Community Research and Development Information Service - CORDIS


SOAR Report Summary

Project ID: 341455
Funded under: FP7-TRANSPORT
Country: Germany

Periodic Report Summary 1 - SOAR (diStributed Open-rotor AiRcraft)

Project Context and Objectives:
The open-fan wing aircraft concept is a completely new kind of aircraft, which is placed somewhere between conventional helicopters and fixed wing aircraft. It provides very good stability, potential hover and short take-off and landing capabilities (STOL).
The propulsion forces are generated using a rotating fan that is mounted horizontally atop of a supporting wing structure; inside the fan develops a vortex which creates a major part of lift for the aircraft.

German Aerospace Centre (DLR) is coordinator of the SOAR project and will find and evaluate suitable markets and missions for this technology. After that, an economic analysis using a conceptual aircraft design study will determine basic performance and cost factors.
FanWing Ltd (FANWING), who have already patented crucial parts of their FanWing propulsion system, will optimise their technology in SOAR to find the optimal blade profile, angle and rotor cavity position, and evaluate the open-fan wing's aerodynamic performance to derive scaling laws for this type of aircraft.

To this end, the Von-Karman Institute (VKI) simulated the open-fan wing design with state of the art computational fluid dynamics (CFD) software, designed and built a specialised balance to measure forces on the wind tunnel model, and performed several weeks of wind tunnel tests to validate findings of the CFD computations.
The Saarland University (USAAR) developed and implemented a fan drive system involving a brushless synchronous torque motor and various sensors. They also created a planetary gear mechanism to enable synchronous adjustment of the blade pitch angle.
During the collaborative wind tunnel tests at VKI, three sets of up to 16 carbon-fibre fan blades were tested at different pitch angles within the rotor, at different angles of attack for the entire wing model, and at different rotational and air speeds. After the first testing campaign, the best airfoil candidate was selected and further derived candidates were tested in consecutive runs. Complementing the rotor tests, the wing shape was systematically modified and tested.

Additionally to the expected short take-off and landing capabilities of this aircraft concept, significant noise reductions are expected by the horizontally distributed thrust generation. This would allow small aircraft to fly within city bounds or avoid night curfews. Other potential uses are automatic, pilotless operation for package delivery or civilian surveillance. Larger versions could serve as agricultural crop dusting planes, optimised for makeshift runways close to their area of use. The downdraft of the air would also help to direct nutrients or seeds to the plants. Another potential market would be port-and-cargo operations or disaster operations like firefighting planes.

Project Results:
During the first months of the project, the open-fan wing model design was completed. Matching the wing, the rotor blades (MS11) and their mould were designed and built (MS12).

The wing section of the model - including the cross-flow fan - was built by FanWing Ltd (FANWING) and by subcontracting relevant parts of machining work and production of the carbon-fibre fan blades and shaft (D1.1).

A total of three sets of 16 fan blades each, having different airfoil shapes were purchased initially, with three more sets of airfoil varations after narrowing down to the best shape.

Saarland University (USAAR) specified the fan motor which was subsequently built by a subcontractor according to USAAR's design criteria. The engine is built as a brushless synchronous torque motor capable of delivering 45 Nm of torque at 1250 rpm. This design was selected based on its compact construction and the ability to incorporate the separate rotor and stator components into the wing model construction. Additionally, a planetary gear mechanism was designed which enables the control of the rotor blade pitch angle for all installed blades simultaneously.
After integration of the motor, the actuated wing model was completed (D1.2).

In preparation of the wind tunnel tests and serving as a validation reference, the Von-Karman Institute (VKI) performed detailed computational fluid dynamics (CFD) studies for the open-fan wing technology setup.
The simulation was performed on a CFD hybrid mesh of about 250.000 elements with a minimal cell size of 2*10^-5 meters, covering an simulation space of 20 by 20 meters around the open-fan wing computer model.
Computation was performed for five air speeds, six rotor speeds, and different airfoil profiles, with a assumed air turbulence of 5%.

USAAR's delivery of the actuated wing model to VKI was followed up by final model assembly tasks, mounting of the open-fan wing model on the wind tunnel balance, completion of the electrical control and measurement installations and finally commissioning of the model for wind tunnel testing.
Because of the unconventional nature of the open-fan wing design regarding production of lift and thrust, VKI designed and built a specialised external balance for the measurement of forces of and on the wing model, taking special care to observe safety factors of the expected forces to avoid damage of the wind tunnel (D2.1).

During three following test campaigns, the open-fan wing model and systems were tested thoroughly (MS21) in the wind tunnel, measuring forces and capturing high-speed video in a particle tracing test.
In the first phase, the model, drive system and wind tunnel balance were installed and the data acquisition system installed and tested. The second phase concentrated on rotor optimisation by testing a focused set of key performance points of angle of attack (AoA), fan rotational speed (RPM), and wind speeds representing take-off, loiter, cruise, dash and auto-rotation landing. Six sets of fan blade shapes were tested with five different blade angle settings each. The best combination candidate was then selected and the optimisation of the fixed wing geometry was started, in steps modifying lower shroud, entry and exit heights. Also setups with less than all 16 blades were tested and did perform not siginificantly worse.
In the third phase the fixed wing and rotor optimisation was continued at the key performance points with regards to the rotor cavitiy, leading edge position and other modifications. This completed the design optimisation in the wind tunnel (MS22).

The full data on wing-flow diagrams and airspeed was gathered (MS23) and first CFD conclusions drawn (MS24). These activities resulted in a evaluation report (D2.2).

In parallel to the wind tunnel tests, Deutsches Zentrum für Luft- und Raumfahrt (DLR) analysed potential markets and missions for a open-fan wing configuration, including use cases as unmanned aerial vehicles (UAV) for civilian surveillance, door-to-door package delivery, crop dusting, passenger transport, port & cargo operations and military vehicle competing in the tilt rotor market. These missions and markets will determine the vehicles conceptual design, which will be analysed in the second project year.

Potential Impact:
The open-fan wing aircraft is expected to be competitive in certain markets through its stability, potential ability to hover and reduced fuel burn in comparison to missions flown today by rotorcraft or specialised fixed wing aircraft.
Potential customers could be amateur pilots, package delivery companies targeting pilotless operation, on-demand cargo operators, or farmers with little space for a runway; also government institutions for use in civilian surveillance.
Through its large distributed thrust systems, an overall noise reduction is expected, helping in abating emissions from the steady increase in air transport demands, but also allowing for transport well inside cities.
The unusually short take-off runway length requirement (including from unprepared terrain) supports new models of use for an open-fan wing type aircraft, for example in mountainous terrain or at future small airport spots.
Due to its stability and virtual inability to stall, the aircraft might need less safety systems, which would reduce costs in certification, maintenance, and even pilot training.
Reduced costs for construction and operation will again allow more people to benefit from this radically new technology.

List of Websites:


Sylke Heinlein, (Contract Officer)
Tel.: +49 551 709 2284
Record Number: 163364 / Last updated on: 2015-05-08
Information source: SESAM
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