Thoughts on the flight model..

[sobek]

Let's face it, if you lose a rotor blade on the contra-rotating you are just as stuffed as if you lose one on a conventional layout.

 

Exactly, the shark shares the vulnerability to main rotor damage but lacks the vulnerability to tail rotor damage, to me that is an advantage, how about you? ;) There is of course the additional complexity of the coaxial rotor but considering the russion doctrine of over-engineering their stuff i'm sure it's not that prone to failure.

[AlphaOneSix]

But the complexity of one shaft driving two rotors in opposite directions seems to me, more complicated than having two shafts in different directions out of the gearbox. The more mecahnical parts you have the higher the chances of a failure.

 

The main gearbox for a coaxial rotor system, all else being equal, is no more complex than a gearbox that drives a single main rotor with a tail rotor. They are also no more prone to mechanical problems, and they have a very similar number of moving parts. In fact, a gearbox for a coaxial rotor system has sligthly fewer parts, at least when compairing main gearboxes from a Ka-32 and an Mi-24. And when you add in the fact that aircraft with tail rotors also require long, vulnerable tail rotor drive shafts, in addition to another two gearbox mounted on the tail (sometimes only one, but almost always two), you just make a single main rotor aircraft even more complex than a similar coaxial rotor aircraft.

[sobek]

Hey Alpha where do you get all this hands-on experience with russian aircraft from? I thought you were some sort of ah64 maintenance guy.

[sobek]

You don't get detailed information about gearboxes from google, i've been down that road.

[AlphaOneSix]

Nothing more than a quick look around on some websites and google...

 

How cruel. How can you make such assumptions about me (while not 100% wrong, it does sting to hear that you think I have no practical experience)?

 

I am an FAA certified Airframe and Powerplant mechanic. I have 6 years of experience as an AH-64A mechanic, and two years of experience as an Mi-17 mechanic. I have also worked on the Bell 412, Bell 407, and AS332L1 Super Puma. I am currently an Mi-17 crew chief. I work daily with mechanics and pilots who have worked on and flown virtually every Western helicopter that is currently in service, as well as a few that are no longer in service. While this practical experience isn't perfect, it helps a great deal in my ability to understand how different aircraft operate, especially in regard to the design philosophy differences between American, European, and Russian helicopters.

 

I am indeed also good at searching the web. The Internet has a great deal of information if you know how to separate the good from the bad. I like to think that my real life experiences help me differentiate between the two. I have a NASA document on my computer titled "Review of the Transmissions of the Soviet Helicopters", which is rather old, but covers the important parts rather well. I got it from the Internet a long time ago, I'm sure it is still out there somewhere. It's NASA Technical Memorandum 103634 from December 1990.

 

And while I am a beta tester, I am sad to say that I have spent the majority of my time writing checklists and proofreading the manual, and only a small amount of time actually flying in-game (lots of ramp work, though!). It's hard to play from my laptop in Afghanistan. ;) But I'll be home in a few days and I'll be hopping right back into the virtual cockpit and helping out where I can.

[sobek]

Well and i was not talking to you, george to begin with. You exhibit some rather rude behaviour lately :noexpression:

[AlphaOneSix]

Spare me the info, I was not even talking to you

 

You were not talking to me, you were talking to someone else about me, I think that's very clear from your post. If that is not what you intended, perhaps you should edit your post to make your meaning more clear.

[Zorrin]

The main gearbox for a coaxial rotor system, all else being equal, is no more complex than a gearbox that drives a single main rotor with a tail rotor. They are also no more prone to mechanical problems, and they have a very similar number of moving parts. In fact, a gearbox for a coaxial rotor system has sligthly fewer parts, at least when compairing main gearboxes from a Ka-32 and an Mi-24. And when you add in the fact that aircraft with tail rotors also require long, vulnerable tail rotor drive shafts, in addition to another two gearbox mounted on the tail (sometimes only one, but almost always two), you just make a single main rotor aircraft even more complex than a similar coaxial rotor aircraft.

