KI-256 calibrating to KFC-200

My avionics work is done by GAMA Aviation at Fairoaks (EGTF). I have a KFC-200 and KI-256. I’m very happy with their work and standard of knowledge.

It’s worth the price of a telephone call to +44 1276 859283.

Hope this helps.

Avionik Straubing in EDMS is about 45 min from your home base. That’s probably the most qualified shop in Europe.

I know the KFC225 – I wrote this – and not the KFC200, but they are probably similar in these aspects.

The KI256 contains pitch and roll pickoff coils – essentially, for each of the pitch and roll axes, an LVDT which is excited with a waveform produced by the autopilot – and the autopilot contains adjustments for the variation in the signals which these produce. On the KFC225, these are stupidly located as trimpots (doubly stupidly on a digital product which could store values in an EEPROM) on the side of the KC225 computer, so to get to them you need the $1500 bus extender (which I have) so you can get a little adjustment screwdriver into these trimpots.

If you get a KI256 Mod 11 and you get the KC225 adjusted for it then it is much less likely that you will ever need to do that adjustment again if you change the KI256 for another Mod 11 unit.

There is no usable adjustment in the KI256.

The autopilot adjustment needs to be done with the whole aircraft; you can’t do just the autopilot on the bench unless you have a complete test harness for that particular model and I am damn sure no European shop will have that. No UK shop has it for 100% sure (I have been to them all). Lees Avionics (Gama) can do it but they need the whole aircraft. And I am not sure whether they can do it unless Harry Lees is personally present (they certainly could not last time I used them for this, c. 2008).

The great thing about sending stuff to the USA (e.g. Castleberry Instruments for the KI256; they actually used to make them for Honeywell in the early days) is that they have the volume and the experience. There is much less experience in Europe. The last KI256 I had repaired in the UK took 6 months (luckily I have a spare on the shelf) and when it came the company said, in the best “British builder fait accompli” tradition, that they no longer can generate any paperwork for it! I am fed up with the crap service I have had in Europe.

sending the Autopilot Computer + KI-256 to USA isn’t really an option either.

I don’t know how many US shops have the bench setup for this test. The big ones like Autopilots Central might have.

They wanted 2500€ for repairing my KS-271A roll servo.

You can probably get a new/overhauled one from South East Aerospace in Florida Just be aware that there is no mandatory replacement at overhaul of either the motor or the tachometer, so you can get an overhauled servo with a knackered motor/tacho in it…

The KFC200 is normally a very good autopilot which doesn’t have the major servo burning-out issue of the KFC225. The servos ought to last 1000-2000hrs on the KFC200.

In my experience, the German firm mentioned has an “interesting” attitude to people who want to give them money – which I find highly unattractive. But others are happy with them, so clearly this varies.

AFAIK the GAD43 (and also Aspen’s EA100 which does the same job for their EFD1000) just emulates the two (pitch and roll) pickoff coils of the KI256.

I think these products take in ARINC429 pitch/roll data (from an AHRS gyro which generates ARINC429 pitch/roll – like my Sandel SG102) and emulate an LVDT.

(It’s quite a fun thing to design; I thought about doing it for the SG102 and getting an FAA STC for it – for use as a backup pitch/roll source for the KFC autopilots. But I think the market is too small.)

The emulation could be done “totally precisely” but if an autopilot has been previously calibrated for say one KI256 and then it is used with the GAD43, it could be out just the same.

My guess is that (unless Garmin and Aspen did a truly crap design) once an autopilot is set up for one of these boxes, it will never need its pitch/roll nulls re-adjusted. But who knows?

BTW the tachos (Faulhaber) are about €40 each – obviously not from an “aviation” source but I can’t see you need that so long as you get a CofC. The Globe motor is not obtainable separately (I have tried) but I vaguely recall it is priced around $500.

Due to these issues, and Honeywell’s refusal to even admit there is an issue for over 10 years, there is a lot of unofficial KS270x servo repair going on in the field. I know of several avionics shops that do it (Europe). Any good electronic engineer can do it. The issues are obtaining some of the parts. If the mechanicals wear out, there is nothing you can do, but they rarely do. The motors cannot be obtained (except the brush assembly which is same as a standard Globe motor, about €200).