The Future of Advanced Air Mobility

Blainjett Says Its Variable Pitch System Gives eVTOL Developers New Propulsion Options

Blainjett Aviation is offering eVTOL aircraft developers what it says will be a more efficient lift rotor propulsion system than currently available tilt-rotor and ducted fan designs. Its patented Dynamic Variable Pitch (DVP) technology was recently adopted by Horizon Aeronautics for its in-development Hoverbike, but the Delaware-based start-up says it could be used for larger vehicles.

According to company founder Cary Zachary, the DVP concept avoids the need to change the angle of attack of an aircraft’s rotors to support the forward thrust required for cruise flight. Instead, the system changes the pitch of the 32-inch-diameter blades using Blainjett’s proprietary cam and flexible plate mechanism.

For Horizon’s Hoverbike, which is similar in appearance to a jet ski, the DVP rotors are to be installed in the lower fuselage, with half of each multi-blade located within the body of the vehicle and the other half exposed. The blade pitch is increased as they pass through the exposed outer half of the spinning rotor arc, with the blade pitch returned to neutral as they pass through a fairing within the hoverbike body.

Zachary told FutureFlight that the architecture for the DVP concept could be adjusted for a larger eVTOL aircraft. “For instance, in one configuration combined with a pusherprop, only the advancing blades of the hemispherical rotor configuration would be exposed and the DVP mechanism is not engaged. The rotors could slow down and operate more efficiently to reduce drag and achieve higher speeds,” he said. “It could offer major improvements over quadcopter as well as other eVTOL configurations.”

In addition to Horizon Aeronautics, which Zachary said could have a prototype built by the end of this year, Blainjett is working with Praxis Aerospace Concepts International on a STOL design for a long-range drone with a 15-foot wingspan. His business plan calls for the DVP technology to be licensed for development and production by other companies.

“It turned out that when we compared our thrust output and efficiency to ducted fans and smaller rotors, we were two to three times more efficient with two or three times more power density while fitting in the same available space,” Zachary explained. “There’s also a reduction in aerodynamic drag in forward flight.”

The basis for this Blainjett claim is the company’s contention that ducted fans in a hover generate around two grams of thrust per watt of electrical power. Zachary stated that while propellers operating at 50 percent power can generate around six grams per watt, they require more space in the airframe. “We can get more efficiency with our hemispherical design and we can get more power,” he said. “We’ve taken a propeller that normally wouldn’t fit and generated a lot more thrust in a small amount of space. The smaller aerodynamic profile of the aircraft can also net some efficiency gains even when there are no space constraints on the ground.”

Describing himself as a “technical inventor,” Zachary has some formal training in engineering and has previously patented and sold designs in other industries, such as the medical and fitness business. In his efforts to progress aviation propulsion innovations, he has benefitted from the support of several aeronautical engineers.