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Rotorhead Types

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There are 2 categories of rotorhead designs: fully articulated and hingeless. The former uses 3 hinges for each blade; one for the feathering axis, one to support flapping up and down, and one to support lead and lag blade movements. On the other hand, a hingeless rotorhead (sometimes known as rigid, which is not a very accurate description) uses materials that are both strong and, to some degree, flexible. Moreover, the blades are also designed to incorporate some form of flexibility.

Both designs have their advantages and disadvantages:

 Fully articulated

Helicopter rotorhead: flapping, feathering and dragging hinges

 Hingeless

Hingless rotorhead

Teetering rotorhead

Of course, in between these 2 solutions, other designs also exist, an important example being the 2 bladed, semi rigid, rotorhead which uses feathering hinges for pitch control. Its 2 (opposite) blades are mounted in one, teetering, hinge. So, if one blade flaps up, the other has to flap down. In this design, the blades are mounted (fixed) in the rotorhead at the average coning angle, in order to prevent blade stress. By using a gimballed teetering head, the rotordisc can tilt in any direction. In this way, the Hookes' joint effect is absent, so there is no need for lead and lag hinges. These are also un-necessary if an underslung rotor design is used. This 2 bladed teetering rotorhead system has already been in operation for many years, ever since the famous designs from Hiller and Bell.

Teetering rotorhead

   Next topic > Pitch Control

Cyclic & Collective

  • The title of this book leads me to wonder what more it will teach me in addition to its content about these two, most frequently used, helicopter input controls. As it turns out, the answer is: a lot more. Of course, all of the obligatory subjects like basic physics, rotor aerodynamics and helicopter performance are dealt with as well, as are piston engine and basic helicopter manoeuvres. Yet the scope of this book is actually much wider than one might initially think. Firstly, it is divided into a 'beginners’ and an 'advanced’ section. This means that the book can treat more complex concepts in depth, even though the focus in the first section is directed more towards newcomers to the field. Secondly, subjects like turbine engines, multi-engine helicopters and autopilots are also examined. This is particularly helpful, since these topics are not usually covered in the majority of helicopter books aimed at this target audience. Thirdly, the book deals with many things that you will not normally find in a text book: helicopter related experiences and a great deal of interesting detail. This is the sort of information that can only be provided if you have flown a lot of different helicopters and have been working in this industry for some time. What’s more, this tone is amplified by the consistently narrative style of the book.
  • 536 pages

Art of the Helicopter (Hardback)

  • Well structured text that covers many technical aspects. It starts with an introduction to helicopters, followed by a treatment of the technical background needed when studying them. Thereafter, dynamics, rotor systems, engines and transmission are explained in detail. The book concludes with a section on performance and other types of rotorcraft. Its main asset is that the text is technically and theoretically very accurate, and rather than mathematics, its focus is always on enabling the reader to achieve an understanding of helicopters from a technical or engineering point of view. The more technically orientated reader will love this work.
  • 416 pages

Principles of Helicopter Flight (Paperback)

  • If you are wondering how a helicopter flies, and really want to comprehend the process, you have no choice but to delve into aerodynamics. This means not only understanding which forces play a role and the laws of physics, but also being able to put it all together and apply your knowledge to a rotating system consisting of a number of rotor blades. This is a demanding task and requires some very hard work. It is, undoubtedly, worth the effort though, and will help you to become a better pilot. There are many books out there to help you with this task of exploring the principles of helicopter flight, but they tend to fall into two camps: populist and taking a rather simplistic approach, or highly technical and assuming the reader has a degree in mathematics. This book is different, because it clearly explains the principles of flight in a step by step way that is easy for most readers to follow. Further benefits are that a lot of attention is paid to flight manoeuvres and operations, and every chapter concludes with questions as a study aid.
  • 320 pages
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3 Comments

ItemInfoText
1  hosein

Saturday, July 30, 2016 8:29 AM

Dear Sir/Madam

as there is no hinge in rigid rotor
how cyclic pitch works in multiple rotor blades
i m looking forward to hearing from you soon

Best Regards
Hosein Araghizadeh
2  helistartgz

Saturday, July 30, 2016 9:27 AM

Hi Hosein,

Good question. I must admit that  it is not explained anywhere on the Helistart website.

In a hingeless rotorsystem, the function of the hinge is done by some rigid stucture. However, that stucture is not totally rigid, it can flex to some degree in the desired planes of rotation. So, have a look a the picture of the hingless rotorhead and focus on the white structure (plate) in the middle. That white stucture is semi rigid an functions like a hinge (actually two: to support flapping and feathering)!

Peter

3  George Ou

Friday, June 23, 2017 8:31 AM

In a Hingeless rotor head, the blade is statically mounted to the head.  Cyclic and Collective pitch moves the Pitch Hinge that twists the entire rotor.

The Fully Articulated rotor head adds two hinges.  The drag hinge and the flap hinge.  Drag hinge allows the rotor to advance ahead or fall behind the rotor rotation.  Flap hinge allows the rotor to tilt up or down.

The Teetering rotor head only adds the flap hinge.

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HeliStart is authored by Peter Goossens.


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