Exploitation of an OPA platform for in-flight validation of RPAS technologies A. Rispoli 1, U. Mercurio 2, L. Vecchione 3, P. de Matteis 4, F. Fusco 5, L. Verde 6, U. Ciniglio 7 * C.I.R.A S.c.p.A.– Centro Italiano Ricerche Aerospaziali, via Maiorise Capua (CE), Italy, 81043 Optionally Piloted Aircrafts (OPA) are recently proving to be valuable flying platforms for flight validation of RPAS enabling technologies, thanks to their inherent advantages: take-off and landing from a normal airstrip, flight trials performed into a non-segregated area, reduced logistic footprint and high operation efficiency. Thanks to the support of the National Aerospace Research Program PRORA, CIRA has developed a multipurpose OPA flying platform named Flight Laboratory for Aeronautical REsearch (FLARE). FLARE is based on a P92 TECNAM ultra-light aircraft, which has been modified to fly as an Optionally Piloted Aircraft (OPA). This peculiar aircraft allows for remote control operation while the pilot in command on board (PIC) ensures the flight safety by overriding the flight commands, if necessary. FLARE has received the first Permit-to-Fly ever released in Italy to an OPA on the 14th of April, 2016 and it has already performed 18 flights in a non-segregated area near CIRA premises.
Nomenclature ADSB AFB AGL AHRS ATM ATCO CA CAPEX CIRA CS CTR DOC EASA ENAC EPCU EPMS FD FLARE FCC FTI FTP GCS GNC GPS INS MTOW NOTAM OPA PIC PRORA
= Automatic Dependent Surveillance - Broadcast = Air Force Base = Above Ground Level = Attitude Heading Reference System = Air Traffic Management = Air traffic Controller = Continuous Airworthiness = CAPital EXpenditure = Centro Italiano Ricerche Aerospaziali = Communication System = Controlled Traffic Region = Direct Operating Cost = European Aviation Safety Agency = Ente Nazionale Aviazione Civile = Electric Power Control Unit = Electrical Power Management System = Flight Director = Flying Laboratory for Aerospace Research = Flight Control Computer = Flight test Instrumentation = Flight Test Plan = Ground Control Station = Guidance, Navigation and Control = Global Positioning System = Inertial Navigation System = Maximum take-off weight = Notice-to Airmen = Optionally Piloted Aircraft = Pilot in Command = PROgramma nazionale di Ricerca Aerospaziale
1
CIRA Flight Demonstration Head,
[email protected] CIRA Aeronautical System Engineering, Head,
[email protected] 3 CIRA Aeronautical Department Head,
[email protected] 4 CIRA Aeronautical Department Deputy Head,
[email protected] 5 CIRA Electronics and Communications, Head,
[email protected] 6 CIRA On-board System and ATM Department Head,
[email protected] 7 CIRA On-board System and ATM, System Engineering Head,
[email protected] 2
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RTK PTF RFO VLA VTS
= Real Time Kinematics = Permit to Fly = Remote Flight Operator = Very Light Aircraft = Vehicle Tracking System
I. Introduction Although still being a largely unexploited concept, Optionally Piloted Aircrafts (OPA) are proving more and more to be valuable platforms for in-flight validation1 of RPAS technologies thanks to their inherent advantages: take-off and landing from a normal airstrip, flight trials performed into a non-segregated area, reduced logistic footprint and high operation efficiency. Thanks to the support of the National Aerospace Research Program PRORA, CIRA has developed an innovative OPA named Flight Laboratory for Aeronautical REsearch (FLARE) starting from a commercial ultralight aircraft TECNAM P92-Echo S (see fig. 1). The ultra-light aircraft was then modified to be used as flying test bed capable to provide flight validation of autonomous flight technologies, to test traffic separation scenario based on ADS-B technology and improve weather-forecast satellite based systems. The test program has confirmed that the OPA is the ideal aerial platform for in-flight validation of enabling technologies and procedures for RPAS integration in the ATM system, providing excellent operational flexibility and low DOC. FLARE is the first, and still unique, OPA flying in Italy2. In order to get the authorization to fly a modified P92 aircraft under the current Italian airworthiness rules, CIRA managed a complex technical effort, which included design, modifications as well as continuous airworthiness maintenance operation of the aircraft and its systems. Also, CIRA was in charge to produce the necessary documentation to ensure the compliance to the CS-VLA (Very Light Aircraft) certification regulation which was selected as a reference in agreement with the Italian Civil Aviation Authority (ENAC).
