Airplane Brake Systems and Safety Concerns

Brake Control Concerns

• Excessive braking can cause a nose-over or ground loop in tailwheel-type airplanes
• Heavy braking can cause tires to slip on rims and pull out valves in large-diameter tires on small wheels

Modern Brake Systems

• Most modern high-speed jet aircraft have multiple wheels on each side, controlled by a single pedal
• No way to know when one wheel begins to skid
• Prompt corrective action needed to release locked-up wheel to prevent tire blowout and loss of control

Brake Friction and Tire Slippage

• Friction from brakes reduces wheel rotation rate and slows aircraft
• Friction between tire and runway slows aircraft, but too much can cause tire to slip instead of grip
• Slowing tire rotation rate too rapidly can cause tire to slip and lead to skid
• Applying only enough brake pressure to cause tire to just begin to slip produces maximum deceleration rate
• Maintaining optimum friction is difficult, as less brake pressure is needed as aircraft slows

Contamination and Runway Conditions

• Contamination like water, snow, or ice on runway reduces coefficient of friction between tire and runway
• Complicates maintaining right amount of brake pressure for maximum braking without excessive tire slippage

Manual Antiskid Control

• Pumping brakes to slow wheel and then releasing before wheel locks up is a simple form of manual antiskid control
• This method only works when control valves can operate very quickly

Ideal Braking Condition

• Applying brake pressure until wheel starts to slip, but not skid, is the ideal condition
• However, pilot has no indication when slip is reached and continues to increase brake pressure

Antiskid System Requirements

• Two features needed: wheel-speed sensor to detect change in deceleration rate and valve that can release pressure before wheel gets into a skid
• Retained pressure prevents brake-return system from pulling pressure plate all the way back, allowing brakes to reapply quickly

Modern Modulated Antiskid System

• Provides fastest wheel-speed recovery and minimum stopping distance on any runway surface
• Pilots need to depress brake pedals all the way to induce maximum braking
• If wheel decelerates too rapidly, indicating impending skid, some pressure is dumped into system-return manifold
• Control circuit measures time required for wheel to spin back up and applies reduced pressure to brake

Auto-Brake Feature

• Works in conjunction with antiskid system
• Automatically applies brakes when system senses weight on main wheels to produce one of several pilot-selected levels of deceleration
• Pilot can override and disarm autobrake system by applying manual brakes

Anti-Skid System Components

• Wheel speed sensors
• Anti-skid control valves
• Control unit
• These components work together without human interference to slow the aircraft without pedal input

Brake Control Concerns

• Excessive braking can cause nose-overs or ground loops in tailwheel-type airplanes
• Heavy braking can lead to tire slippage on rims and valve stem pull-out in large-diameter tires on small wheels

Modern Brake Systems

• Modern high-speed jet aircraft typically have multiple wheels on each side, controlled by a single pedal
• There is no way to detect when one wheel begins to skid
• Prompt corrective action is necessary to release locked-up wheels and prevent tire blowouts and loss of control

Brake Friction and Tire Slippage

• Brake friction reduces wheel rotation rate, slowing the aircraft
• Friction between the tire and runway slows the aircraft, but excessive friction can cause tire slippage instead of grip
• Rapidly slowing tire rotation rates can cause tire slippage and lead to skids
• Maximum deceleration rate is achieved by applying enough brake pressure to cause the tire to just begin slipping
• Maintaining optimal friction is challenging, as less brake pressure is needed as the aircraft slows

Contamination and Runway Conditions

• Runway contamination (e.g., water, snow, or ice) reduces the coefficient of friction between the tire and runway
• Contamination complicates maintaining the right amount of brake pressure for maximum braking without excessive tire slippage

Manual Antiskid Control

• Pumping brakes to slow the wheel and then releasing before it locks up is a simple form of manual antiskid control
• This method only works when control valves can operate rapidly

