Types of Rotor Systems in Helicopters

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This video's topic is covers the types of rotor system designs. I decided to make this video after getting multiple viewer questions seeking clarity on the differences of these systems. That said, keep the questions and comments coming and make sure to hit like and subscribe!

In this video I cover the 3 basic rotor systems: Rigid, Semi-Rigid, and Fully Articulated. During the early stages of helicopter design rotor systems were rigid. This meant that blades, hub, and mast were quite literally rigid and had very limited movement. The blades could rotate and feather and that was just about it. But, as we know blades must flap and feather to compensate for Dissymmetry of Lift (for more detail on why that is, check out my video here: https://youtu.be/culBbvszRpk). In this system, the stressors of this flapping have to be absorbed completely by the blades themselves. To make matters worse, airfoils at the time were designed of lightweight metals like aluminum. So you can only imagine how long this metal held up after flexing up and down repeatedly like a tin can.

It wasn't long before engineers realized how to improve upon this system and a Semi-Rigid system was created. This system, also referred to as a "teetering" or "seesaw" system, incorporated a horizontal or "flapping" hinge. With this in place, the blades themselves no longer had to absorb the stresses or flight. The system could absorb the stresses of Flapping instead. However, this system had a limitations in low G flight and conditions of full cyclic displacement (like slope landings). The system could encounter "mast bumping" which is where part of the rotor system could collide with the mast and, if severe enough, could cause complete rotor separation. Although this doesn't prevent flying, it does limit capabilities and maneuvering of the helicopter.

In the process of constantly evolving rotor systems a Fully Articulated system eventually came to be. This system allowed each blade to flap and feather (aka articulate) independently. The system overcame mast bumping and introduced the concept of "blade hunting." Due to the Law of Conservation of Angular Momentum or Coriolis Force, as a blade flaps upwards, it tends to speed up. This is because the mass of the blade gets closer to the axis of rotation. An easy way to think about this is a spinning figure skater who brings her arms in and speeds up. Vice versa, as her arms extend outwards she slows down. The same thing happens to rotor blades as they flap up and down. Well this is one more point of stress on the blades and a fully articulated rotor system counters this by allowing blades to hunt via a vertical or lead/lag hinge. This ability of an articulated rotor system to absorb the stresses of feathering, flapping, and hunting increase blade reliability and blade life.

All 3 systems are continuously being updated and upgraded and can still be seen today. Red Bull's BO 105 helicopter uses a rigid system because it is the most agile and responsive systems in the world. It's blades are made of fiberglass composite materials that don't wear down like those in the tin can example. The semi-rigid design is one of the most prolific systems worldwide and can be seen in helicopters from the original UH-1 Huey to the modern day Robinson R22. Fully articulated systems are seen on many military and law enforcement helicopters like the AH-64 Apache, the UH-60 Blackhawk, and MH-6 Little Bird. A big takeaway is that rotor systems are always evolving and incorporating more and more composite materials to reduce weight, increase reliability, and improve performance.

That wraps up rotor system design. If you enjoyed the video make sure to hit like and subscribe. Also, don't forget to leave your questions and comments below!

Thanks for watching! As always, safe flying!

If you enjoyed the video or have any questions or comments, hit the like button and comment below.

If you're just getting started and want more information, pictures, and more explanations, I'd recommend reading the Rotorcraft Flying Handbook - http://amzn.to/2ifPlnZ

If you've already got a basic understanding, and want to further your professional helicopter education with advanced helicopter concepts, I'd recommend reading Cyclic and Collective, by Shawn Coyle - http://amzn.to/2ifQGLx

Video and music editing were done via the Splice app.

Видео Types of Rotor Systems in Helicopters канала Helicopter Lessons In 10 Minutes or Less