Developer claims significant benefits from blown-wing configuration for the next generation of runway-independent aircraft.
US developer Whisper Aero has unveiled a new propulsion architecture that it claims will allow the same aircraft to perform vertical, short or conventional take-offs and landings while removing the complexity of competing lift systems.
Called JetFoil, the design integrates Whisper’s ducted electric fans into a wing’s leading edge to achieve a highly efficient blown wing that “passively augments lift”.
This is both stall-proof and highly resistant to gusts and turbulence, it says.
Flight tests of the system installed on multiple prototype aircraft are likely to take place over the next 12 months, Whisper states.
While other developers are also pursuing distributed propulsion architectures or blown-wing designs, Whisper claims that its system offers several distinct advantages.
“Whisper’s JetFoil technology represents a significant engineering breakthrough, enabling the entire wingspan to be blown through an array of propulsors without introducing heat, swirl, turbulence, or additional parasite drag,” it says.
Its UltraQuiet ducted fans operate at low pressure ratios, offering levels of propulsive efficiency in excess of 90% – even at high speeds and compact sizes, it says.
They also produce low levels of swirl – turbulent air flow – generating more concentrated thrust.
Critically, the “highly uniform, high velocity” air flow exhausted by the system is able to be turned at the wing’s trailing edge using a flap, retaining 95% efficiency when turned through 90° and 70% when turned through more than 170°.
“This is in stark contrast to other VTOL [vertical take-off and landing] propulsion technologies that redirect air with complex tilting propulsors, forcefully redirected flow with systems of flaps, or both,” says Whisper.
Because JetFoil “packages” the thrust required for conventional, short and VTOL operations “in the same form factor”, there is no need for “separate powered lift propulsion” – for example the lift-fan used in the Lockheed Martin F-35B – “freeing up space for additional payloads”.
Whisper also claims a near-VTOL flight is possible with a ground roll as short as 15m (50ft) to clear a similarly sized obstacle in less than 90m horizontally.
“The 50ft ground roll avoids the need to take off in a powered lift mode that forces aircraft to generate 1.2 times the thrust of the aircraft’s maximum weight,” again increasing payload and range.
Whisper is continuing to test and validate its propulsors and the JetFoil system “on ground and in flight” with several branches of the US armed forces and NASA.
It is additionally partnering with OEMs “to rapidly design, build, and fly aircraft prototypes propelled by JetFoil over the coming year”.
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