cleared to pressurize the hydraulics

[Commander_K 2]

hi,

when would the Flight Deck say this optional phrase to the Ground Crew? I could not find something about this on the Internet.

[threexgreen 3,156]

Usually it's done to make sure the airplane is clear of any equipment and ground crew before pressurizing the hydraulics for pushback as flight control surfaces on some airplanes will suddenly move into neutral position when pressurized after they've been 'hanging down'. Also, the nose gear may move upon pressurization so it's important that it's free and the tug isn't connected yet. This is all to avoid damage and potentially injury. Most of the time though standard procedures for pushback will make sure the airplane is clear anyway so the confirmation isn't always needed, hence it's optional and only necessary in certain situations. It may however also be always mandatory to confirm this in certain companies as part of their SOPs.

[Chock 17,769]

Normally what happens is when the ramp personnel finish loading the aeroplane's bags and cargo (usually at least ten mins before the thing is due to depart if they know what they are doing), they close the cargo doors and remove the ground service equipment from the aeroplane on the starboard side (belt loaders, high loaders and so on), then the cones are also removed from that side too. On the passenger boarding port side, there may still be steps or a bridge connected for passengers to board, but when all those passengers are on board, the steps are pulled away/bridge is retracted and the passenger door is closed and the cones go off that side too, as do the chocks off the mains and, so long as the tug and bar is connected, usually the nose chocks too, since the tug brakes will be on.

At this point the person doing the headset (i.e. the one who signals the pushback tug, removes the towbar at the tug release point, removes the steering bypass pin, and supervises the engine start etc) will do a final walkaround check of the aeroplane to make sure all the doors are shut and properly showing lock indications and that nothing is left around the aeroplane such as a vehicle, set of steps cone or whatever. When they know that everything is off the aeroplane except the tug and bar, they will go on the headset and call the cockpit and report something like. 'All GSE clear of the aircraft and all doors and hatches closed and secure'. the crew will then acknowledge that and may possibly add 'are we clear to pressurise?' to which the headset person will confirm 'yes, you are clear to pressurise'.

The reason for all that is because many cargo hold doors are forced shut by pressurisation, so the flight deck crew want to know that the ramp personnel will not be opening the hold doors to add any late bags or cargo, since they have finished doing their thing.

Edited July 7, 2021 by Chock

[Commander_K 2]

thanks a lot!