Hydraulic Flashcards
Components
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
Pressurization
With exception of pitch and roll trim actuators in pilot-assist servo assembly (1000 psi), all components receive 3000 psi
HYD Warning
Illuminates when the hydraulic system is severely degraded as a result of several compound malfunctions involving No 1/2 and backup hydraulic systems
Hydraulic Pumps / Components
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)
No 1 Transfer Module
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
No 2 Transfer Module
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
Primary Servo Shutoff
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
Backup System
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
Backup Hydraulic Pump
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
Backup Pump Switchology (WOW/no WOW)
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
Automatic Backup Pump Intiation
- No 1 HYD PUMP
- No 2 HYD PUMP
- # 1 RSVR LOW
- # 1 TAIL RTR SERVO
Utility Module
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
Hydraulic Leak Test (BRAAW)
Requires:
- BACKUP HYD PUMP switch in AUTO
- Rotors engaged
- Ac power
- All hydraulic reservoirs full
- Weight on Wheels (WOW)
Indications:
- # 1 RSVR LOW
- # 2 RSVR LOW
- BACKUP RSVR LOW
- SAS
- BOOST SERVO OFF
- AFCS DEGRADED
- # 1 TAIL RTR SERVO
- # 2 TAIL RTR SERVO
- BACKUP PUMP ON
- MASTER CAUTION
Leak Detection/Isolation (LDI) #1
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
- YES? = leakage in No 1 tail rotor servo supply system =
** 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
- YES (PRI SERVO switch 1ST OFF) =
**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 =
- Loss of No 1 primary servo and No 1/2 tail rotor servos
- CAUTIONS = #1 HYD PUMP, #1 PRI SERVO PRESS, #1 TAIL RTR SERVO, #1 RSVR LOW, BACKUP RSVR LOW
- No advisories
Leak Detection/Isolation (LDI) #2
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
- YES? = leakage leak in pilot-assist servo supply =
** 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
- YES (PRI SERVO switch 2ND OFF) =
**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 =
- Loss of No 2 primary servo and pilot assist servos
- CAUTIONS = #2 HYD PUMP, #2 PRI SERVO PRESS, #2 RSVR LOW, BACKUP RSVR LOW, SAS, AFCS DEGRADED, BOOST SERVO OFF
- No advisories
