Helicopters, while highly versatile in their ability to hover and move vertically, lack aerodynamic efficiency in regards to long distance movement. Combining the versatility of a chopper with the speed and cruise efficiency of an airplane often leads to compromises and troubles, as evidenced by the F-35 program and its difficulties incorporating a lift fan into modern jet design. An all electric tiltrotor design for an aircraft, however, might prove superior when it comes to designing the utility craft of the future.
A team at NASA’s Langley Research Center is opting for such an approach with their electric Vertical Takeoff and Landing (VTOL) craft. The current version is only a prototype Drone for testing purposes, but future iterations could have real practical value, according to aerospace engineer Bill Fredericks. “It could be used for small package delivery…long endurance surveillance for agriculture, mapping and other applications.” Says Fredericks. He goes on to say that a scaled up version for actual human transport is also possible and the idea would be “a great one to four person size personal air vehicle.”
For a ten engine craft, not only is the drone quieter than a lawnmower, it is also quite light. The sleek carbon fiber UAV, named Greased Lightning, or GL-10 for short, weighs a portable 24.9 kilograms (55 pounds). The early iterations were much more humble, ranging from foam mock ups to modified hobby airplane kits.
“We did lose some of the early prototypes to ‘hard landings’ as we learned how to configure the flight control system.” Says aerospace engineer David North. “But we discovered something from each loss and were able to keep moving forward.”
The real accomplishment of the GL-10, however, is that it can successfully reconfigure its wings from vertical hover mode to horizontal wing-borne mode midflight. Due to the complicated aerodynamic forces involved, this is no easy task from either an engineering or a programming standpoint. Nevertheless, the Langley team has managed to translate the wings on five separate flights so far.
Their next goal is showing that their tiltrotor design is, in fact, more efficient at horizontal motion than a traditional helicopter. The electric motors also ensure that the tarmac melting heat of jet based V/STOL craft like the harrier wouldn’t limit NASA Langley’s aircraft to specialty landing zones. If all goes well, the research conducted with GL-10 and its successors could prove critical to creating drones for everyday use that are not only quiet and efficient, but could land in a huge number of locations.