Community A-4E-C v2.2 (October 2023)

[JeffreyC]

Skidding had a bit of a problem. When the rear wheel locks up on one side and skids it should not cause the aircraft to suddenly start going straight forward. Especially if it was already in a turning condition previously. The reverse should happen, exacerbating the turning in the direction of the locked wheel rather than nullifying it.

Edited November 7, 2022 by JeffreyC

[JNelson]

On 11/6/2022 at 11:41 PM, JeffreyC said:

Skidding had a bit of a problem. When the rear wheel locks up on one side and skids it should not cause the aircraft to suddenly start going straight forward. Especially if it was already in a turning condition previously. The reverse should happen, exacerbating the turning in the direction of the locked wheel rather than nullifying it.

 

Static friction for rubber is higher than sliding friction. This means that a wheel which is skidding has less friction and therefore less braking force overall.

[JeffreyC]

11 hours ago, JNelson said:

Static friction for rubber is higher than sliding friction. This means that a wheel which is skidding has less friction and therefore less braking force overall.

Try it in real world if you have to. Your function for skidding is opposite of what is should be. A wheel locked on one side of a vehicle, no matter what the vehicle is, produces far greater friction than a turning wheel. Once again, skidding on one side does NOT cause straight movement! Further, with a caster wheel, locking the inward wheel will NOT reverse the caster movement.

Edited November 17, 2022 by JeffreyC

[Chronocidal]

It's also not even entirely a matter of static vs sliding.. it feels like the brakes locking causes the plane to accelerate, even in an absence of thrust, as if the combination of brake forces is causing a negative friction coefficient in some cases.

Maybe I'm imagining things, but it feels like there's some really weird math going on when using both brakes.  I know the caster front gear is accurate to the aircraft, but the physics of that steering system have sent me over the side of the deck more times in the past week of learning the A-4 than all of the rest of my flying in DCS combined.  

There was a later nosewheel steering upgrade to the A-4, I believe at the F-model, so I feel like it would be worth offering an option to use normal steering, if people want it.

[tigayot228]

2 hours ago, Chronocidal said:

There was a later nosewheel steering upgrade to the A-4, I believe at the F-model, so I feel like it would be worth offering an option to use normal steering, if people want it.

Thanks guy. If has option of nosewheel, I can maybe play again this flight. I had sarcoma in leg and now is dificulty turning flight in deck. Impossible

[Tshark]

2 hours ago, JeffreyC said:

Try it in real world if you have to. Your function for skidding is opposite of what is should be. A wheel locked on one side of a vehicle, no matter what the vehicle is, produces far greater friction than a turning wheel. Once again, skidding on one side does NOT cause straight movement! Further, with a caster wheel, locking the inward wheel will NOT reverse the caster movement.

 

To be clear, if you have two wheels braking and one locks, then the locked wheel produces less friction (stopping ability) that the turning wheel with braking pressure applied.  The vehicle will yaw in the direction of the braking wheel that is still turning. This is the basic physics behind anti-skid brakes.

[JNelson]

2 hours ago, JeffreyC said:

Try it in real world if you have to. Your function for skidding is opposite of what is should be. A wheel locked on one side of a vehicle, no matter what the vehicle is, produces far greater friction than a turning wheel. Once again, skidding on one side does NOT cause straight movement! Further, with a caster wheel, locking the inward wheel will NOT reverse the caster movement.

 

I appreciate your concern, but this is categorically false. Skidding always reduces the friction, a rolling wheel has static friction which can deliver more force through friction when the brakes are applied.

There are two perfect examples in the real-world of this effect:

• ABS (Anti-lock braking system) -> this keeps the wheels spinning to decrease stopping distance (over fully locking your wheels, a driver can out brake ABS but this is only because the cause the wheels to never skid whereas ABS will cause them to skid less).
• Traction control for launching a car, when accelerating it is widely known that when the wheels spin due to too much torque the force put through the wheels is much lower due to the reduce friction due to the wheel sliding.

Lastly google is sliding friction v static friction you will find that static friction is higher than sliding friction, see: 

 

2 hours ago, Chronocidal said:

It's also not even entirely a matter of static vs sliding.. it feels like the brakes locking causes the plane to accelerate, even in an absence of thrust, as if the combination of brake forces is causing a negative friction coefficient in some cases.

