Hello! Just curious why you have your left engine hydraulic pumps turned off before the engine starts. I noticed that this feature is done mostly by North American airlines, while in Europe they used to turn and keep them on after aircraft walk around.
The A system hydraulic pumps control the nose wheel steering on the 737. Most pushback tugs in the US utilize tow bars for aircraft pushback. According to Southwest's company procedure, the A hydraulic pumps should remain off until the tug has been disconnected to prevent unexpected nose wheel movement when interacting with the nose gear and bypass pin. If there is an input to move the nose gear while the hydraulics are pressurized, the nose wheel could swing after the removal of the bypass pin. If the tow bar were still connected, this could potentially cause damage to equipment or injury to personnel.
What's the add on for the push back?
Hello! Just curious why you have your left engine hydraulic pumps turned off before the engine starts. I noticed that this feature is done mostly by North American airlines, while in Europe they used to turn and keep them on after aircraft walk around.
The A system hydraulic pumps control the nose wheel steering on the 737. Most pushback tugs in the US utilize tow bars for aircraft pushback. According to Southwest's company procedure, the A hydraulic pumps should remain off until the tug has been disconnected to prevent unexpected nose wheel movement when interacting with the nose gear and bypass pin. If there is an input to move the nose gear while the hydraulics are pressurized, the nose wheel could swing after the removal of the bypass pin. If the tow bar were still connected, this could potentially cause damage to equipment or injury to personnel.