Basil : quote : 'some misguided souls considered placing them to FF an amusing way to commence taxi. RPM would drop and TGT rise. Not a great idea.'
Is this the answer to my original question then? When would this switch have been triggered on take-off roll - just before pushing the levers forward or during the spool-up. If switched before governing mode but after start of spool-up, this would explain my 70's sound. Given it was not the best idea, perhaps operating procedures were changed to specifically prohibit it in the 80's ....
Chris Scott : as a Twin Wasp and Dart man, is there anything in my 'theory' (see previous post - more like an idle thought) that a piston driver would be in the habit (or be required by procedures) of advancing the throttles faster than a 'pure bred' turboprop driver?
Ref to my other thread - any ideas on the asymmetric Viscount tailplane?