Why do you pressurize hydraulics before pushback (744)

[rudderrudderrat]

Hi RandomPerson8008,

It's been a long while - but from memory SYS 4 did Normal brakes, Sys 1 did Alt brakes & steering. Although the hydraulics to the nose wheel steering is isolated by the steering pin - the body steering is still available and it helps with the tight turns during push back. We pressurised sys 4 first to prevent hyd fluid migrating from sys 1 to 4 through a shuttle valve in the brakes system.