Air Data Probe Fluid Intrusion Sensor Design
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Solution Overview
Problem
Air data probes on aircraft are prone to fluid intrusion due to non-hermetic sealing, leading to potential freezing and malfunction, which requires frequent disassembly and inspection, reducing availability and increasing maintenance costs.
Innovation Solution
An air data probe design with a stationary housing assembly and a rotatable air data measurement unit, featuring a fluid sensing unit with electrically conductive surfaces spaced dielectrically to detect fluid intrusion by measuring changes in electrical resistance, allowing for continuous operation and reduced maintenance needs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the probe interface is not hermetically sealed to maintain sensitivity of movable sensing elements, then the sensing element can move freely, but fluid intrusion occurs causing potential locking up in flight
Solution Approach 1:
The probe is divided into separate sealed chambers with movable sensing elements contained within hermetically sealed housings. This segmentation allows the sensing elements to move freely within their sealed environments while preventing fluid intrusion into the sensitive components.
Solution Approach 2:
Hermetic seals and barriers are introduced as intermediary elements between the movable sensing elements and the external fluid environment. These seals act as mediators that allow mechanical motion to pass through while blocking fluid intrusion.
2Reliability
If the probe is removed, disassembled, and inspected for moisture when intrusion is suspected, then potential fluid contamination can be detected, but aircraft availability decreases and maintenance costs increase
Solution Approach 1:
Fluid intrusion sensors are installed within the probe to detect moisture or fluid contamination before it causes damage or malfunction. This preliminary detection allows the probe to remain in service longer, reducing unnecessary removals and inspections.
Solution Approach 2:
The fluid intrusion sensors provide continuous feedback about the internal environment of the probe, enabling real-time monitoring and condition-based maintenance decisions. This feedback mechanism reduces unnecessary probe removals and inspections.
3Reliability
If protective covers are improperly installed or fail to install over probes prior to wash-down, then fluid intrusion prevention is compromised, but proper installation procedures increase operational complexity
Solution Approach 1:
The probe incorporates self-protecting features through hermetically sealed designs that eliminate or reduce the need for external protective covers during wash-down procedures. The sealed structure itself provides the protection that previously required separate cover components.
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
The solution effectively detects fluid intrusion and prevents freezing, enabling the air data probe to remain operational and reducing maintenance requirements, thereby increasing aircraft uptime and reducing costs.
Implementation Method 1
An electrical resistance value is measured in the fluid sensing unit between a first electrically conductive sensing surface physically and dielectrically spaced from a second electrically conductive sensing surface
Data Source
Figure 1
Figure 2A
Figure 2B
AI summary
An air data probe includes a stationary housing assembly 12, an air data measurement unit 14, and a fluid sensing unit 60 disposed proximate to an interface between the housing assembly and the air data measurement unit. The air data measurement unit is rotatable about a longitudinal axis of the air data probe, relative to the stationary housing assembly. The fluid sensing unit includes a second electrically conductive sensing surface 80B physically and dielectrically spaced from a first sensing surface 80A.