Figure 1- The FLARE OPA This technical process involved the contributions of nearby airframe manufacturers such as TECNAM and OMASUD, the local Flying Club “O. Salomone” and external consultants for the development of the necessary documentation, including the Safety of Flight assessment issued under CIRA responsibility. Thanks to a fruitful technical cooperation with the ENAC, CIRA has finally achieved the relevant Permit to Fly (PTF) on April 14, 2016. The permit, valid for one year, has been issued on the basis of the system engineering and safety documentation produced by CIRA in accordance with the recent ENAC NAV32E regulation relevant in-flight testing activities. As soon as the PTF was available, CIRA started an intensive test campaign, which included a maximum of 38 experimental flights, operating the aircraft from the local Capua airport (ICAO LIAU). A first batch of 18 test flights was carried out from April 18, 2016 to May 6, 2016 in a non-segregated area near the premises of the Italian research center in coordination with the Grazzanise AFB of the Italian Air Force.
II. The OPA Concept According to FAA rules (order 8130.34), an OPA is “an aircraft flown with a safety pilot onboard where remote control of the aircraft may be engaged or disengaged by the safety pilot. Once the system controls are engaged, the aircraft is controlled by a pilot operating the ground control station. Whether the system control is engaged or not, the pilot in command (PIC) will always be the pilot sitting in the aircraft.” The paradigm is 2 American Institute of Aeronautics and Astronautics
therefore based on the presence on board of a safety pilot (i.e. PIC, Pilot in Command) for the purpose of overriding the system in the case of malfunction or any other hazardous situation. The on-board presence of a safety pilot in command of the aircraft provides the unique possibility to consider an OPA flight almost equivalent to a VFR flight, however under specific safety restrictions. Although the FAA order 8130.34 is not applicable in Italy, many of the decisions taken along the process to get the Italian permit-to-fly were quite similar to those suggested or requested by FAA2. The release of the Permit– to-Fly in Italy was, indeed, regulated by ENAC NAV32-E circular, which provides relevant issuance conditions in the case of experimental flights. The validity of the OPA concept is being demonstrated worldwide as it is becoming more and more accepted for its cost and operation benefits. Examples of recent European air vehicles based on an OPA concept are: − AT2TECH RV-OPV-EV: a two-place, single-engine LSA aircraft based on the Evektor Eurostar SLW − Diamond DA42 Centaur Optionally Piloted Aircraft (OPA): developed together with AURORA SCIENCES − Q01 MALE: optionally-piloted aircraft developed by Reiner Stemme Utility Air Systems (RS-UAS), primarily for the Qatar Armed Forces.
III. The aircraft configuration3 Although any traditional manned aircraft is in principle eligible for an OPA modification, CIRA choose to modify a TECNAM P92 Echo Super for its low CAPEX, low DOC, easiness of airworthiness support, close proximity of the OEM factory and for the availability of an EASA certified version. The P92 ECHO S is an ultralight aircraft manufactured by TECNAM Aeronautical Construction with a MTOW of 450 kg and 100 Hp ROTAX engine 912 LS. The ECHO-S was modified3 to allow the higher MTOW due to the installation of the additional equipment and avionics necessary for the use as technology validation platform. In particular, the MTOW was increased to 550 Kg as the equivalent certified version TECNAM P92 JS. The wing struts were modified in order to bear the higher wing loading. Also, in order to provide adequate electrical power to the experimental payload, a 3.5 kW auxiliary alternator (see fig. 2) was installed which required the design of a special bracket and the engine mount design verification for the larger distribution of masses.
Fig. 2 – Auxiliary Alternator Installation The area behind the seats in the rear fuselage and next to the pilot was modified by introducing secondary structures, sized according to CS-VLA, for the installation of experimental pieces of hardware (see fig. 3). Changes were also made to the fire protection system to best meet the requirements of a certified version.
