Biggest problem with blown slats and flaps is not the loss due to bleed
air but the hazards, maintenance and weight of the necessary plumbing.
The USAF gave up on the F4D/E boundary layer control sytem (blown LE
and TE) because of the never -ending problems associated with the BLC
system, primarily the valves but also after losing a few birds due to
ruptured ducts and the very hot (ca 700+F at takeoff) hot air causing
electrical and hydraulic failures plus igniting fires. Net result was
raising the basic approach speed from 122 to 144 KIAS on the D-model.
Nort having to land on carriers and being blessed with 8000'+ runways
teh choice was a simple one.
