has a 142 kW (190 hp) permanent magnet motor, and has the same
output shaft speed as the standard IO-360. Photo by Phil
Drop into the Aviation Learning Center
and you'll see what at first glance looks like an aerial application
version of the Schweizer 300 helicopter, minus the spray booms but
retaining the big pesticide tanks. A second glance, however, reveals
that these are actually battery enclosures; look between them and you
realize that the 200-hp Lycoming is gone, replaced by an electric motor.
Gone, also, are the original fuel tanks, as well as the maze of wiring
and plumbing that decorated the original reciprocating engine
This is Project Firefly, a research
platform under development by Sikorsky Innovations in Stratford,
Connecticut. Project engineer Jonathan Hartman explained that they began
with a proven existing airframe to minimize re-engineering, then
developed the electric power package to replicate the operating
characteristics of the original gasoline engine. Thus, the 142 kW (190
hp) permanent magnet motor, developed by US Hybrid in Torrance,
California, is mounted in the same location and has the same output
shaft speed as the standard IO-360.
Everything "downstream" of the
engine output pulley is the same as in the original helicopter,
including the multi-V-belt primary drive, sprag clutch, transmission,
and rotor system. The motor itself was originally developed for surface
vehicle programs including electric trucks for the Port of Los Angeles
and an electric-powered Humvee for the U.S. Marine Corps; converting it
for the helicopter involved modifying its rpm and torque characteristics
and changing from water to air cooling. US Hybrid also developed the
motor controller, while the lithium-ion battery cells come from Gaia in
Total capacity of the 1,100-pound battery
is 48.1 kWh, which should allow a flight time of approximately 15
minutes with reserves. First flight is expected later this year; at
present, the Firefly helicopter is continuing with ground runs to
validate the power system and gather data. Hartman noted that with an
expected order of magnitude improvement in battery capability, they
could begin thinking about real-world applications.
This fits with the generally established idea that a 20-fold improvement
in battery capacity for a given weight would be directly comparable to
internal-combustion power systems.
For more information, visit www.Sikorsky.com.