Fig. 3 - Design and installation of experimental payload 3 American Institute of Aeronautics and Astronautics
Servo actuators were installed on the command line of the primary control surfaces (see Fig. 4) and on the engine throttle. The mechanical connection of actuatorsurface and throttle is performed via a clutch. In the engaged mode, each electro-magnetic clutch links the actuator to the relevant command line. Even when the actuator is engaged, the PIC may resume the flight control by overriding the actuators, with the consequent slipping of the clutch on the flywheel. When the clutch is in its rest position, the actuator is disconnected. Being the override capability Fig. 4 - Servo actuator installation for rudder a key safety issue, a specific ground test was performed in order to measure the force to be applied to the each of the command lines to recover control of the aircraft. The aircraft was also modified to host electronic hardware to provide electrical power to the different subsystems and command and control functions to enable automatic flight conditions according to the architecture shown in fig. 5. The power supply to the experimental setup was guaranteed through a custom-built distribution system named as EPMS (Electrical Power Management System). The avionic suite for the flight management functions includes a proprietary Flight Control Computer (FCC), which is capable to provide control, in closed loop, of the movable surfaces and the engine throttle using the data coming from the Navigation sensors (AHRS, GPS, INS, ADS, Magnetometer, etc.). The communication, positioning and datalink tasks were allowed by a number of different antennas for the execution of the flight experiments, which were not part of the JS version. In total, 1 VHF antenna, 3 GPS antennas, 2 LOS Data-link antennas, 1 ADSB receiver antenna and 1 ADSB transponder-out Fig. 5 – On board avionic setup architecture antenna plus a satellite link antenna were installed on the upper wing and on top/bottom fuselage. Finally, the original aircraft cockpit was modified to install additional visual alarms, instruments and markings to be managed by the PIC during the remote and automatic flight piloting phases. The FLARE aircraft and the Ground Control Station5 aircraft are equipped with a two-way data-links, called Communication System (CS), used for transferring telemetry, platform housekeeping data, data generated by experiments, on-board video, remote controls and configuration data and service. The Ground Control Station (GCS), shown in fig. 6, is the main component of the ground segment architecture and is made of the following operating sections: −
− −
On Ground Communication Station: it ensures communications between the Ground Control Station and the onboard systems for sending data remote control / configuration data and for the reception of telemetry data. It also allows the acquisition of video generated by the system "RFO Images & Encoding" board over that sending the differential correction generated by the GPS base ground station and sent to the onboard GPS. GPS Base Station: GPS Base Station generates differential correction intended to GPS RTK board. Weather Measurement: Weather Station that provides information on the weather conditions on ground near the runway.
Figure 6 – GCS & CS Antennas
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−
−
−
−
The RFO Station (see fig. 7) is equipped with End Effector. The Remote Flight operator had displays and interfaces control, compliant to avionic standards, to enable remotely the execution of the control function tests of the flying platform. The RFO station was equipped with VHF radio. It includes a customized RFO HMI designed by CIRA upon remote pilot requirements. The Flight Director Station (see fig.8) is equipped with display and interfaces to allow the management of the mission, the supervision of the planned experiments and communication with the FLARE pilot, and that of any traffic simulating aircraft cooperating, via voice connection. Furthermore, a VHF radio was installed to allow communications between on-board pilot and the FD. Monitoring & Control Experiment Station: station equipped with a suitable workstation with the task to monitor, in real time, the performance of the experiments on the functions to be validated in flight. Audio-video recording system: System used to record what happens in shelter during the in-flight testing. This can be helpful during the phases of debriefing or in general the analysis of the results of the experimental phase.
Fig. 7 - Remote Pilot Station
Fig. 8 - Flight Director Station
During the remote piloting, three different piloting mode were available: − − −
Manual Augmented Mode where the RFO may operate the aircraft by using the control stick to command angular velocity of the aircraft with attitude/sideslip hold. The throttle may be commanded, either by direct mode or IAS hold. Autopilot Mode where the RFO may operate the aircraft through the autopilot panel in hold or select mode for attitude, altitude, vertical speed, track, heading and True Air Speed. Automatic Mode (Autopilot+FMS) where the RFO may select a single 3D waypoint and/or a waypoint list which is automatically followed.
IV. The first flight test activity Following the PtF issuance, FLARE was released into service by TECNAM, as OEM of the basic aircraft, on April 18, 2016 after performing a thorough shakedown flight. The flight test program began on April 20, 2016 in order to control the basic performance and basic flying qualities of the vehicle, after the changes made to the basic configuration. A total of 5 flights were performed in this phase, until April 27, 2016 with the specific goal to: − − − −
to check the data-link performance and identify the actual operational envelope; to verify the performance of the navigation and control software; to verify the performance of remote piloting control station; to verify the performance of the ADS-B based system.
