Hydraulics Flashcards
Which is the “heavy” system?
757-
767-
757- left system
767- center system
On the 767 the center system is the heavy system, is the only one with a ___.
The Center systems also has the what three things?
Standpipe
HMG, ADP and RAT
767 Air Demand Pump is known as the “handle pump” and is activated by things with a handle
IE: (3ish things)
- Flaps and slats
- Gear
- Speed Brakes / Ground spoilers
767 HMG - what get prioritized Electrics or Pneumatics??
Pneumatics- The only time you would see this is if you had a dual generator failure and then had to do a Go-Around. HMG would be needed for Gear and Flap retraction and you would need to be on the Standby Instruments for a while.
What protects hydraulic pressure to the flight controls?
RAT
What hydraulic system powers the rudder?
All three of them
When does the PTU run (757)?
Loss of Left Engine or of the Left engine-driven Hydraulic pump
757 Center Hyd system is mostly-
Center standpipe is for the-
- Flight Controls
- RAT which arms at 80 knots on T/O
757 Right Hyd system is mostly___
The standpipe is for-
- Breaking
- Reserve breaking
How many standpipes does the 767 have?
One- in the Center system
On the 757 can the PTU support the HMG?
Yes
Reserve break source on the 757?
Right side
Does the 757 alternate breaking system provide Auto breaking?
No
On 757-200 and 767-300 what IRUs would operate on the HMG
Left and Center.
The right would operate for five minutes on it’s internal battery but then drop off.
What powers the Air-Driven Pump on the 767?
Air from the center pneumatic duct
When the RAT powers the hydraulic system what does it support?
Flight controls.
Does the 767 have a PTU?
Not on the main Hyd system
It has a PTU on the pitch enhancement system which uses the right side to pressurize a small portion of the left side stab trim motor. It is only triggered my the electric trim switches on the yoke and operates at 1/4 the normal rate
FM 6.90.10.9
Does the Hydraulic Press light (757) or HYD PRIM PUMP (767) on the Engine driven pump switch illuminate for low pressure or low quantity?
Low pump output
On the 757 which side powers then PTU and which side does it in turn power?
The right side powers the PTU to supplement the left side
Can the Right Electric demand pump power the PTU if the Engine driven pump fails?
Maybe
“Without the right engine driven pump, PTU output may be insufficient.” FM 6.130.10.8
On the 757 when would the EICAS status page display PTU output pressure?
When the Engine-driven and electric demand pumps are inoperative
If you were on the HMG why might the flight instruments blank on a go-around?
Operating the gear and Flaps were simultaneously can cause the HMG to cavitate resulting in reduced electrical output and the flight instruments could temporarily blank.
HMG = Hydraulic–> Electric power
What happens when you press the “Reserve Brakes” switch on the 757?
- Configures the system to use the reservoir’s reserve fluid
- Activates the electric pump
- Isolates the pump output to only power the brakes
On the center hyd system which pump is inhibited when on one generator or only external power?
The Center #2 pump
Air Demand Pump- Other than when center system pressure drops below a preset value, when would it operate?
Whenever the Gear, Flaps, Slats or or speed brakes are selected it is automatically activated.
What changes if the Air Demand Pump is inoperative?
Gear and Flap operation times increase because it normally turns on to aid in providing pressure when they are extended or retracted
On the 767 what happens to protect pressure to the brakes if center hydraulic system press drops below 50%?
Center #1 hyd pump is isolated, reserve fluid is dedicated to supply #1 electric pump and pump output is restricted to brakes and steering,
How long with the RAT be able to supply adequate pressure on landing?
Down to 130 knots
Can the RAT auto-deploy on the ground?
No
When does the RAT arm?
At 80 knots on takeoff
What extends the RAT?
757?
767?
757- spring force
767- an actuator
What hyd system powers the Rudder Ratio system?
The Left
