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AltonD
09-21-2010, 07:19 PM
Today, I was at 10,500 MSL and dialed up a decent @ 1000 fpm, target 2500 ft. I have a legacy 3500 and an Advanced programmer (aka trutrak). When I first started the decent, about every 15 seconds, I felt a up elevator bump. Almost like the servo was slipping. It did it for awhile, then no longer. Any ideas?

kentb
09-22-2010, 10:58 AM
I have felt this strange behavior also. It puzzled me at first, until I realized that it was the over-speed kicking in. Unless you throttle back as the speed builds up the AP will decrease the decent to reduce the speed.

Kent

AltonD
09-22-2010, 08:22 PM
makes sense. I don't remember what my max speed setting is. I'll bump it up. I love the AP. I am still in phase 1. I have been practicing the GPS approach into my home base, 0J6. It is so cool to just sit there and watch the AP fly the whole approach amd the missed with holding. It has taken me several runs to figure out the power management, but hey, that is what phase 1 is for.

chrisa
09-25-2010, 12:57 PM
Was the trim annunciator indicating out of trim? When on descent if you are falling short of your VS setting the AP will indicate MAX AS. I have never noticed a bump when this happens, just lower descent rate.

AltonD
09-25-2010, 06:20 PM
I didn't see any warnings on the programmer head. I did feed in some down trim and it did not happen again. I have seen the "Low air speed" in the past so I know where to look. I have never seen the trim warning.

Trevor Conroy
09-27-2010, 09:02 AM
What type of aircraft? How fast were you going in your descent? Do you have the auto pitch trim module installed? Is your torque value set at 12? kentb is correct, there is a speed setting in the AutoPilot that could affect that. Were you manually keeping the aircraft in trim?

AltonD
09-27-2010, 08:07 PM
RV7A
I don't really remember the air speed, but it should have been ~150 KIAS.
No auto pitch trim
I'll have to check the torque setting. Is this the programmer head or the AFS setting?
Manually keeping the A/C in trim, probably not.

I am still learning here. New toy and I have not discovered all of the bells and whistles. Although, I really like the setup. I am sure this is an all me thing.

Trevor Conroy
09-28-2010, 01:48 PM
The settings we used in our RV-4 are as follows:

EFIS
Roll Gain: 0.05
Alt Gain: 5.00

AP
Lat Activity: 5
Torque: 12
Micro Act: 0
GPSS Gain: 16
Vert Activity: 3
Torque: 12
Static Lag: 2
Micro: 0

Also verify the MIN and MAX speeds you have setup in the AP. If you exceed the max speed programmed in, it will pitch the aircraft up in a descent.