On 31 January 2020, the new DLR ISTAR (In-flight Systems and Technology Airborne Research) aircraft – a modified Falcon 2000LX – flew from the Dassault plant in Bordeaux-Mérignac to its new home at the German Aerospace Center (Deutsches Zentrum für Luft- und Raumfahrt; DLR) in Braunschweig. The arrival of ISTAR in Braunschweig marks the completion of the first phase of its conversion at Dassault, during which the original aircraft was prepared for the installation of extensive instrumentation in accordance with DLR specifications. Commissioning will now commence at the DLR site in Braunschweig with the integration of a basic measurement system and initial flights. By the mid-2020s, ISTAR will be fully operational as an in-flight simulator, having undergone many additional and extensive modifications. ISTAR will then be used for the evaluation of increasingly automated flight operations, pilot assistance systems and unmanned flight. Two further conversion phases have been planned in close cooperation with Dassault.
"ISTAR is opening a new chapter in aeronautics research at DLR," says Rolf Henke, DLR Executive Board Member for Aeronautics Research. "Our latest research aircraft will develop into a versatile test bed for optimised aerodynamics, flight guidance and flight control. ISTAR also enables a major leap forward in the digitalisation of air transport. We are creating a digital twin for ISTAR, which will accompany it throughout its entire lifecycle."
HighFly accompanying research project
Following the signing of the purchase contract for ISTAR at the Berlin Air Show (ILA) in April 2018 – in the presence of German Chancellor Angela Merkel – the twin-jet aircraft remained at Dassault in Bordeaux. Here, it underwent preliminary work, such as the fitting of numerous sensors, mounting points and cable paths, in preparation for the step-by-step installation of an extensive measurement system. By summer 2020, DLR will have integrated the basic measurement system into the ISTAR cabin. In addition to recording flight data, the system will simultaneously store additional signals from the experimental sensors and antennas. The measurement system includes a workstation with two positions for flight test engineers. These will be used for monitoring and processing the data and for controlling the flight experiments. ISTAR will initially carry out flight research work in the fields of aerodynamics, aeroelasticity, structures and propulsion systems. Over the next three years, the DLR HighFly (High-speed inflight validation) research project will be carried out in four phases, which will accompany the development of the aircraft instrumentation:
- The first measurement flights for Parameter Identification (PID) are planned for mid-2020. The basic measurement system will record the mechanical and dynamic flight properties of ISTAR during specific flight manoeuvres.
- These will be followed in the last quarter of 2020 by a Taxi Vibration Test (TVT) and a Ground Vibration Test (GVT), during which the vibration characteristics – that is, the structural dynamics of the new research aircraft – will be accurately recorded. The aircraft is stationary during the GVT, while during the TVT it moves on the ground. In addition to the permanently installed acceleration sensors, the DLR Institute of Aeroelasticity in Göttingen will attach an array of additional, temporary accelerometers to the exterior of the aircraft for the vibration measurements.
- High-precision optical measurements of the engine exhaust will follow in 2021, during which the turbulent flows behind the running engines and their resulting acoustics will be recorded in detail using laser measuring technology, special cameras and microphones. The Particle Image Velocimetry (PIV) method developed by DLR in Göttingen will be used for this purpose, with the smallest of light-scattering particles making the flow patterns visible under pulsed laser light.
- Finally, in 2022, extensive flight tests will precisely monitor ISTAR during manoeuvres at the edge of its flight envelope. This will take the new research aircraft to the limit of its flight capabilities. The aerodynamics will be monitored using the latest measurement technology from DLR in Braunschweig. This will both improve the models used for computer-based flow simulations and make the design of aircraft more precise, lightweight and energy efficient.
Experimental flight control and in-flight simulation
Upon completion of DLR’s HighFly project, another stay at Dassault is planned for ISTAR in 2023. Here, the research aircraft will be equipped with an experimental fly-by-wire system and an experimental autopilot. This will enable the testing of increasingly automated pilot assistance systems, including automated taxiing and take-off. The system will also be used to test the integration of unmanned aerial vehicles into controlled airspace. In a third phase of development at Dassault in the mid-2020s, ISTAR will become fully functional as a flying simulator, with additional modifications. These include symmetrical ailerons, a direct lift control system and experimental access to the nose landing gear, as well as unrestricted experimental access to the flight control system. Other hardware with which the new DLR research aircraft is already equipped includes an intuitive Enhanced Avionics System (EASy II) cockpit with an Enhanced Flight Vision System (EFVS), a Rockwell Collins head-up display, and a Dassault Falcon Sphere II Electronic Flight Bag suite.
Once fully developed, ISTAR will be able to test the flight characteristics of new aircraft designs – whether real or virtual, crewed or uncrewed – under real operating conditions. The digital twin of ISTAR will provide a digital record of the test vehicle, which will be used to plan and track modifications, maintenance and operational procedures. The new research aircraft will be based at DLR's Flight Experiments facility in Braunschweig and form part of the largest civilian fleet of research aircraft in Europe, with a total of 12 fixed-wing aircraft and helicopters. ISTAR will be available to other national and European research institutions as well as aircraft manufacturers and component suppliers.