Tuesday, September 14, 2010

Envelope Pushers

Two aircraft are getting lots of buzz lately for their advancement of aviation technology.
First up is the electrified Cri-Cri, which looks like a toy but is in fact an important joint electric R&D project of EADS InnovationAero Composites Saintonge and the Green Cri-Cri Association.
The four-engine Cri-Cri originally debuted as a gas-engine powered, homebuilt acrobatic stunt plane many years ago.  EADS modified the Hobbit-sized twin to serve as testbed project for developing electrical propulsion systems on helicopters, drones and other aviation platforms for the future.
The original stunt plane had two piston mills, maxing out around 30 total horsepower.  The all-electric Cri-Cri replaces those with four brushless electric motors.  
The "go-gas" comes from LiPo, or Lithium polymer, batteries, all the rage in RC modeling circles for years for their comparatively high energy density.
Brushless motors boast 80% or better efficiency, compared to the 20% or less of average internal combustion engines.  The technology challenge for electric flight lies in getting the "fuel" -- batteries in this case -- to deliver even close to what gasoline produces per equivalent weight.  Once that Holy Grail is developed, electric transportation will transform all our lives.
Back to the Cri-Cri, which just posted its maiden flight in France.  Current endurance is 20 to 30 minutes -- a little putt-putt of an airplane with a 16-foot span can only carry so much in battery weight -- but the ultimate goal is to develop hybrid propulsion applications anyway, not find electric-only solutions.  Still, there will be positive fallout for all electric flight projects worldwide.
The other consistent newsmaker is Terrafugia's Transition LSA.  The Massachusetts company is gearing up for low-volume production of the car/bird, to start no sooner than late 2011 in a new 19,000 sq. ft. factory in Woburn.
The big changes from the original flying prototype, which made a total of 28 short test hops and demonstrated the need for major mods, include:
<>  single stabilator at the rear rather than the canard, which reportedly did not provide adequate pitch authority
<>  larger, 3-blade pusher prop between the tail booms
<> 100hp Rotax 912S engine is now linked to rear wheels rather than the fronts.
Two prototypes are under construction: one for drive testing, the other for ASTM flight certification.
The price, which has steadily crept up during the R&D phase, is now projected at $200K to $250K. 

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