How do Aircraft BRAKES work?!

How Do Aircraft Brakes Work?

Introduction to Aircraft Brakes

• The discussion begins with an overview of aircraft brakes, including their materials, governing systems, and the ability to absorb kinetic energy during a rejected takeoff.

• The video is introduced as part of a collaboration with Brilliant, emphasizing innovative learning methods in math and coding.

Importance of Aircraft Brakes

• The necessity for brakes on aircraft is highlighted; they are crucial not only for taxiing but also for stopping during critical phases like takeoff.

• Unlike cars, aircraft must be certified to stop from high speeds (V1), which requires robust braking systems capable of handling maximum kinetic energy.

Kinetic Energy Calculations

• An example using the Airbus A380 illustrates the immense kinetic energy involved: at maximum weight (575 metric tons), it can reach 2.2 gigajoules of energy at V1 speed (170 knots).

• This amount of energy is compared to that of an average lightning strike, underscoring the extreme demands placed on aircraft brakes.

Brake System Design

• Certification processes require demonstrating that an aircraft can safely stop from maximum takeoff weight and speed, leading to significant brake heating.

• The design specifics include disc brakes located on main wheels; nose wheels typically do not have brakes due to weight distribution considerations.

Mechanism of Action

• Aircraft utilize multiple stator and rotor discs within each wheel's brake system; hydraulic actuators push these discs together when braking is initiated.

• Friction generated between these discs converts kinetic energy into heat, effectively slowing down the aircraft.

Braking Systems on the 737: Steel vs. Carbon

Overview of Brake Types

• The Boeing 737 utilizes either steel or carbon brake disks, with most early models equipped with steel brakes due to lower manufacturing costs.

• Carbon brakes are preferred for high-performance military jets and long-haul aircraft because they are significantly lighter, which benefits fuel efficiency over long distances.

Performance Comparison

• Steel brakes weigh approximately 320 kilos more than carbon brakes and have a shorter lifespan; carbon brakes can last nearly twice as long.

• Carbon brakes offer superior heat resistance and dissipate heat more effectively than steel, which is crucial during short flights where heat buildup can occur.

Heat Management Challenges

• Steel brakes become less effective when temperatures exceed about 650 degrees Celsius, leading to reduced braking performance.

• During short sectors, repeated braking leads to residual heat accumulation in steel brakes, potentially compromising safety during critical phases like takeoff.

Brake Cooling Procedures

• Airlines implement brake cooling schedules to manage temperature after landings, especially when landing on short fields that require heavy braking.

• Some 737 models feature brake temperature indicators; however, many do not, necessitating manual calculations for safe operations.

Transition to Carbon Brakes

• The cost of carbon brakes has decreased significantly, prompting Boeing's initiative to retrofit them onto existing 737 fleets for improved performance and environmental benefits.

• Maintenance practices differ between brake types: strong braking wears down steel brakes while frequent applications affect the lifespan of carbon brakes.

Understanding the Anti-Skid System

Functionality of Anti-Skid System

• The anti-skid system on the 737 operates similarly to an automobile's ABS by preventing wheel skidding during braking.

• It maximizes friction between tires and runway by monitoring wheel movement and adjusting brake pressure accordingly.

Operational Dynamics

• The system continuously cycles through adjustments; it releases brake pressure if skidding is detected and reapplies once traction is regained.

Brake Systems and Redundancy in Aircraft

Importance of Brake Systems

• The brake accumulator is crucial; losing the anti-skid system significantly reduces weight capacity, often prohibiting passenger transport and limiting operations to dry runways.

• The brake system is essential for stopping aircraft, making it a critical component of flight safety.

Aerodynamic Aids to Braking

• Flight spoilers create aerodynamic drag by reducing lift on wings, enhancing brake efficiency during landing or rejected takeoff scenarios.

• Trust reversers contribute less to stopping than expected; further details are available in a separate video.

Redundancy Mechanisms

• The brake system features a three-step redundancy: hydraulic B powers brakes under normal conditions, with hydraulic A taking over if B fails.

• In extreme cases where both hydraulic systems fail, the brake pressure accumulator provides limited braking applications.

Emergency Procedures

• Pilots must apply continuous pressure on brakes after losing hydraulic systems to avoid depleting accumulator pressure through pumping.

Auto Brake System Functionality

• The auto brake system eases pilot workload and enhances passenger comfort during braking, especially vital during rejected takeoffs.

• There are four auto brake settings (1, 2, 3, Max), each providing predetermined deceleration rates based on runway conditions.

Rejected Takeoff (RTO)

• RTO setting is armed before every takeoff and activates automatically if the aircraft exceeds 90 knots during a rejected takeoff scenario.

• Automatic braking engages immediately upon recognizing an RTO situation, minimizing stopping distance without requiring pilot intervention.

Additional Resources

Learning Tool Recommendations

Overview of the Mentor Aviation App

• The speaker endorses the Mentor Aviation app as a valuable learning tool for users interested in aviation.

• Users are encouraged to download the app for free, highlighting its accessibility and potential benefits.

• The speaker suggests considering purchasing either one of the collections or opting for the all-in-one collection, which is presented as offering the best value.

• A positive tone is maintained throughout, with an emphasis on having a fantastic day, indicating a friendly and engaging approach to communication.