max braking
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YYC the place to be
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max braking
what is the def of max braking. does that mean locking them up and pushing as hard as you can or what.....help me settle a debate. Thanks all.
Locked tire coefficient is lower than that, I think (oh the joys of dead brain cells) plus you just pooched the tire and risk it blowing out and doing bad things to all the expensive bits underneath (remember the Concord?).
Max braking with anti-skid is what you are aiming for without a-skid - a wheel that is close to locking but has not, quite.
Max braking with anti-skid is what you are aiming for without a-skid - a wheel that is close to locking but has not, quite.
"What's it doing now?"
"Fly low and slow and throttle back in the turns."
"Fly low and slow and throttle back in the turns."
Maximum braking occurs when the tire skids approximately 10 to 15 percent of the time it takes to make one revolution. This correlates with the value of time that anti-skid sensors require to recognize a skidding situation before the anti-skid system is enabled.
Note: I have recieved this information through an expert in the automotive industry. However, being that anti-skid systems were originally developed for aircraft and adopted later by vehicles, and that the major tire manufacturers develop both car and aircraft tires, I believe that the above information remains consistent between the two sectors.
Note: I have recieved this information through an expert in the automotive industry. However, being that anti-skid systems were originally developed for aircraft and adopted later by vehicles, and that the major tire manufacturers develop both car and aircraft tires, I believe that the above information remains consistent between the two sectors.
http://www.howtodothings.com/automotive ... ances.html
Same concept for cars:
Same concept for cars:
Emergency braking without ABS (anti-skid): Some cars are not equipped with anti-lock brakes. The technique you will use to stop in emergencies is different from those cars equipped with ABS. Stopping without ABS requires a little more care than stomping on the brake as hard as you can. If you do this, the wheels will lock up, and you may enter a skid and lose directional control of the car.
The correct technique for emergency stops in a car without ABS is to press the pedal to the point of maximum braking effectiveness without causing the tires to “lock up” or skid. This point of maximum braking occurs immediately before the point of locking. If the tires begin to skid, you should ease up a little on the brake pedal just long enough to allow the tires to begin rolling, and then resume maximum braking. Never slam on the brakes. Rather, ease the brakes into maximum braking.
Sorry KFC. No claim was made that the systems operate identically. The end goal of both systems, though through different methods as you mentioned, would be to attain the said proportions of skid to rotation of a tire to attain maximum braking.
Thanx for your clarification.
Thanx for your clarification.
KFC, that's too simplistic - older-technology anti-lock/skid on aircraft released the brake fluid back to the reservoir, which was why you never use it in an hydraulic failure situation lest you lose your braking toute suite. A Challenger is an example of this system.
Newer anti-lock/skid is like a car's, where the fluid is trapped in the line and the pressure is released and re-applied but the fluid does not return to the reservoir. Can't think of an example, but you could probably Google it.
Both systems 'modulate' the brakes, depending upon which system you are equipped with.
Newer anti-lock/skid is like a car's, where the fluid is trapped in the line and the pressure is released and re-applied but the fluid does not return to the reservoir. Can't think of an example, but you could probably Google it.
Both systems 'modulate' the brakes, depending upon which system you are equipped with.
"What's it doing now?"
"Fly low and slow and throttle back in the turns."
"Fly low and slow and throttle back in the turns."
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Flying Nutcracker
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I know a guy that did that trick in a stone boat on wheelskis, he was landing on pavement up in mayo, pukon - did a nose stand and then came down so hard on the tail he drove the wheel through the fuse 
I imagine its been done with a lot worse consequences on a lot bigger a/c.
I imagine its been done with a lot worse consequences on a lot bigger a/c.You will never live long enough to know it all, so quit being anal about it..
Of course you can lock 'em up at that speed.... there's almost no weight on your tires at 90mph!MAG1 wrote:I haven't had to REALLY apply full brake in the King Air 200(no anti-skid/lock anything) but my mechanic says even if I tried to lock 'em up at 90mph I wouldn't have the leg power to do it initially anyways.
You mean it's easier to lock them?Merlinman wrote:Of course you can lock 'em up at that speed.... there's almost no weight on your tires at 90mph!MAG1 wrote:I haven't had to REALLY apply full brake in the King Air 200(no anti-skid/lock anything) but my mechanic says even if I tried to lock 'em up at 90mph I wouldn't have the leg power to do it initially anyways.
Max
Real airplanes have weight-on-wheels systems to prevent locked wheels on landing - you can stand on the brakes on most large ac before touchdown and get a safe, VERY short, very abrupt landing.
Don't try it with the park brake, though.
Don't try it with the park brake, though.
"What's it doing now?"
"Fly low and slow and throttle back in the turns."
"Fly low and slow and throttle back in the turns."
You get the maximum possible amount of braking force when you apply enough brake pressure to almost lock up the tires. This is called "threshold braking"what is the def of max braking. does that mean locking them up and pushing as hard as you can or what.....help me settle a debate. Thanks all.
As was said before, you DO NOT want to lock your tires, under any circumstances. This not only applies to aviation, but also to motorsports. Here's why:
1: A locked tire's only friction coeffecient is that of it's rubber vs the pavement. BUT, if a tire is still turning while you apply brakes, the majority of friction is between the brake rotors vs the brake pads. This gives you a far higher Cf, which slows you down faster.
2: You cannot steer a locked up tire.
3: You will flat spot the tire, probably chord it and possibly deflate it.
4: You will also overheat the tire, which in essence, heat cycles it. Each time you do this, the tire heats up and cools down. Each time it does that, the molecular structure changes, and the tire compound becomes slightly harder. Harder tires offer LESS grip.
This is not entirely correct. Here is the way it should read:Maximum braking occurs when the tire skids approximately 10 to 15 percent of the time it takes to make one revolution. This correlates with the value of time that anti-skid sensors require to recognize a skidding situation before the anti-skid system is enabled.
Note: I have recieved this information through an expert in the automotive industry. However, being that anti-skid systems were originally developed for aircraft and adopted later by vehicles, and that the major tire manufacturers develop both car and aircraft tires, I believe that the above information remains consistent between the two sectors.
When ABS is invoked, the tire skids approximately 10 to 15 percent of the time it takes to make one revolution.
This is not the most efficient braking technique. Ideally, you would want to brake just hard enough to ALMOST invoke ABS.
The feasibility of doing this depends on a lot of things. Firstly, the equipment on the airplane. What kinds of antiskid or abs system does it have? does it have power assist hydraulic brakes, and how powerful is the assist? Can you feel it when the tires lock up? In a big plane, you might not be able to.
Secondly, the ability of the pilot. To put this in perspective, after 4 years of taking my non-ABS equipped Porsche to track days, I still cannot get perfect threshold braking every single time I brake deep into a corner. There is no freakin' way your average pilot is gonna be able to do it in an airplane when they have so much other crap to deal with. It's WAY easier to just mash the brakes and let the ABS/Antiskid deal with it, or if you don't have antiskid, just apply enough to not skid without trying to be a hero.
It depends on the system. Some high end cars have better antilock systems than some aircraft do, however with cars, you don't have to worry about crasy yaw induction when one side grabs and the other doesn't. I think that most newer airliners can automatically deduce if you have applied too much pressure, and will prevent you from locking the tires to begin with. (pro-active system) If they do lock, the system releases brake pressure, lets the tire start to turn again, and reapplies just enough pressure to keep it turning. Most cars will simply start to pulse the brake lines once you have locked the tire. (re-active system) Better systems have faster pulses.There is a big difference between aircraft antiskid and automotive antilock. Antiskid modulates, antilock releases.
