by Octal450 » Sun Sep 22, 2019 5:34 pm
Hi Robert,
the Autopilot is functioning exactly as designed here. I will explain here something:
The NAV mode has 2 possible options - NAV and NAV GPSS. NAV itself follows NAV radio, either NAV1 or 2, whichever is selected on the panel. (by default NAV1). NAV GPSS follows the route manager. APR is not a separate mode, it simply increases the control gain in the deviation control loop. When you press APR, the GPSS mode will kick off. That is because unlike the S-TEC 55, the 55X talks directly with the GPS (Route Manager for now) and thus GPSS commands do not go through the NAV deviation system. APR is only used for ILS/VOR approaches, not for RNAV approaches - those stay in NAV GPSS. When GPSS kicked off, NAV went to seek the radial follow again. In your video: the COURSE on the HSI was set to roughly 050, and the maximum deflection is 45 degrees from course. Thus, the aircraft went on an intercept heading to 050, which since you were to the right of the signal, was roughly 005. The aircraft will remain on that heading until the HSI's deviation point begins to move towards the center. Once it hits a certain amount closer to center (depends on how fast the needle is centering) the system will turn onto a course near 050, and then after roughly 30 seconds or less establish wind correction. The system also modifies the gains and maximum turn rate as the capture occurs, as written on Section 3.1.2 (page 3-3) of the POH I linked on dropbox.
Hence the system acted exactly as it should have. If you are using the Route Manager waypoints for approach, you do not use APR mode, just stay on NAV GPSS.
Hope that clears it up. If you'd like me to make a demo video on how to perform an ILS or GPSS approach with the S-TEC, I can do that.
Kind Regards,
Josh