FEBA
Sorry, but you have to read that sentence you pulled out as a quote in the context of the whole para:
Try reading the whole para again....
Lockheed decided to turn the engine into a sort of turbo prop on the downwind leg by using a shaft to drive a lift fan behind the cockpit. Complicated mechanically, but very efficient when it came to generating lift. Taking 26,000 shaft HP out from the engine reduced the thrust at the back by 6000lb. But that same SHP produced 16,000 lb of thrust when driving the fan. A gain of 10,000lb of hover capability over a pure jet. Rather more than an edge in a competition?
When the clutch is engaged and the fan starts to produce lift it is producing 16,000lb for the loss of only 6000lb at the back. That is VERY good news indeed. The fan is only driven in the circuit.