Brakes vs anti-lock bracking

I tried the anti-lock braking on a runway, not on carrier. I was not happy, going back to regular braking. The braking was too weak and did not slow me like I expected. Not sure if the code needs tweaked or not. Anyone else find the braking lacking on regular runways ? :pilotfly:

Not at all. I never have issues getting the Hornet slowed down

I like anti-lock you can keep your brakes full on and it goes straight. Never have trouble stopping.

I tried the anti-lock braking on a runway, not on carrier. I was not happy, going back to regular braking. The braking was too weak and did not slow me like I expected. Not sure if the code needs tweaked or not. Anyone else find the braking lacking on regular runways ? :pilotfly:

Just made a few rejected takeoff tests at 90kts with and without anti-skid and the difference is surprising.

With anti-skid ON, the F/A-18 needs ~5-10% more runway to come to a complete stop than with anti-skid OFF!

The only advantage of the DCS Hornet anti-skid is that keeping her straight is way easier ;)

Don't know if it's realistic, but at low weight, the brakes can't hold the F/A-18 at more than 90% RPM.

The brakes aren't exactly powerful, but they slow the Hornet down ok IMO.

edit: just compared with YouTube and it looks like the brakes are capable of holding the Hornet back up to (almost?) MIL thrust.

btw, nice find Ramstein :)

They do seem to be a little less effective than desired (especially if you REALLY needed to stop in a hurry), but that's only coming from comparison vs. other DCS aircraft and my own feeling. In a normal scenario, though, I find it's sufficient - I've never had trouble getting down to taxi/turnoff speed by the 2/3 or 3/4 mark.

On runways, deploying the speed brake, full flaps (if not already) and pulling the stabs all the way up helps slow the jet tremendously. You can also use a little L/R deflection on the stabs to make micro-adjustments and keep the jet on center, down to a certain speed anyway. Common practice for field rollouts IRL to minimize wear and damage to the brakes.

It's the same with an auto, ABS brakes requires far more stopping distance but it gives you steering control. You can see this clearly in winter driving...just as you are about to rear end someone

It's the same with an auto, ABS brakes requires far more stopping distance but it gives you steering control.

I have never seen a single aircraft flight manual that reflects better braking performance with the anti-skid off. In fact, computed landing distances of 10 percent or (much) more are the norm, to the point that many aircraft do not even allow dispatch with an inoperative anti-skid system.

This would lead me to believe that the Hornet should behave the same way during a field landing -- shorter landing distances with maximum braking effort when the anti-skid is enabled v when it is inoperative. Of course that is just speculation; is the F18 takeoff/landing performance data public knowledge yet? That would settle this quickly...

It's the same with an auto, ABS brakes requires far more stopping distance but it gives you steering control. You can see this clearly in winter driving...just as you are about to rear end someone

Don't agree and I don't know what car you are driving. A locked wheel always has a much lower friction coefficient than a rotating wheel.

On a wet/snow covered runway (street in your example) the difference between a locked wheel and a rotating wheel is even greater.

.. is the F18 takeoff/landing performance data public knowledge yet? That would settle this quickly...

It is and the performance section says: use full anti-skid braking

It is and the performance section says: use full anti-skid braking

As expected. That answers that. 2nd the good catch to Ramstein.

An anti skid braking system provides improved stopping distance as a secondary effect. A simplified description is that the system is ‘threshold braking’ much more effectively and precisely than an average person can. The primary purpose of anti-skid, and ABS in cars, is to maintain directional control under heavy braking. There are plenty of examples of skilled (professional) drivers being able to achieve better stopping distances with an ABS system disabled.

All that said, I definitely feel the F-18’s brakes are too weak with anti-skid enabled.

On a related note, is it good practice to hold full flaps and speed brake all the way to taxi speed or should you lift flaps at some point to get more weight on the wheels?

It does seem to take a lot of runway to stop (from on speed approach).

Anti-skid isn't used aboard ship because it can result in lag between brake application at brake actuation in some situations at low taxi speeds. It is just a precaution that makes a lot of sense taxiing around a ship in close quarters on a slippery. worn non-skid on the eighth month of a six month cruise.

There are plenty of examples of skilled (professional) drivers being able to achieve better stopping distances with an ABS system disabled.

Sorry sir, I'm going to disagree here (at least for aircraft). By this logic airline captains should disable their antiskid if their factored landing distance is really close to the landing runway distance available. After all, they are by the very definition the "professional" operators you cited and this technique would allow them to stop shorter if that is true.

I would like to see a source on the primary function of antiskid on an aircraft being directional control. I agree that AS systems are all about threshold braking, and when it comes to preventing tire blowout or flatspotting during maximum effort braking I will trust the computer every time. When it comes to contaminated runways, even more so to prevent wheel lockup. But if antiskid really did start out as a measure to prevent direction control loss on landing or RTO, I'll be happy to admit I'm incorrect.

And thanks Victory, that explanation makes sense to me.

An anti skid braking system provides improved stopping distance as a secondary effect. A simplified description is that the system is ‘threshold braking’ much more effectively and precisely than an average person can. The primary purpose of anti-skid, and ABS in cars, is to maintain directional control under heavy braking. There are plenty of examples of skilled (professional) drivers being able to achieve better stopping distances with an ABS system disabled.