Maybe I'm imagining things, but it feels like there's some really weird math going on when using both brakes.  I know the caster front gear is accurate to the aircraft, but the physics of that steering system have sent me over the side of the deck more times in the past week of learning the A-4 than all of the rest of my flying in DCS combined.  

There was a later nosewheel steering upgrade to the A-4, I believe at the F-model, so I feel like it would be worth offering an option to use normal steering, if people want it.

Hi this is not the case, there is still force slowing the aircraft down just less of it. 

[JeffreyC]

26 minutes ago, Tshark said:

To be clear, if you have two wheels braking and one locks, then the locked wheel produces less friction (stopping ability) that the turning wheel with braking pressure applied.  The vehicle will yaw in the direction of the braking wheel that is still turning. This is the basic physics behind anti-skid brakes.

You have an incorrect basis. One wheel is spinning freely and the other is locked it will always turn in the direction of the locked wheel.

22 minutes ago, JNelson said:

I appreciate your concern, but this is categorically false. Skidding always reduces the friction, a rolling wheel has static friction which can deliver more force through friction when the brakes are applied.

 

 

Your own statement shows mine is categorically TRUE. This it not a state of brakes being applied to two wheels and one locks. this is a case of brakes being applied to ONE wheel which locks. The friction of a FREELY TURNING WHEEL is always LESS than that lock a wheel which is dragging. This is very basic rudimentary physics.
Move an object forward, stop wheel on one side, object turns to that side.

[Art-J]

You guys are talking about two completely different things - one of you describes the situation where the wheel on non-locked side rotates freely, the other one describes situation where the wheel on non-locked side brakes, but without locking (like ABS in cars). In such situation both of you are right at the same time, so maybe step back and figure out what the original question / issue was in the first place ;).

Edited November 17, 2022 by Art-J

[JNelson]

46 minutes ago, JeffreyC said:

You have an incorrect basis. One wheel is spinning freely and the other is locked it will always turn in the direction of the locked wheel.

Your own statement shows mine is categorically TRUE. This it not a state of brakes being applied to two wheels and one locks. this is a case of brakes being applied to ONE wheel which locks. The friction of a FREELY TURNING WHEEL is always LESS than that lock a wheel which is dragging. This is very basic rudimentary physics.
Move an object forward, stop wheel on one side, object turns to that side.

Firstly you never said that you were braking with only one side. Secondly the friction is still less when a wheel is skidding when compared to the static friction.

In the condition you go from optimal braking to skidding the wheel there will be less braking force and therefore less turning moment. The only time it will turn into a skidding wheel more is if previously your wheel was freely turning and if you actually test this in the sim this is the case.

A quick way to test is to use the takeoff mission, accelerate to about 40 knots and then slam one brake on, it will turn into the skidding wheel. If however you apply optimal braking on one wheel it will turn in that direction then increasing the brake until it skids will reduce how fast it turns but it will still turn into that wheel.

35 minutes ago, Art-J said:

You guys are talking about two completely different things - one of you describes the situation where the wheel on non-locked side rotates freely, the other one describes situation where the wheel on non-locked side brakes, but without locking (like ABS in cars). In such situation both of you are right at the same time, so maybe step back and figure out what the original question / issue was in the first place ;).

 

Because they said exacerbate the turn I assumed they meant they were already braking with that wheel and were increasing the brake until it skids not going from zero brake -> full brake. To exacerbate would indicate they already turning, which if no brakes applied shouldn't be the case. 

[JeffreyC]

43 minutes ago, JNelson said:

Firstly you never said that you were braking with only one side. Secondly the friction is still less when a wheel is skidding when compared to the static friction.

In the condition you go from optimal braking to skidding the wheel there will be less braking force and therefore less turning moment. The only time it will turn into a skidding wheel more is if previously your wheel was freely turning and if you actually test this in the sim this is the case.

A quick way to test is to use the takeoff mission, accelerate to about 40 knots and then slam one brake on, it will turn into the skidding wheel. If however you apply optimal braking on one wheel it will turn in that direction then increasing the brake until it skids will reduce how fast it turns but it will still turn into that wheel.

Because they said exacerbate the turn I assumed they meant they were already braking with that wheel and were increasing the brake until it skids not going from zero brake -> full brake. To exacerbate would indicate they already turning, which if no brakes applied shouldn't be the case. 

