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Message: <blockquote data-quote="Hashan dis" data-source="post: 19048415" data-attributes="member: 124785">How Auto Brakes Work On Airline Jets <img src="http://www.boldmethod.com/images/learn-to-fly/aircraft-systems/automatic-brake-system/primary1.jpg" alt="" class="fr-fic fr-dii fr-draggable " style="" />       What are auto brakes, and how do they work? We'll look at how the auto brakes work on an MD-80, but for the most part, the concept is the same for all airline jets. <img src="http://www.boldmethod.com/images/learn-to-fly/aircraft-systems/automatic-brake-system/md-80.jpg" alt="" class="fr-fic fr-dii fr-draggable " style="" /> Auto Brakes: Doing The Work So You Don't Have To The Automatic Brake System (ABS), automatically applies brake  pressure during landing. Basically, it does the braking work for you  immediately after touchdown, so you don't have to press the brakes down  yourself. So why would you want the brakes to be automatic? Auto brakes help  ensure that the brakes are engaged at the right time during landing: not  too early, and not too late. That's especially important when you're  landing on a wet or snowy runway. <img src="http://www.boldmethod.com/images/learn-to-fly/aircraft-systems/automatic-brake-system/auto-brake-engagement-md-80.gif" alt="" class="fr-fic fr-dii fr-draggable " style="" /> When Auto Brakes Engage Auto brakes engage after the spoilers  deploy on landing (the spoilers automatically deploy when they sense  the main gear spinning up during touchdown). But there is a delay, based  on the auto brake setting that's used. <img src="http://www.boldmethod.com/images/learn-to-fly/aircraft-systems/automatic-brake-system/auto-brake-deploy.jpg" alt="" class="fr-fic fr-dii fr-draggable " style="" /> There are three auto brake settings that can be used for landing in the MD-80: MIN, MED, and MAX.  When the MIN and MED settings are used, auto brakes engage  approximately 3 seconds after the spoilers deploy, which helps you touch  the nose wheel down  normally. But when the brakes are set to MAX, they  engage approximately 1 second after the spoilers deploy, ensuring that  you have the most braking, for the longest period of time on the runway. The different settings are used based on runway length and condition.  But when the runway is contaminated with snow, like what happened on  the Delta flight, the MAX setting is typically used.   Max Brakes and Anti-Skid Max brakes (or any of the brake settings, for that matter) need  anti-skid in order for them to work. That's because when MAX auto brakes  engage, they apply the maximum braking effort they can. <img src="http://www.boldmethod.com/images/learn-to-fly/aircraft-systems/automatic-brake-system/anti-skid.gif" alt="" class="fr-fic fr-dii fr-draggable " style="" /> That's where anti-skid comes into play. The anti-skid system releases  pressure on the brakes when it senses the wheels are starting to skid.  When they spin up again, it re-applies brake pressure. This release and  re-application of brake pressure happens very quickly, much like what  happens with your car's anti-lock brake system. What all of this means is that combined, MAX auto brakes and  anti-skid give your aircraft the ability to apply the most brake  pressure possible, for the longest time on the runway, without allowing  any of the wheels to lock up and skid.   When Auto Brakes Disarm Obviously, in most cases, you don't want auto brakes to bring you to a  complete stop on the runway. You want to keep rolling so you can taxi  off and let the aircraft behind you land. So how to you disarm auto brakes? There are a few different ways. The first method is accomplished by pressing down on the brake  pedals, which, like most aircraft, are on the top portion of the rudder  pedals. When you press down to about 25% of the travel of the pedals,  the auto brakes disengage. At that point, you are in full control of the  brake pressure applied to the wheels. Remember, though, when this  happens, the anti-skid system is still working, preventing you from  skidding the tires. <img src="http://www.boldmethod.com/images/learn-to-fly/aircraft-systems/automatic-brake-system/pedals-disarm.gif" alt="" class="fr-fic fr-dii fr-draggable " style="" /> The second method to disarm the auto brakes is by pushing the thrust  levers forward. If you needed to go-around, you definitely wouldn't want  your brakes at max, so when the thrust levers start to come forward to  about 22 degrees, the auto brakes automatically disengage. <img src="http://www.boldmethod.com/images/learn-to-fly/aircraft-systems/automatic-brake-system/center-pedestal.jpg" alt="" class="fr-fic fr-dii fr-draggable " style="" /> Third, if the flaps are retracted to less the 26 degrees and the  jet's speed is above 70 knots, the auto brakes disarm. Again, this is  useful in a go-around scenario. And finally, if the spoilers are stowed,  the auto brake pressure is released.     What Happens If The Spoilers Don't Deploy On Landing? Auto brakes engage after the spoilers deploy during a landing. But  what happens when something goes wrong and the spoilers don't  automatically deploy? In the MD-80, you can manually deploy the spoilers by using the  lever, if for some reason they don't pop up automatically when you touch  down. And when they are manually deployed, the auto brakes are  activated.    Putting It All Together Auto brakes help you stop by automatically adding brake pressure  after touchdown and spoiler deployment. And while you're in the most  demanding phase of flight (landing), it's nice to know your jet can take  care of something like that for you. <a href="http://www.boldmethod.com/learn-to-fly/aircraft-systems/automatic-brake-system/" target="_blank">http://www.boldmethod.com/learn-to-fly/aircraft-systems/automatic-brake-system/</a> </blockquote>

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