B737NG Elevator Tab
 

Can someone tell me, is the tab on the 737-700 elevator, hydraulically operated? I cant seem to find much info on the subject. I'd like to know more on the tab operation. Thanks,
JP

In normal hydraulic operation, the tab does not move relative to the elevator. It is locked in place by hyd pressure.
But when you go to manual reversion, loosing hyd pressure,it is unlocked and is geared to the elevator and works as a tab.

Sorry Steve, but this is absolute wrong. :=

When the flaps are up, the elevator tab is working like a balance tab.
When the flaps are not up, the elevator tab is working as a anti−balance tab due to a hydraulic actuator at the elevator tab control mechanism.
In manual reversion there is no hydraulic present at the actuator and the tab works as a balance tab regardless of the flap position.

A picture is worth a thousand words. This one from here:

http://www.b737.org.uk/images/ngelevtabs.jpg