reported aircraft suddenly pitches up when crossing runway threshold

[adirtynurse]

Just had this happen to me as well

[McAnders]

Hi,

I'm flying the A-10C II a lot. I have noticed that the flaps goes down automatically and not when I press the flaps down button. I've assumed that they go down below a specific speed and basically only when the gear is down. But this seem to happen roughly at the same stage during landing and the plane suddenly goes up or starts floating and need more forward pitch to get down.
I looked at the video sample on top, but the flaps indicator is not visible. I usually land or flare at slightly higher speed. Maybe 140 knts.

After long missions, I would assume that maybe the trim setting has been manually altered a lot during the flight due to unbalanced load, or even damages to the aircraft. And perhaps the trim setting is conflicting with the flaps that suddenly goes down unexpectedly.

[Yurgon]

5 hours ago, McAnders said:

I have noticed that the flaps goes down automatically and not when I press the flaps down button.

That is most certainly not related to this problem.

The flaps automatically retract above a specific airspeed; I believe it's in the 190 to 200 KIAS region. And with the flaps switch in the MVR or DN position, they will come down as soon as the aircraft drops below this airspeed.

After takeoff, pilots should retract the flaps well before 190 KIAS, and before landing, they should lower the flaps well below 190 KIAS.

What you're observing is perfectly normal behavior when not following proper procedures.

From the Flight School chapter of the A-10C II manual:

Quote

Climb Out

After becoming airborne at a positive rate, maintain takeoff pitch of 10 degrees during acceleration to
climb speed. Once established in the climb:
• Retract the landing gear from the Landing Gear and Flap Control Panel.
• Retract flaps to the UP 0 degrees position

[...]

Landing

After you have entered final approach from either a straight in approach or circling approach, you need to land the aircraft. It is important that you maintain on-speed angle of attack (indicated by AoA indexer), landing gear is down, speedbrakes open to 40%, and flaps are set to the DN position.

 

[Avio]

Just re-installed everything fresh on a new PC and very certainly confirm that this strong pitch up motion when landing crossing threshold is there and largely repeatable (at Mariana map). Full flaps with airbrake at 60%. However when I intentionally use only half flaps (also tried no flaps), there was no pitching up. Suspect it could be a bug somewhere with the ground effect over-reacting upon the full flaps? Had noticed this problem from years back in the older A10C as well.

On another issue, shortly after take-off while climbing to 3000 ft or so, occasionally the nose would suddenly experience strong pitch down, even though I did not push the stick forward, to trim down.

These two issues are a serious distraction that takes away much of the fun in flying this newer A10C module, and really substracts so much from an otherwise very fine add-on.

Could the developer please comment on this? Have these problems been taken note of already, and is remedial action underway to fix them? Really hope they would be fixed soonest.

 

[=52d= Skip]

7 hours ago, Avio said:

Just re-installed everything fresh on a new PC and very certainly confirm that this strong pitch up motion when landing crossing threshold is there and largely repeatable (at Mariana map). Full flaps with airbrake at 60%. However when I intentionally use only half flaps (also tried no flaps), there was no pitching up.

 

If you actually are able to reproduce at will, then please provide a track file so ED can look into it. 

While I only had this once a rather long time ago I couldn´t reproduce it.

[Yurgon]

9 hours ago, Avio said:

On another issue, shortly after take-off while climbing to 3000 ft or so, occasionally the nose would suddenly experience strong pitch down, even though I did not push the stick forward, to trim down.

Can you report this in a new thread?

[Yurgon]

GOTCHA!

https://www.yurgon.de/uploads/dcs/DCS_2.7.9_A-10C-Pitch-Up-At-Landing.trk

DCS: 2.7.9.18080 OpenBeta
Module: A-10C
Mission:  Shooting Gallery
Track Length: 27 minutes

In this mission, I did 2 attacks with JTAC Deathstar for a type 3 control, then another attack with type 1 control. While setting up for the type 1 attack (the 3rd attack in total), I noticed the aircraft suddenly pitched down at 11:17:50 on the aircraft's clock, which corresponds to 15:17:30 in the F2 view. You can see me act confused, and ultimately apply a good bit of nose up pitch to counter this.

