Brakes vs anti-lock bracking

Nice theory, and there is some truth to it, but you are extrapolating beyond reality.

Modern anti-skid system do take into account optimum tire slip. They use wheel sensors vs INS derived ground speeds. Things like rubber deposits, wet runways, etc, are all factors that anti-skid outperforms the nut behind the wheel.

Additionally, carrier aircraft use inordinately high tire pressures, in the 250-350 psi range. They are like landing on rocks back ashore, and require deft technique if anti-skid isn't available.

The pumping brakes comment earlier by another poster shows how so much irrelevant and erroneous information still persists. Pumping brakes does not, and never did help in stopping distance.

Anti-skid is your friend. Use it when appropriate, but not on a carrier deck where it can release or cause lag, and you end up going over the side out of your ejection seat's envelope. That isn't pretty.

Sooo, any new testing "achievements"? I've tested the brakes on the Hornet myself, and here are my thoughts (not professional). I need almost entire runway to stop this thing with anti-skid on while still trying to avoid brake locking. If I lock up the brakes I leave very nice traces of braking (black stripes down the entire runway...). Of course landing is as it should be, on speed, correct AoA, flaps full down. I extend the airbrake on the touchdown. Pumping the brakes doesn't help as mentioned earlier. If I go full on the brakes, I'm afraid I can pop the tires, and if I don't, I can barely manage to stop, sometimes have to use NWS HI to turn around.

I've tested the brakes on the Hornet myself, and here are my thoughts (not professional). I need almost entire runway to stop this thing with anti-skid on while still trying to avoid brake locking. If I lock up the brakes I leave very nice traces of braking (black stripes down the entire runway...)

Lot's of info missing. Runway length / elevation, approach speed / weight, temperature.

What do you mean with 'anti-skid on and avoid brake locking'? With the anti-skid on, you simply apply full braking and the wheels will not lock up.

Even with the anti-skid on you will produce black tire marks on the runway IRL with some anti-skid systems (although usually not as much as in the DCS Hornet)

Note: Extending the speedbrake during the landing rollout will degrade directional control during a crosswind landing (natops manual).

Nice theory, and there is some truth to it, but you are extrapolating beyond reality.

 

Modern anti-skid system do take into account optimum tire slip. They use wheel sensors vs INS derived ground speeds. Things like rubber deposits, wet runways, etc, are all factors that anti-skid outperforms the nut behind the wheel.

 

Additionally, carrier aircraft use inordinately high tire pressures, in the 250-350 psi range. They are like landing on rocks back ashore, and require deft technique if anti-skid isn't available.

 

The pumping brakes comment earlier by another poster shows how so much irrelevant and erroneous information still persists. Pumping brakes does not, and never did help in stopping distance.

 

Anti-skid is your friend. Use it when appropriate, but not on a carrier deck where it can release or cause lag, and you end up going over the side out of your ejection seat's envelope. That isn't pretty.

This is the answer to the thread. You use anti skid to maximum extent ashore, common procedure is to trap if you’re anti-skid failed ashore as well. You’re not going to beat the machine braking, all you will do is shred your tires instantly. With Anti skid on, you can touch down and slam on the breaks full force and it will modulate the pressures to minimize skids and slips to an exact level that a human cannot, that simple. Any case to be made to the contrary is worthless because that’s not how reality works. I’d be pretty uncomfortable trying to slow a jet down without antiskid.

As for break fires, those can happen with anti skid on and off. That’s just a function of converting the energy into heat. Usually it’s not an issue unless you’re on you’re 2nd high speed abort in a short time or max braking in a very hot environment when heavy.

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.

I think that’s the point, no one should be stopping in a shorter distance with anti skid off, but they are in the sim. We know it shouldn’t happen and there should be penelties for stomping on brakes with AS off, I mean, unless we’re gearing it more towards a game than a sim.

Lot's of info missing. Runway length / elevation, approach speed / weight, temperature.

 

What do you mean with 'anti-skid on and avoid brake locking'? With the anti-skid on, you simply apply full braking and the wheels will not lock up.

 

Even with the anti-skid on you will produce black tire marks on the runway IRL with some anti-skid systems (although usually not as much as in the DCS Hornet)

 

Note: Extending the speedbrake during the landing rollout will degrade directional control during a crosswind landing (natops manual).

In DCS wheels do lock up even with with the anti-skid on, that's the problem... Also I produce tire marks because WHEELS LOCK UP. About that missing info. Runways at Anapa and Gelendzhik, weight, about 3500lbs of fuel, no payload. Speed about 135-140 knots. And I've deployed the airbrake because there was NO WIND. At Anapa it's possible to stop with enough of the runway left. At Gelendzhik it's hard to land without going off for another try.

In DCS wheels do lock up even with with the anti-skid on, that's the problem... Also I produce tire marks because WHEELS LOCK UP. About that missing info. Runways at Anapa and Gelendzhik, weight, about 3500lbs of fuel, no payload. Speed about 135-140 knots. And I've deployed the airbrake because there was NO WIND. At Anapa it's possible to stop with enough of the runway left. At Gelendzhik it's hard to land without going off for another try.

It’s a 5900’ runway, I wouldn’t expect it to be comfortable. Larger, faster, heavier aircraft need more runway to slow down. With higher performance aircraft like this that don’t have nearly as much drag you have to factor in breaking distance when thinking of where to land.

I think that’s the point, no one should be stopping in a shorter distance with anti skid off, but they are in the sim. We know it shouldn’t happen and there should be penelties for stomping on brakes with AS off, I mean, unless we’re gearing it more towards a game than a sim.

Thanks Sniper, that is just what I was trying to get at earlier in this thread, but when I was accused of "missing the point" about how anti skid works I just had to let it be. Some consequences for abusing the aircraft would be welcome in the pursuit of realism.

