Aircraft Airspeed Calculation Using Static Air Temperature
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Solution Overview
Problem
Existing methods for calculating aircraft airspeed are prone to inaccuracies due to sensor contamination, model uncertainties, and computational complexity, particularly in the high subsonic regime, and alternative methods like optical sensing and Flush Air Data Systems are costly or susceptible to environmental interference.
Innovation Solution
The method involves using static air temperature probes mounted on the aircraft fuselage and total air temperature probes positioned away from the fuselage to measure static and total air temperatures, calculating Mach number and airspeed based on atmospheric physics equations, thereby reducing reliance on pressure sensors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If pressure-based pitot-static system is used to calculate airspeed, then the method is simple and conventional, but the measurements are corrupted by contaminants such as ice, volcanic ash, or insect nests obstructing the sensors
Solution Approach 1:
The patent replaces the pressure-based mechanical sensing system (pitot-static system) with a thermal-based measurement system using temperature probes. Instead of measuring pressure differences that are susceptible to blockage by contaminants, the system measures temperature differences between total air temperature (TAT) and static air temperature (SAT) to derive airspeed through thermodynamic relationships, thereby eliminating the vulnerability to physical obstruction of pressure sensors.
2Reliability
If computational model of the aircraft is used to compute airspeed, then alternate method is provided, but the computations are complex and iterative with model simplifications and uncertainties
Solution Approach 1:
The patent extracts the essential physical relationship needed for airspeed calculation from the complex full aircraft computational model. By focusing only on the thermodynamic relationship between TAT, SAT, and Mach number, the invention eliminates the need for numerous other aircraft parameters (angle of attack, lift, drag, weight, aerodynamic coefficients, engine thrust) and complex iterative convergence processes, achieving accurate airspeed estimation with a simplified direct calculation approach.
3Reliability
If optical sensors (LIDAR) are used to compute velocity of remote particles, then airspeed can be determined, but expensive sensing devices and light sources are required
Solution Approach 1:
The patent employs inexpensive temperature probes instead of expensive optical sensing devices like LIDAR. The temperature sensors are simple, robust, and cost-effective components that can be easily manufactured and replaced if needed, whereas optical systems require costly lasers, detectors, and complex optical pathways. This substitution achieves the same airspeed measurement function at a fraction of the cost.
4Reliability
If optical sensors (LIDAR) are used to compute airspeed, then velocity can be computed, but the methods are vulnerable to inaccuracies due to volcanic ash and excessive particles changing light transmission
Solution Approach 1:
The patent substitutes the optical measurement system with a thermal measurement system. Temperature probes measure TAT and SAT directly through thermal conduction and convection, which are not affected by light transmission issues. This replacement eliminates the vulnerability to volcanic ash and particle interference that plagues optical systems, as thermal sensors can accurately measure temperature even in harsh atmospheric conditions where light transmission is compromised.
5Reliability
If Flush Air Data System (FADS) with flush-mounted static ports is used, then airspeed can be calculated, but the sensors are susceptible to precipitation and contaminants when the airplane is not in service
Solution Approach 1:
The patent extracts the temperature measurement function from the complex FADS pressure measurement system. By using dedicated temperature probes for TAT and SAT measurements, the invention simplifies the sensing requirements and reduces vulnerability to contamination. Temperature probes are less susceptible to blockage by precipitation and contaminants compared to the multiple precision pressure ports required by FADS, especially when the aircraft is parked or in storage.
6Reliability
If Flush Air Data System (FADS) with multiple pressure ports is used, then airspeed can be calculated, but anomalous readings from sensors are hard to detect and may cause undetected erroneous airspeed
Solution Approach 1:
The patent employs multiple temperature probes (at least two TAT probes and two SAT probes) and compares their readings to detect anomalies. The system calculates expected relationships between TAT and SAT based on flight conditions and identifies discrepancies that indicate sensor failures or contamination. This feedback mechanism enables real-time detection of anomalous readings, allowing the system to flag or reject erroneous data, thereby improving the reliability of airspeed calculations compared to systems without such validation.
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 approach provides accurate airspeed calculations with reduced susceptibility to sensor contamination and simplifies the computational process, offering a reliable alternative to pressure-based methods.
Implementation Method 1
a static air temperature probe configured to measure a static air temperature
Implementation Method 2
a total air temperature probe that measures a total air temperature
Implementation Method 3
calculating Mach number and airspeed based on atmospheric physics equations
Data Source
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AI summary
A system may include a static air temperature probe attached to an aircraft, an electronic flight instrument system, and a processor. The processor may be configured to measure a static air temperature at the aircraft using the static air temperature probe. The processor may further be configured to calculate a Mach number associated with the aircraft based at least partially on the static air temperature. The processor may also be configured to calculate a true air speed of the aircraft based on the Mach number. The processor may display an indication of the true air speed using the electronic flight instrument system. The processor may also be configured to calculate the speed of sound based at least partially on the static air temperature.