It sounds rather as if the York and the Lincoln auto-pilots were the same as the Lancaster auto-pilot, which went something like this.
An Arrow compressor on number 2 engine supplied air at 45 p.s.i. to spin the gyro and power the motor that drove the elevator control run. There were two control levers, one marked "Spin" and "In" which spun the gyro up and allowed it to erect to the the Earth's gravitational field, or alternatively locked the gyro to the aircraft's pitch attitude. The other lever operated a dog clutch which mechanically engaged the motor to the elevator control run. This clutch allowed you to disconnect the elevator from the motor in the event of a malfunction.
The approved procedure was to engage the clutch before starting engines but this made the elevator control rather heavy and so the the usual method was to engage the clutch and then to move the control column fully forward and back to ensure that the clutch was properly engaged and then to neutralise the control column and disconnect the clutch. It should then engage easily in flight.
However, if you forgot to synchronise the clutch plates and took off with the auto-pilot dis-engaged it might not engage when you wanted it. This could be fixed by the manoeuvre that you described but the preferred method was for the Flight Engineer to go down into the nose and to kick the clutch plates round until they dropped into engagement.
Ah, the smell of 100/130 and hydraulic fluid!
Last edited by Lancman; 9th Apr 2013 at 15:50.