The most accessible and relevant info on this appears to be a couple of warnings from the Maintenance Training manual -
1. WITH ELECTRICAL POWER AVAILABLE, EVEN THOUGH HYDRAULIC AND PNEUMATIC POWER ARE OFF, ALL TE AND LE FLAPS WILL AUTOMATICALLY EXTEND OR RETRACT WHEN THE FLAP LEVER IS MOVED. PRIOR TO MOVING FLAP LEVER, CHECK THAT PERSONNEL AND EQUIPMENT ARE CLEAR OF TRAILING AND LEADING EDGE FLAP SURFACES.
2. LEADING EDGE AND TRAILING EDGE FLAPS WILL MOVE TO THE POSITION SELECTED BY CONTROL LEVER WHEN ALTERNATE ELECTRIC CONTROL IS DISARMED. CHECK THAT ALL PERSONNEL AND EQUIPMENT ARE CLEAR OF OPERATING PATH.
Leading Edge Flap sequencing Primary Control :
Extension - Group A LE flaps extend when the flap lever is moved to 1. Group B LE flaps extend when the flap lever is moved to 5.
Retraction - Group B LE flaps retract when the flap lever is at 1 and the inboard TE flaps are less than 41/2 (four and a half)units. Group A LE flaps retract when the flap lever is UP and the outboard TE flaps are up.
So, CCA, the answer to your questions are:-
Hydraulics? - not necessary.
TE signal - yes, for RETRACTION.
PS - This applies to the 747 - 400. The Classic is sufficiently different to require a further look-see. Will try to do that, if time permits.
[This message has been edited by Cornish Jack (edited 09 October 2000).]