Last week the world of aeronautics gathered at the International Council of the Aeronautical Science (ICAS) conference in Stockholm: this event takes place every two years and represents a unique opportunity for academics, research centres and companies to share their progress in the new aeronautical sector.

Paolo D’Alesio (Piaggio Aerospace) participated in this event presenting and discussing the main results of the Model Testing of High Lift System (MOTHIF) project, funded by Cleansky 2 in collaboration with von Karman Institute and SONACA company.

MOTHIF project aims at designing and performing a wind tunnel test campaign of an innovative high lift blown flap device. This will allow short take-off/landing capabilities for a future affordable and green commuter, thus paving the way to meet the demanding target of the European FlightPath 2050.

The MOTHIF blown flap has been designed to solve a specific issue arising from the ACARE (Advisory Council for Aeronautics Research in Europe) vision for the future of European civilian aviation.

From one side there is the need to improve small air transportation in order to allow aircraft to take off from reduced runaway; on the other, the need to use green energy source to reduce emissions: the latter leads the future aircraft, both powered by batteries or hydrogen, to have an increased weight.

In a nutshell, we end up facing two opposite requirements: a reduced take-off runaway and a heavier aircraft.

MOTHIF, developing the blown flap device, aims to cover the gap between these two opposite criteria, by developing a technology allowing for reduced stall speed, so easing a heavier aircraft to take off from smaller runaway.

The MOTHIF blown flap is based on the mechanism of “boundary layer dragging”, because of a blown jet from the main airfoil trailing edge. This dragging effect will activate a super-circulation, capable to develop more lift, reduced drag and to delay stall: this will reduce take-off speed and consequently take off length.

Furthermore, the MOTHIF blown flap is able to withstand failure, since it is designed considering both a specific STOL (Short take-off and Landing) airfoil with an optimized Fowler flap and a system cross-feeding valve on the SAT aircraft.

Thanks to the collaboration with SONACA and VKI, it has been possible to perform experimental wind tunnel tests, so looking for the parameters influencing blown jet performance and a better understanding of the physics behind the super circulation activation, by means of PIV (Particle Image velocimetry) and smoke visualizations. Using the CTDR (Critical test Design Review) approach, consisting in a mutual correlation between CFD (Computational Fluid Dynamics) and Wind tunnel tests, it has been possible to obtain reliable results to be transferred to the future SAT aircraft in order to give consistency to the MOTHIF blown flap forecast improvements.