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Questions and Answers
What can excessive braking cause in tailwheel-type airplanes?
What is a challenge of modern high-speed jet aircraft brake systems?
What happens when the friction between the tire and runway is too great?
What is the ideal braking condition?
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What feature is needed in an antiskid system to detect changes in deceleration rate?
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What happens in a modern modulated antiskid system when a wheel decelerates too rapidly?
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What is the purpose of the auto-brake feature?
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What components work together in an antiskid system without human interference?
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What is a potential consequence of heavy braking on large-diameter tires on small wheels?
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How do multiple wheels on each side of modern high-speed jet aircraft affect brake control?
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What happens when the friction between the tire and runway slows the aircraft?
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What is the purpose of pumping brakes in manual antiskid control?
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What is the function of the control circuit in a modern modulated antiskid system?
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What happens to the brake-return system in an antiskid system?
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What is the effect of contamination on runway surfaces on brake control?
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What is the purpose of the auto-brake feature in conjunction with the antiskid system?
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Study Notes
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
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Description
Learn about the concerns and modern systems of airplane brake controls, including excessive braking risks and corrective actions to prevent tire blowouts and loss of control.
