Ground resistance

[Voodooflies]

As in the title, the plane seems to be restrained by the ground when taxiing which induce excessive usage of thrust.

[bkthunder]

I noticed this in the last patch. It seems that they fixed the problem on landing, in which the plane wouldn't slow down past 106 Kts, maybe they made the ground "more sticky" somehow for this reason??

[Davee]

I noticed this in the last patch. It seems that they fixed the problem on landing, in which the plane wouldn't slow down past 106 Kts, maybe they made the ground "more sticky" somehow for this reason??

 

+1

I've noticed that the nose hardly stays up at all during landing now. Perhaps IMHO, a correction too far in the other direction whereby the nose was staying up too long previously.

 

Ground resistance was one of the issues in another SIM that corrected similar issues.

[gospadin]

it should have very high yaw resistance (lateral traction of rubber tires), infinite roll resistance, and almost zero pitch resistance. The rolling resistance of the tires should be very low, but more than the pitch resistance from the ground/landing gear system. Without applying brakes, once the nose settles down, the plane should be able to roll for a mile or more I'd imagine, unless the tires were not inflated enough.

[bkthunder]

+1

I've noticed that the nose hardly stays up at all during landing now. Perhaps IMHO, a correction too far in the other direction whereby the nose was staying up too long previously.

 

Ground resistance was one of the issues in another SIM that corrected similar issues.

 

I don't think you should connect the nose staying up and the ground resistance. They have nothing in common (apart from the small friction of the main gear wheel axles). The nose was staying up because 106 Kts is still enough to keep it up. The problem was that the airplane wasn't slowing down.

 

I haven't tested, but if the nose now doesn't stay up at 100 Kts, then I don't think this is aerodynamically correct. The reason could be that they either modified the FM (but I don't think so), or that the wheels are generating too much friction NOT with the ground, but on the wheel axles, so like pulling the brakes.

[3rd Wing - Raiden]

Hi,

 

I was told by a French M-2000c pilot that they usualy put the nose wheel down around 110-115 kts otherwise the engine would touch the runway and you could smash the nose wheel trying harder to put the nose down.

 

The current behavior seems to match with the pilot's statement.

[Davee]

I don't think you should connect the nose staying up and the ground resistance. They have nothing in common (apart from the small friction of the main gear wheel axles). The nose was staying up because 106 Kts is still enough to keep it up. The problem was that the airplane wasn't slowing down.

 

I haven't tested, but if the nose now doesn't stay up at 100 Kts, then I don't think this is aerodynamically correct. The reason could be that they either modified the FM (but I don't think so), or that the wheels are generating too much friction NOT with the ground, but on the wheel axles, so like pulling the brakes.

 

Hi bkthunder,

I agree with your summation regarding aerodynamics keeping the nose up and wheel friction on axles as a possibility or combination thereof. (Although axles a bit finite to calculate and implement in a SIM at this level) However, ground resistance can also affect nose up duration for example by applying too much resistance to the wheels (like putting brake pressure on the rear wheels at the moment of touchdown) it will throw the center of balance forward and influence just how long the nose stays up. (I worked on another SIM team wherein this feature was adjusted to make just that situation change the landing roll-out and length of nose up attitude after touchdown. So IMHO, it is another possibility.

 

I also noticed when touching down there is great improvement in the roll-out compared to previous versions, but also, the nose slams down immediately for me unless I apply back pressure to keep it up. (This is at varying landing speeds and angles.) An interesting balance.

 

I'm glad CaptSmiley is making those fine adjustments and taking note of the feedback.

 

Cheers,

[Frederf]

It is also very important how the FCS deals with these torques. For example if you are at 14 degrees nose up, hands off, and the FCS is holding this pitch when a small nose position deviation is applied it should be seen that the control surfaces move to counter the nose motion and attempt to maintain the pitch.

 

It's a FBW airplane and if the nose is not held steady with no pilot input and enough air flow for the control surfaces to be effective then there's an issue with the control laws.

[Knock-Knock]

I landed the other day, and stopped well short, without using airbrake, drag chute or even the brakes. Only had the 2 Magic's and 2 530's on the pylons, and just shy of 2000kg of fuel, so wasnt a heavy plane.

 

Is better than before for sure, but maybe went a little too far?

