Cornered ???
 

Nick,

You're strong support of the tail rotor configuration and objection to the lateral twin rotor configurations is understandable, and commendable. Your employer only manufactures this configuration.

Opposing this; I have never found a knowledgeable employee of a firm that manufactured laterally mounted twin rotors, who stated that his configuration was an inferior one. Have you?

Both sides of the argument are quite theoretical and speculative, until there is actual flying proof. Any ideas on how to relieve the V-22 project of a few million dollars, so that a modern lateral dual rotorcraft can be built? :ok:

the only laterally mounted twin rotor helicopter that I know of is the Soviet Mi-12. It was not a success - but was this due to it's size, or something else.
The problem is handling and dynamic instability- the cheap and easy answer is a stabilization system. Having seen several of these, I can attest that even a simple rate damping system transforms the handling - underslung loads become a piece of cake, IFR flying is easily achieved, and so on.
The winner will be the person who develops a low cost, reasonable AFCS for light helicopters.

Variable speed rotor
 

I can't help but notice how recent developments in the UAV arena are proving that much can be gained from moving away from traditional concepts.
For example the A160 Hummingbird , rather than slowing down its rotor at high speed (likethe CarterCopter and others), slows its rotor at LOW speeds.
They achieve a 50% payload increase and 50% reduction in fuel burn. Yet interestingly, the design keeps the tail rotor and single main rotor concept. No syncropters needed.
Here's a blurb:
******************
A contemporary helicopter features lightweight flexible rotors that are connected to the rotor hub through articulated joints. Such rotors are designed to provide smooth flight operation with little vibration and good control authority.

However, they can only do so within a limited range of speeds, normally at as high an RPM as possible before the wingtips break the sound barrier. The helicopter's rotor RPM is roughly constant while the aircraft is in flight. This is inefficient, particularly when the helicopter is flying below maximum speed or with an optimal load.

The A160's carbon-fiber composite rotor blades are tapered, and their cross-section varies from root to tip. They are light but stiff to avoid vibration, and their stiffness also varies from root to tip. The rotor system is rigid and hingeless, and features a larger diameter and lower disk loading than that of a conventional helicopter with the same lift capacity.

The A160 rotor can be operated from 140 to 350 RPM. Coupled with a fuel-efficient piston engine results in a helicopter that not only has unbelievable fuel efficiency, but good speed, unprecedented altitude capability, and is very silent.
********************************************

This aircraft is now flying, BTW,and a mpg movie can be seen here: http://www.darpa.mil/body/NewsItems/...ght2-10-03.mpg

and an article here:
http://www.globalsecurity.org/intell/systems/a160.htm

Dave,
You fall into the trap that catches many folks who are good with language and low on technical knowledge, you think this is a vote.

the only vote that counts is what the customer buys. If you read the papers published by Sergei Maheyev, you would see the same losses I report, and the same drag issues dioscussed, as well as reasonable assumptions of the weight penalties. It is rumored that he built a few coaxials. His latest helo is a single rotor, with fan.

Regarding this thread, it is not about change vs same. That is Dave's last refuge for his poor argument- that I must not want change if I don't think his symmetrical stuff is a good idea. Let the record show, I have flown more experimental helicopters, and more changes than ost other folks, change is the coin of an R&D pilot! I certainly advocate change, it is syncropters and symmetry that I describe as lost causes.

The Hummingbird has neither of those features, it is a single rotor helicopter with a tail rotor. Somehow, Chiplight, you would like to show me that the Hummingbird proves me incorrect, which is a mystery. Its variable rpm is a great idea, let it prosper!

For the record, I think change to introduce improvements is always good, change to introduce mystical properties of symmetry is almost never good.

Nick, I was supporting your point about the tail rotor not being the liability some would make it out to be.

Chiplight

Shawn,

Yes, both the Germans and the Russians have built a number of side-by-side rotorcraft. The German Fa223, actually saw limited service during the Second World War.

The downside to a totally new rotorcraft OR a computerized system is the cost, just as you and Nick said.

