Aircraft Braking Capability Determination Using Selective Wheel Actuation
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Solution Overview
Problem
Aircraft braking systems face reduced effectiveness in varying weather conditions and ground surfaces, leading to inaccurate braking capability assessment, which can complicate landings, especially on short runways or at high speeds.
Innovation Solution
The system applies brakes to only one symmetric pair of aircraft tires during initial braking, reaching an anti-skid limit to determine braking capability without rapid deceleration, and then engages all tires for maximum braking, using a braking circuit and control circuit to manage brake actuation and traction assessment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If all braking wheels are actuated simultaneously during initial braking, then maximum braking power is achieved, but rapid deceleration occurs making it difficult to accurately assess braking capability
Solution Approach 1:
The braking system divides the braking wheels into two groups: a first set of braking wheels and a second set of braking wheels. During initial braking, only the first set is actuated to determine braking capability, while the second set remains inactive. This segmentation allows the system to assess braking capability without applying maximum braking force that would cause rapid deceleration.
Solution Approach 2:
The system applies partial braking action by actuating only a subset of braking wheels (the first set) during the initial braking phase. This partial action is sufficient to determine braking capability by detecting when these wheels reach the anti-skid limit, without the excessive deceleration that would result from actuating all braking wheels simultaneously.
2Loss of information
If ground vehicles are used to measure ground conditions, then braking capability information can be obtained, but measurement accuracy is poor
Solution Approach 1:
The aircraft's own braking system serves dual purposes: it provides the braking function needed for landing and simultaneously measures the braking capability of the runway. By actuating the first set of braking wheels and detecting when they reach the anti-skid limit, the system self-determines the braking capability information that would otherwise require separate measurement devices.
Solution Approach 2:
The braking wheels act as an intermediary between the aircraft and the runway surface, transferring force and enabling measurement of the friction coefficient. The anti-skid system monitors the braking wheels to detect when they reach the limit of traction, providing indirect but accurate measurement of ground conditions through the interaction between the wheels and runway surface.
3Power
If braking power exceeds the transmission capacity between tires and runway, then braking system capability is sufficient, but braking effectiveness is reduced in poor conditions
Solution Approach 1:
The anti-skid system continuously monitors the braking wheels to detect when they reach the anti-skid limit, indicating that the maximum available friction has been reached. This feedback information is used to determine the actual braking capability of the runway and to control the application of braking force, ensuring that the braking system operates within the reliable transmission capacity between tires and runway surface.
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 method provides a more accurate assessment of braking capability, allowing for better landing predictions and safer operations by determining the maximum traction available, which can be communicated to other aircraft for improved landing strategies.
Implementation Method 1
The power that can be transmitted between the wheels and the ground surface depends on weather conditions, tire properties, ground condition, the normal force on the tires, and other factors.
Implementation Method 2
actuate braking of the first braking wheel of the first main landing gear assembly and of the first braking wheel of the second main landing gear assembly in response to initial receipt of a braking command
Data Source
Figure 1
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Figure 4
AI summary
An aircraft includes a first landing gear assembly, a second landing gear assembly, a braking circuit, a brake control circuit, and a braking capability circuit. The landing gear assemblies each include a first braking wheel and a second braking wheel. The braking circuit may apply brakes independently to each of the braking wheels. The brake control circuit actuates braking of the first braking wheels in response to initial receipt of a braking command in a first braking phase and restrict braking at the second braking wheels during the first braking phase until the first braking wheels reach an anti-skid limit at an end of the first braking phase. The braking capability circuit determines a braking capability of the aircraft based on an amount of braking applied to reach the anti-skid limit at the first braking wheels.