Squadron Signal Walk Around Number 9- F6F Hellcat; states on page 23:
"The flaps on the F6F-3 are hydraulically actuated via the engine driven
hydraulic pump. By use of a manual selector valve, the flaps can still
be operated after an electrical failure. They can also be lowered by
use of hydraulic hand pump. It takes some thirty-five cycles of the
hand pump to extend the flaps, and twenty-five to retract them."
...so - in normal operation they are electrically switched and
hydraulically driven, with a manual hydraulic pressure backup for