KI256 Repair and Turn Coordinator Replacement with RCA 2610-3

[moosebreath]

I recently completed an IPC during which we did some partial panel work.  After this I decided it was time to replace my turn coordinator with a second AI.  I have a KFC 150 installed in my M20J and the main AI, a KI 256, is the only vacuum instrument in the panel.  I have both an engine mounted and a backup electric vacuum pump.

I simply do not like the look of most modern electronic instruments.  I want my AI to be an AI not a multifunction display.  Electric mechanical gyro AI are expensive and require a hole to be drilled in the panel for the erecting knob.  If possible I did not want to install another mechanical gyro.  I discovered the RC Allen 2610-3 which is simply an electronic AI.  They are available with several different combinations of options including a rate of turn display, pitch sync, an electronic or physical slip/skid indicator, and a battery backup.  The cost is approximately $2600 new depending on the options selected.  Installation requires two wires, power and ground, plus the correct size breaker.

I believe it was on Mooneyspace that I saw that RC Allen occasionally has reconditioned units for sale.  I called them expecting to hear that none were available and instead was told "Why yes we have two!  Our complete model with pitch sync, electronic slip/skid, and rate display is $1500 with a two year warranty."  I purchased one immediately.  Battery backups are listed as an option but I was told they were having difficulty getting the parts for them.  This was not critical for my installation as I would now have an electronic AI and a mechanical gyro AI with two vacuum sources.

The 2610-3 requires a one amp breaker and the existing turn coordinator had a two amp installed.  The new breaker was $25 from Aircraft Spruce.  Unfortunately the breaker is mounted in the middle of the breaker panel, the least accessible possible place.  It was VERY tempting to cheat and simply put a one amp breaker in line behind the panel. However, I decided to have it done properly and there was significant labor involved in removing the breaker panel and swapping the breaker.  It is interesting how the simplest modifications can have unexpected complications particularly instrument / avionic mods.  Take a look at your breaker panel, it was not designed for easy maintenance and modification.

The final cost for purchase and installation of the 2610 including the $350 I made selling the old turn coordinator on eBay was $2300.  This is less than a new 2610 alone so I am quite happy.  The instrument works perfectly and does nothing but provide an AI, turn rate indicator, and slip/skid ball which is what I desired.  The display is a bit washed out in direct sunlight but direct sunlight is not when it is going to be most needed.

From a failure analysis perspective I now felt I had a great system.  The only critical single point failure was of the KI256 itself which would disable the autopilot.  Two weeks later an hour into a three hour flight home in perfect weather the KI256 decided the plane was flying at 10 degree pitch up while it was straight and level.  This made me sad but not nearly as much as if it had occurred in IMC with only my turn coordinator as a backup.

There are a lot of posts that say at this point I have the perfect opportunity to install a GI 275 and rip out my vacuum system completely.  I discovered it IS possible to make the GI275 simply act as an AI with flight director and drive the KFC 150.  At retail a GI275 with autopilot option is $5215 and a KI256 adapter plate is $119.  That is $5334 for parts alone.  Further, I actually like my KI256 display and prefer it to the look of the GI275.  In addition installation of the 275 means having the avionics folks spelunking deep into my panel and autopilot which currently works perfectly aside from the KI256 failure.

Bob Bramble of Aerolab Aviation Services specializes in the repair of KFC autopilot systems.  I am apparently not the only owner in the world that simply wants to fix their existing system instead of replacing it with the latest Garmin equipment.  Bob replaced the rotor and bearings in my KI256 in two days for $1750 with a two year warranty.  Removal of the KI256 involves disconnecting one electrical connector and two vacuum hoses then removing it from the panel.  I admit we did have to cut one of the 23 year old vacuum hoses to get it out.  However that is nothing compared to the complication of replacing it with a 275.  The total cost of the repair including two day round trip UPS shipment and installation was $2400.

The point of this post is that I now have an electronic backup AI and an overhauled KI256 for a total installed cost of $4700.  This is less than the cost of a GI 275 without installation and provides an independent backup AI.  I also avoided, from my perspective, the inevitable aggravation of having to troubleshoot the installation of an electronic replacement for the KI256 which I wished to keep.  The KI256 will not last forever, but I will not either.  The air driven gyro has a backup pump and can be overhauled twice for less than the cost of a GI 275.

I admit to a strong preference for the look and function of my existing panel and also a dread born of experience of letting the avionics folks into it.  I was honestly surprised however both how much less expensive it was NOT to install a GI 275 and how rapidly the work I had done could be accomplished.

As a final note, Bob Bramble has repaired a bazillion KI256 and states that it is almost never required to align a repaired one on the bench to the KC192 computer.  He also stated that bench alignment normally is required if the KI256 is used in the older KFC200 system.  This might explain the diversity of experience with replacement KI256 found when you search for posts on the subject.