myrv9a
03-21-2010, 09:55 PM
I have a Tru Trak Digitrack II with GPSS and an HS34, installed in my RV9A.
The A/P was installed approx 1 year ago. Although only 20 hours have been placed on the airplane since installed, the A/P had been used on most on the flights. All functions had been used, including GPSS to perform an LPV approach. All had worked fine.
A failure occured March 19th on a trip from KMTN to 7FL6, with a stop at KRWI and KSSI.
First leg of trip went well. I used the GPSS mode to follow my Garmin 420, and used the altitude hold.
On the second leg of the trip, while climbing out from KRWI, the A/P appeared OK when I engaged it, as it came up in heading mode, except the ALT display came up displaying I was making a 2000 f/m climb. I was climbing about half or less. I ignored that, and pressed the mode button to get to GPSS mode, but nothing happened. The NAV part of display continued to display HDG. I tried to change the heading with the knob, but the display was frozen. I realized it was frozen from the moment I engaged it. I could not change anything with the buttons either. I tried to turn the A/P off with both the disconnect button on the stick, and the pushbutton on the unit itself. In response, the display completely blanked out. I cycled the electrical power, and when everything came back up the A/P display remained blank. I would have pulled the circuit breaked too, but I have the button kind that you can not pull out manually.
I was at cruise altitude at this point, I figured the A/P was powered off, so I just left it that way and continued on to KSSI. My route was direct, the MOAs were cold, so all I had to do was sit there for the ride. I was suprised I was getting an unusual amount of light chop I wasn't expecting, but you get what you get.
After my initial descent to KSSI, when I started to manuever, I realized the the something was wrong as the plane would not roll smoothly, but in jerky steps. I realized the servos had power applied to them. I found the same true for the pitch servo when I was slowing on final. I had enough control to land safely.
I realized the chop I was getting earlier was not that, but the servos slipping and grabbing when I made small adjustments.
On the ramp, I confirmed that as soon as I turned the master on, that in spite of a bland display, the servos would have power applied and try to lock the controls in what ever position they were in when the power came on. I could not pull the breaked for the A/P, so before I left KSSI, I crawled under the panel and disconnected the A/P power from the back of the breaker. That effectivily killed the power to the servos and allowed me to 7FL6 with no problems.
Do you have any idea how I should approach trying to solve this problem? I expect the servos are good, and are just getting power from the unit as an error. Since the display does not come on, there is nothing I can change or do to get more information.
Thanks,
Paul Lilly
Oh, I am going to change the breaker out for the kind tha has a switch on it.
The A/P was installed approx 1 year ago. Although only 20 hours have been placed on the airplane since installed, the A/P had been used on most on the flights. All functions had been used, including GPSS to perform an LPV approach. All had worked fine.
A failure occured March 19th on a trip from KMTN to 7FL6, with a stop at KRWI and KSSI.
First leg of trip went well. I used the GPSS mode to follow my Garmin 420, and used the altitude hold.
On the second leg of the trip, while climbing out from KRWI, the A/P appeared OK when I engaged it, as it came up in heading mode, except the ALT display came up displaying I was making a 2000 f/m climb. I was climbing about half or less. I ignored that, and pressed the mode button to get to GPSS mode, but nothing happened. The NAV part of display continued to display HDG. I tried to change the heading with the knob, but the display was frozen. I realized it was frozen from the moment I engaged it. I could not change anything with the buttons either. I tried to turn the A/P off with both the disconnect button on the stick, and the pushbutton on the unit itself. In response, the display completely blanked out. I cycled the electrical power, and when everything came back up the A/P display remained blank. I would have pulled the circuit breaked too, but I have the button kind that you can not pull out manually.
I was at cruise altitude at this point, I figured the A/P was powered off, so I just left it that way and continued on to KSSI. My route was direct, the MOAs were cold, so all I had to do was sit there for the ride. I was suprised I was getting an unusual amount of light chop I wasn't expecting, but you get what you get.
After my initial descent to KSSI, when I started to manuever, I realized the the something was wrong as the plane would not roll smoothly, but in jerky steps. I realized the servos had power applied to them. I found the same true for the pitch servo when I was slowing on final. I had enough control to land safely.
I realized the chop I was getting earlier was not that, but the servos slipping and grabbing when I made small adjustments.
On the ramp, I confirmed that as soon as I turned the master on, that in spite of a bland display, the servos would have power applied and try to lock the controls in what ever position they were in when the power came on. I could not pull the breaked for the A/P, so before I left KSSI, I crawled under the panel and disconnected the A/P power from the back of the breaker. That effectivily killed the power to the servos and allowed me to 7FL6 with no problems.
Do you have any idea how I should approach trying to solve this problem? I expect the servos are good, and are just getting power from the unit as an error. Since the display does not come on, there is nothing I can change or do to get more information.
Thanks,
Paul Lilly
Oh, I am going to change the breaker out for the kind tha has a switch on it.