Originally Posted by
Kitbag
Jaguar PTR was indeed introduced as for AAR. It was found that the need to throttle the RH engine back at altitude to prevent surging left the driver without sufficient fine control of his airspeed on the LH engine- effectively he would have been at max dry or thereabouts, and any further increase in airspeed would necessitate going to Min reheat. This made the aircraft too fast.
Solution was to provide reheat from 80%Nh or Part Throttle Reheat, thus giving the driver a much greater degree of control at a critical point in AAR.
To ease commonality it was applied to all Jaguar engines and only required a bit of extra electrical string as far as the airframe was concerned. Think its the only type to have that facility but then when you look at the origins of the FCU its hardly surprising that little extras had to be added on to make it a militarily user friendly engine
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Use of 'n' is indeed as a result of maths/physics equations indicating rotational speed.
Utter balls. It was because the aeroplane above anything much above minimum landing mass had a hole on one engine thrust at max dry to maintain level flight and too much thrust at min reheat. Proven by the two incidents that happened to the French A single seater prototypes in May 1969. Brit test pilot saved the second by a blast of full reheat but scared the living daylights out of him. Jimmy Dell.