In DCS wheels do lock up even with with the anti-skid on, that's the problem... Also I produce tire marks because WHEELS LOCK UP. About that missing info. Runways at Anapa and Gelendzhik, weight, about 3500lbs of fuel, no payload. Speed about 135-140 knots.

Again, the wheels can lock up slightly IRL with the anti-skid. The rapid opening and closing of the brakes produces tire marks on the runway. When looking at the Hornet in the external view, this seems to be actually the case.

If you turn the anti-skid off, your Hornet will start to skid almost immediately.

3500lbs fuel means a gross weight of approx 30000lbs which results in an approach speed of 130kts.

The corresponding landing roll is 4500ft and for a no flare landing from a 3deg GS, the total landing distance is 5500ft.

For the too high approach speed (135-140kts) you need to add 6-12% of the landing distance. 5900-6200ft.

Some consequences for abusing the aircraft would be welcome in the pursuit of realism.

The consequences are there, the Hornet starts to skid. With less non-anti-skid braking you wouldn't run into directional control problems but the landing roll would be longer.

The consequences are there, the Hornet starts to skid. With less non-anti-skid braking you wouldn't run into directional control problems but the landing roll would be longer.

Your argument is that if you stand on the brakes in an airplane as soon as you touch down (I don't care if it is a C172, and airliner, or a fighter jet) and continue to keep the tires locked the only consequence will be possible control issues? Okay.

Again, the wheels can lock up slightly IRL with the anti-skid. The rapid opening and closing of the brakes produces tire marks on the runway.

Tire marks on the taxiway or runway in RL are not indicator of wheel lock on aircraft tires. Aircraft tires tend to have a softer rubber compound and could leave marks even without locking the wheel. The tire do have a higher ply count that car or heavy truck tires. Truck tire can have 10 to 16 ply while I seen aircraft tire as high as 40 or more.

To the OP, only seen an aircraft land without anti skid once. IIRC, it was in Luke AFB, student pilot in a F-16, and he went to 10 cord line on one spot on the tires and blow them up, brakes where glowing red and almost catch fire.

Edit:

My point is that no using anti skid can increase stopping power but increases the chance to blow tire, catch brakes on fire and losing control above certain speed.

One question, at what speeds is the F/A-18 anti-skid on? I ask because on aircraft anti-skid normally comes on above certain speed and turns off below a certain speed.

Your argument is that if you stand on the brakes in an airplane as soon as you touch down (I don't care if it is a C172, and airliner, or a fighter jet) and continue to keep the tires locked the only consequence will be possible control issues? Okay.

Where did I say that all consequences are simulated? Fact is that there's a noticeable difference between anti-skid and non anti-skid braking.

Where did I say that all consequences are simulated?

The consequences are there,

There. Right there is where I saw you say that the consequences are simulated. When I tell my wife I put the trash out, I don't mean I left one of the cans out back and later try to explain "I never said I put all the trash out." But fair enough, I concede you never specifically said all of the consequences are modeled and that there is the possibility of losing control landing without anti skid that potentially offsets more stopping ability in DCS in this case.

Thanks to mvsgas for a good RL scenario relating to the dangers inherent to the equipment landing without antiskid.

There. Right there is where I saw you say that the consequences are simulated. When I tell my wife I put the trash out, I don't mean I left one of the cans out back and later try to explain "I never said I put all the trash out." But fair enough, I concede you never specifically said all of the consequences are modeled and that there is the possibility of losing control landing without anti skid that potentially offsets more stopping ability in DCS in this case.

 

Thanks to mvsgas for a good RL scenario relating to the dangers inherent to the equipment landing without antiskid.

Many of those other consequences you can encounter with the anti-skid on too though, so I'm not sure what point you're trying to make is?

Ummm...the only point I have been making this entire time is that I was agreeing with bbrz in post #4 of this thread.

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

My claim was and still is that such performance, absent severe consequences for the aircraft (like those pointed out by mvsgas in post #37), isn't correct. I really don't know why people want to argue with someone who agrees with them.

Those are two separate points.

Are you talking about stopping distance or damage from excessive braking?

Those are two separate points.

No, respectfully they are not.

Leaving a 2500 foot skid mark from locked tires and being able to simply refuel, rearm, and go is not realistic. And I don't think that being able to consistently and repeatedly stop shorter with the antiskid off, as documented by bbrz in post #4, and doing so with an airplane that is fit to immediately fly again because such effects are ignored, is realistic. The points are one and the same. And once that tire would blow, the pilot would be faced with learning how much braking action can be achieved on a bare wheel. Suffice to say the landing distance required calculation will be exceeded.

All that said, while an interesting issue it isn't something I would advocate ED dropping everything to fix when there are other pressing issues; this is a relatively minor thing. And if you think that aircraft tires can stand that sort of abuse without ill effect, then party on.

You're not listening. Additional failures from not using anti-skid would be welcomed, and would make its use more important, but it certainly does not magically provide more grip.

Since the Hornet is still EA and WIP we might see features like shredded tires later on like in the Su-25.

Additional failures from not using anti-skid would be welcomed, and would make its use more important....

Precisely what I have been saying. I guess I need to apologize for being unclear, I thought my last post laid out most clearly that I have no false notions of the "magic" properties of the antiskid switch. Yet twice in this thread you have set up and knocked down the strawman argument that I am claiming antiskid has anything at all to do with how a tire grips the runway (where the rubber meets the road, quite literally in this case) when I have clearly never said that. If something I said made you infer that, then my mistake for being less than succinct.

Since the Hornet is still EA and WIP we might see features like shredded tires later on like in the Su-25.

That would be a welcome addition IMO.