Evolution & Future Direction Of Griffon Aerospace’s eVTOL

Mr. Larry French, CTO of Griffon Aerospace shared that they’ve been in business obviously since the mid-1990s when they produced the Lionheart kit planes, which declined in the late 1990s to early 2000s. They then bid as a prime contractor to be the Army’s Air Defense Training Contractor, and they are now a prime contractor for the United States Army, building training drones.

The ‘Stingers’ being shot over in Ukraine and around the world are actually Griffon aerospace targets and pilots. We [Griffon] are training those guys how to use Stinger missiles and MANPADS so our primary revenue stream is from the US Army and the Marine Corps. Griffon manufactures about 45 airplanes a month, and it is the genesis of many years of his love of making things that fly.

"Griffons’ aircraft have always been dependent upon runways or launchers and they’ve learned that, for being able to be expeditionary, and move, and operate wherever we want, VTOL is the future of unmanned aircraft” said Mr. French who went on to say “particularly where you drop an airplane, and drop soldiers under remote locations… and then the other thing that drove this design is that I wanted long endurance, and the equations for endurance aspect ratio….is long skinny wings. We all know long skinny wings, as you see in sail plane… if you want to fly efficiently…and low drag, you need to have long skinny wings, so that has been rumbling around in my brain as far as what configuration can we do…VTOL and tilt-rotors, yet have long skinny wings is what evolved then towards this aircraft”.

Mr. French commented that “it has large rotors in the front, small rotors in the back, and we were able to have the highest aspect-ratio efficient wing design, like a sailplane, and V tail. The large props in front carry 70% of the hover thrust, and the back carries the other 30%. Those rotors are tilting front and rear, all four quad tilts, and once it goes from hover to forward conversion, it takes about 45 seconds for us to go up 80 feet, convert, and go to forward flight. As soon as we go to 45 knots or so, we break the front electric motors, the props fold [backward], so the aircraft is optimized towards cruise, but yet, it’s a VTOL aircraft.”

For less than 0.5% of the mission, it needs 34 horsepower to hover. That energy comes from stored batteries in the front but, after it converts, there’s a generator and gas heavy field generator back, in the aft fuselage that produces electricity for forward flight. In hover it takes about 34hp in forward flight, in hover it takes about 3hp, so the generator is sized for forward flight to maximize endurance. They consider it a synergistic design; big blades for hover 70%, do the conversion, stop and fold the front blades, and then we fly off the back motors.

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