When flying in NAV mode my AP KFC 150 tracks the route always about 1-1.5 dots left of the track. During an approach when being vectored I am in heading mode, on my last vector for the Loc intercept coming from the right I select Approch mode and instead of turning to the right the AP turns to the left. The sole time I was coming from the left it turned correctly to the left.
It looks my AP has a left tendency, what could the cause be for this?
Thanks for your help.
Placido
If you were using GPS I’d say you had Parallel Track setup, but since you are in NAV mode… might be wise to have a chat to an engineer? Certainly not meant to be that way. I have noticed however in stiff crosswind it ends up on the downwind side of the track quite easily. (This is in a Caravan)
If it doesn’t do it in GPS mode, I’d guess something could be off with the interface between your VOR deviation and the autopilot. If you have two VORs you could verify that both indicate the same track deviation, to see if the VOR itself is faulty.
I have a similar problem but ONLY en route and only in GPS nav.
KFC150 autopilot on NAV mode with the BENDIX/KING HSI (and no GPSS steering).
GNS530 (not the W model).
I set the track of the magenta line in the HSI with the rotary knob and start tracking it with NAV mode.
After a few minutes the aircraft positions OFFSET PARALLEL by 1~1.5 nm to RIGHT of track and it continues this way for the whole flight.
Note: In VLOC mode (VOR/ILS) it captures and tracks the radial spot on without deviations.
When I get in TERM (Terminal) airspace accuracy mode (some 30nm from destination if I recall correctly) “TERM” white light annunciator lights up and then the aircraft sways left and right to adjust again to the new relative position (again to the right) of the magenta line with increased accuracy.
I have searched the GNS530 manual and I have not found any option for offset parallel track (like they have in airliners FMCs !)
Any clues ?
My set up: http://hellasga.com/gallery/kyp/sxatk/sxatk_new_panel/DSC03620ss
and here you can see the usual offset in progress
http://hellasga.com/gallery/kyp/sxatk/sxatk_new_panel/IMG_3129
I forgot to say that I have found this for the W model
http://www.manualslib.com/manual/256156/Garmin-Gns-400w.html?page=86
but mine is not the W.
When the lateral deviation offset occurs in flight, is the artificial horizon level and is the slip ball centred? If flying in HDG mode, does it track the desired heading with the bug exactly at the top of the HSI card?
I think the autopilot is controlled by an analog voltage, and an offset has crept in. Maybe a grounding problem? Or there is a null adjustment on the autopilot which has moved.
When I said NAV mode I meant GPS NAV not VLOC. I don’t know how the parallel track mode could have been entered but I will check. When flying in heading mode the lubber line never is in the center of the heading bug but almost always on the left edge of the bug.
wigglyamp wrote:
When the lateral deviation offset occurs in flight, is the artificial horizon level and is the slip ball centred? If flying in HDG mode, does it track the desired heading with the bug exactly at the top of the HSI card?
I will come back with some close up picture(s) next week after my upcoming weekend’s flight..
Yes there is some heading (magnetic / bug / slave gyro ) deviation in the range of 4~8 degrees from what I recall.
Slip Ball is always centered.
Thanks.
petakas wrote:
I have searched the GNS530 manual and I have not found any option for offset parallel track
The GNS420, 430 does it as well as the GTN650/750. So it would surprise me if the GNS530 could not do it, but you are right, it is not mentioned in the Pilot’s Guide.
You should be able to see pretty quickly if it is using parallel track, as you will have the letter P with an arrow somewhere on your flight plan display/leg info. It is normally accessible if you press Menu from the flight plan page.
By the way it doesn’t sound like parallel tracking is the issue.
Please state again the mode you are in when this occurs.
I understand that you do not have the problem when on HDG mode, i.e when the AP follows the bug in the HSI, right ?
And you do have the problem when you couple the AP to the Garmin ?
Or is it in both cases ?
EDIT: before trying anything else, you might try to set the 530’s CDI scale to something like 1nm not AUTO or 5NM. I read that on another forum and it might help here. Try this first before trying a centering adjustment on the autopilot.
