DFC100 pre-flight test

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When testing the autopilot prior to flight, I sync the heading bug, engage heading mode, and then move the heading bug. The yoke responds almost imperceptably - it moves but very slowly. Same is true both directions. This has been the case in all but one pre-flight test since the DFC100 was installed. (The VS test works as expected.)
During the pre-flight, the roll trim works normally from the manual trim control.

Of course, when at the avionics shop, it works normally - the yoke moves quickly in response to a heading bug change.

It finally occured to me (after leaving the avionics shop)  that the tests at the avionics shop have been done on battery with the engine off and my pre-flights have been done with the engine running and alternator on. Every test I have done with the engine off works as expected.

The shop tells me that the roll trim cartridge is working normally. (Of course, that was observed with the engine off.)

The auto pilot flys just fine, so this may not be critical, but it is still of some concern.

Any ideas?

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rdawson Members Profile Send Private Message Find Members Posts Add to Buddy List Release 9 Insiders Joined: 09 Mar 2010 Location: Daytona Beach Status: Offline Points: 14	Post Options Post Reply Quote rdawson Report Post Thanks(0) Quote Reply Topic: DFC100 pre-flight test Posted: 17 Jul 2011 at 1:33pm
	When testing the autopilot prior to flight, I sync the heading bug, engage heading mode, and then move the heading bug. The yoke responds almost imperceptably - it moves but very slowly. Same is true both directions. This has been the case in all but one pre-flight test since the DFC100 was installed. (The VS test works as expected.) During the pre-flight, the roll trim works normally from the manual trim control. Of course, when at the avionics shop, it works normally - the yoke moves quickly in response to a heading bug change. It finally occured to me (after leaving the avionics shop) that the tests at the avionics shop have been done on battery with the engine off and my pre-flights have been done with the engine running and alternator on. Every test I have done with the engine off works as expected. The shop tells me that the roll trim cartridge is working normally. (Of course, that was observed with the engine off.) The auto pilot flys just fine, so this may not be critical, but it is still of some concern. Any ideas?

AviJake Members Profile Send Private Message Find Members Posts Add to Buddy List Admin Group Joined: 26 Mar 2009 Location: Lincoln MA Status: Offline Points: 2815	Post Options Post Reply Quote AviJake Report Post Thanks(0) Quote Reply Posted: 17 Jul 2011 at 2:41pm
	Hi Rick, Just to be clear, the question is why you didn't see/feel the yoke responding in the roll axis during the one pre-flight where you had the engine running and alternator on, correct? If so, no immediate explanation (or concern) jumps to mind. I usually perform those pre-flight tests with the engine running myself and it has always been fine. I'll spend some time early this week looking into your observation. It is possible that I may ask for a data download via the IFD USB port. If I do, it will be helpful to know what date (and even approximate time) you witnessed this. More to come early this week but at this point, I'm not concerned about that observation. Regards, Steve
	Steve Jacobson sjacobson@avidyne.com

rdawson Members Profile Send Private Message Find Members Posts Add to Buddy List Release 9 Insiders Joined: 09 Mar 2010 Location: Daytona Beach Status: Offline Points: 14	Post Options Post Reply Quote rdawson Report Post Thanks(0) Quote Reply Posted: 18 Jul 2011 at 10:16am
	Not quite. Since the DFC100 was installed, the pre-flight test (engine running) has been what I consider normal (controls move at about the same rate as a manual roll trim) only once. On every other occasion (dozens) the controls move, but very slowly. The motion is almost imperceptable.

AviJake Members Profile Send Private Message Find Members Posts Add to Buddy List Admin Group Joined: 26 Mar 2009 Location: Lincoln MA Status: Offline Points: 2815	Post Options Post Reply Quote AviJake Report Post Thanks(0) Quote Reply Posted: 18 Jul 2011 at 10:31am
	Sorry for being dense but your concern is the slow, almost imperceptible motion during some of your preflights, right? I'm used to very, very slow motion of the flight controls during pre-flight and consider that normal.
	Steve Jacobson sjacobson@avidyne.com

rdawson Members Profile Send Private Message Find Members Posts Add to Buddy List Release 9 Insiders Joined: 09 Mar 2010 Location: Daytona Beach Status: Offline Points: 14	Post Options Post Reply Quote rdawson Report Post Thanks(0) Quote Reply Posted: 18 Jul 2011 at 10:34am
	Right -- really slooooooooow I'm glad to know that that is normal - Thanks.