I understand that if a new rotorcraft was built today, the required pilots' seats will cost $25,000,00 each.

Nick can give a better answer, but I believe that the software for the Comanche involved hundreds of thousands of lines of code. This is not cheap. Microsoft can write off the cost of an operating system against 5,000,000 copies. Sikorsky must write off the cost against, say, 500 copies.

This high cost of writing off R&D expenses is also a partial answer to Hans Conser's earlier statement "What the helicopter really needs is a low cost powerplant...". As I recall, only 3,500 reciprocating aircraft engines are built each year. Lycoming or Continental has mentioned that this makes it impossible to develop a next generation reciprocating engine.


Chiplight,

The Hummingbird A160 is another attempt to push the frontiers of rotorcraft and that is good. I believe that their patent is US 6,007,298. It's not a new idea but since the craft is unmanned, in hover they can risk operating the main rotor closer to total stall.

For simple hover, unquestionably, NOTHING can beat two side-by-side rotors in close proximity.


Nick,

We have already discussed Kamov's calculations about tail-rotor losses verses the earlier western calculations. Leishman and other westerners have now move closer to the Russian's claim of higher losses. Whatever, I have never suggested that the coaxial is a better configuration.

I have only claimed that the intermeshing configuration is probably the best configuration for short small fuselages. Your guru, Stepniewski, concluded, in his last known report, a couple of years back, that the intermeshing configuration was even the best for large transportation craft. The latest issue of the AHS Journal arrived today. You will notice that the first article is 'Preliminary Design of Transport Helicopters' and in this article, Stepniewski is cited in 2 of the 8 references.

In addition, I have never talked about 'mysticism', only about 'nature' and about man's striving to technologically get closer to what it took hundred of millions of years for evolution to achieve.

"the only vote that counts is what the customer buys",

We all know the value of marketing. We also know of many, many instances where the best product was not the best seller.
_________________


Fact: In 1945, the best helicopters in the world were the two German lateral twin rotor helicopters.
Fact: Countries developing helicopters at this time, such as Germany, Italy, Russia, France and England all lost the war ~ financially. The exception was the US, which was predominantly single rotor oriented.
Fact: Since 1945, far, far more money has been spent on single rotorcraft development than has been spent on lateral twin rotorcraft development.
Assumption If the allocation of this money had been reversed, today's rotorcraft would be far ahead of what they currently are. :oh: :oh:


~ and the $hit just hit the fan ~

hi all,



2rotors:

you mentioned the R-22 being unstable. By now I have about 600hrs in it (out of 6500).

Actually I think it is a VERY STABLE helicopter. Just flew it for 12 hrs in 2 days right into mountains with a bit turbulence.
On the way home I even got it to fly hands of for 30 sec. at a time (horsing around to cut bordome on the ferry...)
I think what you call unstable in the R-22 is rather light weight. Of course a little ****** like the R-22 will be thrown around in any little breeze there is, so would any other small helicopter.
However sofar I do not know of any like small helo that is so maneuverable and fast (relative . . . vne 102 kts and I did 90 on cruise)

Rotordisk distance to the hull:

I am definitely not any match to discuss this issue amongst you guys, but observe this on the R-44 (I know I like the R-product a lot, .....I fly it a lot - for Nick this is probably a couple of thousand pounds below his lower weight redline........). This machine has the rotorhead rather far away from the hull. The new Raven II does on regular cruisepower some easy 110 kts in ISA+15 deg conditions, versus 90 for the old model. Remeber this chopper has a max gross of 2400lbs (2500 the Raven II), so it is still a light weight chopper. And it still is extremly stable, not to mix this up with agile - you can do amazing things with it and you can do them fast (AGAIN relative - we have a simple underslung rotor and all its limits - no loops and rolls here, as far as I know)

Last 2 cents:

Everyone talking off making even the small choppers easier to fly. I do not know if this is so good. There is a reason why only seasoned pilots do certain work. I would not want to have a lot of folk up there to get in trouble because of the extended flightenvelope a helicopter gives them versus a fixed wing.