Firstly, I said right from the start it locked up on one side. You assumed, wrongly, there was braking on both. The condition you stated is exactly what happens. Maybe I can make it more clear:

Condition 1: start vehicle moving straight, press full right (or left) brake, that wheel locks and vehicle continues straight.
Condition 2: while vehicle is moving use light to moderate right or left brake as needed on that one side only to induce a turn. While turning, apply full brake only on that inward wheel (no brake on outer wheel). When wheel locks vehicle snaps to straight movement.

Hopefully this makes it more clear. Text can certainly be a limitation in conveying information at times and not a condition where a screen capture would be useful.

Oh, I should mention also, I did delete 2.0.1 for a clean install of 2.1.0 (DCS 2.8) to prevent weird copy over things from happening.

Edited November 17, 2022 by JeffreyC

[Chronocidal]

2 hours ago, JNelson said:

Hi this is not the case, there is still force slowing the aircraft down just less of it. 

This is the part that doesn't feel like it's actually working though.  It feels like there is -no- force slowing the plane down when both brakes lock, because they stop working, and the plane just starts gliding over the edge of the deck with no way to stop, as if pushed by something.

I'll go try it out in a few different conditions, it might have been a combination of wind and weather making things worse yesterday on the server I was on.

[SkateZilla]

2 hours ago, JeffreyC said:

You have an incorrect basis. One wheel is spinning freely and the other is locked it will always turn in the direction of the locked wheel.

Your own statement shows mine is categorically TRUE. This it not a state of brakes being applied to two wheels and one locks. this is a case of brakes being applied to ONE wheel which locks. The friction of a FREELY TURNING WHEEL is always LESS than that lock a wheel which is dragging. This is very basic rudimentary physics.
Move an object forward, stop wheel on one side, object turns to that side.

 

 

The Braking and grip Co-efficient of the wheel not locked is greater than the wheel that's locked.

 

If you accelerate then idle the throttle:
-Apply ONLY Left brake full, and locking the left gear, the aircraft will yaw left,
As the right gear is simply rolling w/ zero friction between tire and surface,
While the left is locked and skidding and the friction is greater than it's grip and moment of friction limits.

-While keeping left brake fully engaged, and left gear locked, Apply Right brake slowly and smoothly, but do not lock the gear/tire, the aircraft will begin to yaw to the right,

Because the left tire is already past the moment of friction limits and sliding, vs the right tire still having full grip and bring below it's grip and moment of friction limit.
Right side tire has braking grip and braking authority, vs Left side being in a slip state, has no authority, it's simply surface drag.

Now, while keeping consistent braking on the right gear, slowly release pressure from the left, and allow the tire to get below moment of friction limits, and begin to roll again, while still applying braking pressure, once the braking and moment of friction equalizes between left and right, the aircraft will stabilize and yaw in either direction will only happen due to uneven braking or surface deflection/drag.

 

 

this is how ABS works, if the OBC detects 1 wheel spinning faster than another (left to right and front to back),  it will lower pressure to the one wheel to keep them spinning at the same rate as the others, in heavy breaking most ABS Systems use Data between front and rear tires, as the front brakes are prone to lock up in heavy braking vs the rear.
 

Edited November 17, 2022 by SkateZilla

[JeffreyC]

Apply ONLY Left brake full, and locking the left gear, the aircraft will yaw left: NO, this is NOT what happens. That is what SHOULD happen but instead it goes straight.

There is no ABS on the A-4E so all this about ABS is meaningless.

 

[JNelson]

 

1 hour ago, JeffreyC said:

Firstly, I said right from the start it locked up on one side. You assumed, wrongly, there was braking on both. The condition you stated is exactly what happens. Maybe I can make it more clear:

Condition 1: start vehicle moving straight, press full right (or left) brake, that wheel locks and vehicle continues straight.
Condition 2: while vehicle is moving use light to moderate right or left brake as needed on that one side only to induce a turn. While turning, apply full brake only on that inward wheel (no brake on outer wheel). When wheel locks vehicle snaps to straight movement.

Hopefully this makes it more clear. Text can certainly be a limitation in conveying information at times and not a condition where a screen capture would be useful.

Oh, I should mention also, I did delete 2.0.1 for a clean install of 2.1.0 (DCS 2.8) to prevent weird copy over things from happening.

