reported Caged FPM Behaves weird in crosswind.

Hey all.

Noticed that when you select the drift compensated Flight Path Marker in the HUD (or Caged, in Hornet Lingo) using the UFC, when you bank the aircraft the FPM goes up and down instead of staying at the pitch angle where it should be. Its difficult to describe but it looks like it's rolling around where the uncaged FPM is instead of around its own centre point, the more the crosswind offset between the caged and uncaged FPM position the bigger the distance vertically it moves when you roll.

Made a track to explain.

DriftCompFPVIssue.trk

Hey all.

 

Noticed that when you select the drift compensated Flight Path Marker in the HUD (or Caged, in Hornet Lingo) using the UFC, when you roll the aircraft the FPM goes up and down instead of staying at the pitch angle where it should be. Its difficult to describe but it looks like it's rolling around where the uncaged FPM is instead of around its own centre point, the more the crosswind offset between the caged and uncaged FPM position the bigger the distance vertically it moves when you roll.

 

Made a track to explain.

As far as I can tell this changed after last update?

Haven’t had a chance to check.

In the current Open Beta build this still appears to be an issue.

Can we get a reported for this?

Can confirm that this still is an issue and when I brought this up previously it got marked as 'already reported'.

Maybe not a bug since the FPM shows INS computed actual flight path / velocity vector, which does not necessarily align with the velocity vector relative to the air mass in constant crosswind conditions. And the FLCS does not use INS values as inputs so it will still roll the aircraft around its velocity vector relative to the air mass.

This video at 38:03 shows the aircraft rolling in crosswind, and the FPM is moving all over the place. (Moving up/down and left/right around the gun cross marker).

(short cut to 38:03

When you switch on drift C/O, the lateral component of FPM is eliminated and you'll see the FPM movement being confined to a vertical plane through the gun cross marker. If you do this to the video above you'll see the FPM moving up/down.

In the vid when the FPM pass the horizon, you can see the altitude change from climb to decent or conversely. That means the relative position of FPM to horizon is correspond to the +/- vertical velocity at least.

And I don't think the FPM is caged in the vid. When the drift c/o is engaged, the FPM will stick to the center line of the HUD even with yaw input. It's not just cut the wind drift. You may also notice the heading change during the roll. If the FPM was caged, it would be the center of the circle of gun cross movement.

In the vid when the FPM pass the horizon, you can see the altitude change from climb to decent or conversely. That means the relative position of FPM to horizon is correspond to the +/- vertical velocity at least.

The issue that FPM is not corresponding to vertical velocity is related to the bug reported here: https://forums.eagle.ru/showthread.php?t=252743. It may not be related to what OP describes that the FPM is moving up/down when rolling in crosswind, which is normal behaviour no matter drift c/o or not.

And I don't think the FPM is caged in the vid. When the drift c/o is engaged, the FPM will stick to the center line of the HUD even with yaw input. It's not just cut the wind drift. You may also notice the heading change during the roll. If the FPM was caged, it would be the center of the circle of gun cross movement.

Clearly not caged in the vid and I'm afraid no one would said otherwise. You're saying exactly the same as my last paragraph. If the FPM were caged in the vid, it would be moving up/down only. Pretty easy to imagine.

That out of HUD FPM position issue is for uncaged mode only, I think. And that problem exists in F/A-18C as well. The caged velocity vector in F/A-18C is correct. So, I think they are two different problems.

The issue that FPM is not corresponding to vertical velocity is related to the bug reported here: https://forums.eagle.ru/showthread.php?t=252743. It may not be related to what OP describes that the FPM is moving up/down when rolling in crosswind, which is normal behaviour no matter drift c/o or not.

Please go test it in the sim, set up a 50knot wind and fly perpendicular to it, set the FPM to Drift C/O and then bank the aircraft. The FPM will be moving erratically up and down regardless of your vertical speed. This is not correct behaviour.

This is presuming it hasn’t already been fixed. I’m going to make another track and a video soon.

Looks like when the FPM is caged, it didn't keep the same pitch information as the uncaged one, instead it just simply moved horizontally in the HUD. Same as previously reported FPM outside the HUD issue.

An image to elaborate:

The pitch ladder is also at the wrong position. It should be always rotate around the FPM regardless of drift c/o.

Looks like when the FPM is caged, it didn't keep the same pitch information as the uncaged one, instead it just simply moved horizontally in the HUD. Same as previously reported FPM outside the HUD issue.

 

An image to elaborate:

[ATTACH]220231[/ATTACH]

 

The pitch ladder is also at the wrong position. It should be always rotate around the FPM regardless of drift c/o.

Yes. Exactly.

This is still an issue as of 2.5.5.41371.

Would providing another track help?

Hi!

We had the same issue on "another sim" because of a wrong implementation of the Drift C/O.

On level flight, whatever the Drfit C/O switch, FPM should say on horizon and should no be affected by the wind.

Regards.

Pitch ladder with Drift C/O is wrong (at least on the stable version). It should not have lateral deltas.

Drift cutout forces FPM to center laterally in the HUD but remains at the same flight path angle. E.g. if true FPM position is for 3 degree flight path climb then it is also there when forced centered. When banked this means that shift of FPM position between normal and drift cutout is not directly lateral in the HUD but along lines parallel to the horizon (lines of constant FPA).

This is still an issue as of 2.5.5.41962

Here is a new track in this version.

Can we pleased get this fixed, it makes the caged FPM utterly useless.

You can see it goes up and down so much with roll that it can be several degrees above or below the horizon while the aircraft is clearly not climbing or descending.

I'd really like to see this as reported.

Thanks D

DriftCompFPVIssueNew.trk

THANKS NL!

Just checked and this is still unresolved as of 2.5.6.58125.

Is there any chance we can get this bumped up the priority list? This is one of a basic features of the HUD that should work correctly. I makes flying accurately in crosswinds a real PITA with the FPM dancing around all over the place. Specially crosswind landings where the wind is strong enough for the FPM to be outside of the HUD.

Cheers

D

F-16HUDissueDec2020.trk

If is it what I think, it is not simply a HUD issue but a FM issue (major FM issue) ... And it could also explain why the wind act on engine thrust.

This particular issue is not FM related and it has been here since day one. When the FPM goes outside of the HUD it will give incorrect information vertically and this gets exacerbated when banking. Normally how it should work is that if the FPM is outside the HUD and you're in a 5 degree climb, it should be displayed at the edge of the HUD along the 5 degree pitch line which it currently does not. Caging the FPM with the DRIFT C/O switch will center it on your HUD, but indicated pitch angle will still be incorrect and it will display the same faulty pitch angle as it does in the uncaged mode.

Check your VVI/and ALT. If it is correlating with the FPM going up/down, it is FM. If not ... it should be only HUD display.