I had a hunch this would develop into the exact problem upon landing that we've been trying to nail for months, so I checked out from the JTAC and went for the nearest airport, in this case Kobuleti, and low and behold: sudden and severe pitch-up right as I was crossing the runway threshold. I allowed the aircraft to do that and quit the mission right thereafter.

@BIGNEWY @NineLine we've been chasing this for months. Can you make sure the devs and the internal testers see the track? Hopefully this will help nail the source of the problem.

Edited January 16, 2022 by Yurgon

[Yurgon]

On 1/14/2022 at 8:16 AM, Avio said:

On another issue, shortly after take-off while climbing to 3000 ft or so, occasionally the nose would suddenly experience strong pitch down, even though I did not push the stick forward, to trim down.

On second thought, this may well be the initial cause for the pitch-up during landing. If this ever happens, or if you happen to still have the track, please upload the track here to help chase this thing down.

Edited January 16, 2022 by Yurgon

[Foka]

I just exprienced it myself, and thanks to this thread I even predicted it
During flight (multiple attacks on an airfield) I noticed at some point, that plane is starting to fly nose down, regardless of speed, and I have to trim her "nose up" to stay level. I thought that during landing it will sky rocket and it did. So most definitly the issue is connected with trimming in-flight.

[Avio]

Just to update that I had flown some random flights and missions around Syria map at some 5 different airports and so far, none showed up the ballooning problem on flaring to land. Nor was there any sudden pitching down mid-flight.

But as I reported earlier, over at Mariana map (Antonio airport), both issues were rather consistent. Had also encountered the pitch-up on flaring over at Abu Dhabi airport, PG map. Have not tried the rest yet, but there have been reports of similar problems for those who fly PG missions.

So while it could be a trimming problem, why then is it that the problems are so specific only to certain maps / airports? This is puzzling.

The pitching up problem has been bugging the A10C for some years on and off now, and this thread has been around for many months by now. Is ED even aware of this? Any fix coming up? This is obviously a pretty serious bug, for it spoils an otherwise awesome aircraft at the conclusion of an exciting mission, for example.

DCS is an awesome program, THE only authentic fighter simulation in the market, but definitely not the only flight simulation program. Over the years / months, like many others I suspect, I have been much drawn to flying MSFS many a time instead. It would pay ED to be more attentive to devotees, for flying enthusiasts attention could easily switch to other platforms and stay there for extended duration. Segments that could have stayed loyal with ED for much longer otherwise.

Used to buy pre-releases in the past, but not anymore. Most should know why. Not wanting to be paid beta-tester.

 

[jaylw314]

Is there any chance this is connected to the "Force Feedback" feature?  Every now and then, I find that setting turned on, and I'm not sure why, and it certainly messes up stick control in a similar fashion.  I thought it might be that it happens after some updates, or after I plug a new controller in, but it doesn't happen all the time and I've not been able to figure out when it happens.  

[MAXsenna]

1 hour ago, jaylw314 said:

Is there any chance this is connected to the "Force Feedback" feature?  Every now and then, I find that setting turned on, and I'm not sure why, and it certainly messes up stick control in a similar fashion.  I thought it might be that it happens after some updates, or after I plug a new controller in, but it doesn't happen all the time and I've not been able to figure out when it happens.  

Interesting. Do you have an FFB stick, and do have FFB enabled with out one? 

[jaylw314]

1 hour ago, MAXsenna said:

Interesting. Do you have an FFB stick, and do have FFB enabled with out one? 

Never had a FFB (pretty much nobody in the universe does), but somehow it randomly gets re-enabled.  I can't tell what it is that triggers it, or if what triggers it could do so mid mission.

Edited January 21, 2022 by jaylw314

[MAXsenna]

9 hours ago, jaylw314 said:

Never had a FFB (pretty much nobody in the universe does), but somehow it randomly gets re-enabled.  I can't tell what it is that triggers it, or if what triggers it could do so mid mission.

 

If it randomly turns on, I'd report it if were you. But does it make a difference in this case? Can't really see why it should, and I've never experienced it, though I do have an FFB stick connected.  

I have purchased five MS FFB2 the past 1, 5 year, with an average price of 45 Euros, so it's not impossible to come by. 

[Yurgon]

20 hours ago, jaylw314 said:

Is there any chance this is connected to the "Force Feedback" feature?

