HYDRAULIC SYSTEMS Flashcards
Hydraulic system components include:
three identical and interchangeable hydraulic pumps
two transfer modules
one utility module
three dual-stage primary servos
tail rotor servos
the pilot-assist servo assembly
the APU accumulator
the rescue hoist
With the exception of the pitch and roll trim actuators in the pilot-assist servo assembly ( _____-psi hydraulic pressure), all components of the
hydraulic system receive approximately _____ -psi pressure from the hydraulic pumps
1000 psi
3,000 psi
No. 1 Hydraulic System provides pressure to the:
first stage of the primary servos
first stage of the tail rotor servo
No. 2 Hydraulic System provides pressure to the:
second stage of the primary servos
pilot-assist servo assembly
When either 1ST OFF or 2ND OFF is selected, the associated servo shutoff valve is energized ____ and hydraulic pressure to the respective stage is secured
closed
Backup Hydraulic System provides pressure to the:
No. 1 and No. 2 hydraulic systems prior to rotor engagement
provides the only source of hydraulic pressure to the rescue hoist system recharges the APU accumulator
emergency hydraulic pressure to the No. 1 and No. 2 hydraulic system
second stage of the tail rotor servo when pressure loss occurs
After ___ seconds on APU or external power, or ___ second with either main
generator on, the backup pump will energize
4 seconds
0.5 second
With weight on wheels and BACKUP HYD PMP switch position:
Off
On
Auto
OFF — The backup pump remains off.
ON — With the No. 1 and No. 2 hydraulic pumps operating normally, the backup pump recirculates hydraulic fluid to and from each transfer module and maintains pressure in the APU accumulator and rescue hoist systems, as
required. The backup pump remains on until it is secured.
AUTO — The backup pump automatically maintains hydraulic pressure to the No. 1 and/or No. 2 hydraulic systems, including the second stage of the tail rotor servo (as required for hydraulic system pressure and/or fluid losses
detected by the LDI system).
With weight off wheels and BACKUP HYD PMP switch position:
Off/ Auto
On
OFF or AUTO — The backup pump automatically maintains hydraulic pressure to the No. 1 and/or No. 2 hydraulic systems, including the second stage of the tail rotor servo (as required for hydraulic system pressure and/or fluid
losses detected by the LDI system). The backup pump also maintains hydraulic pressure in the second stage of the tail rotor servo when the TAIL SERVO switch is placed to BKUP.
ON — With the No. 1 and No. 2 hydraulic pumps operating normally, the backup pump recirculates hydraulic fluid to and from each transfer module and maintains pressure in the APU accumulator and rescue hoist systems, as
required. The backup pump remains on until it is secured.
Automatic backup pump module operation is initiated by the LDI system when:
- Loss of No. 1 hydraulic pump pressure (#1 HYD PUMP caution).
- Loss of No. 2 hydraulic pump pressure (#2 HYD PUMP caution).
- Loss of No. 1 hydraulic reservoir fluid (#1 RSVR LOW caution).
- Loss of pressure to the first stage of tail rotor servo (#1 TAIL RTR SERVO caution)
The utility module routes hydraulic fluid from the backup hydraulic pump to:
No. 1 and No. 2 transfer modules
second stage of the tail rotor servo
rescue hoist
APU accumulator
The following criteria must exist to initiate the Hydraulic Leak Test
- Ac power.
- BACKUP HYD PMP switch in the AUTO position.
- All hydraulic reservoirs full.
- Weight On Wheels.
- Rotors engaged.
A satisfactory hydraulic leak test is indicated by the appearance of the following cautions/advisories:
- # 1 RSVR LOW.
- # 2 RSVR LOW.
- BACK UP RSVR LOW.
- SAS.
- BOOST SERVO OFF.
- AFCS DEGRADED.
- # 1 TAIL RTR SERVO.
- # 2 TAIL RTR SERVO ON.
- BACKUP PUMP ON.
- MASTER CAUTION.
