helicopter-for-one-can-be-folded-up-carried-by-one-person

[barnstorm2]

Does anyone know the name (or type name) of the helicopter that ducted the turbine through the boom to replace the tail rotor?

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[StanFoster]

Tim: The McDonnell Douglas MD520N has no tail rotor and does duct its turbine exhaust out the tail boom to counter torque.. Now..that would be a win win....eace:


Stan

 

[StanFoster]

Brett: I just cant imagine the twin rotors stacked over each other would be near as efficient. Like you said...the mechanical complexity of such an arrangment......arrrgghhh....:suspicious:


I would think that a single ....large diameter rotor would be more efficient than two smaller rotors...even if the smaller rotors were side by side and in their own clean air.

I dont know....I am no engineer....:suspicious:


Stan

 

[brett s]

The MD 520N & 600N don't duct turbine exhaust out the tailboom - there's a variable pitch fan, driven by the transmission. More moving parts than a regular tail rotor actually

They use a combination of that fan thrust ducted through the tailboom exiting through a movable nozzle at the end & through slots on one side to take advantage of the Coanda effect.

 

[StanFoster]

Brett: Hey...thanks...learning more and more...
Is there one that ducts the turbine exhaust out the tail ?

Stan

 

[Rotor Rooter]

Stan,

The side-by-side is the most aerodynamically efficient configuration.

That is why it was the first practical helicopter to fly. https://www.aviastar.org/helicopters_eng/fw-61.php


The earlier Cornu helicopter was also essentially a side-by-side.https://www.aviastar.org/helicopters_eng/cornu.php


Dave

 

[Arnie Madsen]

Does anyone know the name (or type name) of the helicopter that ducted the turbine through the boom to replace the tail rotor?

.

Tim : This may be the one you are looking for ...Sud-Ouest SO.1221 "Djinn"..

SUD also tried a variety of other tip powered rotors ...compressed air jets , compressed air jets with fuel added at the tips and ignited etc.

Arnie Madsen
Bell 47 G2

 

[Arnie Madsen]

Tim Forget my above post , I didnt read your question through. You were looking for tail rotor jet thrust , not tip jets .

Arnie

 

[WaspAir]

anti-torque ducting

anti-torque ducting

Brett: Hey...thanks...learning more and more...
Is there one that ducts the turbine exhaust out the tail ?

Stan

Ducted thrust has been tried from the earliest days for anti-torque control, but typically with a fan devoted to that purpose and not using jet exhaust. The Hiller J-5 is one very early piston example that looks a bit like you might have in mind (a sideward facing duct for direct anti-torque effect, in contrast to the Coanda Effect scheme used in the Notar system). The turbine powered Piasecki Pathfinder used vanes in the wake of a separate fan (it's also easier to see what's going on in the Pathfinder than in the Notar which has the fan of interest hidden inside bodywork) but that's a compound propulsive unit as well as an antitorque device. Some of the earlier Kaman helicopters have very long exhaust systems, but they're not modulated for thrust.


I've always suspected that the goal of a turboshaft engine designer is to extract as much energy as possible with the final turbine, leaving a hot but not terribly powerful exhaust flow. I've been told that on the world record speed setting Westland Lynx (the trick one with the BERP tips and so forth) they tried to arrange the exhaust direction to help squeeze out every bit of thrust they could for more speed.

 

[Arnie Madsen]

Does anyone know the name (or type name) of the helicopter that ducted the turbine through the boom to replace the tail rotor?

.

Hughes used an internal fan in the boom and ducted sideways to eliminate the tail rotor. (NOTAR)

I can't find them right now , but I have a couple of pictures of a Hughes 500 NOTAR hovering with the tailboom submerged in a lake , and one hovering with the tailboom in a hedge.

They are also about 30 % quieter than using a normal tail rotor.

Arnie

 

[barnstorm2]

Hughes used an internal fan in the boom and ducted sideways to eliminate the tail rotor. (NOTAR)

I can't find them right now , but I have a couple of pictures of a Hughes 500 NOTAR hovering with the tailboom submerged in a lake , and one hovering with the tailboom in a hedge.

They are also about 30 % quieter than using a normal tail rotor.