 

If you had said these conditions from the start it would have saved some confusion  . Condition 1 is not reproducible on my end. When I apply full brake on one side it turns towards that side, if you could demonstrate in a video that would be great.

For condition 2: I suspect what you are seeing is the transient of there being less force, aircraft and the caster on the front straightens a bit and the suspension compresses less, but if you let this transient settle (a few seconds) it will continue to turn in the direction of the locked wheel just slower than before. 

5 minutes ago, JeffreyC said:

Apply ONLY Left brake full, and locking the left gear, the aircraft will yaw left: NO, this is NOT what happens. That is what SHOULD happen but instead it goes straight.

There is no ABS on the A-4E so all this about ABS is meaningless.

 

People are using ABS as an example to explain static and sliding friction to you. Perhaps you should look closer because no one is suggesting the A-4E has ABS.

Edited November 17, 2022 by JNelson

[Chronocidal]

I messed with rolling around on taxiways a little, and I think I know what feels off to me.

It feels like the force necessary to reorient the nose wheel is too high.  It's not free-spinning, it takes a significant force to start trailing once it's oriented sideways.

Say I start with the front wheel oriented forwards, the plane will start rolling nicely at about 70% RPM.  If you apply little bits of brake, you can weave back and forth at that amount of thrust.  It's a comfortable taxi speed.

Now, say I want to make a sharp turn from a stop.  I lock the left brake, and gradually apply thrust.  At about 82% RPM, the plane will start to pivot around the left wheel, making a hard left turn.  That works fine.

The problem comes when you stop that turn, and don't coast forward long enough to reorient the front wheel.  You're now attempting to force the wheel to rotate back the other direction.  Except, now your thrust is perpendicular to the front wheel.  Locking the opposite brake, and attempting to pivot the other way on the right wheel will now take approximately 95% RPM to break free.  At that thrust?  You overcome the friction of both the locked right wheel, and the sideways front wheel, and start skidding directly ahead at near mil power.  You don't reverse direction, the wheels stop steering you at all.

I'm not sure where the physical description of the length of the lever arm for the front wheel caster is defined, but it might need either a longer lever arm, or a lower breakout force to induce rotation about its pivot.  I believe at least a couple of the times I've been having these weird coasting issues were caused by losing traction on the front wheel, and just skidding around with no control.  (Also, the slow spool time of the engine might be a factor, since it may still be giving a significant amount of thrust, despite cutting the throttle.)

I'm not familiar enough with the sim to know if it even has this sort of lever arm definition actually, or how the physics of this nosewheel work at all, so not sure whether this is fixable.  I'm only guessing that the way this works is something like an inverted taildragger.  I wonder if there is any mechanic to allow the wheel to roll backwards to let it pivot in place when a hard reversal is attempted.

-----

As a semi-unrelated side note.. the plane absolutely will not roll on grass.  I don't know why, but if you roll off the taxiway pavement, you stop dead, and no amount of thrust is going to budge the plane. 

Edited November 18, 2022 by Chronocidal

[JeffreyC]

25 minutes ago, JNelson said:

People are using ABS as an example to explain static and sliding friction to you. Perhaps you should look closer because no one is suggesting the A-4E has ABS.

 

The only reason to mention ABS is to presumes it was in the aircraft. I do have an understanding of physics and do not need badly done attempts at "explaining" things.

I have had both the conditions stated happen. It's strange you're getting different results. I will attempt to get a track file but we know how reliable those can be at times.

[JNelson]

1 hour ago, Chronocidal said:

I messed with rolling around on taxiways a little, and I think I know what feels off to me.

It feels like the force necessary to reorient the nose wheel is too high.  It's not free-spinning, it takes a significant force to start trailing once it's oriented sideways.

Say I start with the front wheel oriented forwards, the plane will start rolling nicely at about 70% RPM.  If you apply little bits of brake, you can weave back and forth at that amount of thrust.  It's a comfortable taxi speed.

Now, say I want to make a sharp turn from a stop.  I lock the left brake, and gradually apply thrust.  At about 82% RPM, the plane will start to pivot around the left wheel, making a hard left turn.  That works fine.

The problem comes when you stop that turn, and don't coast forward long enough to reorient the front wheel.  You're now attempting to force the wheel to rotate back the other direction.  Except, now your thrust is perpendicular to the front wheel.  Locking the opposite brake, and attempting to pivot the other way on the right wheel will now take approximately 95% RPM to break free.  At that thrust?  You overcome the friction of both the locked right wheel, and the sideways front wheel, and start skidding directly ahead at near mil power.  You don't reverse direction, the wheels stop steering you at all.

