Landing: on hard ground vs soft ground

[Dagobert666]

I noticed this with a F.A.R.B that I put on south-east of the LAR airfield in the Gulf.
The ground there is pretty level and even. It's just desert and not concrete.

The problem that is exaggerated there is the "dynamic rollover".

If I don't touch down the chopper at absolute 0.0 knots, it rolls sideways.

Additionally, as soon as I land and start reducing the collective, I need to bring the "Anti Torque" to neutral immediately. Otherwise, the thrust from the tail rotor is sufficient to tilt the helicopter as well.

But if I'm standing at the airport, then I can give 50% "anti torque" with the rear wheel locked without any problems without the helicopter moving or starting to tip over. Landing with one or two knots sideways or diagonal movement is also not a problem.

In my opinion this is somehow illogical and must be a programming error.
I know that sand is soft and therefore gives more friction, but that only explains the tipping over with slight lateral movement. However, not the tipping over due to the thrust of the tail rotor.

[MusicOn]

I observed something similar at the Syria map (single player):
Cold start from Kharab Ishk, flying a little mission (no wind) just for target practice and landing after at Kharab Ishk.
At touch down there was a rolling movement to the right that flipps the AH-64D.
After a second try and landing the speed indicator shows 1, not 0.

Might that be the problem?
Can you reproduce it?
Might be a bug worth posting in the bug forum

Picture after landing, standing still:
 

Edited April 14, 2022 by MusicOn

[Swift.]

22 minutes ago, MusicOn said:

I observed something similar at the Syria map (single player):
Cold start from Kharab Ishk, flying a little mission (no wind) just for target practice and landing after at Kharab Ishk.
At touch down there was a rolling movement to the right that flipps the AH-64D.
After a second try and landing the speed indicator shows 1, not 0.

Might that be the problem?
Can you reproduce it?
Might be a bug worth posting in the bug forum

Picture after landing, standing still:
 

 

That is a bug, and its been reported

[BIGNEWY]

Please include short track replay examples if you think there is any issue. 

thanks

[Dagobert666]

On 4/14/2022 at 11:56 AM, BIGNEWY said:

Please include short track replay examples if you think there is any issue. 

thanks

ok,
here's a trek from just the approach.
After landing, the heli tipped to the side just because I gave it a little more left rudder. Although I'm already firmly on the ground.
https://www.dropbox.com/s/m8iihfukuq3a7tz/Dynamik_Rollover_onSand.trk?dl=0



and here is a link to the mission, to recreate it. Select the SLOT:  Lande-Übung-FARB
https://www.dropbox.com/s/s3kk34fwi6lerrg/AH-64_Mission-1.miz?dl=0

Edited April 15, 2022 by Dagobert666

[AstonMartinDBS]

I'm unable to download the track and misson.

[Dagobert666]

3 minutes ago, AstonMartinDBS said:

I'm unable to download the track and misson.

123 / 5.000

1. Click on the link
2. press the registration with the X away
3. in the top left corner is the download button

[BIGNEWY]

9 minutes ago, Dagobert666 said:

ok,
here's a trek from just the approach.
After landing, the heli tipped to the side just because I gave it a little more left rudder. Although I'm already firmly on the ground.
https://www.dropbox.com/s/m8iihfukuq3a7tz/Dynamik_Rollover_onSand.trk?dl=0



and here is a link to the mission, to recreate it. Select the SLOT: "Lande-Übung FARB"
https://www.dropbox.com/s/s3kk34fwi6lerrg/AH-64_Mission-1.miz?dl=0

check your collective axis. You still had torque set and the collective was not all the way down. 

thanks 

[Dagobert666]

1 minute ago, BIGNEWY said:

check your collective axis. You still had torque set and the collective was not all the way down. 

thanks 

Yes, but if I do the same thing at an airport with the exact same values, then there is no "Dynamic Rollover" that only happens on the sand.. That's the weird thing.

[BIGNEWY]

Just now, Dagobert666 said:

Yes, but if I do the same thing at an airport with the exact same values, then there is no "Dynamic Rollover" that only happens on the sand.. That's the weird thing.

the ground you are on is not even and can be soft, I dont see a bug here sorry. 

[Dagobert666]

4 minutes ago, BIGNEWY said:

the ground you are on is not even and can be soft, I dont see a bug here sorry. 

ok of course if you say so. Thanks for looking/work!

Can you tell me where the tilting moment comes from? The helicopter doesn't move. And the tail rotor is supposed to turn the helicopter, not tilt it?

[gottel]

I don't know how it should feel in the real helicopter, never landanded an Apache on sand , but in DCS it feels kind of light when it slips to the side like described above - not like putting 10 tons in the sand. Maybe not not a bug - I expected more sticking to the ground, but as said, in no way an expert

[Ram69]

1 minute ago, Dagobert666 said:

ok of course if you say so. Thanks for looking/work!

