# Talk:Coaxial rotors

WikiProject Aviation / Rotorcraft (Rated Start-class)
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## WikiProject class rating

This article was automatically assessed because at least one WikiProject had rated the article as start, and the rating on other projects was brought up to start class. BetacommandBot 09:46, 10 November 2007 (UTC)

## Angular momentum discussion

There are some problems with the discussion on angular momentum. Angular momentum is always conserved, but if the fuselage is not rotating, it has no angular momentum even though the tail rotor is applying torque. Usually one compares two different points in time when equating momenta - momentum at time A = momentum at time B.

The net difference of the torques are what really matters. It is sufficent to say that the torque of the tail rotor on the fuselage balances the torque from the main rotor on the fuselage. Torques are not momenta, they are the time rate of change of momenta. This a subtle but important difference. 71.28.202.161 (talk) 17:24, 4 October 2009 (UTC)

The problem is the level of academic coverage necessary to convey the concept for student pilots learning to fly helicopters and the engineering discussions held by those involved in rotorcraft design. Every time a physics or aerodynamic subject is discussed in one of these articles, there becomes this back and forth between several different groups; instructors (with the way they prefer to teach it), students or pilots (with the way they've learned it) and engineers (with the math and physics they use to figure out how to make it all work). Somehow, all these need to come together to benefit the article, to be accurate, and to maintain just a summary style about what can be more complicated related subjects. --Born2flie (talk) 17:38, 4 October 2009 (UTC)

Well I'm pretty sure Mr./Ms. 71.28.202.161 is correct but angular momentum is mostly--if not completely--secondary to the torque caused by the drag on the rotor blades. This very strong drag is caused by the very high speeds that the typical helicopter rotor operates at. Thus the very strong torque. Focusing on angular momentum is wrong. Focusing on angular momentum with a theoretically flawed (in terms of BASIC physics) and very lengthy paragraph is even worse. Now can we change the article? Ewthmatth (talk) 23:35, 28 October 2010 (UTC)

## General theory needs moving to Helicopter

The info about angular momentum is all good, but isn't specific to this article. I think it should be merged into Helicopter or another article, and only a summary should be given here (possibly with a link to the other article or article section) Hertzsprung (talk) 12:06, 31 March 2008 (UTC)

If the discussion of angular momentum is too much for this article, then it will be too much for the Helicopter article. It should be summarized here with a link to the Angular momentum article using the {{Main}} template. --Born2flie (talk) 17:40, 3 April 2008 (UTC)

"Rotational maneuvering is a more complex topic with respect to these designs, and involves engineering beyond the scope of this article." - is it anything more complicated than rotation being accomplished by a speed differential between the rotors? —Preceding unsigned comment added by 146.6.200.213 (talk) 19:22, 22 May 2009 (UTC)

## R/C coaxial helicopters

The part about R/C coaxial helicopters is a bit inaccurate. The stability, low speed, and inability to be controlled under wind conditions of those models, doesn't have anything to do with the fact that they're coaxial designs. It's just that only the lower rotor is directly controlled by cyclic input through a swashplate, while the top rotor is gyroscopically stabilized to always remain parallel to the ground and thus counteract the cyclic input, by its linkage with a large flybar at the top (can be seen in the photo). Jtsiomb (talk) 12:16, 6 July 2009 (UTC)

## History

Russian wikipedia mentions that coaxial rotor design was invented by English inventor Henry Bright back in 1859, who get patent for it. I think it should be mentioned in this article. Shcha (talk) 10:50, 17 April 2012 (UTC)

UPD: can somebody please expand history section using info in NASA Technical Paper 3675 or any other sources? Shcha (talk) 11:08, 17 April 2012 (UTC)

## Assessment comment

The comment(s) below were originally left at Talk:Coaxial rotors/Comments, and are posted here for posterity. Following several discussions in past years, these subpages are now deprecated. The comments may be irrelevant or outdated; if so, please feel free to remove this section.

 Born2flie: The voice of the article seems a little disjointed but lots of good information. Only a couple pics tho. --21:43, 7 January 2007 (UTC) Born2flie: Recommend that an actual article called contra-rotating rotors or Dual main rotors be created and that Tandem rotors and this article be merged into it. --00:38, 8 January 2007 (UTC)

Last edited at 00:47, 8 January 2007 (UTC). Substituted at 11:57, 29 April 2016 (UTC)

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## Drone with two rotor blades

I suggest to add the innovative configuration describing a drone with only two rotors. A link can be found here: https://www.heise.de/make/meldung/Copter-Prototyp-Zwei-Motoren-und-zwei-Rotorblaetter-reichen-3779859.html Felixmwunner (talk) 13:58, 5 June 2018 (UTC)