[A.A. Cunningham]

but in combat an aircraft would have to to lose airspeed to do it making themselves a sitting duck.

Don't know much about VIFFing, do you?

[Hillarys Gate Cult]

Yes I do. So what.

“Viffing also allowed a much tighter turn in combat manoeuvres, although there is little evidence to suggest that it was regularly taught to pilots, as the loss of airspeed could make the aircraft vulnerable to attack.”

http://en.wikipedia.org/wiki/Vectoring_nozzles