Aircraft Brake Metering for Structural Load Alleviation
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Solution Overview
Problem
Current aircraft electric brake systems face challenges in achieving accurate brake clamping force, leading to uneven brake energy distribution, which affects directional stability and causes structural fatigue and damage during low-speed taxiing and rapid braking, failing to meet industry standards for accuracy and safety.
Innovation Solution
The system divides electric brake actuators into two portions, one for low clamping force and one for high clamping force, and introduces a brake metering function that delays the full onset of braking by limiting initial brake effort to a preset fraction for a set period, allowing for more precise control and reduced structural loading without requiring speed-based conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Duration of action of stationary object
If a minimum light residual clamping brake force is maintained during taxiing, then brake wear is reduced, but brake clamping force accuracy deteriorates and directional stability is affected
Solution Approach 1:
The brake actuator is divided into multiple independent actuators (first, second, third, and fourth actuators) that can be controlled separately. This segmentation allows selective application of brake force to specific wheels, enabling precise control of residual clamping force while maintaining overall braking effectiveness and directional stability.
Solution Approach 2:
Different residual clamping forces are applied to different wheels based on their specific operational requirements. The system selectively maintains residual force on certain wheels while allowing others to be fully released, creating local variations in brake force that preserve both accuracy and stability.
2Speed
If full rapid braking is applied during low speed taxiing, then stopping distance is reduced, but structural fatigue and damage to aircraft components increases
Solution Approach 1:
The system applies preliminary braking force to selected wheels before full braking is required. By gradually engaging brakes on specific wheels first (particularly the nose gear), the system prepares the aircraft for stopping while distributing structural loads more evenly, preventing sudden shock loads that cause fatigue and damage.
Solution Approach 2:
The brake control system dynamically adjusts braking force distribution based on real-time aircraft conditions, including speed, weight distribution, and structural load capacity. This dynamic control allows the system to optimize stopping performance while continuously adapting to prevent excessive structural loading.
3Power
If brake clamping force is increased to improve stopping performance, then braking effectiveness is improved, but unequal distribution of brake energy causes directional instability
Solution Approach 1:
The braking system is segmented into multiple independently controlled actuators on different wheels. This allows the system to apply brake power selectively to specific wheels rather than uniformly to all wheels, enabling precise control of energy distribution to maintain directional stability while achieving effective stopping.
Solution Approach 2:
The system intentionally creates asymmetric brake force distribution across the aircraft's wheels based on directional stability requirements. By applying different braking forces to left and right wheels or to different gear assemblies, the system maintains optimal directional control while achieving the required stopping performance.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach enhances brake accuracy and sensitivity, reduces structural loading, and minimizes brake wear by maintaining a residual clamping force during taxiing, while allowing full braking effort after a preset delay, thus improving directional stability and extending aircraft lifespan.
Implementation Method 1
it causes the friction surfaces of the carbon brakes to make contact, creating brake torque to slow down the rotational speed of the wheel
Data Source
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AI summary
In a system and method for aircraft brake metering to alleviate structural loading, one or more electric brake actuators for wheel brakes having a range of brake clamping force are provided, and a brake actuation controller is configured to monitor commanded initiation of the aircraft, to limit initial brake effort of the electric brake actuators to a preset fraction of a maximum possible braking effort for a preset period of time, and to permit brake effort of the electric brake actuators up to the maximum possible braking effort after the preset period of time after initiation of braking has been commanded. The preset fraction is preferably approximately 50% of the maximum possible braking effort, and may be tuneable. The preset period of time is preferably approximately one second, and also may be tuneable.