Pitot-Static Probe Water Drainage Design
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Solution Overview
Problem
Pitot-static air data probes are susceptible to water ingestion in rain and warm supercooled liquid water conditions, leading to large induced pressure errors that affect the calculation of air data parameters such as speed, altitude, and angle-of-attack.
Innovation Solution
The air data probe design includes a pair of ports on opposing ends of the probe barrel, with a first static inlet port and an outlet or drainage port at a different location, creating a drainage path to minimize the impact of water on measured pressures and allowing for quick purging of water after exiting icing or rain conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If water management systems prevent complete blockage of sense lines, then reliability is improved, but measurement precision deteriorates due to residual water affecting pressure measurements
Solution Approach 1:
The sense line is segmented into multiple sections by introducing intermediate drainage ports along the probe body. This divides the single long drainage path into multiple shorter segments, allowing water to be removed at multiple locations rather than relying on a single drainage point, thus preventing blockage while minimizing water presence in pressure sensing zones
Solution Approach 2:
A pneumatic control system acts as an intermediary to manage water drainage. The system uses controlled pressure differentials to open and close drainage valves at appropriate times, coordinating between preventing blockage and protecting measurement precision by ensuring drainage occurs only when water is present
2Productivity
If drainage ports are positioned to quickly purge water, then productivity is improved, but measurement precision worsens due to potential disruption of pressure sensing
Solution Approach 1:
Different regions of the probe have different port configurations optimized for their specific functions. The forward portion has drainage ports positioned to quickly purge water, while the rear pressure sensing zones have protected inlet ports that maintain measurement precision. Each location has quality characteristics tailored to its local requirements
Solution Approach 2:
The drainage system transitions from a static open drainage port to a dynamically controlled valve system. The drainage valves can be opened wide to maximize purging speed when water is detected, then closed or throttled to minimize impact on pressure sensing, allowing the system to adapt its drainage characteristics based on real-time conditions
3Reliability
If multiple drainage ports are added to improve water management, then reliability improves, but device complexity increases
Solution Approach 1:
The intermediate drainage ports serve multiple functions: they act as water egress paths during rain conditions, provide pressure equalization during maneuvering, and can function as sensor locations for detecting water presence or ice formation. This multi-functionality reduces the need for separate dedicated components for each function
Solution Approach 2:
The drainage system is merged with the probe body structure rather than being a separate external system. The drainage ports are integrated into the existing probe walls, and the pneumatic control lines are routed through existing cable pathways, combining multiple functions into existing structural elements to minimize additional complexity
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 configuration effectively manages water ingestion, minimizing its impact on pressure measurements and ensuring accurate calculation of air data parameters by providing a drainage path for water, thus reducing errors in air data parameter calculations.
Implementation Method 1
a first static inlet port on one end and an outlet or drainage port at a different location to provide a drainage path for water impinging on the inlet ports
Implementation Method 2
create a drainage path that encourages movement of liquid toward the outlet port
Data Source
Figure 1
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Figure 3
AI summary
An air data probe (16) includes a housing and a probe head (18) with a body (28), total pressure (44) and alpha (46A, 46B) chambers, total pressure (34) and alpha ports, and alpha drain ports (40A, 40B). The total pressure chamber (44) extends through a radial center of the body (28). The alpha chambers (46A, 46B) are disposed radially outward from the total pressure chamber (44). The total pressure port (34) is disposed in a distal end of the body (28) is collinear with a centerline axis of the body (28). The total pressure chamber (44) is in fluid communication with the total pressure port (34) and with the housing. The alpha ports (36A, 36B) are disposed downstream of the total pressure port (34) and upstream of the housing. The alpha chambers (46A, 46B) are in fluid communication with the alpha ports (36A, 36B). The alpha drain ports (40A, 40B) are disposed downstream from the alpha port (36A, 36B) and upstream from the housing. The alpha drain ports (40A, 40B) fluidly communicate with the alpha chamber (46A, 46B).