KFC150/KFC200 Auto-pilots

[William Wolcott]

There are three of us that are shopping for an A36. We noticed during our research that the later model Bonanzas (1990 and newer)seem to come equiped with a KFC150 a/p, and the older models (1980-1990) seem more likely to have the KFC200.

Are the capabilities and/or reliability of the two models different?  We've spoken to a few owners with the KFC200 that said they were very happy with its performance both in cruise and approach modes.  We want to make sure that the KFC150 is not a step backwards.

[Tracy Ryan]

As far as flight characteristics and capabilities are concerned there really is no difference. The two main differences are that the KFC150 controller is mounted in the radio stack, and the KFC 200 is a more modular system for more panel space restriced aircraft. But it also allows for a better pilot functional layout since you can put the mode controller in a place closer to you without reaching.

 

The other most notable difference is in the servo motors. The standard KFC150 system came with KS17x series servos, and the KFC200 system came with KS27x series servo motors. The KS17x series are all in one servos where the motor and bridle cable capstan are essentially one piece. This makes maintenance a bit more difficult and costly since anytime the server has to come out, the bridle cable also has to be loosened, or removed.

There was an optional KFC150 system number that included the KS27x series servo motors and these are much superior to the KS17x series. These servo motors are a two piece arrangement. The motor itself is one unit with a small spur gear that meshed with the mating gear in the more permanent KM27x servo mount. The KM27x is the part that is hard mounted into the aircraft and includes the bridle cable capstan. The servo motor itself then bolts to the servo mount. This way you don't have to disassemble the bridle cable for servo motor maintenance, and this is a big time saver. Thats not to say that the mount doesn't have to come out at some time or other, but its far less likely that it will need to be removed than the servo motor itself. The KS27x series servos are a heavier duty servo and will last longer between maintenance. All KSxxx series servos can be expensive to repair or replace, depending on condition. And the KS27x series being more robust gives the autopilot a bit more authority which will show up in turbulence.

Both of these autopilots are long since retired from manufacture by Honeywell Bendix/King, but parts availability and overall reliability is good and many shops gladly work on them. Reliabilty is only as good as the last shop that worked on it. The KI525 HSI and the KG102 gyro should be looked at very closely. I've seen many that have never had any maintenance at all, and the rattling/grinding of the bearings, and general instability in the compass system, can make for one nervous autopilot and some very unhappy passengers as well as pilots.

Tracy Ryan2011-02-10 20:48:12

[William Wolcott]

Wow.. Thank you Tracy.  Much more information than I had hoped for, and extremely helpful.

I am happy to hear that characteristics and capabilities of the two a/p are essentially the same.  We're still in the midst of our search, but my bet is that we will likey choose an early to mid 80's A36, and so more likely a KFC200 along with it.  That being the case, I will direct my energy to a functional test of the a/p, and investigate what, if any, attention has been paid to the HSI and KG gyro.

Beyond examining the logbooks what can be done to assess their condition?  Is it possible to have them bench tested.  I can understand that without properly functioning gyros the auto pilot would likely be erratic at best.  Seems like a good thing to do as part of the pre-buy.