-assist servo supply =
    1. No 2 pump continues to supply No 2 primary servo
    2. Pilot assist servo functions lost
    3. CAUTIONS = BOOST SERVO OFF, SAS, AFCS DEGRADED, #2 RSVR LOW
    4. No advisories

** NO?

> Complete loss of No 2 reservoir hydraulic fluid = #2 HYD PUMP [#1 PRI SERVO may flicker]

> Backup pump turned on = BACKUP PUMP ON

> Pilot-assist servos turned on = BOOST SERVO OFF, SAS, AFCS DEGRADED all off

> PILOT ACTION?

• • YES (PRI SERVO switch 2ND OFF) =
    1. Loss of No 2 primary servos
    2. Pilot asist servos pressure supplied by backup pump
    3. CAUTIONS: #2 HYD PUMP, #2 PRI SERVO, #2 RSVR LOW
    4. ADVISORIES: BACKUP PUMP ON

**NO

> DOES LEAK STOP?

• *YES = leak upstream of No 2 transfer module
  1. Backup pump supplies entire No 2 hydraulic system
  2. CAUTIONS = #2 RSVR LOW, #2 HYD PUMP
  3. ADVISORY = BACKUP PUMP ON

**NO > leak in primary servo No 2 stage

> Partial loss of backup reservoir fluid = BACKUP RSVR LOW

> Total loss of backup reservoir fluid = BACKUP PUMP ON turns off =

1. Loss of No 2 primary servo and pilot assist servos
2. CAUTIONS = #2 HYD PUMP, #2 PRI SERVO PRESS, #2 RSVR LOW, BACKUP RSVR LOW, SAS, AFCS DEGRADED, BOOST SERVO OFF
3. No advisories

Question 16

Hydraulic Fill System

Answer 16

Hand pump and manual selector valve in hydraulics bay

Contains sight gauge and serves as rotor brake reservoir

Question 17

Utility Hydraulic System

Answer 17

Independently operates sonar reeling machine

Mounted right, rear quarter of transmission

OFF: operates at reduced pressure of 1000 psi for recirculation and cooling

ON: closes bypass valve, increasing pressure to 3000 psi

NOTE When use of the sonar reeling machine is not required, the UTILITY HYD PUMP switch should be OFF