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# HYDRAULIC
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### ENG PUMP SHUTOFF BUTTON
**PUSH IN:** Closes the hydraulic shutoff valve (SOV), isolating the respective engine driven pump (EDP) from the associated hydraulic system.
**PUSH OUT:** Normal position.
### ELECTRIC HYDRAULIC PUMP SELECTOR KNOB
**OFF:** Turns the respective pump off.
**AUTO:** Back-up for the respective EDP.
In flight: Activates in case of
* EDP or engine fail, or
* Flaps selected > 0.
On ground: Activates in case of flaps selected >0, and
* TL set to takeoff thrust, or
* Groundspeed > 50 kts.
**ON:** Pump operates continuously, overriding system logic.
Note: ELEC PUMP 2 in AUTO: If engine 1 running and parking brake released pump turns on (Single engine taxi logic).
### PTU (POWER TRANSFER UNIT) KNOB
**OFF:** PTU is turned off.
**AUTO:** Allows the PTU to operate automatically, according to hydraulic system logic.
**ON:** Operates continuously, overriding system logic.
### HYDRAULIC SYSTEM 3 SELECTOR KNOBS
**OFF:** Turns the respective electrical pump off.
**ON:** Turns the respective electrical pump on. 3B overrides system logic.
**AUTO (3B):** Turns 3B on automatically if AC Electric Pump 3A fails.
{% hint style="info" %}
The PTU does not work on the ground.
{% endhint %}
Note: HYDRAULIC SYSTEM 3A pump is powered by the AC ESS BUS (Electrical Emergency).