magine the friction is not set properly before takeoff..
roll down the runway, airborne, hand off lever to raise the gear... and this happens. hardly enough time for the lever to go back?
A common well known example of throttle semi-closure was the Dakota (DC3) which had a throttle friction nut directly beneath the throttle quadrant. Occasionally a throttle or even both could fall back towards idle if the thottle friction nut had not been sufficiently tightened by the PM. That was one reason the PF kept his hand firmly on both throttles during the takeoff run and initial climb. Same reason that the PM kept one hand behind the throttles in case the friction nut didn't do its job because of faulty servicing or more often if some pilot did not write up the defect in the MR after flight.
On rare occasions where the Dakota was flown by only one pilot up front and no one in the RH seat to whom you could delegate operation of flaps and landing gear levers, that was where failing to have the throttle friction nut firmly tightened could cause a problem. As the pilot reached across and down to retract the gear leaving the throttles momentarily unguarded, one or more throttles would close towards idle. A competent pilot would be aware of this probability and delay retracting the landing gear so he could keep one hand firmly on both throttles.
In the case of the Kingair Essendon accident I would have thought it would be extremely doubtful one throttle would "migrate" towards idle without the pilot being aware of it and taking immediate action to restore power.
Back in the 1950's an airman at RAAF Base East Sale got pissed and decided to have a go at flying a Dakota. I think it was night time. He started both engines and taxied to the runway and took off. Witnesses heard the sound of an engine surging after the aircraft lifted off. It was also possible the airman (who had no flying qualifications) failed to uncage the gyro instruments after start up meaning the artificial horizon did not work. That was pure speculation as to why the aircraft crashed shortly after getting airborne. Another theory was when the airman let go of the throttles to retract the landing gear he had forgottem to tighten the throttle friction nut. One or more throttles would have certainly slipped back causing the aircraft to yaw and/or roll and a crash was inevitable.
In the case of the Kingair accident where one theory was a throttle slipping back due to a friction nut defect. if this is a common "problem" with the friction nut design on the Kingair, why was it not written up earlier in the MR as a airworthiness defect.? It might have saved a few lives.. Would not this defect been apparent during scheduled servicing if the servicing had been diligent? Do all Kingairs still have this defect of a dodgy throttle friction nut? . If so, looks like some pilots may have a complacency problem. Isn't that what the much vaunted subject of TEM is all about?