Honeywell KFC-225 autopilot - what could cause this failure?

[Rich Grise]

Hmm, good question. Still, it might be possible that rapid, very small
repositions could be imperceptible. I was just taking a wild shot at
this one.
--

I read somewhere that the F-16 is so unstable that a human
can't fly it without the computer control. I'd think that
means it makes corrections faster than a human can, but it's
making corrections to a known airframe, I guess. I'd think
they'd want the response time of an autopilot to be fairly
slow so it doesn't do abrupt stuff - but then it really
wouldn't be able to handle weather.

Cheers!
Rich

 

[Julie]

I read somewhere that the F-16 is so unstable that a human
can't fly it without the computer control. I'd think that
means it makes corrections faster than a human can, but it's
making corrections to a known airframe, I guess. I'd think
they'd want the response time of an autopilot to be fairly
slow so it doesn't do abrupt stuff - but then it really
wouldn't be able to handle weather.

Cheers!
Rich

Yes, this is true of all modern fighters.

If you watch movies of a takeoff or landing, you will notice the ailerons and
horizontal stabilizers fluttering all over the place in what is pretty much
straight flight.

 

[Joerg]

Hi Peter,

That's correct; also I have not been able to find the schematic of the
KFC225 servos anywhere. I have found out that there is no service
manual as such. One could design an exact functional replica easily
enough but frankly I have more pressing things to do

Would be a nice biz opportunity though if the legal side is properly
covered. If this problem is widespread people would be willing to pay a
premium for a servo that doesn't give up. You don't have to design it
yourself.

I remember a muffler maker in Europe who created an exhaust set for a
popular car that wouldn't corrode out in just a few years. It cost a lot
more but still the muffler replacement sales of the car manufacturer
then dropped substantially.

Yes, I could try placing some on the wires close to the oil pressure
gauge amplifier; that would not require any paperwork.

The clamp-on versions (just for ground tests) are often available at
Radio Shack. But usually only the large ones that still have the toolbox
type metal drawer shelves. Then when it works you could use real cores
but this often means re-doing at least one connector unless you select a
very large core (they come up to two inches O.D.).

Regards, Joerg

 

[Peter]

Would be a nice biz opportunity though if the legal side is properly
covered. If this problem is widespread people would be willing to pay a
premium for a servo that doesn't give up. You don't have to design it
yourself.

I am not sure about a premium price - the Honeywell servo goes for
about US$2000 already. I estimate the manufacturing cost to be around
US$100, plus maybe US$100 for the mechanicals.


Peter.

 

[Matt Whiting]

Yes, this is true of all modern fighters.

If you watch movies of a takeoff or landing, you will notice the ailerons and
horizontal stabilizers fluttering all over the place in what is pretty much
straight flight.

But it is only straight and level flight because of all of the control
surface "fluttering!"

Matt

 

[Paul Sengupta]

In the two years from new I have had perhaps a dozen failures.

It's not someone leavnig their phone on in flight is it?
That's been attributed to APs going a bit funny on
more than one occasion.

Paul