It’s all about the BellMouth shape and Bernoulli law

The Adaptive Ducted Fan is a scalable and lightweight propulsion system. Depending on its Ø varieties the ADF in its deployed mode can increase efficiently the thrust N up to 80% and can operate in all weather conditions


The deployed ADF is a configured BellMouth convertible mechanism (the slats are deployed) at the inlet duct section. Giving a very substantial area increase, this configuration provides the maximum amount of air in the duct with minimum loss. Combined with the difference of air pressure this mode significantly increases the thrust from 40% to 80% during vertical takeoff and landing


The ADF annular slats inlet section has the autonomous working regime of segmentation of each slat improving the flight dynamics during the transition from hover to cruise minimizes the drag and maximises the controllability. Also has the uniform retracted/deployed regime and depending on various weather conditions and different atmospheric pressure these two regimes combined will maximize the flight control and efficiency


The retracted mode is the narrowing of the slats of the BellMouth inlet section in a keened nacelle design. This mode substantially reducing the drag increasing the speed in cruise or straight flight due to the sharp aerodynamic section of the hull

August – November 2021 the Continuum Dynamics Inc., validates the Adaptive Ducted Fan with the following results:

  • ADF offers good hover and cruise efficiency for eVTOL application

  • Hover performance for the Deployed ADF duct is identical to the 60% larger fixed-geometry duct (Bell X22)

  • Bell X22 Duct volume is over 4x larger than the Retracted ADF duct

  • The reduced volume of the ADF will contribute to lower weight relative to the larger fixed geometry duct

  • The Retracted ADF contributes to lower drag 20% in cruise flight, enhancing the potential for higher flight speeds and longer range

  • ADF also offers the ability to adjust the duct geometry in transition between hover and cruise – greatly assisting flight control

  • Further optimization of the ADF design may allow up to 10-15% further improvement in hover performance

ADF vs Bell X-22 DF

*ADF vs Bell X22 DF sections sized for equal hover performance