[bkthunder]

Hi bkthunder,

I agree with your summation regarding aerodynamics keeping the nose up and wheel friction on axles as a possibility or combination thereof. (Although axles a bit finite to calculate and implement in a SIM at this level) However, ground resistance can also affect nose up duration for example by applying too much resistance to the wheels (like putting brake pressure on the rear wheels at the moment of touchdown) it will throw the center of balance forward and influence just how long the nose stays up. (I worked on another SIM team wherein this feature was adjusted to make just that situation change the landing roll-out and length of nose up attitude after touchdown. So IMHO, it is another possibility.

 

I also noticed when touching down there is great improvement in the roll-out compared to previous versions, but also, the nose slams down immediately for me unless I apply back pressure to keep it up. (This is at varying landing speeds and angles.) An interesting balance.

 

I'm glad CaptSmiley is making those fine adjustments and taking note of the feedback.

 

Cheers,

 

Yeah I agree, that's what I meant. I think they added some extra brake pressure to "cheat" (no offence intended here) on the landing behaviour. Maybe went a bit too far as you guys are saying.

From a purist perspective, the slowing down should really come by adjusting the aerodynamic drag, with a bit of drag from the wheels, and not by adding brakes in a scripted way. Anyway I guess this can be part of the mastery of tuning the FM to match all those charts and numbers in a sim..

[bkthunder]

Hey guys got some fixes in the next update to hopefully improve some of this stuff.

 

Full disclosure, no cheating in regards to the wheel braking is done to aid aerobraking its all done in the aerodynamics modeling.

 

That's great to hear! Thanks for chiming in :thumbup:

[VTJS17_Fire]

Hey guys got some fixes in the next update to hopefully improve some of this stuff.

 

Full disclosure, no cheating in regards to the wheel braking is done to aid aerobraking its all done in the aerodynamics modeling.

What does this mean exactly?

 

Currently, we can't set 100 RPM at take-off (but somebody mentioned it in the past), because the brakes don't hold it. Will this be solved?

[Voodooflies]

What does this mean exactly?

 

Currently, we can't set 100 RPM at take-off (but somebody mentioned it in the past), because the brakes don't hold it. Will this be solved?

 

As far as I know, real procedure involves usage of N=80% RPM on the brakes, not more, followed by an AB takeoff (by the way go arounds are made without AB). The plane usually holds itself at N=80% RPM but in some cases it starts to move a little bit for some reasons.

[jojo]

No, the break pressure increase when break engaged and N > 80%.

[Azrayen]

As far as I know

You know nothing, John Snow... :D

 

Joking aside, as jojo said, brakes should hold N=100 (specific high pressure). So I don't know where your 80% data comes from? AFAIK, 100% should be better (*).

OTOH, I agree that you have to go full A/B after releasing the brakes.

 

(*) currently (in DCS) this doesn't work (skiding when > 80ish %). Some more work for CptSmiley I guess :)

[Voodooflies]

You know nothing, John Snow... :D

 

Joking aside, as jojo said, brakes should hold N=100 (specific high pressure). So I don't know where your 80% data comes from? AFAIK, 100% should be better (*).

OTOH, I agree that you have to go full A/B after releasing the brakes.

 

(*) currently (in DCS) this doesn't work (skiding when > 80ish %). Some more work for CptSmiley I guess :)

 

Gotta get back to study then. :cry:

[jojo]

Gotta get back to study then. :cry:

 

Parking brake use 80 bars of hydraulic pressure.

But if you hold break pedals and apply > 80% RPM you activate holding point break, which send 280 bars of hydraulic pressure in break system.

 

Source BEAD report on Mirage 2000D take off incident.

Rapport public BEAD-air-A-2008-006-A.pdf

[Voodooflies]

It worths what it worths (well that's BMS)... but there are other sources regarding those N=80% RPM on the brakes runup procedure. That's how I've been taught so far. Unless being a real-word military pilot, it's pretty hard to find the real deal from the "idea" we get about the thing.

 

[ame]

[/ame]

 

 

EDIT: Flight manual states buster then burners at brakes release. However, the brakes don't restrain the aircraft at N=100% RPM.

 

Edited July 29, 2016 by Sacha

[TrigaNZ]

On taxi out the aircraft following me reported that I was leaving skid marks on the taxiway when I wasn't braking.

 

1.5.4 Beta MP

[Ilyushka00]

I overshot a taxi turn and went over the grass. That was basically the end of my flight because no amount of wet thrust was able to make that plane move again, not sure if this is also the way off-tarmac ground resistance is modelled.

[Rlaxoxo]

Welcome to DCS my friend

 

Happens with all jets