How do aircraft brakes work

These are the called the spoilers as they literally spoil the airflow over the wing. This dumps any remaining lift the wings are generating, allowing the wheels to take all the weight and achieve maximum efficiency from the brakes.

The final part of the braking process comes from reverse thrust. This causes blockers inside the engine to deploy and a door in the side of the engine to slide backward. The air which normally leaves the engine out the back is deflected forward by the blockers and out through the door.

There are two stages of reverse thrust — idle reverse and max reverse. Idle reverse is used on most landings and max reverse is used when the landing performance requires it, normally when the aircraft is landing at hot or high elevation airfields. This forward directed airflow helps slow the aircraft down but is most efficient at high speeds. If using max reverse, we drop this down to idle reverse at 60 knots 70 mph and then back to normal thrust as we vacate the runway at around 20 knots 25 mph.

For every takeoff and landing which we carry out, we run a performance calculation to ensure that it is safe to do so. A large part of this is based on the braking effectiveness. On takeoff, we have to calculate the point at which it is no longer safe to stop. This speed, V1, marks the point after which we must continue to get airborne, no matter what the problem is.

The calculation of this speed is based mainly on the ability of the aircraft to stop. If the runway is slippery or a brake unit is inoperative, it will take a greater distance to stop. As a result, the V1 speed will be much slower than in normal dry conditions. This means that we will reach that speed sooner and there will be more runway remaining on which to stop. The aircraft is a lot lighter having used most of its fuel in flight and we are touching down at the start of the runway.

This gives the brakes much more distance to bring the lighter weight aircraft to a safe stop. All this is great at the design stage, but how did Boeing know for sure that the systems would perform as expected for real? Before the first was approved for flight, Boeing had to prove that vital systems, such as the brakes, would work in conditions far worse than would ever be expected in normal operation.

The greatest strain on the brakes comes not on landing as you might expect, but in the event of a rejected takeoff. In these situations, the aircraft is much heavier and there is far less runway remaining on which to stop. The aircraft was then loaded up to its maximum takeoff weight and accelerated to its maximum takeoff speed.

The pilots then slammed the thrust levers closed and allowed the rejected takeoff autobrake to do its thing. With the aircraft stopped safely on the runway, the brakes glowed red. They became so hot that the fuse plugs melted and the tires deflated. Yet still there was no danger to the aircraft. The firefighters even waited five minutes before dousing the brakes with water. This replicated the time it may take emergency services to reach an aircraft in a real world scenario.

Part of the reason behind testing the aircraft so rigorously is to determine how well it performs when the systems are degraded. This may have just been something minor such as a rivet missing up to something more important such as a brake unit not working. In these situations, pilots consult the Dispatch Deviations Guide to see what is legally acceptable to fly without and what implications this may have.

As a result of the degraded stopping ability, there are extra operational procedures which we must apply. This includes calculating the takeoff performance with two brakes inoperative and also leaving the gear down after takeoff.

When we select the gear up after takeoff, the wheels will be spinning at around mph. Finally, many jet airplanes use reverse thrust to assist with braking during landings. When landing, however, pilots may use the reverse thrust feature. Rather than projecting out the rear, the thrust will be projected out the front.

This reversal of thrust provides deceleration that allows airplanes to slow down more quickly when landing. Hoses are commonly used in both automobiles and airplanes. Consisting of rubber tubes, they are We use cookies to improve your experience.

By your continued use of this site you accept such use. For more information, please see our privacy policy. The Man Behind MechanicalJungle. I started this site to spread knowledge about Mechnical Engineering.

I am a Degree Holder in Mechanical Engineering. You can find him on Facebook , Tumblr, and Google News. Your email address will not be published. And although they are controlled by the computers, in the case of an emergency, the pilots are prepared to take over manually. Today, all modern airplanes are equipped with brakes. For an airplane to land successfully on the ground, it is imperative that those brakes function properly. The brakes are responsible for reducing the speed of the airplane.

In doing so, the airplanes take a significant amount so they can stop at the right time. They are also responsible for holding the airplane stationary during the engine run-up process and are responsible for steering it during the taxi. Most of the wheels of an airplane are equipped with a brake unit. The nose and the tail wheel however, do not have brakes. The brakes work in a rather simple way: they convert the kinetic energy of motion into heat energy. This is done with the help of friction.

Due to friction, a lot of heat is generated. For brakes to function effectively, it is important that they are properly maintained, inspected , and adjusted. Modern airplanes use disc brakes. The disc rotates as the turning wheel assembly rotates, but when brakes are applied, a stationary caliper resists the rotation by causing friction against the disc.

The design of the disc brake system and how complex it is varies from one airplane to another. It all depends on the size, weight, and the landing speed of the aircraft. Although there are a lot of types of brakes, we will study the most common ones: single brakes, dual brakes, and multiple brakes.

The large aircraft use segmented rotor brakes while older, larger aircrafts used expander tuber brakes.