Talk:Tandem-rotor aircraft

message: What part of the data do you claim is false? 
Kitplane01 (talk) 21:19, 27 April 2009 (UTC)
replies: text: The part you changed was false, as at least half the tandem rotor helicoptor designs had piston engines, and most of those had only one engine. There weren't that many anyway, so "many" is a bad word to use. But most of all, you did not cite any sources for what you wrote, so it is considered Original research. That's a policy, not a suggestion, which someone who's been on WP for 5 years or so should not have to be told. - BillCJ (talk) 04:56, 28 April 2009 (UTC)

message: I can't help but feel that some better citations and more clarity would be helpful in this article. I'm not an expert in helicopters but have a solid understanding of aerodynamics and mechanics: opposite cyclic would cause the rotors to tilt in opposite directions, cancelling out any rolling moments on the fuselage, allowing the rotors to 'remain tilted' and maintain (opposing) lateral components of lift - no problem. 'Non-opposite' cyclic would directly impart a moment to the fuselage (except in the case of teetering rotors) and also tilt both rotors (& lift vectors) in the same direction (regardless of the type of rotor); both effects would cause the helicopter to roll - not mentioned here, but the citation used suggests that this would make the helicopter move sideways. I'm almost certain that if the rotors were kept in this position, the helicopter wouldn't (just) move sideways, but would start to move sideways while also rolling, and would then keep rolling and probably crash. This makes me doubt the authority/accuracy of this citation, and what it/this page says about pitch.
From the outset, it is stated that the point of the tandem rotors is to cancel out torque. Even if the rotors weren't constrained to rotate at the same speed, the lift to drag ratios of the blades/rotors couldn't be increased at will. Since they are constrained and the only way to alter a rotor's lift is to increase the angle of attack, it is in fact probable that an increase in collective pitch would actually reduce the lift to drag ratio. The point being, is that the drag wouldn't stay the same and since the torque is proportional to torque, an opposite collective pitch would also lead to differential torque from the two rotors. How is this opposed? At a glance, there is clearly more scope for differential lift from the two rotors than there is for differential cyclic (the rotors can only be tilted so far, plus the yaw authority is dependent upon both rotors producing lift, in order for a 'lateral component of lift' to be available - if one rotor is producing less lift, opposite cyclic would lead to one rotor dominating, leading to roll as well as yaw being coupled to the pitching.
An alternative solution to pitch control which I've come across is simply forward cyclic on both rotors, analogous to a single rotor. But this would afford no additional pitch authority, or larger C of G range, than a single rotor, which I'm fairly sure isn't the case.
As I said, I'm not an expert, so am forced to speculate, but that is only the case because there are gaps/contradictions/flaws in this article/citation.  — Preceding unsigned comment added by 80.229.172.13 (talk) 02:08, 9 May 2016 (UTC)
thread_title:  Better citations/clarity 

message: Substituted at 01:15, 12 June 2016 (UTC)
thread_title: Assessment comment

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