Aurora Flight Sciences just released video of its first test flight of what is surely one of the most ambitious projects in aviation today. It’s a 20 percent-scale version of LightningStrike, the concept DARPA selected with a goal of flying more efficiently than an airplane and hovering more efficiently than a helicopter. Aurora’s announcement of the test flight was light on details—including where it flew, and for how long, and exactly what they hope to accomplish—but back in September 2015, when we published an article about the DARPA contest, the plan was to fly the demonstrator from NAS Patuxent River, the Navy’s premier testing ground located not far from Aurora’s factory.
Fixed-wing aircraft are great for flying fast, but they hover inefficiently by pushing small columns of air downwards rapidly. Helicopter rotors push great masses of air down slowly, and so are excellent for hovering, but they can’t move forward very fast because the rotating blades are flung forward with much greater airspeed than the fuselage beneath. Combining each vehicle’s strengths has proven one of the most vexing concepts in aerospace. Dozens of suitable aircraft have been built, but all ended up with serious drawbacks that severely limit their use. Few even went into production, and even the most successful—the Boeing AV-8 Harrier and V-22 Osprey, and more recently Lockheed’s F-35B—are highly complex and costly.
DARPA wants to do better.
Aurora beat three other innovative designs with what looks at first to be the most outlandish design of all: a hybrid-electric tiltwing. Tiltwing aircraft aren’t new, but they are devilishly complicated and expensive, and despite a handful of testbeds and prototypes, none have entered production. It’s generally easier to tilt the engines or propellers only, instead of the whole wing. What makes Aurora’s tiltwing practical is distributed electric propulsion: instead of gas-burning engines, which favor central fuel tanks and complex engines, electric motors are simple and can be placed virtually anywhere. LightningStrike will have 18 such motors, placed along its wings and stabilizer, which allows for aerodynamic fine-tuning in flight.