After the successful testing on-board a CESSNA 182 late April 2017 with the complete GRICAS team, the TAS members of the GRICAS H2020 project conducted a new field trial with the GRICAS ELT-DT based on a COSPAS-SARSAT SGB this time on-board a helicopter.
The main objectives of the test were to:
- Test the GRICAS ELT-DT SGB on-board an helicopter, including in particular automatic triggers
- Analyze the performances during various trajectories with higher dynamic than during 1st field trial
- Analyze the impact of the rotor on the quality of the SAR transmission
Test equipment and environment
The test helicopter, an AS 350 B2 “Squirrel” Eurocopter, was equipped with the exact same test platform as the one used for the first field trial:
- 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.
The ELT-DT prototype was connected to the SAR antenna of the rotorcraft and an additional GNSS antenna, used to feed the on-board demonstration platform and the beacon, was set on the left door of the helicopter.
The same MEOLUT was used as well: the L-band MEOLUT Next located in Thales Alenia Space and implementing a SGB real-time processing software.
Only three test cases were planned for this field trial:
- Automatic activation by the ODP emulating the avionics
- Automatic activation under detection of an unusual flight altitude
- Manual activation
But a particular attention was dedicated to the trajectories:
- Linear trajectory at constant altitude
- Circular trajectories
- Saw tooth trajectory with various vertical speeds
- Static flight
On Monday 17th of July, the TAS engineers met the helicopter pilot and mechanics at the flight-club of Graulhet, region of Toulouse, France, to integrate the test equipment in the rotorcraft and prepare the flights. A first set of ground tests was performed with excellent results and good reception rate at the MEOLUT.
Tuesday 18th of July was the day selected for the flights due to a good Galileo coverage over the region of Toulouse during the entire afternoon. After a second set of ground tests and some final adjustments, the ground team and the flight team were ready for take-off and flight tests.
From a global point of view, the tests were all successful; in particular the automatic activation under detection of an unusual flight altitude was successful several times. The beacon transmissions were received correctly by the MEOLUT despite the effects of the rotor pales on the transmission and for all the trajectories even the most constraining, in particular the circles and the saw-tooth trajectories.
The detection rate in single-burst (reception via at least one satellite) was around 90%, under the detection rate observed during previous flight tests (100%) but still satisfying. We however clearly observed effects due to the rotor degrading the demodulation performances of the visible satellites ahead of the rotorcraft, and TAS engineers are then processing the raw signal and data collected in detail to come up with more conclusive analysis.Detailed results of the performances analysis will be published at COSPAS-SARSAT Joint Committee 31 in October 2017.
TAS team addresses special thanks to PILDO and ECA Group for providing the equipment used for the tests.
Nicolas REY (TAS-F) on-board the AS 350 B2 "Squirrel" during the tests of the GRICAS ELT-DT prototype based on COSPAS-SARSAT SGB developped by ELTA (ECA Group) using the On-board Demonstration Platform developped by PILDO. Both test elements where developped in the frame of the GRICAS project.
The GNSS antenna (flat and white antenna) was mounted on a PVC support and attached to the left door of the rotorcraft
The ELT-DT prototype was connected to the SAR antenna of the rotocraft.