All that said, I definitely feel the F-18’s brakes are too weak with anti-skid enabled.

It's not really possible to compare an aircraft anti-skid system with a car anti-skid.

1. On most aircraft only the main 'rear' wheels are used for braking.

2. Since the braked wheels are way behind and below you, contrary to a car, you have usually no feedback or any clue if you are locking up the wheels when applying brakes without anti-skid.

Just did a quick test at 32000lbs where the landing roll should be 4500ft and I used approximately 4700ft (500ft field elevation ISA +5°C) This doesn't look too far off, if at all. I'll do a few more tests…

@danny875 No way you retract the flaps during the landing roll. This is mostly applicable to bush flying ;)

The main answer to the OP's question lies in the fact this is a game. We don't get brake fires in game nor can we perceive the brakes working (or not) in wet conditions. Lately folks are saying this or that needs tweaking because it doesn't seem right. My thought would be that the modeling has been done with RL Hornet drivers and maintainers. While there are lots of bugs in the module, some can be related to game effect over real feel.

I'm not going to buy that argument mariner. If data is available that clearly shows ac performance under a given set of circumstances doing one thing in reality and in the sim it does another, there is no reason not to point it out. And the issue isn't brake fires, the issue is that standing on the brakes during rollout on a dry runway with the AS off should shred tires almost instantly, or at the very least should not allow for shorter stopping distances than landing with AS on. Since the data is available, the RL hornet drivers you speak of would probably say the same.

I certainly don't consider this a game breaker or anything like that, but if people start using the "it's a game" excuse instead of pointing out issues that can clearly be defined in the frame of available data, I don't think that is a positive direction for the community or the devs. DCS seems like a special community to me and I would hate to see that change.

I just have the general feeling that anti skid isn't about right in DCS. The Yak-52 also brakes best with screeching tyres...

Well, Tom, believe as you will but as a RL pilot of both fixed and rotor-wing aircraft, brake fire is a real possibility with anti-skid or non equipped planes. I am the ultimate proponent of reality in DCS and have spent a LOT of time and money building a very well equipped simpit but, and this is what I said, unless you have a 6 dof platform that's allowing you to feel deceleration then you can't judge brake action in a sim. Not to many folks can afford that setup. Even with a motion seat like my Jetseat you can get the feel the brakes are on but not how much force is actually being applied. That is no a conclusion that can not be argued. As far as shredding tires, there is a little to say for that. The brakes on an aircraft are similar in form and function to a car.

The landing distance penalties are huge with anti-skid disabled in a jet, even more so in a heavy jet. If operable, it is on for takeoff and landing. See what I wrote above for why it is off for taxi on a flight deck.

Ugh. I think both Eldur and Victory have it spot on correct.

Mariner maybe you should tell us what RL type ratings you hold? As I said before...the book says the F18 stops shorter with antiskid on...why are you arguing against the AFM?

Ugh. I think both Eldur and Victory have it spot on correct.

 

Mariner maybe you should tell us what RL type ratings you hold? As I said before...the book says the F18 stops shorter with antiskid on...why are you arguing against the AFM?

You're still missing the point. Mariner is telling you that the physics of grip do not change when you turn anti-skid on or off. The reason quoted braking distances get longer with it off is because the pilot has to be much more cautious with brake application, not because there is less grip.

There's no contradiction between the AFM and what mariner is saying.

ABS should reduce braking distance since it reduces skidding allowing for more energy dissipation.

I'm adding 2 cents a little late, but hopefully this helps OP a bit.

ABS in a car is better than pumping your breaks to prevent skidding in a hard stop or on a slick surface because without it your wheels stop moving but you don't. Before ABS was common, you had to pump your brakes to be able to steer through adverse circumstances. Constant brake pressure on dry pavement, that doesn't lock your wheels, tends to work better in a normal stop.

For your test case, check to see if your wheels are locked up. Whether they are or aren't, it could be your wheels brake controller sensitivity isn't high enough to locked them up, or it could just be a sim improvement to potentially be addressed in a future update. We aren't going know unless ED decides to tell us.

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ABS should reduce braking distance since it reduces skidding allowing for more energy dissipation.

Not necessarily. Maximum grip between a tyre and ground is achieved with a limited amount of slip (the tyre has actually started to lock) of around 15%. Depending on how conservative the anti-skid is it may almost completely prevent any slip at all, thus not achieving the theoretical shortest braking distance.

Keeping the OP's point in mind (shorter braking distance with anti-skid off) I'm going to try and summarise some points and explain why this may not necessarily be wrong.

• Maximum deceleration is achieved with some wheel slip.
  
• Anti-skid may not necessarily provide the minimum theoretical stopping distance.
  
• Feedback for manual braking in an aircraft is not reliable.
  
• Brake locking is dangerous, as it can lead to loss of directional control or burst tyres.
  

The most important point is that anti-skid doesn't magically provide more grip than manual braking, and may in fact not even use all the grip that is available.

Manual braking can theoretically use all available grip, but in practice due to a lack of feel and the dangers of exceeding available grip this isn't something you would ever do in reality, but we can try this in DCS.

In short, if you can get a better result from manual braking, it might be due to a lack of punishment for doing something that would probably end badly in reality, rather than anything wrong with the way the braking distances are simulated themselves.