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helicopter rotor blades
8

helicopter rotor blades

helicopter rotor blades

(OP)
Anyone have any information on helicopter rotor blade design and construction?
We are building a light helicopter, and would also like to build our own composite blades.  We could use an aluiminum spar but would prefer to construct the whole blade from composites.
Royce

RE: helicopter rotor blades

I would not like to offer you any information, because I would be very worried about anyone other than the experts building such a part.  

The fact that you are asking for designs suggests a dangerous lack of knowledge.

Be careful, that last 'light helicopter' I heared about crashed into a school play ground, killing the pilot.   

Nigel Waterhouse
n_a_waterhouse@hotmail.com
 
A licensed aircraft mechanic and graduate engineer. Attended university in England and graduated in 1996.  Currenty,living in British Columbia,Canada, working  as a design engineer responsible for aircraft mods and STC's.

RE: helicopter rotor blades

(OP)
Hi Nigel
We are also a licensed aircraft mechanic, but only in Helicopters, and only in the bell 540 rotor system. We are fully licensed in the UH-1E type in all areas except avionics.
We have built and repaired rotor blades constructed of all aluminum, with a honeycomb core, but that is old technology, so want to move into composite technology.
We are fully capable of constructing an all aluminum blade. We can also do wing composites.
The light helicopter that crashed into a school yard and killed the pilot is like all the G/A heavy helicopters that crash almost daily into various things, and also kill the pilot and everyone aboard. Much like the airliners that crash constantly. Not to mention the light twin that crashed into a neighborhood and killed the whole crew, and destroyed several houses, and the UH-1's and jetrangers that do the same thing.  As well as the CH-53's, and other  "certificated" aircraft that crash daily, or the Lear jet that flew from Florida to the midwest and killed the whole crew.  Or the Bell 47G that lost a rotor blade and crashed in the back woods of Canada.
And then there is the origial helicopters that fly with wooden rotor blades, and are still flying, (Bell 30's and 47's) and the ones that were wood and fabric.  And the Huey's that we flew in Vietnam with tape over the bullet holes in the blades to keep them quite.
No, construction of a rotor blade is construction of a rotor blade, regardless of who constructs it.
Royce  

RE: helicopter rotor blades

Thanks for the information on mortality rates of helicopters.

I would have to disagree with the final statement of your post, "No, construction of a rotor blade is construction of a rotor blade, regardless of who constructs it".  Construction of a rotor blade, of any material, is a skilled process.  Especially one made from composite material.  Being licensd helicopter mechanics with experience in composites, you must aware of this.  The use of prepreg materials, stored correctly, with correct records of remaining cure life resulting from being removed from the freezer, correct lay up techniques and conditions, cure times, cooking temperatures and durations, the list is endless.  So, it is important "who constructs it".  Especiallly if I was putting my name to it.  I am not casting any doubt on your skills, by the way.

Any way, putting that a side.  The helicopter you are building, is it of the home built experimantal type, or does it have a type certificate?

If it has a type certificate, you with have to get (FAA if in USA) approaval to install moddifications of any type.

Changing rotors, however, is an involved process.  You have to consider more than the material.  Also important are the dynamics and aerodynamics of the blades, plus a whole host of other things.  You need to be more specific in your request. Ok?
 

Nigel Waterhouse
n_a_waterhouse@hotmail.com
 
A licensed aircraft mechanic and graduate engineer. Attended university in England and graduated in 1996.  Currenty,living in British Columbia,Canada, working  as a design engineer responsible for aircraft mods and STC's.

RE: helicopter rotor blades

1Blessed, Nigel;

There are many experienced custom rotor blade manufacturers and suppliers.  Search YAHOO with "rotor blade composites".  Most manufacturers and suppliers will review your requirements and suggest composite rotor blades for you based on current inventories.

Good luck!

RE: helicopter rotor blades

Royce,

I have no usefull information to pass on as yet (I seem to recall I have photocopied part of a 1970's book which contains some info on contruction of composite rotorblades) but I came across this site while searching for NACA 8-H-12 airfoil data.
http://www.icon.fi/~jtki/gyrocopt.html
It's for passing interest only.

I'll look into finding that material.

Nigel,
No, not anyone can construct an rotorblade but someone with the skilled background in composites ought to be capable of it right?
At least as a starting point what this builder would require is a knowlege of designs that have been researched/tried/tested/proven to be the best construction solutions. What's good in blade construction and what not to do. We don't want to re-invent the wheel and kill ourselves doing it, now that's really stupid.
If it's too expensive or not possible to have the blade built (the best solution!)isn't it at least sensible to try to obtain this information rather than being wreckless.
Maybe the'll find how complex the task is and leave it to the pros!

BOB

RE: helicopter rotor blades

I think for the most part that one confuses rotorcraft mechanics from rotorcraft engineers. Now if you go look that topic up you probably wont find it. But there is an entire branch of Aero and Mech Engineers that are devoted to Helicopter Engineering and I have had the opportunity to meet most of them.  

There is an inherent difference from "Constructing" an Airfoil from parts and components, to "Designing" one from scratch.

