A Two-Stage Framework for Sensor Selection and Geolocation for eVTOL Emergency Localization Using HF Skywaves.

Area of Science:

• Aerospace Engineering
• Signal Processing
• Geophysics

Background:

• High-Frequency (HF) geolocation is vital for locating missing aircraft and supporting emergency operations.
• Electric Vertical Take-off and Landing (eVTOL) aircraft may experience communication loss, necessitating robust geolocation methods.
• Existing geolocation techniques can be sensitive to noise and non-line-of-sight (NLOS) conditions.

Purpose of the Study:

• To propose a novel two-stage framework for HF skywave propagation-based geolocation of eVTOL aircraft.
• To enhance the reliability and accuracy of geolocation, especially in scenarios with communication interruption or NLOS.
• To provide a methodological basis for emergency eVTOL recovery operations.

Main Methods:

• A two-stage approach: Stage A involves receiver selection (with and without bias priors), and Stage B employs Random Spatial Spectrum (RSS) geolocation.
• Stage A utilizes geometric observability and non-line-of-sight (NLOS) bias priors with robust weighting for receiver selection.
• Stage B uses grid objective function matching for RSS-based geolocation, mitigating sensitivity to time difference estimation errors.

Main Results:

• The proposed 'select first, geolocation later' framework demonstrates superior performance compared to direct geolocation methods.
• Simulations and real-world measurements validate the effectiveness of the two-stage approach.
• The method maintains robustness under NLOS conditions, improving geolocation availability.

Conclusions:

• The developed HF skywave-based geolocation framework offers a significant improvement for emergency eVTOL search and rescue.
• The two-stage receiver selection and RSS geolocation strategy enhances accuracy and reliability.
• This research provides foundational evidence for practical application in critical aviation scenarios.