as i read in the 737 manual from Smartcockpit.com all the surfaces of the plane can be power either A or B hidraulicsif the electrical system is working but not the engines, the hidraulic system must be able to move the flaps, but it does notin the other side, with the engines running the flaps can move. this is not good done, because with one of the sistem running (A or :( all the surfaces of the plane must work (elect or eng)

Before I forget, you should sign your posts in this forum with your name.The 737's two hydraulic systems are redundant, as you infer. However, I don't believe the aircraft has an electrically-driven pump to power hydraulics; therefore, either the APU or an engine needs to provide the power.The flaps are probably powered by a hydraulic motors, as are most larger aircraft.So, the logic is an APU or engine is required to power hydraulically driven surfaces including flaps. Electric power alone is not enough.That's my understanding.

On a 737NG, the trailing edge flaps drive unit is powered by the B hydraulic system in normal mode. If you loose the B system, then the trailing edge flap drive unit is powered by an elctric motor when the Alternate Flap mode is selected on the overhead panel.Bur your right, with the engines shut down, and B hydraulic pumps on, you would be able to cylce the trailing edge flaps and the leading edge flaps with hydrualic power.John Floyd

Just to add, the PMDG 737 trailing edge flaps are correctly modeled. With the engines shut down, electrical buses powered and the B hyd pumps on, the flaps will cycle on the ground. Make sure the B Hyd pumps are on and the Low pressure lights are out on the overhead panel. Operating trailing edge flaps electrically is an alternate mode in flight and used mainly in an emergency if there is no B hyd system pressure. Good luck,John Floyd

"as i read in the 737 manual from Smartcockpit.com all the surfaces of the plane can be power either A or B hidraulics"Not really true. The Trailing Edge Flaps are powered by system B and only half the spoilers will work if you lose a hydraulic system."if the electrical system is working but not the engines, the hidraulic system must be able to move the flaps, but it does not"Are all your electrical busses powered? If only the Battery Bus is powered, your flaps are not going to move (either hydraulically or electrically).I think you may have misunderstood something which has been written on Smartcockpit (or Smartcockpit has made a generalisation). It may have been referring to ailerons, elevator and rudder, not the other surfaces.Also remember that electric powered motors/pumps are generally weaker than engine/air-powered motors/pumps. Surfaces like flaps may move slower using electric hydraulic pumps (and a lot slower using electric motors)Hope this helps.Cheers.Q>