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with the phenomenon of “Power Lever Migration,” (PLM). That action may have played a role in the crash at KADS. For sure, it has contributed to other fatal King Air takeoff accidents. A spring at the engine-end of the power lever cable is always trying to retard the Fuel Control Unit (FCU) to its idle setting. Why? To ensure that the engine is not damaged when subjected to torque and temp limits that would be exceeded if/when the power lever cable malfunctions/ disconnects and tells the FCU to go to maximum Ng speed. Because (1) the Power Lever (PL) connects to the FCU on the right side of the PT6 and (2) the cockpit end of the PL sits slightly left of fuselage centerline, the left PL cable is significantly shorter than the right. Hence, it tends to move more freely, to have
less “stiction”... a combination of friction and stickiness. If the individual PL friction knobs are not both sufficiently “snugged up,” it is probable that both PLs will move, migrate back toward idle when unattended. Since the force a spring exerts increases as it is lengthened from its resting position, the pullback force increases as PLs are advanced.
Try it yourself in your hangar on your actual King Air. Turn both friction knobs fully counterclockwise (the looser direction) and push the PLs fully forward then take your hand away. Some of you will see no result, some will see one or both PLs move aft a little, and some will likely see the left lever move most of the way to idle and the right lever come maybe halfway back. It all depends on the “stiction” in your
actual airplane. Before you leave the cockpit, remember to turn the friction knobs clockwise enough to ensure they are “snugged up” to where you want them!
If the checklist step of setting proper PL friction before takeoff is overlooked and if the friction is too loose, the stage is set for a huge surprise when the pilot releases the power levers to reach for the gear handle! In most cases (thank you, Lord!) the outcome is more humorous than scary. Of course the pilot sees the levers move and he immediately puts his hand back on them and advances them as desired ... probably with the gear still down. Now it’s a matter of taking his left hand off the control wheel long enough to (A) get the gear up if the handle is on the left side of the cockpit as it is in all newer
OCTOBER 2020
KING AIR MAGAZINE • 27