GRICAS successfully triggers automatically a Second Generation distress beacon on-board a flying aircraft!
GRICAS 1st in-flight demonstration took place from April 24th to April 26th 2017 in the flight-club of Sabadell, close to Barcelona, Spain.
After 15 months of operational concept definition, solution design and demonstrator development, including 3 months of integration, verification and validation, GRICAS end-to-end demonstrator of an Autonomous Distress Tracking system based on Cospas-Sarsat distress beacon and space segment flew for the first time and completed successfully the Test Case Plan developed by the engineering team to demonstrate the compliance of GRICAS solution to ICAO recommendations and EUROCAE specifications. As reminder, GRICAS end-to-end demonstrator is composed of:
- An ELT-DT prototype (distress tracking) based on a Second Generation COSPAS-SARSAT distress beacon representative of what a real ELT-DT could be (in terms of electronic components, mechanical and functional interfaces and functions implemented) integrating a GNSS chipset Galileo and GPS compatible.
- A remote control panel for the ELT-DT, based on the existing remote control panels for ELT present in the cockpits.
- An on-board demonstration platform emulating the Beacon Activation Logic (based on avionics) and then sending the automatic triggering commands to the beacon and the GNSS receiver of the avionics (GPS only). The ODP also provides the logging functions and the GNSS reference trajectory.
- A L-band MEOLUT Next in Thales Alenia Space implementing a SGB real-time processing software
The pre-operational RLSP (Return Link Service Provider) being still under development the RLM reception (for remote activation, deactivation and acknowledgment), the reception of a real RLM transmitted via the Galileo satellites could only be tested on ground through emulation of the Return-Link signal with a Spirent signal generator, and was not considered in the in-flight demonstration. However, the reception and processing by the beacon of the complete Galileo navigation signal through its GNSS chipset proved its capability to receive and process a RLM encoded in it.
On Monday 24th of April, the GRICAS engineering team met at the aeroclub to finalize the integration and prepare the in-flight demonstration, installing the demonstrator on-board the Cessna 182 test aircraft. The excellent results of dry-run and non-regression tests and the very good weather condition encouraged the team and the test pilot to do the first flight test one day earlier than initially planned and for the very first time the GRICAS ELT-DT flew, was activated on flight and transmitted a distress signal, well received and processed by the French MEOLUTs (in real-time by the L-band chains in Thales Alenia Space and by sampling and post-processing by the S-band chains in CNES)
Tuesday 25th of April was the D-Day of GRICAS project, the date expected by the entire consortium and sponsors of the SGB solution for Autonomous Distress Tracking. Indeed, that day was specifically dedicated to tests with automatic activation of the beacon based on commands transmitted by the Beacon Activation Logic to the ELT-DT. More than 1 hour of the SGB ELT-DT transmitted signals were recorded and for comparison an hour of FGB classical ELT transmission was also recorded in-flight on the same test environment to provide comparison elements of the performances of SGB and FGB for independent localization of fast moving beacons. The aircraft trajectory inluded various attitude variations and curves to assess the performance of GNSS receiver and MEOSAR independent localization with high beacon motion dynamic. One of the tests performed was entirely automatic, the beacon being triggered automatically by the beacon activation logic based on GNSS information on the flight altitude of the test airplane. As a sake of simplicity and because GRICAS project never aimed at developing a representative beacon activation logic based on flight-dynamic engineering, the used Beacon activation logic computed an automatic trigger based on a too high altitude (instead of a low altitude). The reader will anyway note the representativeness of the automatic activation process though the source of the trigger is not part of the triggers specifically listed by EUROCAE. After take-off, the pilot pursues the ascent until overtaking a threshold altitude (agreed with the GRICAS engineers and encoded as the threshold altitude in the beacon activation logic of GRICAS). The BAL, collecting the position data provided by the GNSS of the demonstrator (emulating the GNSS receiver of the avionics for the tests), identifies the unusual altitude, computes a trigger “Unusual altitude” and sends it to the ELT-DT. The ELT-DT receives the trigger and start transmitting a distress signal every 10s with the relevant “activation method” encoded. The French MEOLUTs receive and process the signal being able to compute in real time a single and multi-burst independent localization, and to deliver the alerts to Barcelone team in less than 60 seconds. Finally, after 15 minutes, the pilot flies again under the threshold altitude, the BAL computes a cancellation trigger, the beacon starts transmitting a cancellation message, as well received, processed and delivered to Barcelona operators by the French MEOLUTs.
The GRICAS team was able to complete the Test Case Plan within this single day of test, thanks to the excellent results and because no dysfunction were to deplore.
Finally, Wednesday 26th of April, the weather conditions being not propitious to a lot of flight tests, the pilot and the flight team performed a set of touch-and-go with the ELT-DT SGB prototype, we could collect at MEOLUT levels data with significant variation of vertical speeds to be post-processed to assess the performances of independent localization as a complement of horizontal curves that were tested the days before.
GRICAS manager insisted on the unique aspects of GRICAS’s demonstration and the excellent results:
- It was the first time a prototype representative of what a real ELT-DT SGB could be flew and was automatically triggered in-flight
- It was the first time an independent localization of an SGB was computed during a transmission on-board a flying airplane and this was done only using Galileo SAR segment
- Finally it was also the first time FGB and SGB modulated distress messages transmitted on-board a flying airplane was recorded (in the same test environment) to provide consistent data to compare the relative performances of both modulations for independent localization of fast moving beacon.
NASA showing interest for GRICAS in-flight tests, the GRICAS manager communicated them the flight hours and they were able to detect and record the messages transmitted by the GRICAS ELT-DT with their MEOLUT based in Greenbelt, Maryland, US.
Groupe photo: A smiley team on a rainy day! GRICAS team (from left to right: Daniel Martinez (PILDO), Nicolas Rey (Thales Alenia Space), Lluis Badia (ACBS), Alain Cavan (ELTA), Karine Dupin (ELTA), Christophe Chatain (ELTA), Pauline Martin (Thales Alenia Space), Tim Dufourmont (NLR for GSA), Josep Montolio (PILDO)) successfully completed the Test Case Plan for this first in-flight demonstration of GRICAS operational concept and solution! Congratulations!