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Prandtlplane ARchitecture for the Sustainable Improvement of Future AirpLanes

Periodic Reporting for period 2 - PARSIFAL (Prandtlplane ARchitecture for the Sustainable Improvement of Future AirpLanes)

Reporting period: 2018-11-01 to 2020-07-31

"Aiming to demonstrate the technical, environmental and economic feasibility of a box-wing aircraft configuration known as “PrandtlPlane” (or PrP), the PARSIFAL project has been focused on the needs of the short-to-medium routes air traffic (<4000 km), for which today most of the aircraft in service today belongs to category ""C"" of the ICAO reference code of airports (wingspan within 36 meters). Since this category of aircraft is expected to play the main role in the future air traffic growth, PARSIFAL has faced the challenge of designing an aircraft of the same category, hence compatible with current airports and with most of their infrastructures, but with higher mission performance.

PARSIFAL has achieved relevant results which demonstrate that comparing the designed PrP to a conventional competitor, represented by the common reference model called CeRAS-CSR01, the fuel consumption per passenger can be reduced up to 20%, with a significant impact on environment and market opportunities. This performance improvement is made possible thanks to the adoption a wider fuselage, which increases the number of passengers from less than 200 to more than 300, without enlarging the wingspan. Whereas for any conventional tube-wing configuration this change would be detrimental for the wingspan efficiency, the box-wing system efficiency is weakly affected, hence the aerodynamic efficiency of such aircraft configuration remains high.

The impact assessment analysis has been facing all the aforementioned aspects, providing results about the potential advantages in terms of global warming and noise annoyance reduction, increase of profitability for airlines, possibility for travellers to fly at lower costs, possibility for airport managers to introduce PrP aircraft without affecting airport logistics and infrastructures.

In addition, PARSIFAL has achieved the additional goal of developing design tools and procedures, suitable for the implementation in collaborative Multi-Disciplinary Optimization processes. All the partners have provided their contribution for such achievement, and many design tools have been set-up and calibrated for this purpose.

Among additional project results, it is worth mentioning the successful test of a scaled radio-controlled flying demonstrator, which allows to push the TRL resulting from the project beyond the expected level."
The following results achieved summarize the final project progress:
• the operational and economic assessment of the PrP introduction in the Air Transport System has been performed by means of a set of activities concerning economic, environmental and logistic aspects;

• starting from the baseline PrP configuration achieved in the 1st period, the preliminary PrP design has been refined integrating the results obtained from specific optimizations. The updated PrP has been analysed to evaluate fuel consumption, atmospheric and noise emissions, turnaround time, etc. needed for impact assessment purposes;

• a design methodology has been defined as well as possible scaling procedures. In addition, a subset of the design tools adopted have been implemented in a collaborative framework with MDO capabilities;

• aerodynamic and acoustic analysis of the baseline PrandtlPlane have been completed and optimization activities have been performed for an accurate evaluation of maximal potential gains;

• the PrP structures have been studied considering both metallic and composite materials, adopting optimization algorithms suitable for hyperstatic structures such as the box-wing. Furthermore, aeroelastic analyses have been performed on the metallic solution, investigating both static and dynamic phenomena;

• flight mechanics studies have addressed the flight dynamics, control surfaces sizing, performance analysis for different mission requirements, as well as advanced flight control strategies to improve flight safety. In addition, a 1:18 scaled demonstrator has been tested in order to assess the PrP flight dynamics;

• propulsion system studies have been devoted to the PrP turbofan engines sizing and analysis, including the evaluation of the atmospheric emissions and a feasibility study on the use of very large BPR turbofan engines has been performed;

• Dissemination and external communication activities have been performed according to the initial plans, with the only exception of the “2nd PARSIFAL International Workshop” which has been replaced with a virtual final event, because of COVID-19 emergency. More than 25 journal and conference papers have been published and at least 8000 persons have followed the project development through project website and social channels. Exploitation activities have been performed, mainly through the constant involvement of the External Expert Advisory Board in project activities.
The overall impact of PARSIFAL project can be summarized as follows:
• High potential for new market opportunities and enhancement of EU aviation industry competitiveness: according to project outcomes, the PrP would represent a much profitable alternative to present ICAO C aircraft used on short-to-medium routes. In addition to fuel consumption reduction, the reduced wingspan means that the airport requires up to 17% less parking space to move the same amount of passengers. The market analyses show that most interesting routes are in Eastern Asia, whereas from an airport perspective hub airports in the U.S. are also prime candidates for the PrP. All these aspects suggest that the introduction of the PrP in EU aviation industry would bring to a stronger competitive advantage on a global scale.

• Reduction of the global environmental impact of air transport by increased aerodynamic efficiency compared to conventional aircraft, thus resulting in lower CO2 and noise emissions during all the flight phases. More in details:
- up to 20% reduction in Carbon dioxide (CO2), water vapour and Sulphur dioxide (SO2) emissions per pax-km;
- more than 15% reduction in unburnt Hydrocarbons (HC) emissions per pax-km;
- expected reduction in Carbon monoxide (CO) emissions per pax-km;
- not relevant effects on Nitrogen oxides (NOx) emissions per pax-km;
- up to 17% and 18% reduction of Global Warming Potential on 20 and 100 years horizon, respectively;
- up to 23% and 20% reduction of Global Temperature change Potential on 20 and 100 years horizon, respectively;
- day-evening-night average level of noise decreased for a given airport scenario with assigned daily passengers traffic.

• Increase of flight safety of civil aviation, thanks to a smoother stall and post-stall behaviour and more precise pitch control: advanced flight control concepts to increase safety and passenger comfort have been investigated, showing that Direct Lift Control (DLC) and Pure Couple Control (PCC) strategies con be implemented in the PrP with the following advantages:
- at landing, DLC is both more accurate and more precise when a prescribed touchdown position on the runway has to be reached;
- DLC allows to drastically reduce the oscillations of the pitch attitude angle, hence improving the feeling of comfort on board;
- PCC is the most effective way to protect the aircraft from incipient stall or limit load factor.