Ideal Braking Condition

• The ideal braking condition is when brake pressure is applied until the wheel starts to slip, but not skid
• However, pilots have no indication when slip is reached, and often continue to increase brake pressure

Antiskid System Requirements

• Two essential features are needed: wheel-speed sensors to detect changes in deceleration rates and valves that can release pressure before the wheel skids
• Retained pressure prevents the brake-return system from pulling the pressure plate all the way back, allowing brakes to reapply quickly

Modern Modulated Antiskid System

• This system provides the fastest wheel-speed recovery and minimum stopping distance on any runway surface
• Pilots must depress the brake pedals all the way to induce maximum braking
• If the wheel decelerates too rapidly, indicating an impending skid, some pressure is dumped into the system-return manifold
• The control circuit measures the time required for the wheel to spin back up and applies reduced pressure to the brake

Auto-Brake Feature

• This feature works in conjunction with the antiskid system
• It automatically applies brakes when the system senses weight on the main wheels, producing one of several pilot-selected levels of deceleration
• Pilots can override and disarm the autobrake system by applying manual brakes

Anti-Skid System Components

• Wheel speed sensors
• Anti-skid control valves
• Control unit
• These components work together without human interference to slow the aircraft without pedal input

Brake Control Concerns

• Excessive braking can cause nose-overs or ground loops in tailwheel-type airplanes
• Heavy braking can lead to tire slippage on rims and valve stem pull-out in large-diameter tires on small wheels

Modern Brake Systems

• Modern high-speed jet aircraft typically have multiple wheels on each side, controlled by a single pedal
• There is no way to detect when one wheel begins to skid
• Prompt corrective action is necessary to release locked-up wheels and prevent tire blowouts and loss of control

Brake Friction and Tire Slippage

• Brake friction reduces wheel rotation rate, slowing the aircraft
• Friction between the tire and runway slows the aircraft, but excessive friction can cause tire slippage instead of grip
• Rapidly slowing tire rotation rates can cause tire slippage and lead to skids
• Maximum deceleration rate is achieved by applying enough brake pressure to cause the tire to just begin slipping
• Maintaining optimal friction is challenging, as less brake pressure is needed as the aircraft slows

Contamination and Runway Conditions

• Runway contamination (e.g., water, snow, or ice) reduces the coefficient of friction between the tire and runway
• Contamination complicates maintaining the right amount of brake pressure for maximum braking without excessive tire slippage

Manual Antiskid Control

• Pumping brakes to slow the wheel and then releasing before it locks up is a simple form of manual antiskid control
• This method only works when control valves can operate rapidly

Ideal Braking Condition

• The ideal braking condition is when brake pressure is applied until the wheel starts to slip, but not skid
• However, pilots have no indication when slip is reached, and often continue to increase brake pressure

Antiskid System Requirements

• Two essential features are needed: wheel-speed sensors to detect changes in deceleration rates and valves that can release pressure before the wheel skids
• Retained pressure prevents the brake-return system from pulling the pressure plate all the way back, allowing brakes to reapply quickly

Modern Modulated Antiskid System

• This system provides the fastest wheel-speed recovery and minimum stopping distance on any runway surface
• Pilots must depress the brake pedals all the way to induce maximum braking
• If the wheel decelerates too rapidly, indicating an impending skid, some pressure is dumped into the system-return manifold
• The control circuit measures the time required for the wheel to spin back up and applies reduced pressure to the brake

Auto-Brake Feature

• This feature works in conjunction with the antiskid system
• It automatically applies brakes when the system senses weight on the main wheels, producing one of several pilot-selected levels of deceleration
• Pilots can override and disarm the autobrake system by applying manual brakes

Anti-Skid System Components

• Wheel speed sensors
• Anti-skid control valves
• Control unit
• These components work together without human interference to slow the aircraft without pedal input

Learn about the dangers of excessive braking in airplanes, including nose-over and ground loop risks, and understand modern brake systems in high-speed jet aircraft. Identify corrective actions to prevent tire blowouts and loss of control.