I'm not sure where the physical description of the length of the lever arm for the front wheel caster is defined, but it might need either a longer lever arm, or a lower breakout force to induce rotation about its pivot.  I believe at least a couple of the times I've been having these weird coasting issues were caused by losing traction on the front wheel, and just skidding around with no control.  (Also, the slow spool time of the engine might be a factor, since it may still be giving a significant amount of thrust, despite cutting the throttle.)

I'm not familiar enough with the sim to know if it even has this sort of lever arm definition actually, or how the physics of this nosewheel work at all, so not sure whether this is fixable.  I'm only guessing that the way this works is something like an inverted taildragger.  I wonder if there is any mechanic to allow the wheel to roll backwards to let it pivot in place when a hard reversal is attempted.

-----

As a semi-unrelated side note.. the plane absolutely will not roll on grass.  I don't know why, but if you roll off the taxiway pavement, you stop dead, and no amount of thrust is going to budge the plane. 

 

I've spent hundreds (not joking) of hours on trying to get the caster to spin more freely and on the suspension in general and there is nothing I'm afraid. The not rolling on grass is common theme with most planes in DCS.

[JeffreyC]

Got together a couple tracks.
First locked left brake from straight movement resulting in very little left movement over a long stretch.
Second started a left turn then applied full left brake. Turn straightened out immediately as is left brake had been tapped to pull the caster back to center then little turn remained to left. Even if drag force was exactly equal as the wheel with no brake, which of course it isn't, it should have remained in the caster turn and slowly straightened rather than the effect of opposite direction pull.

left turn strightens out to very little turn.trk left brake hardly any left pull.trk

[Chronocidal]

Thanks for the clarification, guess it doesn't really have the physics built in to run it well.

Though.. I have to wonder, is there a way to define an invisible tailwheel, and see if that improves the functionality any?  I know taildragger aircraft exist, so I'm wondering how the plane would behave if you could give it a wheel back there that would drag, rather than being pushed ahead of the main gear.  No idea if that's possible, but it would be hilarious if it worked.

Don't mind me, I have a history of making making crazy work-arounds to get simulator mods to imitate things not natively possible.  

[UN9249]

Hi! after last update my plane is crashing on start up from ground. It seems he fell from 1m of high. On a carier and on a field.

[western_JPN]

8 hours ago, UN9249 said:

Hi! after last update my plane is crashing on start up from ground. It seems he fell from 1m of high. On a carier and on a field.

In my testing A-4E-C mod v2.1.0 on DCS World 2.8.0.33006 openbeta with A-4E's Instant Actions (Caucasus or Marianas / Takeoff or Cold Start),
A-4E looks a bit (perhaps 5cm or 10 cm) falling in its ground mission starting , but not so big value like 1m.

One reason I can think; mod's update failed like some same named files not overwritten.
How about once clean-up A-4E-C mod folder from your Mods/aircraft/ and install the latest v2.1.0 ?

[UN9249]

9 hours ago, western_JPN said:

How about once clean-up A-4E-C mod folder from your Mods/aircraft/ and install the latest v2.1.0 ?

That helped. Thank you.

[inni51]

Несколько не по теме. Уважаемые пилоты, кто может подробно описать, как работает навигационный компьютер AN/ASN-41 ? Как выставить координаты точек D1 и D2 и как их изменять в полете. Посмотрел несколько видео на эту тему,  но так как объясняют, у меня не работает (версия 2.1.0) и в мануале тоже не совсем понятно изложено. Буду очень признателен.

[JeffreyC]

4 hours ago, inni51 said:

Несколько не по теме. Уважаемые пилоты, кто может подробно описать, как работает навигационный компьютер AN/ASN-41 ? Как выставить координаты точек D1 и D2 и как их изменять в полете. Посмотрел несколько видео на эту тему,  но так как объясняют, у меня не работает (версия 2.1.0) и в мануале тоже не совсем понятно изложено. Буду очень признателен.

Set the dial to the point you'd like to set/change, D1 or D2. on the small knobs to the left of the coordinates right and left click the base portion to change the value higher and lower. This can be done both on the ground and in flight.