Current conditions favorable for ElectraFlyer C's electric flight

What with all this electric car business going on down on terra firma, it was clearly about time we all got to work flying the negatively-charged skies as well. The ElectraFlyer C, built by the Electric Aircraft Corporation, recently got some extended hang time on its maiden flight, powered by a 5.6 kWh lithium battery capable of flying for between 1.5 to two hours at a cruising speed of about 70 mph (and topping out at 90). Presumably close to silently. Read link hits EAC's site, more photos of the ElectraFlyer C here.

[Via Autopia, thanks Sam]

[Switchbitch Posted Aug 10th 2008 11:20AM]

Will, I'm spot on in saying that prop noise comes from transonic shock waves. Almost all a/c noise comes from the props, unless the a/c itself is at transonic velocity in which case it will create 'sonic boom' N-waves at its leading edges.
You contradict yourself in your comment by saying that prop tips aren't transonic, but still as noisy as a combustion engine prop. All props are noisy because the tips have transonic velocities, creating an N-type compression wave at the leading edge of each prop. Remember also that the speed of the prop is in addition to the speed of the aircraft, so an a/c with prop tips at low velocity would be travelling very slow or the engine would be idling.

There are many types of propeller engines designed to have supersonic prop tips, especially when combined with the speed of the aircraft. Of course, the further away you get from transonic velocities (away from the Prandtl Glauert singularity in either direction) then the less the compression wave is in intensity, so the quieter the sound.

[(Unverified) Posted Aug 10th 2008 1:26PM]

This is a Perm 132 Motor--- Google it..

Good for 35 HP bursts at 72 volts..

Battery density has been getting better in the last few years... Too bad lithium Poly batts are too dangerous --- Lithium ion. / phosphate (like the A123) are safe but still weigh too much for the amount of power they put out---


I'm building an electric paraglider............
Uphill battle cause for the same amount of weight i can fly for 5 hours on gas,, 45 minutes on electric

[(Unverified) Posted Aug 30th 2008 2:10PM]

A shrouded prop would make a world of difference with the noise level . May increase performance slightly too.

[(Unverified) Posted Aug 30th 2008 2:12PM]

A shrouded prop may be the ticket for less noise and better performance