THE S- 98 FIREFLY is an all-electric technology demonstration aircraft from Sikorsky Innovations, the advanced technology development organization of Sikorsky Aircraft Corporation. It was a close
second for our choice as the Most Likely to Succeed. The
Firefly team began by selecting the S-300C helicopter
as a test platform, due to its proven safety record and
a desire to minimize development time. While this
helicopter is unlikely to be a game-changer, Sikorsky’s
history of innovation and success leads us to believe it
will be the steppingstone to a viable electric helicopter;
therefore, we feel it has the Most Potential.
First discussed in late 2008 and debuting at
AirVenture Oshkosh 2010, the goals of Project Firefly
are to provide a proof-of-principle concept aircraft
to validate the benefits of an electrically powered
rotorcraft and to drive future development of improved,
state-of-the-art “green” technologies and practices.
The legacy propulsion system was removed and
replaced with a high-efficiency motor and lithium-ion energy storage system from U.S. Hybrid (Torrance,
California). Eagle Aviation Technologies LLC (Hampton,
Virginia) executed the custom airframe modifications
and assembly of the demonstrator aircraft.
The current configuration of the Firefly features
a 190-hp, custom electric motor that is more than 95
percent efficient, weighing less than 200 pounds with
digital controller. The electric motor was designed to
mimic power profiles of the legacy engine to minimize
integration time and complexity.
Two battery packs, each containing 150 individual
45 amp-hour lithium-ion cells, complete the energy
storage system. The battery cells are a custom chemistry formulation combining the advantages of both
high-energy density and high-power formulations.
Within each pack, the cells are first split into groupings
of three cells connected in parallel. The 50 three-cell
packs are then connected together in series (also
known as a 50s3p configuration). Both battery packs
are connected in series, yielding a 100s3p energy storage configuration. Operating at a nominal rating of
370 volts, these battery packs provide the continuous
power needed for flight.
Sensors embedded within the mechanical, electrical, and energy storage components provide real-time
data, which is monitored automatically through a
flight computer. Potentially hazardous conditions are
separately displayed to the pilot with suggested corrective actions.
The integrated, rugged LCD display also serves as the
interface for the text-based caution and warning message system driven by the sensor network. Through the
electrical conversion, propulsion efficiency of the aircraft
has been increased roughly 300 percent from baseline.
The Firefly aircraft is currently undergoing full-configuration bench and ground tests. First flight is
anticipated later this year, upon completion of all
ground tests and safety of flight reviews in accordance
with Sikorsky standard practice for all aircraft programs.
For more information: www.Sikorsky.com
MOST LIKE A
AIRCRAFT MAKE & MODEL: Cessna 172
LENGTH: 27 feet, 2 inches
WINGSPAN: 36 feet, 1 inch
HEIGHT: 8 feet, 11 inches
WEIGHT: about 1,300 pounds
POWERPLANT MAKE & MODEL: 150-k W
WEIGHT: 45 pounds
PROPELLER: composite, six-blade
FOR MORE INFORMATION:
THE IDEA of an electric Cessna 172 is certainly appeal- ing. Retrofitting the most successfully mass-produced light aircraft in history with a green powerplant could
revolutionize the world of flight training and aviation as a whole, if
Bye Energy can pull it off.
When the collaboration
between Bye Energy and the
Cessna Aircraft Company was announced
in October 2010, the goal was to fly an electric-powered proof-of-concept Skyhawk demonstrator in
the first quarter of 2011. As of this writing the aircraft has
not yet flown.
In some ways, this is like a Rube Goldberg with
all the potential energy generating devices—but that’s
what makes this project so interesting and one of the
most complex aircraft in the Class of 2011. The idea is to recharge the batteries through solar panels on the wings, and
use a six-blade prop that windmills, wingtip vortex generators and braking to reclaim energy.
The phase one electric 172 will be a two-place aircraft
capable of about an hour’s worth of flight time. At the current rate of technology improvement, Bye Energy expects its
phase two aircraft to have an endurance of two hours.