NATOPS CH2.8 Hydraulic System Flashcards
To what do the hydraulic pumps provide pressure?
Three hydraulic pumps provide pressure to the hydraulic omponents of the flight control system, the APU accumulator, and the rescue hoist system
A utility hyydraulic pump also provides pressure for the sonar reeling machine
What is the hydraulic system pressure?
With the exception of the Pitch and Roll trim actuators in the pilot-assist servo assembly (1000 psi) all components of the hydraulic system receive 3000 psi from the hyd pumps
What does the No. 1 Hyd Pump operate?
The No. 2 Hyd Pump?
The No. 2 Hyd Pump operates the first stage of the primary servos and the first stage of the Tail Rotor Servo
The No.2 Hyd Pump operates the second stage of the priamry servos and the pilot assist servo assembly
What is the purpose of the Trasnfer Modules?
They route fluid from the Hyd Pump to the appropriate servos and system (TR or PASA)
They also contain the logic to route backup pump fluid in the event of a leak and to secure fluid from from the main pump when the Servo Switch is used
How do you supply/remove power to the various parts of the Pilot Assist Servo Assembly?
Hydraulic pressure (1000 psi) to the pitch and roll trim actuators is controlled by the TRIM push button
Hydraulic pressure (3000 psi) to the Boost servos and SAS actuators is controlled with the SAS/BOOST push button
What does the Backup Pump provide pressure for?
The backup pump provides hyd pressure to the
- No.1 / No.2 hyd systems prior to rotor engagement
- Pressure to the rescue hoist system
- Recharges the accumulator
- Emergency pressure to the No.1 / No.2 Hyd systems and the Second Stage TR Servo
If the Backup Pump CB is popped, how do you reset it?
If the CB is out and a condition exists that requires the backup pump to operate, either the hydraulic system must be configured so that the backup pump WILL NOT activate upon resetting the CB (setting the Switch to OFF satisfies this on the ground) or AC power must be secured, prior to reseting the CB.
Damage to the current limiters may accure and will be indicated by a loss of all loads on the No.1 AC Primary bus
What is different about the backup pump?
How long does it take to energize?
The backup pump is powered electrically and requires a depressurizing valve to reduce output pressure until the pump can supply the full 3000 psi
It takes 4 sec on APU/External power, or 0.5 sec with either main gen on to energize
Describe how the backup pump will react to the various switch positions
On the ground
- OFF: Pump stays off
- ON: Pump stays on until secured
- If Main hyd pumps are operating backup pump will keep pressure in APU accum and rescue hoist, and circulate fluid to transfer modules
- AUTO: Pump automatically maintains pressure to No.1/No.2 Hyd systems and TR servo as required
In flight
- OFF or AUTO: Automatically maintains pressur to No.1/No.2 hyd systems and TR servo as required
- ON: Pump stays on until secured
- If Main hyd pumps are operating backup pump will keep pressure in APU accume and rescue hoist, and circulate fluid to transfer modules
How long does the backup pump run to charge the accumulator?
When the APU accumulator is low and the backup pump is activated, it will run continuously for at least 90 sec (180 sec if winterization kit is installed) regardless of the switch position
When will the backup pump automatically be initiated?
- Loss of No.1 Hyd Pressure (#1 HYD PUMP caution)
- Loss of No.2 Hyd Pressure (#2 HYD PUMP caution)
- Loss of No.1 Hyd Reservoir fluid (#1 RSVR LOW caution)
- Loss of pressure to the first stage tail rotor servo (#1 TAIL RTR SERVO caution)
What does the Priority Valve do?
When the backup pump is supplying pressure to the #2 Tail Rotor Servo, the priority valve may s_ecure hydraulic pressure to the rescue hoist_ due to low system pressure
Describe the function of the Velocity Fuse
The velocity fuse, installed in the utility module, secures fluid flow to the APU accumulator if the flow rate exceeds a perscribed limit
(if you have a slow leak in the accumulator it isn’t going to help you any)
What is the purpose of the Leak Detection and Isolation system?
The LDI is designed to assist in the isolation of hydraulic leaks
When and how does the LDI work?
What if it didn’t work?
if the LDI detects a low fluid level condition in one of the hydraulic pumps it will attempt to isolate the leak.
If the leak is in the No.1 Hyd system, the LDI assumes the leak is in the first stage of the tail rotor servo and secures hyd pressure to that stage (This turns on the backup pump pressuring the second stage servo)
If the leak is in the No.2 Hyd system the LDI assumes the leak is in the Pilot-assist servo assembly and secures pressure to that assembly
If the leak continues after the initial isolation, the LDI system will r_e-open the respective shutoff valve_ after which pilot action is required (EP)
