SBuzzkill Posted January 22, 2011 Report Share Posted January 22, 2011 Examples of a "soft-in-plane" rotor system being a Bell OH-58D or a 407. What does this mean? I understand how the system works to allow the blades to lead and lag, etc by using the elastomeric bearings. What I don't understand is what type of rotor system is it? Is it fully articulated? Is there a noticable difference between this type of rotor system and an articulated/rigid rotor system as far as control feel? Basically I'm just looking for a further explanation than what my books are giving me. Gracias. Quote Link to comment Share on other sites More sharing options...
iChris Posted January 22, 2011 Report Share Posted January 22, 2011 (edited) Examples of a "soft-in-plane" rotor system being a Bell OH-58D or a 407. What does this mean? I understand how the system works to allow the blades to lead and lag, etc by using the elastomeric bearings. What I don't understand is what type of rotor system is it? Is it fully articulated? Is there a noticable difference between this type of rotor system and an articulated/rigid rotor system as far as control feel? Basically I'm just looking for a further explanation than what my books are giving me. Gracias. The terms soft-in-plane and stiff-in-plane are use to compare lead-lag frequency, in the plane of rotation, to the shaft rotational frequency. If it's soft-in-plane the lead-lag frequency is normally less than the shaft rotational frequency (soft follower of the shaft rotational) In other words, the elastomerics allow for less lead-lag than a fully articulated rotor system with traditional dampers . That term started around the Bell 412. In general terms, soft-in-plane was any blade with mechanical lag hinges or structural flexibility in place of the hinges. Stiff-in-plane was a blade without any mechanical or virtual lag hinge, as on the bell two-bladed rotor system or the R22/R44. Soft-in-plane - U.S. Patent Soft-In-Plane Helicopter Rotor Patent Assignee: Textron, Inc"Elastomeric bearings have previously been utilized to replace metal-to-metal bearings in a helicopter rotor-hub to reduce mechanical wear and failure. However, there exists a need for a rotor-hub which incorporates eIastomeric bearings to accommodate lead-lag and pitch motion of rotor blades while at the same time damping the lead-lag oscillation of the rotor blades." "A helicopter blade-yoke coupling comprises a blade grip secured to the blade and extending inboard of the end of a yoke and an elastomeric blade retention bearing mounted between the inboard portion of the grip and the outer part of the yoke for transferring centrifugal forces from the blade to the yoke while accommodating blade pitch changes and lead-lag motion. Further, a soft-in-plane coupling is placed inboard of the blade retention bearing and between the yoke and the inboard portion of the grip to permit blade pitch motion and lead-lag pivotal motion about the retention bearing while reacting the out-of-plane loads and providing damping for the lead-lag oscillation of the blade. " Edited January 24, 2011 by iChris Quote Link to comment Share on other sites More sharing options...
SBuzzkill Posted January 22, 2011 Author Report Share Posted January 22, 2011 Awesome. Thanks! Quote Link to comment Share on other sites More sharing options...
Gomer Pylot Posted January 22, 2011 Report Share Posted January 22, 2011 Soft-in-plane definitely doesn't refer to the perceived ride feel. The 412 has one of the worst, roughest, rides I've been in. You can never track a 412 to smoothness, just to an acceptable level of vibration, which is still pretty rough. And they only got there by adding 100 lb or so of weight to the head, in the form of pendulum dampeners. When the blades start out in different planes, it's difficult to get decent tracking on the ship, and I've seen weeks spent on tracking, sometimes without success until the blades were changed. It's another Bell non sequitur, which really means very little. Quote Link to comment Share on other sites More sharing options...
SBuzzkill Posted January 22, 2011 Author Report Share Posted January 22, 2011 (edited) Great replies. Much appreciated! I am trying to learn the systems of the OH-58D and the written material they give us uses a bunch of buzz words and no explanations. Very hard to understand sometimes! Found this on google: http://books.google.com/books?id=nMV-TkaX-9cC&printsec=frontcover&dq=principles+of+helicopter+aerodynamics&hl=en&src=bmrr&ei=uTo7TYq9KYKosQPnoLmEAw&sa=X&oi=book_result&ct=result&resnum=1&ved=0CC4Q6AEwAA#v=onepage&q&f=false Score! Edited January 22, 2011 by SBuzzkill Quote Link to comment Share on other sites More sharing options...
iChris Posted January 24, 2011 Report Share Posted January 24, 2011 (edited) Great replies. Much appreciated! I am trying to learn the systems of the OH-58D and the written material they give us uses a bunch of buzz words and no explanations. Very hard to understand sometimes! Found this on google: http://books.google....epage&q&f=false Score! Take away all the buzz words and it's the same old thing. Your traditional articulated rotor head allows each blade to flap, drag, and feather independently. So it is with the soft-in-plane rotor system. Instead of the traditional mechanical hinges, bearings, and dampers, composite material is used to create virtual hinges, pivot points, and damping via bending and flexing of the composite structure. All these arrangements combined the same principles and functions you already know. The modern composite hubs are just generally lighter, require less maintenance, have longer service life, and thus, increased reliability. So you have one manufacturer (Eurocopter) that calls their hub arrangement "Starflex". Then you have another (Bell) that patents its hub design "Soft-In-Plane". Example; the Starflex lead-lag pivot is at the elastomeric frequency adapter block. Were as, the Soft-In-Plane patent places its lead-lag pivot at the elastomeric spherical bearing. Different buzz words same function.What do you have? If it walks like a duck and quacks like a duck, it may just be a duck. Edited January 24, 2011 by iChris Quote Link to comment Share on other sites More sharing options...
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.