After these preliminary tests, FLARE was ready to be used as flying platform for the validation of RPAS technologies, finally exploiting the conceptual advantage of the OPA flying platform. Therefore, in the period of time from April 27 to May 6, a total of 12 test flights were performed within the RAID (RPAS-ATM Integration Demonstration) project funded by the JU SESAR, whose goal was to perform live flight trials, simulating scenarios where an RPAS traffic may conflict with manned and unmanned intruders4. Fig. 9 – Test ATCO customized HMI 5 American Institute of Aeronautics and Astronautics
FLARE executed the flight trials with surrounding traffic under the control of a test ATCOs (see fig. 9). FLARE simulated the following flight scenarios: − − −
traffic separation with conflicting manned intruder; traffic separation with conflicting manned intruder in the case of Data-link Jamming and GPS Spoofing; on board self-separation in case of head-on approach with unmanned intruder and ownship in level flight.
Overall, FLARE was capable to fly, from April 18 to May 6, a total of 18 flights with no major drawbacks, proving the logistics and operational advantage of the OPA concept over an RPAS in the case of flight validation of RPAS technologies. Finally, a significant key factor to the success of the flight test campaign was the choice of the Flight Test Area (FTA). Thanks to the OPA concept, there was no need to segregate the airspace but a specific NOTAM was released by ENAC with the endorsement of the local Grazzanise AFB, in order to make the interfering traffic aware of the experimental activity. The FTA was 18.5 km long and 6.5 km wide, large enough to accommodate the traffic scenarios to be simulated within the RAID project6 and to include Capua Airport LIAU from where all flights took off and landed. Since the flight trials were restricted to an altitude below 3000 ft, commercial traffic was allowed across the FTA at higher flight levels without interfering with CIRA flight operations, even in the case of incoming and outgoing traffic from Naples International Airport (LIRN). As the FTA was including the Grazzanise AFB CTR, tight coordination with the local AFB controller was necessary during the tests. Therefore, a specific procedure was agreed for the engagement of the airspace, from test planning to test operation. The FTA definition, in terms of size and positon, took also into account an additional requirement from ENAC such as to to avoid towns and densely populated areas but no other specific restriction was required.
V. Conclusion In conclusion, the choice to use an OPA for RPAS technology validation at CIRA provided several advantages over a fully RPAS platform including: − − − − −
take-off and landing from a normal airport; flight trials performed into a non-segregated area covered by NOTAM; reduced logistics footprint, high operation efficiency up to 3 flights per day; simplified process to get the PtF; lower operation cost and logistic footprint.
Acknowledgments Many CIRA colleagues have contributed to the challenge of getting the first Italian Permit to Fly dedicated to an OPA. Among them, the authors like to thank A. Vozella, L. Travascio, A. Pagano, G. Esposito, V. Saracino and L. Pellone. The authors also like to thank G. Bronzone, R. Delise and S. Mechelli from ENAC (Italian Aviation Authority) and Lt. Col. G. Esposito from 9th Wing of the AMI (Italian Air Force) who have provided their helpful guidance along the entire project. Thanks also to TECNAM, OMASUD, the local flying club “O. Salomone”, IDEAE and Fly4Data for their valuable contributions during the design, manufacturing and flight operation of FLARE.
References 1
Olson R., McElroy C., “Development, certification, and flight testing of an optionally piloted aircraft for unmanned aircraft system”, 44th SFTE Annual International Symposium, Fort Worth, Texas, USA, 2013. 2Vecchione L et alii “FLARE: An OPA for Technology Validation used at the Italian Aerospace Research Center”, SFTE, 47th SFTE Annual International Symposium, Wichita, Kansas, 2016. 3Palazzo S. et alii, “Configuration of an Optionally Piloted Vehicle as Flying Laboratory for Aeronautical Research”, RTO-SCI-202 Symposium on Intelligent Uninhabited Vehicle Guidance Systems, Neubiberg (D), July 2009. 4 Rocchio R. et alii, “Flight Testing Avionics of an Optionally Piloted Vehicle for UAS Integration in the Civil Airspace”, IEEE-AIAA DASC 2017 (to be published) 5 Castrillo V. et alii, “Ground Control Station for flight tests of an Optionally Piloted Aircraft of the Italian Aerospace Research Center”, European Test and Telemetry Conference ETTC 2017, Tolouse (F), (to be published) 6RAID RPAS ATM Integration Demonstration, SESAR JU Project, http://raid-sjuproject.eu/
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