TDR Fuel Gauge with Segmented Cable for Aircraft Tank Measurement
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Solution Overview
Problem
Conventional aircraft fuel gauging systems require numerous capacitance-based probes, leading to high weight and installation costs, and existing time domain reflectometry (TDR) systems are limited in measuring fuel levels accurately across complex tank geometries.
Innovation Solution
A TDR fuel gauge system that uses a single fuel gauge to generate two independent fuel level measurements by receiving reflected pulses from multiple cable parts positioned at different angles and locations within the fuel tank, allowing for accurate estimation of fuel volume and redundancy in measurement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If multiple capacitance-based probes are used to measure fuel levels at different locations, then measurement coverage and accuracy are improved, but system weight and installation complexity increase significantly
Solution Approach 1:
The single TDR cable is segmented into multiple parts (first cable part, second cable part, third cable part) that are positioned at different locations and orientations within the fuel tank. Each cable part provides measurement at a specific location, collectively achieving comprehensive fuel level coverage equivalent to multiple separate probes while using a single integrated system
Solution Approach 2:
A single TDR fuel gauge system performs multiple measurement functions that would traditionally require separate probes. The system can measure fuel levels at multiple locations (first location, second location), detect water presence, and provide redundant measurements simultaneously, replacing what would otherwise require multiple specialized sensing devices
2Device complexity
If a single TDR gauge is used to reduce hardware requirements, then device complexity is reduced, but measurement coverage across complex tank geometries is limited
Solution Approach 1:
The cable parts are arranged in three-dimensional space within the fuel tank, extending in different directions (vertically, horizontally, at angles) from different walls. This spatial distribution allows a single gauge to cover the full horizontal dimension and complex geometries of the tank by utilizing multiple spatial dimensions rather than relying on a single linear probe
3Measurement precision
If cable parts are positioned at different locations and angles, then fuel level measurement coverage is improved, but cable installation complexity increases
Solution Approach 1:
Multiple cable parts that would traditionally require separate installation procedures are merged into a single continuous cable assembly. The first, second, and third cable parts are connected in series within a single cable, allowing them to be installed together as one unit rather than requiring separate routing and connection of multiple independent cables
Solution Approach 2:
The cable configuration allows the system to automatically achieve proper positioning and measurement coverage through its own structure. The cable parts naturally extend to different locations and orientations based on their physical arrangement in the tank, and the TDR system automatically processes signals from all parts without requiring complex external positioning mechanisms or adjustments
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
Enables accurate fuel level measurement across a wide range of filling levels with reduced hardware requirements, providing redundancy and improved accuracy by using a single gauge to cover the full horizontal dimension of the tank, while also detecting water presence and level if necessary.
Implementation Method 1
A time domain reflectometry (TDR) fuel gauge for measuring a filling level of fuel in an aircraft fuel tank comprises a signal generator arranged to generate an electromagnetic pulse and a cable within the fuel tank and coupled to the signal generator
Implementation Method 2
The times of receipt of the first and second reflected pulses are used to determine two independent fuel level measurements
Data Source
Figure 1
Figure 2~3
Figure 4a
AI summary
An aircraft fuel tank system comprising an aircraft fuel tank and a time domain reflectometry (TDR) fuel gauge for measuring a filling level of fuel in the aircraft fuel tank (1, 2). The TDR fuel gauge comprises an electromagnetic signal generator (30) and a cable (20, 22), the cable comprising a first cable part (20) and a second cable part (22) which are coupled in series to the signal generator. The first cable part extends downwardly within the fuel tank and the second cable part extends upwardly within the fuel tank. The first and second cable parts are arranged such that for at least one filling level the first cable part extends down into the fuel from an ullage space at a first location and the second cable part extends up out of the fuel into an ullage space at a second location which is spaced apart from the first location.