Route Manager /AP

[Robertfm]

The route manager is not flying headings pre progammed when in AP Nav mode. However it will follow Heading Bug when set to the bearing in RM. I have had a look at the various RM threads but can't see this. I am flying IDG PA28 AP x55

[D-ECHO]

Hi Robert,
hasn't this issue been discussed numerous times in the PA28 thread?

[Robertfm]

No the only thing that was discussed was why the curvature of the earth would create an unusual track, not why the AP would not follow defined bearings/headings in the RM.

[D-ECHO]

Do you have the GPSS indication in the AP or only the NAV indication? Additionally, could you please send a screenshot of the AP display and the route manager dialog in the situation where you think that it behaves incorrectly?

[Robertfm]

GPSS is on.

software cek keyboard

Edit: In addition to this when on ILS approach the HSI is set correctly @ 245 according to the FGMap. However the in bound final course on the HUD and G5 was 235 with the Giro fluctuation between 235 & 245 when the plane deviated course. Finally the HSI needle was 2 degrees right of the HSI course.

[D-ECHO]

Okay, I just tested it and at least for me, it works fine.

I'll need some more info:
*what is the heading difference between the heading it flies and the heading you expect it to fly?
*Do you reach the waypoint it is supposed to fly to?

[Robertfm]

It varies but it's any from 5 to 30 degrees off track after 3/4 of flight. It follows the correct heading for few miles and then drifts to the right normally. It can end up 200 miles off track.

As for the way point. It follows SIDs fine then on the main route is when it drifts off but always comes back from where ever it is to the first inbound way point, ie in this case 25-12. Changing heading as it goes.


Edit: I just tried a short flight using the basic PA28 and the generic AP and the same issue the heading on HUD was 10 degrees off that of the RM heading. The AP was also 10 degrees off. All very weird.

[D-ECHO]

What you are experiencing seems to be magnetic declination (difference between magnetic and true heading), maybe combined with wind effects on ground track vs heading. Do I understand correctly that you always end up at the destination, even though your route does not match the route drawn?

[Robertfm]

Yes. However the plane can go over terrain not plotted for and has as a result crashed on a number of occasions. Surely this wouldn't happen on AP in real world. I've read that AP's correct for wind deviation etc to always maintain correct course.

Edit. Just started a flight from EGPF to EGAA initial bearing on RM of 217 however on HUD/G5/Giro the track is 207 of course it is now following a different route to RM on blue line track of Phi. Clearly this is not a wind deviation more like some form of calibration issue. Now after 15NM it has deviated 5nm but has now settled on correct bearing, but still 5NM off course. Seriously odd

[D-ECHO]

Looking at the code, to me it seems that the AP is working correctly, so maybe the line is off. I don't know though how this line is generated and what when compensates for the earth's curvature, maybe someone else can help here?

[Robertfm]

The line get's it track from the Route Manager course set for various way points which are pre-programmed automatically. S it obviously begs the question, are the way points tracks correct but given the plane always finds it's way to each way point regardless how far of course it was seems to suggest they are fine. The only other thing is are the way points in RM synced to HUD/G5/gyro as these 3 are the same within 3 degrees.


Edit: I have just checked the data on the FG1000 PFD and the heading is the same as the RM. So HUD/G5/Gyro are 10 degrees greater than RM & PFD and yet visibly the plane is parallel with the Phi line but appearing to track correctly but HUD/G5/Gyro indicates differently.

[Robertfm]

Sorry to return to this but I am trying to understand these anomolies.

New Flight: Set Heading bug to runway heading 129 Took off and activated HDG and it followed. Switched on route manager and the plane was following the SIDs perfectly, which was odd as the bearing on RM was 111, at this time the HUD showed 115 and the gyro 132. How on earth can it be 4 different courses./tracks. Any ideas would be welcome.

[WoodSTokk]

True heading: 115
Magnetic heading: 111 (Offset: 4° East)
Gyro: 132 (21° offset, not calibrated)

Have you checked the gyro after start up?
Hint: a gyro can drift and the gyro isn't slaved. The pilot should calibrate it on start up and around all 30min in flight.

[Robertfm]

Sorry been using the wrong terminology. When I said Gyro, I meant Magnetic Compass. There is no Directional Giro on the IRG PA28 so how do I ensure the MC is correct.

[WoodSTokk]

Sorry been using the wrong terminology. When I said Gyro, I meant Magnetic Compass. There is no Directional Giro on the IRG PA28 so how do I ensure the MC is correct.

I see, there is no setting knob or switch for HSI.
As a workaround, configure the aircraft to use the DG.
On parking position, look at the compass (it should stay stable, not swing around).
Set the DG with the knob in the lower left corner to show the same heading like the compass
Now you can configure the aircraft back to HSI

Check also in-flight in intervals of 30min.
For in-flight check, fly straight and level for around 3min so that the compass can settle down
After 3min, check compass reading with the HSI, recalibrate if necessary