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Session 10: UAV Operations and Flight Inspection Applications

Employing UAS to Perform Low Altitude Navaids Measurements
Jochen Bredemeyer, FCS Flight Calibration Services GmbH, Braunschweig, Germany; Thorsten Schrader, Physikalisch-Technische Bundesanstalt (PTB), Germany
Location: Regency Ballroom
Date/Time: Thursday, Apr. 19, 1:35 p.m.

An unmanned aerial system (UAS)-based measurement process to supplement ground inspection of ILS (LOC, GP) and (D)VOR is described. In addition to locations of typical ILS ground inspection with vehicles and masts, the platform permits for quasi-stationary hovering in critical areas formerly not accessible by the measurement van or a mast. This new development holds the promise to perform more economical and improved ILS ground measurements, which ICAO requires to be done on a regular basis by CNS maintenance staff.
An octocopter (size ~1m diameter in rotor plane) is used as a carrier UAS. Due to the wavelength of 3m (LOC, VOR) and 1m (GP), respectively, a dedicated antenna was designed to match both electromagnetic and mechanical requirements. The UAS carries a dedicated dual ILS (LOC/VOR,GP) receiver and recorder payload based on a highly miniaturized, FPGA-controlled system that handles large bandwidth data streams in real-time. Like the antenna, RF and signal processing hardware components are also specially designed to meet the application’s requirements, as well as mechanical constraints.
One major issue is to separate the wanted ILS/VOR signal-in-space from near field effects generated by the UAS itself. Effects that must be carefully removed from the incoming ADC-sampled signal is e.g. propeller induced amplitude modulation (AM) or the short-term dynamics of a flying UAS.
In contrast to conventional methods, the raw channel band pass signal-in-space covering the complete channel bandwidth is sampled at a high data rate, and is directly recorded without any pre-processing. This preserves maximum opportunities for any signal post-processing to extract all essential parameters of interest. During flight time, there is a need to down link the essential ILS /VOR parameters (e.g. DDM) in real-time. This was implemented using a combined solution of hardware (FPGA) and software (C) signal processing. A separate radio link between the ground and the UAS allows for the individual remote control of the sensor, apart from flying the UAS. A tablet PC on the ground is employed both for controlling the sensor and the display of relevant signal parameters.
The paper describes experiences gained with the system, and provides recent measurement results obtained from ILS localizer/glidepath and VOR installations.



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