I personally apreciate the rather demanding training one has to go thrue to get a helicopter licence, and I am glad that all those who do not cut it, do not get themselves into trouble.

Artificial stability and control is all fine, until it fails (that one time out of a million...),keep these systems in the big machines and keep the smaller ones sensible, it sorts the ones that should from the ones that do not!!

3top:cool:

Kuhn Takes Command from Charles at Kaman ~ Rotorcraft Report, March 19, 2004
 

______________________

The future of the rotorcraft industry is in dire straights. This is evident from the limited current projects, the proposed concepts, the lack of supporting funds, and the depressing industry articles. In essence, there are very few VTOL configurations currently contending for future high-speed/vertical aircraft, and all of them are flawed.

In my opinion, there is only one realistic future VTOL configuration. It is the unification of the Intermeshing Configuration and the Advancing Blade Concept. A configuration that appears to have no show-stopping flaw.
______________________

John K. Northrop (1895-1981) was a project designer at Lockheed's Skunk Works. His lifelong passion was to build a flying wing. Out of deep respect for this gentleman, Lockheed showed him the secret B-2 bomber, just before he passed away. It was done in appreciation and acknowledgment that his dream was finally becoming a reality.

The 80-year-old Charles Kaman, started his aerospace career in 1942 as an engineer with United Technologies, working as an aerodynamicist with Igor Sikorsky. When Kaman's ideas were rejected, he left, and with $2,000.00 started his own company, to produce an intermeshing helicopter. His decision to emphasize lift over forward speed may have been based on his inability to compete with the larger United Technologies.

Sikorsky has the most experience in the Advancing Blade Concept and Reverse Velocity Utilization. Therefor they have the advantage in developing this style of advanced rotorcraft.

Out of consideration for their former employee, might they invite Charles Kaman to come and see the potential of his intermeshing dream. :D

Perhaps it's a secret project, and they already have. :D :D

Hi Dave, all very interesting stuff, I'm sure. I never got round to asking you, but what do you do for a living?

regards,

TC

Hi TC,

When not writing provocative postings, my 'life' is spent trying to develop, and disseminate information on, a better rotorcraft. :O :O

Dave
UniCopter

It was said that there has been no heavy lift helicopter built since the CH-47 Chinook? What about the Sikorsky CH-53E?

As for other technology, the Navy is funding Piasecki's work on the Vectored Thrust Ducted Propellor modification to the H-60. Anyone have any comments or observations about it?

46Driver:

A couple of notes on the Vectored Thrust Ducted Propeller, which were probably not mentioned in last year's thread, are;

• Sikorsky's Reverse Velocity Rotorcraft
• A gentleman who was involved in researching and developing the VTDP concept dropped the project after coming to the conclusion that it could not be what it was hoped to be.

DJ,

You stated or attributed a statement in an earlier post that helicopters are inefficient.

I am sure as a customer looking for a machine that I would look for alternatives to helicopters if this was the case. It is not.

Todays helicopters are as efficient as they can be as the state of the art develops.

You argue that nobody wants change yet millions are spent trying to get that little bit more out of the machine by the manufacturers to make the customer buy their product.

I have yet to fly a helicopter that has been inefficent at what I have asked it to do.

My many clients must think as I do.

Some of your theory needs a bit of brushing up also. (too much to go into here).

:bored: :bored:

Efficiency
 

deeper,

'Efficiency' is a comparative characteristic.

I humbly submit that no one would claim the helicopter to be more aerodynamically efficient than its brethren, the airplane. It might also be stated that with a ratio of one helicopter for every half million people, it is obviously not a cost efficient form of transportation. What it does do is fill a niche market. A market that would be bigger, if helicopters were more efficient.

Unlike biotechnology or artificial intelligence, transportation is a mature industry. Yet, I believe that there is room for a significant increase in the efficiency of rotorcraft. Not by 'tweaking' improvements out of existing products, but by developing a new one. This appears to be possible by unifying the old ideas of the Intermeshing Configuration and Advancing Blade Concept with new ideas such as Active Blade Twist and Absolutely Rigid Rotors.


