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MAINTENANCE TIP
Troubleshooting Autofeather
by Dean Benedict
In recent months I’ve fielded quite a few calls on the autofeather system in King Airs. In one case I was engaged to assist a shop with unraveling an autofeather mystery. The system was inoperative on one side and they had taken every conceivable step to fix it, with no luck.
As the tech outlined the actions they had taken, it sounded much like what I would have done. They swapped things from side to side. They replaced pressure switches and relays. Maybe they went a little overboard in changing every switch and relay in the system, but nothing fixed it and they were desperate to solve the problem.
It happens. When the source of the problem proves elusive, the tendency is to change everything and hope for a fix. As the story unfolded, there was one thing I kept wondering about – engine torque – is it really getting down to 200 foot-pounds?
Remember: Prop blades are kept in flat pitch by oil pressure. Engine torque drives oil pressure to a pressure
APRIL 2023
KING AIR MAGAZINE • 15