Some idea of the possible/probable asymmetric problems of the PR9 may be gained from the following tale. It should be remembered that there was not, of course, a two stick PR9. So the first time that a pilot flew it solo, was the first time that he flew it.
There were 2 crews on my conversion course, my crew and that of ‘M M’. After a few ‘solo’ sorties, we were at the phase of experiencing the different ‘wind up’ rates of the various RR209s.
Most people will know that, the time from ‘flight idle’ to full power could vary by quite a few seconds, with different engines. Also, as has been stated, most of the sharp end of the power came in the last 10% of the RPM range, i.e. from 8000lb thrust at 90%, to the max 11250lb at 100%.
To demonstrate this, and to give some practice at ‘rudder juggling’, the following profile was flown.
The aircraft was to be flown to FL200 (about 20,000ft to our non flying friends) and towards the top of the climb, the speed allowed to decay from climbing speed of 330kts/0.72M, to about 130kts (ish). Then a good old look around etc, and select 2 extra fuel pumps. The throttles were then to be fully closed, and the speed allowed to decay to 90kts, i.e. getting towards stalling speed. And, of course, way below the safety speed of 170kts.
At this point, both throttles were to be slammed fully open. This is where the fun started.
My Nav and I did this first, in the morning slot. And believe me it was an exciting ride. But I was lucky, and both of my engines wound up reasonably well together, and with judicious and fast juggling of the rudder pedals, the aircraft was kept basically straight and level.
Then, in the afternoon slot, it was the turn of ‘M M’ and his Nav. However they did not have the same aircraft that we had used in the morning.
After they had landed from the sortie, I went to have a chat with M M. As I approached him, I though that his eyes seemed a bit wild, and he had aged somewhat.
He told me that he had flown the aircraft as briefed, and slowed the aircraft down to 90kts etc. He then ‘whanged’ the throttles open. The stbd engine did its best, but just could not keep up with the port one. And just as the port reached 100%, the stbd was struggling past 70%. It was at this point that the PR9 flicked. He recovered the aircraft at about FL100.