 

I understand the gearbox side. And agree that a gearbox for a coaxial will indeed, in principal have fewer parts, as you only have a single exit shaft. What I meant was the actual rotor system becomes a hell of a lot more complex.

What about the complexities of the rotor heads? They have to be rigid rotors right? Otherwise you'd have blade flapping... And then it gets nasty.

How does the shaft split the power and then have it contra-rotate?

What about the extra swashplates? Surely this extra engineering makes it a lot more complicated.

 

And overall does this 'extra safety' actually cost a lot more in maintenance? I would say it does, because surely if the entire system was that much easier, would it not be the norm?

Or does that just stem down to what we know as the norm in the West and perhaps a refusal to accept something of Eastern origin?

[sobek]

The rotors are of the conventional fully articulated type if im right, theres no problem with blade intersection as long as you stay within flight parameters. the shaft is actually two coaxial shafts with a simple gear at the base that lets them contrarotate. The only thing thats a bit complicated about the swashplate is the differential pitch system needed for yawing, everything else is practically just "doubled" for the 2nd rotor. Actually i dont know why there are not more designs of this nature, it has some interesting advantages.

[Yellonet]

How does the shaft split the power and then have it contra-rotate?

Well it isn't really one shaft.. would be hard to spin in two directions at the same time then.. :) And, although knowing nothing about helicopter gearboxes I would guess that it works basically as a differential system on car.

[diomedes33]

It's NASA Technical Memorandum 103634 from December 1990.

NASA Tech Memorandum 103634

 

NASA Technical Reports Server, has the majority of technical reports and briefs published by NASA (even a few by NACA). It may not be open to people outside the US, but it is a great source of information for research and empirical data. Not sure about how much info there is on soviet helos, but there are boat loads on rotary wing.

 

http://ntrs.nasa.gov

[amalahama]

It may not be open to people outside the US...

 

Yes, it is, I have collect hundred of them for my final degree project. It's impresive that so many good quality documents are there for free, in the most capitalized country around the world:D

 

Regards!!

[AlphaOneSix]

NASA Technical Reports Server, has the majority of technical reports and briefs published by NASA (even a few by NACA). It may not be open to people outside the US, but it is a great source of information for research and empirical data. Not sure about how much info there is on soviet helos, but there are boat loads on rotary wing.

 

ntrs.nasa.gov

 

Far out. I did a search for "kamov" and got one article:

 

Title: A Survey of Theoretical and Experimental Coaxial Rotor Aerodynamic Research

 

Abstract: The recent appearance of the Kamov Ka-50 helicopter and the application of coaxial rotors to unmanned aerial vehicles have renewed international interest in the coaxial rotor configuration. This report addresses the aerodynamic issues peculiar to coaxial rotors by surveying American, Russian, Japanese, British, and German research. (Herein, 'coaxial rotors' refers to helicopter, not propeller, rotors. The intermeshing rotor system was not investigated.) Issues addressed are separation distance, load sharing between rotors, wake structure, solidity effects, swirl recovery, and the effects of having no tail rotor. A general summary of the coaxial rotor configuration explores the configuration's advantages and applications.

 

I guess I have something to read tonight now!

[sobek]

 

Abstract: The recent appearance of the Kamov Ka-50 helicopter and the application of coaxial rotors to unmanned aerial vehicles have renewed international interest in the coaxial rotor configuration.

 

 

What i'd like to know is, why wasn't there more interest in the first place, UAVs set aside.

[-sulan-]

What i'd like to know is, why wasn't there more interest in the first place, UAVs set aside.

 

Perhaps fear of more maintanance or other complications?

But the Ka-50 (and other Kamov helo's) has proved that's not necessarily the case(?)

[sobek]

Something i've always wondered about: Since there's a comparatively large rotating mass, is there a problem with gyro effects on single rotor helos or is this compensated through the rotor not being completely rigid (flapping for example)?

[plane00]

simulation game needs time, patience

I'm also fairly hard to master flight simulation games till now...

and

Also hard thing --devices ..

you will need wide and fixed desk at first and at least respondable joystick and so on...