Maybe. My experience is that my trim is ignored when Force Feedback gets activated with my non-FFB stick. That's not what I saw in this case, though. Trim response was okay, it's just that the aircraft developed a nose-down-tendency mid-flight, which I could trim away, and then the nose-down-tendency disappeared over the runway threshold and now my trim was a lot nose-up. Could still be related to FFB, but it's not my first guess.

[jaylw314]

On 1/22/2022 at 1:12 AM, MAXsenna said:

If it randomly turns on, I'd report it if were you. But does it make a difference in this case? Can't really see why it should, and I've never experienced it, though I do have an FFB stick connected.  

I have purchased five MS FFB2 the past 1, 5 year, with an average price of 45 Euros, so it's not impossible to come by. 

When it's happened (without a FFB stick), I've gotten profound nose up or nose down problems that initially seem trimmable, but then it continues to run away to the point of being near uncontrollable.  That's usually been my cue to check the setting.  But it's been intermittent enough there's nothing really to report.

[prof_laser]

@NineLine@BIGNEWY I encountered the bug again today. Any news on this? Are the devs looking into this one?

Edited February 28, 2022 by prof_laser

[Scarecrow]

I am encountering this using the A10c Legacy in the Persian Gulf map in the Operation Persian Freedom campaign. I've noticed the pitching up on landing and also nose down on a couple of occasions. Never seen this behaviour before but I've also had issues with losing SAS, EAC and antiskid in this campaign for no apparent reason. Very confusing.

[Lurz]

Just happened to me at Al Dhafra airport, OPF campaign.

EDIT: Twice. The second time was at different airbase.

Edited May 8, 2022 by Lurz

[malone13]

I have experienced this pitch up problem in persian freedom campaign, mission 3 at Al Minhad.

[Scarecrow]

I've switched off wake turbulance in the options and this seems to have eliminated the issue in the Persian map where I was experiencing it. Maybe others could check if this helps.

[Yurgon]

9 hours ago, Scarecrow said:

I've switched off wake turbulance in the options and this seems to have eliminated the issue in the Persian map where I was experiencing it. Maybe others could check if this helps.

That's a good idea, but I've only encountered this problem maybe 3 or 4 times in the last couple of years; the reproducibility is a big problem in tracking it down.

I really hope that the devs can use the existing tracks to figure it out.

Meanwhile, I like the general wake turbulence effect so I'll keep those on, knowing that every once in a while my landing may be botched because of this bug. Then again, so far it's only a theory that wake turbulence has anything to do with it anyway. 

[shagrat]

vor 7 Stunden schrieb Yurgon:

That's a good idea, but I've only encountered this problem maybe 3 or 4 times in the last couple of years; the reproducibility is a big problem in tracking it down.

I really hope that the devs can use the existing tracks to figure it out.

Meanwhile, I like the general wake turbulence effect so I'll keep those on, knowing that every once in a while my landing may be botched because of this bug. Then again, so far it's only a theory that wake turbulence has anything to do with it anyway. 

This happened even before wake turbulence was a thing. As you said, reproducing this phenomenon or tracking it down is horribly difficult.

My theory is that the transition over different terrain types or the switch from "normal ground" to "runway" messes with the ground effect calculation, in some weird way. 

I had this very sporadic in the A-10C, the Huey and the Bf.109 back when we flew Caucasus only, but had it at least once on the Persian Gulf map.

[Yurgon]

43 minutes ago, shagrat said:

My theory is that the transition over different terrain types or the switch from "normal ground" to "runway" messes with the ground effect calculation, in some weird way. 

At this time I'm strongly convinced that for whatever reason there is an initial nose-down tendency that develops rather suddenly, and is intuitively countered by pilots by trimming it away.

Just before touchdown, which can come many minutes after the problem originally developed, the original problem seems to disappear, and now all the nose-up-trim makes the aircraft float over the threshold.

So the question is, a) why does this nose-down tendency develop in the first place and b) why does it go away just before touchdown?

[Vakarian]

Hmmm, while reading this it dawned on me that I happened to experience this sudden pitch-up "issue" just about when I was to cross a threshold a lot when coming in to land on Qeshm island rwy 05. In our group we had a campaign where I had to land there 4 times and out of those 4 times at least 2 times I got this pitch up movement. 

I'll try to do couple of landings there to see if I can reproduce it in a short track as I know without them it's next to impossible to find the reason for this.