You are definitely correct in saying that "Some of your theory needs a bit of brushing up also.', but, I would argue that it is better to submit theories for critique then to resign oneself to the status quo.

For example;

The Sikorsky XH-59A ABC was a remarkable craft. It showed the promise of VTOL ~ with fast-forward. Unfortunately, vibration, resulting from an oscillating lateral dissymitry of lift, limited the craft to 230 knots. I theorize ;) that the craft could have gone much faster if 4-blade rotors had been used, instead of the 3-blade rotors.

The http://www.unicopter.com/Sleep.gif stuff;
Vibration - Rotor Induced - Analysis of Sikorsky ABC ~ Coaxial
Rotor - Disk - Lateral Dissymmetry of Lift - 3-blade Rotors
Rotor - Disk - Lateral Dissymmetry of Lift - 4-blade Rotors

Deeper

As much as I love my spiralling bladed flying machine it is not efficient, in the proper sense of the word.

Scientifically speaking efficieny is the ratio of input to output the bang for the buck principle.
When I hear about the input output raios for my friends fixed wings I can only feel envious. Same engine as mine drives their machines at nearly 200 knots (Long Eze) at a fuel burn of about 22 litres an hour or for the same engine and fuel burn as me carries four fat blokes, their bags and plankers nav bag (Piper warrior) while I have to sweat about whether I take my lunch with me!

But................ I go and land on a beach, go for a swim, go fishing camping and stuff. Land in my mates backyard and fly him to the airport so he can get in his fixed wing etc etc

Its is as efficient as it can be, in the current state of the art but it fills niche (that can't be filled by any other known flying machine) and does that very well, but at poor efficiency.


Dave Jackson

I think even synchromeshes and all other bladed spinning things are still just tweaking round the edges. They are all just variations on a theme. The quantum leap is only going to come when someone discovers some completely unheard of anti-gravity system (God knows what it will be or when it will be - maybe only in a galaxy far, far away):p

From an 'American Helicopter Society' email. ~ dated January 28, 2005

" As of today we don't have anyone nominated for the Gruppo Agusta International Helicopter Fellowship Award. Ditto for the Grover E. Bell Award. How about candidates for the Captain William J. Kossler Award which is given for the greatest achievement in practical application or operation of rotary wing aircraft? We know that there are individuals and teams out there that should be nominated for these prestigious awards. We are giving you one last chance to get your nominations in to the Society. We have decided to extend the deadline for receipt of the award nominations until Monday, February 7th.

Can it be that one of the university Rotorcraft Centers of Excellence don't have any qualified candidates for the Vertical Flight Foundation scholarships? As of today, we haven't received any applications from this institution. In order to make sure that we get in as many applications as we can, we are also extending this deadline until Monday, February 7th. We encourage all students interested in pursuing careers in vertical flight to apply for these scholarships."

How depressing. :(

Does this imply that there are few, if any, significant developments left in rotorcraft technology? Or, does this imply that there are few, if any, American manufacturers and institutions that have the ability or the motivation to 'think outside the box'?

Maybe it's time for the mass to get the benefits of all those wonderfull things achieved ?
or maybe the helicopter, in it's actual definition is simply prone to disapear... dinosaurs left the place to smart and small creatures .

2nd Generation XH-59 (ABC)
 

It sounds as if you are discussing a 2nd generation XH-59. The XH-59A aircraft had very rigid coaxial rotors that gave it very reasonable forward speed capability with thrust augmentation and more importantly good rotor performance at higher altitudes. It is a shame that this concept was retired so early in its developmental cycle.

Jack,
when you say "rigid", you're talking about something like the BO105 i suppose ?
thanks

The article 'Looking for Lift' in the 3-9, May, 2005 issue of Flight International is about the future of rotorcraft research & development in the US; for those that are interested.

Dave J