Aircraft Brake Control Using Axle Reference Speeds

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Solution Overview

Problem

Aircraft brake systems face challenges in determining the appropriate time to apply braking forces after landing to avoid wheel lock and damage, particularly on contaminated runways where wheel acceleration varies due to different friction coefficients.

Innovation Solution

The system calculates axle reference speeds using wheel speed sensors and allows braking when both axle reference speeds exceed a predetermined threshold, or after a set time has elapsed since the aircraft was determined to be on the ground, ensuring safe braking and preventing premature wheel lock.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Loss of time

If braking is applied immediately after touchdown, then stopping distance is reduced, but wheel lock and damage may occur

Engineering Contradiction:

Improvestopping distanceVSAvoidwheel damage risk

Core Design Contradiction:

Loss of timeVSReliability

Solution Approach 1:

The system performs preliminary detection of wheel acceleration state before allowing braking. The brake control unit monitors wheel speed sensors to determine if wheels have reached sufficient velocity, and only then permits brake application. This preliminary assessment prevents premature braking that could cause wheel lock and damage.

Inventive Principle:

Principle #10Preliminary action

2Measurement precision

If wheel speed sensors are used to calculate reference speed, then braking timing accuracy is improved, but system complexity increases

Engineering Contradiction:

Improvebraking timing accuracyVSAvoidsystem complexity

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The wheel speed sensors serve multiple functions: they provide data for calculating axle reference speeds to determine braking timing, and also serve as inputs for the weight on wheel detection system. By making the sensors multi-functional, the patent avoids adding separate measurement devices, thus improving measurement precision without proportionally increasing system complexity.

Inventive Principle:

Principle #6Universality (Multi-functionality)

3Reliability

If a weight on wheel system with time limit is used, then braking permission is granted reliably, but response time may be delayed

Engineering Contradiction:

Improvebraking permission reliabilityVSAvoidresponse time

Core Design Contradiction:

ReliabilityVSLoss of time

Solution Approach 1:

The system dynamically adjusts the braking permission criterion based on actual wheel acceleration conditions. Instead of using a fixed time limit alone, the brake control unit continuously monitors whether calculated axle reference speeds exceed the on ground threshold. This dynamic approach allows the system to grant braking permission as soon as wheels reach sufficient velocity, regardless of the elapsed time since weight-on-wheel detection, thereby reducing response time while maintaining reliability.

Inventive Principle:

Principle #15Dynamics

Data Source

PatentEP2821301B1System and method for detecting an on ground condition of an aircraft

Publication Date: 2018.11.28 GOODRICH CORP

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AI summary

Systems (300) and methods for detecting an on ground condition of an aircraft (100) are disclosed. A weight on wheel (WOW) system may determine that an aircraft (100) is on the ground. Wheel speed sensors (322,324,326,328) may measure the speed of the aircraft wheels (132,134). Axle reference speeds (ARS) may be calculated for each landing gear (110,120,130) based on the speed of the aircraft wheels (132,134). A brake control unit (310) may determine that the axle reference speed (ARS) for each axle of the landing gears (110,120,130) is above an on ground threshold (OGT) speed, and the brake control unit (310) may allow braking to be applied.