On 2017-08-25 18:03:55 +0000, "Byker" said:

"Miloch" wrote in message news
In article , Byker says...

"Miloch" wrote in message news

Flying rule of thumb:

"Anytime you can walk away from a landing...it was a good landing".

After seeing so many crashes attributable to tail rotor failure, I wonder
why there aren't more twin-rotor manufacturers, like Kaman and Kamov?

Interesting observation:

"The US uses tandem rotor helicopters because they are easier to make
and maintain; its biggest requirement is a sophisticated transmission
design that needs to be placed between the two rotors to ensure they
rotate evenly and the blades never intersect (even when one engine
fails).

"Co-axial helicopters are much harder to make and the entire engine and
rotor design is extremely mechanically complex.

"Just building a regular engine axel is difficult, and the finished
axel is virtually impossible to inspect for internal voids or cracks.
Any internal defects will result in a catastrophic failure when the
engines spins up to speed the first time. Even now, many turbine engine
manufacturers do their first engine start in something that looks like
a giant steel bunker because there's just no way to be sure the axel at
the heart of that engine won't explode; literally explode. You want to
make axels that go inside axels and spin in opposite directions? That's
a lot harder...

"Personally, I have no idea why Russia chose such a complex and
difficult to manufacture helicopter design. Igor Markov may be able to
explain the logic behind that decision. He is very knowledgeable about
Russia and has written some of my favorite Quora answers about that
part of the world. I'm sure there is a reason; I just don't know it.

"Personally, it reminds me of the Russian booster rocket designs from
the race to the moon. The US built the Saturn V stage 1 rocket with
five engines that had to fire simultaneously and equally. The Russians
designed the N1 lunar rocket that contained 30 (smaller) engines in
stage 1 that had to fire simultaneously and equally. The Americans got
the the moon first (in part) because it's much easier to control and
balance 5 engines simultaneously than it is to control and balance 30
simultaneously."

https://www.quora.com/Why-hasnt-Russ...tor-helicopter

I

don't believe the K-Max K-1200 is dependant on a co-axial system, but
uses an inter-meshing "eggbeater" dual rotor.
http://www.kaman.com/aerosystems/solutions/air-vehicles-mro/k-max
http://fireaviation.com/tag/k-max/
http://www.flyingmag.com/aircraft/helicopters/kaman-restarting-k-max-k-1200-production
https://youtu.be/4dJyUFgY0a8
--


Regards,

Savageduck