Many of our Beechcraft Bonanzas, Barons and Travel Airs were/are
equipped with the ubiquitous Century Autopilot back in the day.
Yours truly has been flying behind a Century III since 2004 and I've
grown very fond of its capabilities of heading and altitude control.
Over these >2000 flight hours I've had to have the main brain box
repaired and a couple of servo overhauls done by an outstanding source, Autopilots Central.
IMHO, Autopilots Central has been the best a quickest source for
dispatching Century A/P gremlins and problems. I have found them not be a
CSOB priced solution, however, but you can take it to the bank that
your problems will be fixed.
I'm going to devote this page to some of the problems and CSOB
solutions that have been found by Century Autopilot owners that may be
able to address some gremlins fairly easily and inexpensively by your
Problem #1: Upon Altitude engagement, aggressive nose down occurs in CIII.
After checking with a couple of ace electrical geniuses who flew
behind CIII units, the guidance was to check the 2N3055 transistors in
the computer brain box.
Most digital V/Ohm meters have a transistor testing function
embedded. After checking the transistors, several were indeed found to
have failed. Transistor and pad replacement restored full functionality
of Altitude hold!
Suggestion is to photograph the innards of the box before detaching
any wires to insure that they all go back in the correct places.
Allied Electronics has the 2N3055 Transistors HERE @ <$2 each and the insulating pads are HERE @ <$2 each.
Problem #2: Intermittent Pitch Engagement
F33 owner Steve B., reported intermittent Pitch and diagnosed it to
high resistance in the pitch engagement switch that wouldn't always
close the servo solenoid. Some contact cleaner improved his situation
but he was looking for a longer term solution.
Steve reports that the switch is a direct connection to the
solenoids on the Roll and Pitch switches so they are prone to arcing.
He also reports that the Heading and Altitude switches are
logic/small relay control and in a pinch, could be swapped over to carry
the arcing load of the Roll and Pitch functions.
The switch PN is DB3C-A1AA and is available from Allied Electronics HERE and Newark HERE at about $2 each.