If you are working with any of the flight controls, it is always better to switch OFF the 2 flight control switches and 2 flight spoiler switches in the cockpit on the P5 panel. Because of this all flight controls and flight-spoilers will be without hydraulic pressure even when hydraulic pressure A and/or B is present , by means of closing the shutoffvalves in the wheel well. For activities on the tail the 6 valves in the tail-compartment can be closed also, for extra security. This is possible only at -3/4/500 and NOT at -6/7/8/900!
However convince yourself always if the shutoff valves in the wheel well are closed indeed. Moving the switches on the P5 panel to OFF gives you no guarantee that the valves really close. This is because frequently you don’t look at the circuitbreakers of the valves. If these are pulled then nothing happens, and it gives you a false feeling of being safe. And if the de-activation-tools are placed on the valves, it is difficult to see in what position they are. It happened they where “de-activated” in OPEN position instead of closed ! Therefore always look in the wheel well to see the position of the valves . See pictures.
Open : the RED lever is at position 1 (to the RIGHT)
Closed: the RED lever is at position 2 (to the LEFT )