Honeywell KFC225 autopilot roll servo failure

Peter wrote:
I've just had my 6th failure of the roll servo, since 2002. This time
I got a video of it, showing that the power-up tests pass even with a
dead roll servo:

http://www.zen74158.zen.co.uk/misc-f...ure-2005-1.mpg

Evidently Honeywell have not fixed this - even though the KFC225 has
failed on every aircraft whose owner I have managed to contact over
the last few years.

Can anyone offer me any info on this servo, e.g. schematics? I already
have the KFC225 main unit schematics so I have the interface (which is
very simple).


Peter.
--

Did you contact Honeywell in Phoenix Arizona?

Mark

H are looking at it; I have no idea how far up the organisation any of
this has gone.


By "IT" do you mean they are repairing your one particular unit or are
they looking at the more general issue?

I would contact QC or engineering, not just the warrantee repair
people.

Mark

Hello Peter,

The indications to me (I am an experienced h/w and s/w design
engineer) is that nobody has done any analysis on the failures, and
that the failed units are simply repaired and recycled into the
production process, or perhaps into "warranty exchange" units, as is
normal in the avionics business.

If they really did that they would be racking up a huge liability
portfolio. In the world of med electronics the FDA would pretty quickly
shut down everything from production to sales, followed by a "root
canal" type audit of the QC process.

If you have the impression that the problem hasn't percolated to upper
management you could help that process along by a letter to the CEO.
Sometimes that does wonders.

In avionics, one tends to get items which are often several years old,
when getting a warranty exchange unit. I've had a 10 year old KI229
RMI supplied in this way.

That may be ok if it's a full refurb like it is done on engines, IOW
where you get a zero-hours paper with it. But from an ethics point of
view they should tell you if it's a refurb.

I wonder if there is some kind of lemon law for those parts. If you buy
a car in California and repair attempts failed x many times you can
demand a full refund.

Other than that, could there be spikes caused by either the servo motors
or by some other gear that fry something?

Regards, Joerg

http://www.analogconsultants.com

Hello Peter,

A unit comes back with a "defective" tag on it. It is going to go to
the person who originally designed it, and be checked out with lots of
instrumentation? Of course not. It will go back into the factory test
process, and if it passes the factory test then it is classed as
working.

That would be a normal process.

If there is an obvious fault that will get fixed, and statistically
that will likely be the only fault, so that is OK. The problem is with
faults that are intermittent, or faults that don't get picked up by
the factory test. I've been in electronics design/mfg for 25+ years so
know this problem well; in my business we scrap anything that comes
back, just to make sure.

If intermittent is flagged this should cause more diligence in the
repair process. If the test folks can't duplicate the error there should
be further investigation, at least in cases that involve a lot more than
one unit. That's where the QC system should kick in with its database
information. Or in the med biz, that is where the QC system has to come
in on a mandatory basis.

My warranty avionics bill totals something like US$100,000 and that is
mostly Honeywell avionics, added up at list prices, over 2 years.

I wonder how they survive. I ran a business for several years and
warranty overhead was factored in on a "per product" basis. My boss
would probably have fired me with cause if I had ever failed to see an
epidemic trend in one of the lines we offered. It never happened but we
watched that stuff like hawks.

On the part of the user I'd be mighty concerned about what happens after
the warranty period ends. After that, every time the servo hangs you'd
hear that slurping sound coming from your bank account.

Regards, Joerg

http://www.analogconsultants.com

Hello Peter,

Absolutely right! But you are assuming that there is a process for
feeding back the info from the original pilot. ...

Quite scary. In medical, if there isn't a process for that the FDA or
another agency shuts the place down.

I guess they survive because in a piece of avionics listing at $2000
the materials come to $100-$200. So the actual cost of supply of a
replacement is just the latter figure. This ratio would be true for
all avionics I've seen - right up to any IFR GPS.

I am not a pilot. My guess is that a roll servo failure usually doesn't
lead to a crisis situation but I don't know. If that happens on gear
that can cause grief the liability can be huge. $200 won't even pay for
a single attorney hour.

My warranty ended over 1 year ago. Honeywell offered me an indefinite
extension on the KFC225, all the time it keeps packing up. I also
purchased their extended warranty on all my other Honeywell kit -
$4000 for two extra years. I got that back within 6 months when the
KI229 RMI packed up (its 3rd failure) - that lists here in the UK at
about US$7000.

They really need to have someone look into that. Whenever I do that for
a client they usually break even on my fees within a month or so, just
because of reduced field returns. Others shy away from hiring a
consultant or other experts and try to hang on. Long term that won't work.

Just imagine if I would realize my dream of becoming a pilot. I'd
probably rent because of the cost but what if I didn't and needed an
autopilot? After reading your story here would I buy a Honeywell
autopilot? Probably not. That's the hidden cost of sub-par designs.

Regards, Joerg

http://www.analogconsultants.com