Electric Helicopter Transmission

[Agile]

Long, ago (about 30 years) I remember reading one of best helicopter theory book in French from P. Lefort. The was making the point that in the future Electric Transmission would become the most prevalent technology. That was a bold forecast knowing the state of the technology at that time. Today with the way technology has evolved (hybrid cars), is that such a bold idea?,


you have the Tesla power train outputting above 700Hp on electric alone.
you have every single F1 engine package using some electric boost.


Could it be a used as an emergency 1 minute power source?
Could it be integrated into the transmission-hub it-self?
Could it make things like the Pearl Harbor accident more manageable?


The light comes on, you have 1 minute of electric power regardless of broken power shaft.

[CRAN]

Agile,

I have worked on this for two major manufacturers and in terms of the electric drivetrain it is and has been for a long time far superior to piston/turbine engines and gearboxes in every conceivable way. Power-to-weight has long since been good enough...however, the problem remains energy storage. Will still don't have a sufficiently energy dense way of storing electricity. The latest battery technology is still too heavy and while fuel cells themselves are light enough, reliable enough and extremely efficient, the problem is the volume of hydrogen that you have to carry around with you which leads to a huge heavy fuel tank. Hydrogen has a density of about 70.8kg/m^3 as a liquid!

There will be an almost overnight switch to electric cars and electric helicopters the moment we can store electricity in an energy-dense manner, it will be just as quick as the mobile phone and satnav revolutions. However, progress on the battery front is very incremental as is the issue of storing hydrogen efficiently for fuels cells.

It will come, but I don't know when.

CRAN

[RVDT]

EC flew an AS350 as you describe back in 2011.

Article here. (http://www.upi.com/Business_News/Security-Industry/2011/10/07/Eurocopter-tests-hybrid-aircraft/34631317987259/)

[chopjock]

Could we still use fuel / engine as an APU to drive the electric motor, whilst still having a modest battery for emergencies I wonder?

[Agile]

Thanks CRAN, RVDT, great answers


also glad to know that the technology prediction is still relevant


Another point beyond energy density might also be:
how quickly that energy can be transferred out
30 sec to 1min is probably much below the standard discharge rates
(landing safe but on fire does not help either :})


Just reviewed F1 rules, I saw 161hp, 30sec are the regulated limits
This how the pack looks for that job, large cables and cooling lines


http://insideevs.com/wp-content/uploads/2014/12/williams_news_2.jpg

[riff_raff]

Agile,

A couple years back AW (briefly) flew their Project Zero tilt rotor demonstrator aircraft. It was an all electric propulsion system and was basically a test bed for various technologies they were developing, such as electric propulsion motors/controls, electromechanical IBC actuation, etc. The aircraft was unmanned and of limited scale, but to me the most impressive aspects of the project were that it was funded internally and had a very short (6 month) design/build cycle. Would be great to see more of this in the aerospace industry.

Here's a 2013 video with an interview of the project engineering lead (https://www.youtube.com/watch?v=ZvelR2aoheE). At 2:15 of the video he talks about the problems with energy density of current battery systems.

Here's a US patent application published in 2013 covering the concept (http://www.google.com/patents/US20130026303) that is worth a read if you're interested in electric rotorcraft propulsion systems.