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Community Friendly Miniliner

Periodic Reporting for period 2 - UNIFIER19 (Community Friendly Miniliner)

Reporting period: 2021-04-01 to 2022-08-31

MOTIVATION
In the EU, where communities without adequate infrastructures struggle to attract investments and create jobs, the introduction of a new, environmentally friendly and cost-efficient air mobility solution can positively impact the life of hundreds of millions of citizens across all 28 member states. While near zero emission CS-25 airliners are still being beyond today’s technological horizon, the key enabling technology maturing in the next decade and the recently approved CS-23 Amdt. 5 enable the development and certification of a 19-passenger hybrid-electric commuter, designed in this project as a community friendly miniliner.

The potential of the proposed design goes beyond a mere cleaner replacement of existing commuters: UNIFIER19 aims at providing an innovative zero emission air mobility solution for our communities, towards the Flightpath 2050 4-hour-door-to-door goal.

GOALS
The overall objective is to develop a conceptual design for a 19-passenger commuter with multiple cargo and passenger-seating cabin layouts, powered by a modular liquid hydrogen hybrid-electric power-train. The modularity of the propulsion design enables the development of a single airframe capable of accommodating multiple combinations of propellers, batteries and hydrogen fuel cell systems, each tailored for commercially successful zero-emission operations on specific markets.

OTHER OBJECTIVES ARE:
To define the design requirements by estimating the European mobility demand in at least two market segments: the miniliner service, aimed at connecting small airports among them via scheduled or on-demand flights; and the microfeeder service, where small community airports and unpaved airfields feed travellers to hubs served by regularly scheduled commercial air transport.
To develop a commuter that is as easy to use as a bus, by integrating passenger boarding and authentication technology in the airframe and designing for unpaved runways, this aircraft can take advantage of the numerous, sparse and underused small airports in Europe without overwhelming burdens for new ground infrastructures, providing communities with a new mobility opportunity.
To eliminate CO2 and NOx emissions and to reduce acoustic emissions by at least 20% compared to the 19 -seaters that entered into service in 2014.
To justify the investment in a project follow-up phase, aimed at building a demonstrator.
Due to 100% gaseous emission reduction, the focus was on configurations supporting liquid hydrogen propulsion system.

Four potential candidates were selected for conceptual design loops procedure. Candidates' main features were variable incidence wing, drag optimized airframe, tail cone propeller and control-type canard, cantilever wing, distributed electric propulsion on the wing, tail cone propeller, high-aspect ratio wing, tail cone ducted fan...
Candidates were compared on the basis of manufactural complexity level, success index and (noise) emission index. A combination of candidates was chosen (C7A-HARW), featuring high aspect-ratio wing and tail cone propeller.

Higher fidelity analyses were performed to define the building blocks of the subsystems in more detail and to verify technical assumptions made within design loops.
Mid-fidelity panel methods used in sizing loops were validated against CFD and wind tunnel test results, allowing build up a realistic aerodynamic model of the entire aircraft.
Structural FEM design indicated a potentially lighter wing design due to DEP installation, with critical flutter speed indicated well above selected cruise speed of the aircraft.
Tank gravimetric index and power density of the fuel stack were estimated. The difference between values used in sizing loops and from detailed design were below 5%.
The power delivery system was designed with 2-sub-systems redundant architecture, increasing redundancy in case of building blocks failures.
A non-linear, 6-DOF, flight dynamics simulator was built in Simulink, and flight control laws were developed to handle activity of DEP propellers, pusher propeller and control surfaces in normal operation and emergency conditions.
A comprehensive safety analysis indicated high redundancy in propulsion units, power supply system and their independence on architecture.
Noise emission analysis was focused on the departure procedure. It showed 10dB - 20dB reduction with respect to classical twin turboprop aircraft, optimized for UNIFIER19 mission.
Production and operating cost analysis indicated 22% higher purchase price for C7A-HARW that for classical twin turboprop aircraft, however, direct operating cost analysis yielded 10% lower cost-per-available-seat-kilometer for C7A-HARW than twin turboprop aircraft.
Progress beyond the state of art:
- by using publicly available census data, airport locations and road travel distances, UNIFIER19 will model data-driven market demand on the European scale to define aircraft design requirements.
- UNIFIER19 features a flexible cabin that can seat up to 19 passengers, cargo or a mixed combination and a modular propulsion to serve a broader set of missions.
- UNIFIER19 will seek energy efficiency on the overall airframe and propulsion level by tailoring the airframe for a modular hybrid-electric propulsion system.
- UNIFIER 19 aims to be as easy to use for travellers as a community bus.

Expected results until the end of project: The ambition of UNIFIER19 is to develop a conceptual design for a 19-passenger commuter aircraft that is the enabling vehicle for commercially successful near-zero emission air mobility. In the European Union, where communities without adequate infrastructures struggle to attract investments and create jobs, the introduction of a new, environmentally friendly and cost-efficient air mobility solution can positively impact the life of hundreds of millions of citizens across all 28 member states. While near zero emission CS-25 airliners are still being beyond today’s technological horizon, the key enabling technology maturing in the next decade and the recently approved CS-23 Amdt. 5 enable the development and certification of a 19-passenger hybridelectric commuter, designed in this project as a community friendly miniliner. The potential of the proposed design goes beyond a mere cleaner replacement of existing commuters: UNIFIER19 aims at providing an innovative nearzero emission (NZE) air mobility solution for our communities.

Potential impacts:
- Reducing CO2 emissions; Reducing NOx emissions; Reducing noise emissions: the direct and indirect effects: we expect 100% reduction in CO2 and NOx emission. Indirect effect is in the microfeeder scenario, a battery powered 19-seater connecting municipality airstrips to airports can offset the emissions of up to 19 vehicles driving on a highway towards the airports.
- Improving EU competitiveness: The vocation of Small Air Transport as CleanSky 2 transverse activity is further enhanced in UNIFIER19 with the CleanSky technology radar task to consider candidate technologies developed under Airframe, Engines and System ITDs in the manufacturability analysis.
- Improving mobility: With the light market mapping the mobility potential for the miniliner market and microfeeder market and the vehicle designed to integrate embarking/disembarking and passenger authentication provisions, UNIFIER19 aims to invent a credible, attractive-for-customers air mobility solution.