Can you tell me where the tilting moment comes from? The helicopter doesn't move. And the tail rotor is supposed to turn the helicopter, not tilt it?

Presumably from when one of your wheels gets jammed up in the softer surface from the weight of the heli, which causes you to begin tilting, rather than rotating. 

[ARM505]

DCS's tire interaction with surfaces is.......a compromise. Hard/soft, tarmac, grass.....it's kind of simplified. Resulting in some weirdness. There have been quite extensive discussions on this, the F16, the warbirds (taildraggers being a challenge) etc. At all times (IMHO), the common theme is oddities with input variables of coefficient of static and dynamic friction, normal force, velocity etc. This isn't a racing sim, but it crops up often enough, across a lot of modules, that tire modelling might merit a global rework.

 

I might have misunderstood the gist of this though.

[S. Low]

I agree with arm505. Ground interaction always pops up because it’s never felt right to pilots or simmers here. One example is if i remember correctly the dcs p51 takes more manifold pressure to get rolling than the real life version and this has something to do with ground interaction. But as arm505 stated this is a flight sim not a racing sim. While ground interaction is part of the simulation it’s not the primary part.

Until such time as we could get quality of life improvements, just be very careful when landing and taxiing. 

[Swift.]

So this doesn't look like any issue with tire interaction or anything like that. Its as BN said, you still had a heft chunk of torque being pulled and you stomped on the left pedal.

30 minutes ago, Dagobert666 said:

Can you tell me where the tilting moment comes from? The helicopter doesn't move. And the tail rotor is supposed to turn the helicopter, not tilt it?

This rolling moment is because the apaches tail rotor is so high up, that as you push the left pedal, you are making that tail rotor push to the right. Simultaneously it will try to make the tail tip over to the right. On smooth ground this can be accounted for with a little bit of left cyclic, but on a soft desert like you landed on, that rolling moment will be the only motion produced by the tail rotor. So your massive left pedal input is doing only one thing and thats tipping the heli to the right, which is exactly what we saw.

So lesson learned. Don't ground taxi when you land off field in the desert.

Edited April 15, 2022 by Swift.

[Dagobert666]

I may have just found a workaround.

If you land off-road then you should release/unlock the tail wheel during the landing approach.
I've only tried it 3x but it seems to make landing in the sand much more stable. No more "Dynamic Rollovers" at the moment. 

[Swift.]

3 minutes ago, Dagobert666 said:

I may have just found a workaround.

If you land off-road then you should release/unlock the tail wheel during the landing approach.
I've only tried it 3x but it seems to make landing in the sand much more stable. No more "Dynamic Rollovers" at the moment. 

You landing was stable until you pressed on the left pedal whilst on the ground. You don't need to land with the tail wheel unlocked, just don't try and turn with it locked.

[Dagobert666]

14 minutes ago, Swift. said:

You landing was stable until you pressed on the left pedal whilst on the ground. You don't need to land with the tail wheel unlocked, just don't try and turn with it locked.

Thank you, I know what you want with your advice!

However, the track is an attempt by me to artificially create the problem.
But this has happened to me more often during the landing process (not only after I was already standing on the ground. Especially when landing with a heavy weight.
Then I have to push the left rudder down 60-70% every now and then just so that the bird stays straight and not turning to the right.
When I touch down, I have to be extremely careful to reduce the "anti-torque" synchronously with the colleciv, otherwise the Apache will immediately tip to the side.
I find that extremely difficult. I avoid this by unlocking the rear wheel trouble now.

Addendum: the 40% collective and 50% left rudder while already in contact with the ground situation also occurs during a normal landing. That's what I want to say. right now that's a death sentence in DCS. To avoid that, I simply unlock the rear wheel. This reduces the tilting moment to almost zero.

Edited April 15, 2022 by Dagobert666

[Swift.]

7 minutes ago, Dagobert666 said:

Thank you, I know what you want with your advice!

However, the track is an attempt by me to artificially create the problem.
But this has happened to me more often during the landing process (not only after I was already standing on the ground. Especially when landing with a heavy weight.
Then I have to push the left rudder down 60-70% every now and then just so that the bird stays straight and not turning to the right.
When I touch down, I have to be extremely careful to reduce the "anti-torque" synchronously with the colleciv, otherwise the Apache will immediately tip to the side.
I find that extremely difficult. I avoid this by unlocking the rear wheel trouble now.

I see, well its difficult to know what's going on without an accurate reproduction of the issue I guess. Apache is known for being a bit tippy afaik, and the track you did provide shows it being surprisingly stable on what amounts to not very stable ground at all.

[doclucio]

hi guys, noticed this thing and was trying to figure out the solution; i notuced it when landing on grass bit strangely also landing on parking lots or road all around.I understand that when the floor is soft, but why in parking lots?!?if you look at F2 ext cam you notice landing gears are under the floor...why that?!?it should be a hard surface...Any idea on how to solve that?!?