Just because you have some NACA data, does not mean that your airfoil or rotorblade will withstand the stresses setup in the rotor. Composites can pose another serious problem if not taken into account. one of which if not done correclty is delamination. Bell Textron found this to be a problem with their early 680 composite yoke assemblies and their other rotor blades of like natures.

I would also ask you to take into consideration for the needs of "inertia". if a rotor blade is made of composites, a couple of things off the top come into mind.

1.) Rotor Dynamic and static ballancing becomes more critical.
2.) Blade Mass, which if not high enough or with enough weight(s), can lose inertia rapidly during any power failures, I personally would not want a composite blade for such reasons.

3.) in composite designs of rotor blades, blade flapping and blade center of mass can become compounded problems during both normal and not so normal flights. If your rotor does not have the proper ballancing, then your coning angles are most likely to be quite high, which will force teh blade cm inward. when this happens lift is lost due to ever increasing blade cone angle. In other words, as the blades flap up, their lift gets destroyed. So the lighter the blade, the greater your tip weights should be to offset this, plus tip speeds. which brings us to another point.

4.) Your composite blade will now have to be calculated for the centrifugal forces and centripetal accelerations set up whithin the rotors. This means that unless you pay attention to the coefficients of expansion, along with a myriad of other problems, your rotors are going to "de-elaminate".

I would strongly urge you to find one of two things:

A.) Already constructed 0012, 23012, SC1095R etc, or the like airfoils and use them, or.

B.) find someone that knows the "Design" aspects for helicotper rotors, spindles and cuffs, lead lag motion and damping, and feather hinges. There's too much to go wrong, will you sacrifice your life for the 6 seconds prior to delamination?


Hope this helps.

I Have designed a method for tilting the main rotor of a helicopter independant of the fuselage and transmission. I own a Company Called Moylan Grass LLC in Minden, NV. We are startup and are in the process of acquisition of funding to begin helicotper manufacturing. U.S. Pat. 5,740,987

Good Day all.

 


RE: helicopter rotor blades

4
For someone to write

 I personally would not want a composite blade for such reasons.'

I can only assume there that there are a people who do not know what they are doing, making and selling rotor blades more suitable for a windmill than a helicopter.

Nobody in their right mind uses composites 'Just to save weight'?

The mechanical properties of composite materials allows responsible engineers to create rotor blades that out-perform metal ones.

The materials are lighter so one can use more of them, allowing redundant loadpaths, 'soft' modes of failure, etc.

A properly designed and manufactured composite blade is safer and will last longer than a metal one.

We found that composite blades were easier to balance and were more tolerant of balancing errors than metal blades.

The impoved aerodynamic shapes and tolerances allow more thrust and control and reduced power requirements.

Etc. Etc.

Making a composite rotor blade is not a 'Garden Shed' operation, but should still be within the capability of many companies.


A design pointer (or, how to avoid the main cause of delamination other than manufacturing faults)

Many designers (and many/most software stressing packages) overlook, underestimate or neglect 2 very important aspects, namely;
'Interlaminar shear strength' and
'Transverse Tensile' loads

Even the big boys get it wrong, i have even seen aircraft flying with clamps bolted around the root end of the blade to stop 'Transverse Tensile' loads causing delamination.



I have been involved in the design, development and manufacture of composite rotor blades / systems in the UK since 1975.
Now Performance Composites Ltd.

RE: helicopter rotor blades

Abaris teaches a course in Reno on composite design, and if you look at the syllabus it gives a hint at the complexity one can suffer through to understand composite design well enough to design blades. You also need autoclavable resins to take full advantage of composite capabilities. Room temperature vacuum bag cures will only give you properties like 7075-T6, although of course, they'll weigh half as much.  I still think there's room for better fundamental understanding of the techniques for composite design and fabrication, when you look at the design safety factors NASA still wants to apply to spacecraft applications. So you really need guys who are artists with a feel for the materials, and gurus who know how to make Nastran dance. Tough to find both.

RE: helicopter rotor blades

There is several manufactures of composites gyrocopter rotorblades around.  If you look at the regional websites for the associations (Popular rotorcraft association and Australian Sport Rotorcraft association, etc)you might be able to contact some of these people.  One lot of rotorblades from the US was called Dragonwings.  Some other places that use similar technology are propellors and wind turbines.  

Best of luck.
Daniel

RE: helicopter rotor blades

3
I will be making carbon fiber rotorblades shortly and think you are asking for practical advice rather than engineering theory so here are a few tips. The spar is made by twisting unidirectional fibers around a core at 45 degrees in both directions to make a torsion tube. The blade gets its tensile strength from unidirectional fibers running from the tip of the blade to the root, around the mounting bushings and back out to the tip. Weights are needed in the tips to give the mass of a heavy blade and still get the weight savings. The "A Star" uses fiberglass blades and uses the weight of the torsional fibers in the leading edge
to ballance the blade however I will be using carbide grit epoxied in the leading edge and carbon fibers. Foam cores or honeycomb are made to precision size and a sheet metal mold is drawn down over the blade with vacuum and in my case autoclaved with additional pressure to take out the bubbles in the resin. Aluminum spars can expand and warp a composite blade so not a great idea.
Hope this helps,
George

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