Arnie

Thanks guys!

Isn't there also a problem with tail rotors at high speed?

I assume the Farie design posted above would be a solution to that...

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[StanFoster]

Tim: The advancing blade on the tail rotor has to flap like the advancing blade does on the main rotor because it has more airflow than the retreating blade.

On a tail boom...its better not to have a regular flapping hinge so that the rotor can be kept closer to the tail boom.. The delta three hinge minimizes the amount of out of plane flapping and this works real nice. Its really not a problem.:yo:


Stan

 

[barnstorm2]

gotcha, as usual I must have been reading something old and out of date.

I assume there was a problem before the delta three hinge.

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[StanFoster]

Tim: Its always interesting to me all the aerodynamics that goes on making a helicopter fly. I wish I understood it all....but I am busy learning right now. Just the delta hinge is an amazing little piece brainwork!

Stan

 

[StanFoster]

Tim: That coaxial copter is cool....but not for me. I would really like to know how twin stacked rotors are more efficient. I really dont care if they are or not...cause I wouldnt want one...but just cant see how that bottom rotor can be that efficient...after all I have read how a rotor just loves going into translational lift and getting more efficient as the inflow speed lessens. In this case that bottom rotor is getting a lot of induced flow being fed to it...and then adding even more inflow velocity....

Interesting to think about anyway....


Stan

 

[barnstorm2]

Tim: That coaxial copter is cool....but not for me. I would really like to know how twin stacked rotors are more efficient. I really dont care if they are or not...cause I wouldnt want one...but just cant see how that bottom rotor can be that efficient...after all I have read how a rotor just loves going into translational lift and getting more efficient as the inflow speed lessens. In this case that bottom rotor is getting a lot of induced flow being fed to it...and then adding even more inflow velocity....

Interesting to think about anyway....


Stan

Stan, I think you are correct in this. If not one of the numbers gurus will stop by and let us know (if the rotor temp thread ever cools down anyway.. ).

I remember reading about a Kamov (sp?) helicopter and I think it was a sync not stacked, and they said something about being able to use the power in the rotors that was normally lost by using a tail rotor. Presumably, that's what made it a good heavy lifter.

Glossy brochure stuff, not textbook stuff.

Heli's are COMPLEX. I was flying one of my R/C choppers up by my face (yes not smart) today just so I could see all the bits spinning in a blur. Crazy. I am going to take the body off tomorrow and fly it naked just to amaze myself with all the spinning parts....

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[JEFF TIPTON]

K-1200 Helicopter

K-1200 Helicopter

Kaman helicopters are not seen but seem to be well adapted to heavy lift.

 

[karlbamforth]

WOW thats a lot of water, he dropped enough to make a lake.

 

[Bruno]

I seem to remember reading somewhere that sychronized overlapping (intermeshing) rotors -- as on the Kaman K-Max flying truck -- are said to be more effective than than a single rotor in terms of lift produced. That's apparently why the Kaman (not to be confused with the Russian Kamov) is such a successful heavy lifter. It is much used in logging operations and similar applications where hover with very heavy loads is required. To my eye, it's by far the sexiest civilian helicopter produced. A very macho machine.

 

[StanFoster]

Bruno: Hey....when I say I dont see how a stacked set of rotors can be as efficient....thats just my pea brains opinion....ok?:suspicious:


I post opinions and many times my opinions get changed.. I never plan on flying coaxial rotors...but there is a void in my brain wanting to be filled ...and if these are indeed more efficient...I want to understand why. I have been studying single rotor dynamics and this inflow that that "poor" bottom rotor has me challenged to find out if indeed my gut feelings are right or wrong.....and if it can be made more efficient...I need to hit the books and learn some new dynamics!

Tim: Good thread you have going here.....and please dont take my question prodding as challenging your view....I just am knee jerk typing my initial gut feelings. Just like my initial gut feelings were that the power to overcome torque being consumed by a tail rotor was also happening with counter rotating rotors. After thinking about it...I can clearly see that is a freebie with a twin rotor. I just refocused on the efficiency of a stacked rotor and my gut feeling is its not as efficient....but again...someone may come on here and say it is...and most importantly....why.eace:


Stan