Landing Gear Strut Friction Correction for Accurate Aircraft Weighing
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Solution Overview
Problem
Existing aircraft weight and balance systems face inaccuracies due to landing gear strut seal friction, which can lead to false measurements of aircraft weight, as breakout friction values are assumed to remain constant and are not accurately updated for changes in temperature, humidity, and wear, resulting in potential errors in weight determination.
Innovation Solution
A system that continually monitors and updates breakout friction values using sensors for internal pressure, telescopic movement, temperature, humidity, and axle deflection, creating a dynamic database to predict and correct for friction errors in real-time, reducing the reliance on outdated look-up tables and minimizing the weight and complexity of hardware needed to measure strut pressure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If breakout friction values are assumed to remain constant and stored in look-up tables, then device complexity is reduced, but measurement precision deteriorates due to errors from temperature, humidity, and wear changes
Solution Approach 1:
The patent transitions from static breakout friction values stored in look-up tables to dynamic, real-time measurement and updating of breakout friction values. Sensors continuously monitor strut pressure, telescopic movement, temperature, and humidity to calculate current breakout friction, which is then stored in a dynamic database for immediate correction of weight measurements. This resolves the contradiction by making the system adaptive to environmental changes while maintaining manageable complexity through automated sensing and calculation.
Solution Approach 2:
The system implements feedback loops where sensors continuously monitor strut parameters (pressure, movement, temperature, humidity) and feed this data back to the processor. The processor calculates updated breakout friction values based on this feedback and stores them in the dynamic database. This closed-loop feedback mechanism ensures measurement precision is maintained despite environmental variations, while the automation of this process prevents excessive complexity increase.
2Measurement precision
If multiple sensors are added to monitor pressure, movement, temperature, and humidity for real-time friction updates, then measurement precision improves, but device complexity increases
Solution Approach 1:
The patent makes the landing gear strut serve multiple functions: it remains the primary shock-absorbing component while simultaneously acting as a weighing scale and a source of friction data. The same strut components (piston, seals, cylinder) that provide mechanical support also generate the friction signals that sensors detect. This multi-functionality allows the system to obtain weight and friction information from existing structural elements, reducing the need for separate dedicated components and thereby limiting complexity increases.
Solution Approach 2:
The system uses the strut's own operational characteristics (its natural telescopic movement, pressure changes, and friction during normal landing gear operation) to generate the data needed for correction. The sensors monitor parameters that the strut naturally produces during its normal function, and the processor calculates breakout friction from this self-generated data. This self-service approach eliminates the need for external calibration equipment or separate friction measurement mechanisms, containing hardware complexity while achieving high measurement precision.
3Device complexity
If breakout friction is not corrected for, then device complexity is minimized, but measurement precision deteriorates due to falsely low or high strut pressure readings
Solution Approach 1:
The patent replaces complex mechanical friction compensation mechanisms with an electronic/software-based solution. Instead of using mechanical devices to physically compensate for friction effects, the system uses sensors to detect friction-related parameters and a processor to calculate and apply software corrections to the weight measurements. This substitution of mechanical correction systems with electronic sensing and computational correction achieves high measurement precision while keeping the added complexity manageable through the use of standard electronic components and algorithms.
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 provides more accurate aircraft weight determinations by continuously updating friction correction values, accounting for environmental and operational changes, thereby improving the reliability and precision of weight measurements and reducing errors caused by seal friction.
Implementation Method 1
landing gear strut seal friction, which is created by the rubbing of telescopically sliding components within the landing gear such as the seals, gland nut, piston wiper and piston scraper; against the strut piston surface
Implementation Method 2
The aircraft weight is transferred to and is identified by the pressures contained within the landing gear struts. More simply said . . . 'the weight of an aircraft rests on three pockets of compressed gas.'
Data Source
AI summary
Aircraft landing gear strut breakout friction values are used to correct measured strut pressure as related to the amount of weight supported; with the ability to generate and refine the breakout friction value database, and ability to predict a future breakout friction correction value by trending historical measurements, as compared to recent measurements, as further compared to real-time breakout friction values. The system is used in monitoring, measuring, computing and displaying the weight and center of gravity for aircraft utilizing telescopic oleo landing gear struts. Pressure sensors, temperature sensors, humidity sensors, axle deflection sensors, accelerometers, inclinometers are mounted in relation to each of the landing gear struts to monitor, measure and record strut pressure as related to strut telescopic movement, rates of strut telescopic movement, axle deflection, current temperature, current relative humidity, vertical acceleration; experienced by landing gear struts, as the aircraft proceeds through typical ground and flight operations.