BELL PHOTO
Above: Bell’s electrically distributed
anti-torque (EDAT)
system, shown being tested on a Bell 429, controls thrust by
changing the rpm of the fixed-pitch blades.
Opposite:
Airbus plans another series of flight tests
of its electric backup system, this time on the H130.
its ability to handle larger payloads and/or enable the aircraft to take off faster under normal operating conditions.” And, he says, in case of an engine-out situation, instead
of relying on the autorotation to land the aircraft—a maneuver that requires quick reactions and appropriate flight inputs by pilots—the electric subsystem would provide enough electric torque to maintain a controlled rotation of the heli- copter rotor and therefore enable the aircraft to “land safely in an area of the pilot’s choosing.” Te sizing of the battery in a mild hybrid system, says
Mekhiche, will be determined by the available space within the aircraft and the minimum torque required to enable the aircraft rotor to continue to operate for a handful of minutes in the case of an engine failure. “Te electric machine and the associated power-conversion electronics can operate as a motor or as a generator,” he says. “Te latter operating mode enables battery charging via the engine upon depletion.”
Issues to Solve Reaching the goal of an electrically powered helicopter will require sufficient battery energy density to meet the unique power needs mandated throughout a helicopter mission. Tose needs, unique to rotorcraft, pertain to sustained hover as part of the mission profile, according to Jonathan Hartman,
40 ROTOR 2020 Q4
Sikorsky Innovations’ disruptive technology lead for Sikorsky (a Lockheed Martin Company) in Stratford, Connecticut. (Sikorsky hasn’t publicly announced a hybrid or full-electric helicopter project at this time.) “Te end-of-flight hover and landing is the most onerous
part of a helicopter mission because you would need to pull a lot of power at the time the energy stored in the battery would be at its lowest level,” says Hartman. “To address this issue, the performance of batteries has to improve.” At present, reports Hartman, there are a number of
“interesting energy storage technologies” being developed—all at various stages of maturity—that could have a substantial impact on future aircraft design. “But it’s still too early to know if one technology will meet the rigorous performance requirements for certified flight more affordably or reliably than any other,” he stresses, adding that how the electric propulsion technology will be applied could vary significantly depending on the helicopter mission requirements. “Te answer will come down to payload and range, which
is why, at this time, the technology for some type of an electric helicopter looks very promising,” Hartman remarks. “Specifically, that would be smaller vehicles flying shorter distances, carrying smaller and lighter payloads.” Marc Brodeur, VP, military and commercial sales, at MD Helicopters in Mesa, Arizona, emphasizes that in order
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