Originally Posted by
tartare
Was thrust split between the main nozzles fore and aft to control pitch in hover and low speed flight, as well as the puffers in the nose and tail?
How was that done, given front nozzles were cold and back nozzles were hot?
No, the thrust split between the front and rear nozzles couldn’t be adjusted so all jetborne pitch control was on the puffers. The rear nozzles generated more thrust due to their higher exhaust velocity; this was dealt with by positioning the rear nozzles slightly closer behind the CofG than the front nozzles were in front of it so the moment arms balanced.
Differential nozzle control for roll and pitch was proposed at one point by a certain John Farley, as he recounts among other fascinating insights from page 120 onwards at
this link. Most interestingly in the context of this thread, he talks about the perceived ‘heresy’ of his aim to simplify the STOVL control system and the scepticism he faced both from the Hawker design office and from pilots who considered mastery of the nozzle control lever to be a marker of their elite status. He says the advantage of the VAAC testbed being a 2-seater was that test pilots with no Harrier background could fly and assess the control system with no such prejudice. Brilliant engineering that played a large part in establishing the UK’s early privileges in the JSF programme - and here we are in 2020 with F-35B STOVL such a walk in the park that no 2-seater is needed.