Is my KFC 200 working properly?

[RobertE]

When on either heading or nav mode if I disconnect the alt setting, even if I've established some nose down pitch, my aircraft pitch increases in what appears to be the autopilot's attempt to maintain altitude, Sort of makes you wonder what "alt" is all about. I thought that the AP was designed to maintain whatever pitch existed when engaged, unless in alt mode. Am I wrong or is my AP not working quite right?

Thanks.

[PTK]

I'm not sure how you establish any pitch attitude with alt hold still engaged. Does your unit have a vertical trim switch? On my KFC150 alt hold has to be disengaged in order to establish a pitch attitude, which is accomplished by the CWS function, without disconnecting the ap. CWS releases the servos and initiates synchronization mode. After CWS is released ap will command whatever pitch it finds itself in. Alternatively, the vertical trim switch can be used, while alt is still engaged, to initiate a climb or descent.

If the ap is flying along in alt hold presumably it has trimmed the airplane. Now, if you disengage alt hold and the airplane wants to pitch up perhaps it was in out of trim condition all along and masked by the alt hold. Have you tried holding an altitude and trimming manually first and then engage ap and alt hold on then off? Does it still want to pitch up?

[RobertE]

I see I worded my question improperly. Specifically, if I engage the AP either in heading or nav mode, even with pitch down, it pitches up as soon as engaged. My question is, should it do this or, rather, simply maintain whatever pitch angle is then in effect?

[FlyDave]

With my KFC200, if I enable either HDG or NAV mode (no Alt mode) and engage the autopilot it will keep a level pitch attitude but not necessarily hold altitude. If I push either UP or DN on the pitch trim rocker switch the autopilot will pitch up or down accordingly and hold that pitch attitude - again Alt not enabled. If I enable the Alt mode, the autopilot will hold the altitude the airplane is at when I push the Alt button (pitch trim rocker switch ineffective).

I have a PDF of the KFC200 operating manual. PM me if you want me to send you a copy.

 

Dave

[PTK]

Have you tried to isolate the issue by using the fd? If it still happens with fd indicating a correction wanting to pitch down but the airplane is climbing then the ap is behaving properly and the pitch servo may need attention.

Does the pitch up happen right away upon engaging hdg or nav or is it delayed? If it's delayed then perhaps the trim servo is misbehaving. Do you notice out of trim condition when you simply disconnect the ap? If so auto trim may need a look.

I'd take the airplane up for a spin and do these and any more tests you can think of. It will save a lot of troubleshooting time. Then give Bob a call at Autopilots Central and discuss your findings with him. He is excellent. Number is (918) 836-6418.

Good luck!

[rainman]

The operation of my autopilot used to do the same thing you are describing. What I was told is that I need to turn off the FD when changing the ALT because it remembers the pitch setting from the last time it was engaged. When changing altitude when the NAV and ALT is engaged, if I change the trim, it disconnects the autopilot. If I just turn the autopilot back on at some new altitude, the prior altitude pitch info is stored so I need to turn off the FD then engage ALT. is this what you're talking about?

[RobertE]

The operation of my autopilot used to do the same thing you are describing. What I was told is that I need to turn off the FD when changing the ALT because it remembers the pitch setting from the last time it was engaged. When changing altitude when the NAV and ALT is engaged, if I change the trim, it disconnects the autopilot. If I just turn the autopilot back on at some new altitude, the prior altitude pitch info is stored so I need to turn off the FD then engage ALT. is this what you're talking about?

Maybe. I used it today in a climb (engaged heading mode only when pitched up) and it held the pitch attitude, just as desired. Tomorrow I'll experiment with the same thing while descending ( that is, engaging the AP when proper descent pitch is established) and see how it does. I'm wondering if my problem has been that heretofor I've been expecting it to maintain proper pitch simply when disconnecting alt. Time will tell.

[kortopates]

Always, always, always push the CWS button before engaging the autopilot to set the pitch or altitude where you want it; i.e. whether in ALt hold mode or not! Otherwise the the plane will dive or climb for the pitch or altitude the flight director last had - which could have been what you tested it with back on the ground - not necessarily what you are expecting. Rainman is correct, but no need to turn off the FD, just push the CWS button with the plane at the desired pitch or altitude.

[RobertE]

Always, always, always push the CWS button before engaging the autopilot to set the pitch or altitude where you want it; i.e. whether in ALt hold mode or not! Otherwise the the plane will dive or climb for the pitch or altitude the flight director last had - which could have been what you tested it with back on the ground - not necessarily what you are expecting. Rainman is correct, but no need to turn off the FD, just push the CWS button with the plane at the desired pitch or altitude.

Good to know.  I've never done that and, since I've never had a big pitch up or down upon engagement, I've probably been spared that simply because I'm in the habit of disconnecting the AP just prior to descent.  In other words, the last setting was level. Thanks for the info.