Bug: F-15C altitude hold doesn't work

When I engage altitude hold, it first reduces the climb rate (sometimes all the way 0, sometimes only partially), but then the climb rate drifts, until it reaches the limit of ±2000 fpm when the altitude hold disengages. Here's a video demonstration - watch the autopilot switches on the left console or the lights on the caution lights panel to see when the autopilot is engaged, and watch the VVI to see the diverging decent rate:

 

 

I feel like this used to work in the recent past, but I might be misremembering. Hope this can be fixed soon, though, because it's quite annoying to be always adjusting pitch to maintain altitude on longer flight segments.

 

Also, when the altitude hold disengages upon reaching the 2000 fpm limit (e.g. at

in the above video), there's a significant attitude upset, even though attitude hold is still engaged. I imagine that's not supposed to happen?

 

A track file is attached. I'm running 2.5.6.52437.

F-15C altitude hold bug.trk

Now I see this - All this time I thought I was doing something wrong. It wasn't working.

 

Please ED get this fixed or explain me on what I am doing wrong

Are you engaging Attitude hold first?

Are you engaging Attitude hold first?

 

Thanks for the suggestion! But yes, I am (see the video). If attitude hold is not engaged first, then altitude hold will not engage at all. Here, though, altitude hold engages (the switch flips and the respective light illuminates in the caution lights panel), and it does have some effect (as I mentioned, it reduces the climb/descent rate when first engaged), but it does not hold altitude. (Or were you talking to spacefox?)

OK

 

I did some testing this morning. (Track attacked). I was able to engage the autopilot without issues BUT it took some fine tuning to get it to hold level flight. I asked if this is correct on the Tester Forums and received this reply:

 

cofcorpse - Today at 9:25 AM

Vy should be less than 2000 feet and your stick should be in neutral quite precisely

 

Almost all issues with altitude channel on F-15C I've investigated violated these two rules. And the stick not in neutral is the most frequent reason.

 

Actually, I can suggest to make small deadzones for joystick both in pitch and roll. 2-3, for example, for good, precise devices

 

When I checked MY settings I found I did not have any dead zones for my Stick and Rudders. I added a dead zone of 3 to each and it seemed to work much better.

 

Give that a shot and see if that helps.

F-15C_AP_Test.trk

I added a dead zone of 3 to each and it seemed to work much better.

 

Give that a shot and see if that helps.

 

Thank you! I added a dead zone of 3 to pitch, roll, and yaw, and it seemed to help in level flight. However, in a bank (e.g. if I want to hold altitude while orbiting) I have basically the same problem, where my descent rate increases until it hits 2000 ft/min and the altitude hold disengages. (My bank angle is within the limit of 60º.) Is altitude hold working for you in a bank?

still broken in my experience

i've experimented with this a bit and I've found that, inexplicably, the aircraft is still trying to follow the trim even when on autopilot. That is to say, if you are slightly trimmed nose down, the altitude hold will follow the nose down trim. you see the F-15 at least in game autotrims such that speed changes don't affect trim per se, at 250 knots or 550 knots if you have a slight nose-down trim it will always be a slight nose-down trim. the autopilot is not taking control of trim or something along those lines

This might be "couple" of years later, but I recently just became aware of same "problem" in f-15C, after cruising around hours with f-22 altitude hold on. In F-15C (and many other planes) you also need / can trim at the autopilot modes. (I dunno if this is F-15C IRL stuff, maby) Or atleast this helped me with this very same problem (altitude drops faster and faster until hold releases itself..). I recommend trimming before and in autopilot mode. What really annoys me many times is that F-15C does not have trim reset. Thats one ED could add, more or less optional in every aircraft. That would help a lot while learning trimming in "tuff" places. Oh how many times did I drop my SU-25t after using autopilot  

Edited August 9, 2022 by Wiggo

every time this gets reported somehow ED can't find anything wrong with it, even though if you go back to FC2 or earlier the aircraft will latch onto a specific altitude and hold it like a rabid alligator. Or the fact the other FC3 planes did not get their altitude hold broken.

 

Also for the record F-15 does not have a trim reset function, take-off trim explicitly gives a slight nose-up command for reasons I won't go into however what it does have is the ability to manually reset trim to 0 that DCS lacks...if you ever trim a plane in DCS you will never be able to get it back to zero, sometimes even with a trim reset feature. this is most notable with roll trim

Yup. Seems so. Same thing with flickering / bilnking black screen bug. I can trigger it any time on high altitudes, and / or totally random triggers.. I have tried to even ask, could they please just tell if that is viral bug under investigation, but no answer. First threads that i found about "black boxes and full screen black screen "blinking / flickering", with fast search, was from ~2.5 

1 hour ago, Wiggo said:

Yup. Seems so. Same thing with flickering / bilnking black screen bug. I can trigger it any time on high altitudes, and / or totally random triggers.. I have tried to even ask, could they please just tell if that is viral bug under investigation, but no answer. First threads that i found about "black boxes and full screen black screen "blinking / flickering", with fast search, was from ~2.5 

This is totally off topic. Stop spamming the forum, please.

Added some deadzones, still no reliable altitude hold. Saw a marginal improvement, but only insofar as the speed at which it drifted away from level flight was slower.

Bizarre that every other ED jet when put into altitude hold (or attitude hold), clamps onto that altitude and holds it like a rabid dog, except the F-15. Not only that but I absolutely remember it working perfectly in Flaming Cliffs 2, what happened?

I'm new to DCS (like 3 days new!).  Very satisfied to know, at least, this issue is NOT on my end.  

Welcome to you Keith Briscoe
welcome to the big DCS family and its adventures.
Good flights to you

still not working right?

 

no its working! but it has to be in its parameters which is weird..

no I thought it is working but it dont.

 

edit: YES IT IS WORKING IN ITS CERTAIN PARAMETERS!!!!!

Edited January 26 by FlyingCoffin

On 1/25/2024 at 9:09 AM, FlyingCoffin said:

still not working right?

 

no its working! but it has to be in its parameters which is weird..

no I thought it is working but it dont.

 

edit: YES IT IS WORKING IN ITS CERTAIN PARAMETERS!!!!!

 

It is not.