View Full Version : Herky jerky pitch Dynon VNAV

06-18-2018, 06:50 PM
Started training recently to get back to IFR currency for the first time in my new to me RV-9A with full Dynon hardware +

Found that when tracking the glide slope in VNAV with speed 90-95kts no flaps, the pitch servo would command quick sharp up/down commands, the screen would show slipping clutch and commands for trim up/down (it has working electric trim). The glide slope deviations were modest and on average it stayed on the GS.
The doesn't happen on a non coupled descent at the same speed.

Thoughts/ suggestions?


06-18-2018, 07:50 PM
Hi Carl,
Have you done the complete In-Flight AP Tuning? Find the procedure on Dynon website. Help with mine. Here?s the document overview;

1. Overview Purpose
The goal of the AP tuning procedure is to maximize the performance of the Autopilot in your aircraft. The steps described accomplish this systematically and reduce guesswork, so follow them carefully.
All procedures in this guide should be exercised regardless of how the autopilot is intended to be used in the aircraft. In particular, if you are using the vertical navigation features of the autopilot, pay special attention to the IAS Hold tuning procedure. Tuning this well will give the best results when using vertical guidance.
Once IAS hold is well tuned, the AP will be able to get the best performance during normal climbs and descents in either expert or simplified modes, and the altitude capture and hold procedure should be used to finalize vertical performance.
Once you have configured the autopilot to capture and hold airspeeds and altitudes, you may wish to adjust the ride quality in turbulence, particularly on the glideslope.
Similarly, the Roll Axis TRK and Turns Procedure will ensure best performance both in normal turns and when following lateral guidance on approaches.
HDG mode performance is only as good as your compass calibration. If you have concerns about your compass, refer to the compass calibration guide in the SkyView System Installation Guide.
The SV-AP-PANEL is enabled when AP CONTROLS are set to EXPERT mode. For tuning procedures performed in SIMPLIFIED mode, the buttons on the SV-AP-PANEL will not be active.
It is critical that once tuned, you familiarize yourself with AP procedures, and verify
the performance of the autopilot on approaches in VMC before use in IMC.
Performance of the AP is degraded by excessive servo slippage. If during
verification of approach performance you find that the servo is slipping, verify that
you have the torque set to the maximum value, and if slips continue, contact Dynon
for advice on servo sizing.
SkyView Autopilot In-Flight Tuning Guide - Revision B 1-1