On Sun, 22 Mar 2015 13:12:37 +1300, Dave Doe wrote:

In article ,
, Larry Dighera says...

On Sat, 21 Mar 2015 13:02:34 +1300, Dave Doe wrote:

In article ,
, Larry Dighera says...

Mentioned in the NASA video at the YouTube link below are the reasons this
revolutionary technology are an exciting step forward for aviation.

* Four horsepower per pound are achievable with electric systems. This is
comparable to turbine engine performance.

* Ninety-five percent efficiency is possible with electric propulsion
systems compared to 45% turbine engine efficiency. This translates into
reduced fuel costs and emissions.

* The technology aims to achieve an 80% reduction in energy requirements.


Notice the rear-facing wing-tip engines on this concept drawing:
http://www.aero-news.net/images/content/aerospace/2015/Airborne-NasaLeapTech-031915.jpg.
Is this a means of overcoming the drag produced by counter rotating wing-tip
vortices inherent in virtually all current aircraft?

I don't think so. Have a look at this...
https://www.youtube.com/watch?v=QKCK...PLCdGBvDMYlr8-
tm7kQibn0iDCBbgpLbX6

https://www.youtube.com/watch?v=QKCK4lJLQHU

Dr. McLean, who earned a Ph.D. in Aerospace and Mechanical Sciences from
Princeton University, is discussing aeronautics in terms far beyond my ability
to comprehend. That said, at 39:50 minutes into the video Dr McLean does
mention that a propeller placed at the wing tip is capable of reducing drag to
a limited extent. Therefore, if one is using the propeller to produce thrust,
and is able to also reduce drag to some extent at the same time, I'd say that
is a win with little cost.

Perhaps you have a deeper understanding of the issue, and are able to provide
an alternative explanation for the rear-facing propellers NASA has chosen to
place on the wing tips.

Naa it's beyone me too Larry I did note when I watched the vid
(couple of weeks ago) that he talked also about transferring wing tip
vortices. So for example the propellor system on the wing tips... the
propellor tips also have vortices. So they just get moved around.
That was my take on it.


The NASA LEAP project will be a remarkable step forward in aeronautical
progress is if achieves its goals. I look forward to following the milestones
it achieves.

Thanks for your input with the video.