If your autopilot is not performing as well as it once was, there are a few quick items you can easily check.
If your King Air has an AP-105 system and is exhibiting symptoms of "loose" altitude hold, it may be time to take a look at your 590A-3( ) altitude control sensor. The 590A-3H sensor is a motor-driven gear train that with time wears and causes altitude hold "bumps," or intermittent pitch excursions, when altitude hold mode is engaged. This can also cause altitude preselect capture overshoots.
Another common squawk is porpoise in altitude hold mode. If your system has a 590A-3K1 installed, even though it does not have a mechanical gear train like the 590A-3H, it can cause the same symptoms.
Of course this is only one of the components that can cause degraded autopilot performance. Feel free to call a Duncan Aviation Components Tech Rep with your symptoms and we will help you to determine the most likely cause.
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