Laser Airspeed Sensor Using Exhaust Aerosol Backscatter
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Solution Overview
Problem
Current laser-based air data systems face limitations due to inconsistent distribution of gas molecules and aerosols, which affect their reliability and availability, particularly in determining air data parameters from light backscattered by target areas on an aircraft.
Innovation Solution
A laser air data system that uses coherent light pulses to interact with exhaust air flows rich in aerosols, incorporating a SmartProbe with an electronics module to calculate air data parameters based on light returns from both aft and forward target volumes, compensating for variances in aerosol concentration and aircraft orientation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If laser energy is used to interact with gas molecules and aerosols for air data measurement, then air data parameters can be determined, but inconsistent distribution of gas molecules and aerosols reduces measurement reliability
Solution Approach 1:
The patent inverts the traditional forward-scatter measurement approach by measuring light backscattered from the aft target area instead. This reversal allows the system to utilize exhaust aerosols that are naturally present in the measurement path, transforming the inconsistent aerosol distribution from a source of measurement error into a reliable measurement target that enhances signal strength and measurement consistency
Solution Approach 2:
The patent introduces exhaust aerosols as an intermediary medium between the laser source and the detection system. These aerosols act as scattering centers that enhance the light backscatter signal, providing a more consistent and measurable intermediate target than gas molecules alone, thereby improving measurement reliability without requiring direct laser-gas molecule interaction
2Device complexity
If a single target area is used for laser measurement, then the system is simpler, but the system is more vulnerable to common failure modes
Solution Approach 1:
The patent segments the measurement system into two distinct measurement paths: one measuring light backscattered from the forward target area and another measuring light backscattered from the aft target area. This segmentation creates redundant measurement capabilities that can operate independently, allowing the system to maintain functionality even if one measurement path fails, thereby improving system availability without significantly increasing overall system complexity
Solution Approach 2:
The patent implements prior cushioning by pre-configuring redundant measurement paths that can compensate for potential failures. The dual-target-area design ensures that if aerosol distribution becomes inconsistent in one area or the measurement path fails, the other measurement path is already in place to provide backup measurements, preventing system failure before it occurs
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 system provides reliable air data parameters by utilizing the SmartProbe to determine engine and aircraft parameters, increasing the dissimilarity of air data systems and reducing the risk of common failure modes by using laser backscatter from a reliable aerosol source, thus enhancing system reliability and availability.
Implementation Method 1
determine at least one air data parameter based on light returns from the target area
Implementation Method 2
Both laser system types use Doppler shift to determine relative velocity of airflow along the axis of the laser beam
Data Source
Figure 1A
Figure 1B
Figure 2
AI summary
An air data system includes a laser emitter (74), a laser receiver (75), and an electronics module (72). The electronics module includes a processor (86) and computer-readable memory (88) encoded with instructions that, when executed by the processor, cause the laser to emit a coherent light pulse into a target volume locating within an exhaust flow aft of an aircraft. The laser receiver detects backscatter produced by the coherent light pulse interacting with the aft target volume, and the electronics module determines an air data parameter based on the backscatter and at least one of an engine parameter indicative of an engine condition of the aircraft and an aircraft parameter indicative of a state of the aircraft before outputting the air data parameter to a consuming system of the aircraft.