Air Data Probe Asymmetric Openings for Angle of Attack Accuracy

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Solution Overview

Problem

Air data probes face challenges in providing accurate air speed measurements due to air recirculation and boundary layer separation, especially at pronounced angles of attack and in environments with ice crystals, which affect total pressure recovery.

Innovation Solution

The air data probe design incorporates bleed holes or fluted slots that reduce recirculation and boundary layer separation by decreasing the inner flow path's cross-sectional area and incorporating heater elements to manage ice, ensuring uniform airflow and improved pressure recovery.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If the air data probe operates at a pronounced angle of attack, then the probe can measure air speed at various flight attitudes, but air recirculation and boundary layer separation occur within the opening or tap, degrading measurement accuracy

Engineering Contradiction:

Improveability to measure at various angles of attackVSAvoidair speed measurement accuracy

Core Design Contradiction:

Adaptability or versatilityVSMeasurement precision

Solution Approach 1:

The opening is divided into a first opening and a second opening positioned at different locations and orientations. The first opening faces generally forward to capture undisturbed airflow, while the second opening is positioned to receive airflow from different angles. This segmentation allows the probe to maintain accurate total pressure measurement across a range of angles of attack by providing multiple airflow entry paths that avoid recirculation and boundary layer separation zones.

Inventive Principle:

Principle #1Segmentation

2Measurement precision

If the pitot tube tap is positioned to receive air for total pressure measurement, then air speed can be determined, but recirculation and boundary layer separation occur adjacent to the tap, affecting total pressure recovery

Engineering Contradiction:

Improvetotal pressure recovery accuracyVSAvoidair recirculation and boundary layer separation

Core Design Contradiction:

Measurement precisionVSObject-generated harmful factors

Solution Approach 1:

A cap is provided that defines a cap opening and is positioned at the forward end of the pitot tube, upstream of the tap. The cap acts as an intermediary structure that guides undisturbed airflow to the tap opening, preventing direct exposure of the tap to recirculation zones and boundary layer separation. The cap opening is specifically oriented to face generally forward, capturing clean airflow from the freestream before it encounters the aircraft body or probe structure.

Inventive Principle:

Principle #24Intermediary (Mediator)

3Measurement precision

If the air data probe opening faces forward to reduce recirculation, then total pressure recovery improves, but the probe cannot effectively measure at pronounced angles of attack

Engineering Contradiction:

Improvetotal pressure recoveryVSAvoidperformance at angle of attack operation

Core Design Contradiction:

Measurement precisionVSAdaptability or versatility

Solution Approach 1:

The first and second openings are positioned asymmetrically at different locations and orientations on the probe. The first opening faces generally forward optimized for low-angle operations, while the second opening is positioned and oriented to capture airflow at pronounced angles of attack. This asymmetric configuration allows the probe to maintain total pressure recovery accuracy across the full range of operational angles by providing specialized opening geometries for different flight conditions.

Inventive Principle:

Principle #4Asymmetry

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 design enhances air data probe performance by eliminating recirculation and boundary layer separation, maintaining accurate total pressure recovery and improving air speed measurement accuracy across various operational conditions.

Implementation Method 1

incorporating heater elements to manage ice

Methodology Applied

Scientific EffectHeating: Heating

Implementation Method 2

air recirculation and boundary layer separation may occur within an opening or tap into the air data probe

Methodology Applied

Scientific EffectBoundary layer separation: Boundary Layer

Implementation Method 3

air recirculation and boundary layer separation may occur within an opening or tap into the air data probe

Methodology Applied

Scientific EffectFlow recirculation: Turbulence

Data Source

PatentEP3575803B1Air data probe with improved performance at angle of attack operation

Publication Date: 2022.05.04 ROSEMOUNT AEROSPACE INC

Figure 1A
Figure 1B~2C
Figure 2A~2B

AI summary

An air data probe (46) has a pitot tube with a tap (47) at a forward end (48) that defines an inner flow path. The inner flow path decreases in the cross-sectional area until reaching a throat (50). The inner flow path has cross-sections that are generally cylindrical and also has sections of removed material (52).