Tandem rotor helicopters

[Groundpounder]

Is there a significant difference in how a tandem rotor helicopter (CH-46 or 47) flies versus a conventional helicopter?

 

[flyingron]

They both beat the air into submission.

Generally the tandem has better aerodynamic and performance features and a wider CG range at the cost of increased mechanical complexity and a bit more drag.

 

[Groundpounder]

Are the flying characteristics any different?

 

[benyflyguy]

They require two satchels Of fairy dust to fly compared to the usual one.

 

[Doc Holliday]

Are the flying characteristics any different?

Not sure what comparison you are looking for. Can you be a bit more specific?

 

[Groundpounder]

Are there any torque effects, since there are two rotors?

Anything different with auto rotations?

 

[Jeff Oslick]

Two Jesus nuts. Need to pray twice as often.

 

[Bell206]

Are there any torque effects, since there are two rotors?

The main rotors turn in opposite directions cancelling out each others torque effects on the aircraft. Same as with coaxial and inter-meshing type rotor systems.

Anything different with auto rotations?

Not that I've heard, but was told they auto a bit faster than smaller conventional helicopters. However, don't know that personally.

 

[Salty]

I flew an RC Chinook once and it did not turn like a normal helicopter at all. I'm assuming because there's no tail rotor, getting the thing to change direction is different. I flew it for a half hour and never did figure out how to make it turn gracefully. That may be because of bad design of the RC, however.

 

[Doc Holliday]

Gotta love all the non rated rotorcraft types chiming in with snarky replies. PoA at it's finest.

Anyway,

On a single rotor helicopter, we have what's called translational tendency.

Of course on a dual rotor helicopter this would not be the case since each rotor cancels out the torque.

Since all the power in the tandem rotor helicopter can be used for lift, versus the single rotor which must give up some of it's power to the anti torque device (tail rotor), the dual rotor will be better at lifting. Plus, in a single rotor, depending on wind direction and speed, plus humidity and weight, the amount of tail rotor needed will reduce MR torque available.

 

[Bell206]

I'm assuming because there's no tail rotor, getting the thing to change direction is different.

Yes but not so much different. Just as a conventional helicopter changes directions with the M/R cyclic the tandem does the same thing except in the yaw axis each M/R tilt opposite each other and drive both ends around. FYI: a T/R usually only comes into play in a hover, low speeds, and certain flight maneuvers.

 

[Groundpounder]

Gotta love all the non rated rotorcraft types chiming in with snarky replies. PoA at it's finest.

Anyway,

On a single rotor helicopter, we have what's called translational tendency.

Of course on a dual rotor helicopter this would not be the case since each rotor cancels out the torque.

Since all the power in the tandem rotor helicopter can be used for lift, versus the single rotor which must give up some of it's power to the anti torque device (tail rotor), the dual rotor will be better at lifting. Plus, in a single rotor, depending on wind direction and speed, plus humidity and weight, the amount of tail rotor needed will reduce MR torque available.

Yes but not so much different. Just as a conventional helicopter changes directions with the M/R cyclic the tandem does the same thing except in the yaw axis each M/R tilt opposite each other and drive both ends around. FYI: a T/R usually only comes into play in a hover, low speeds, and certain flight maneuvers.

Cool, that's what I was curious about. Thanks gents!

 

[Salty]

Yes but not so much different. Just as a conventional helicopter changes directions with the M/R cyclic the tandem does the same thing except in the yaw axis each M/R tilt opposite each other and drive both ends around. FYI: a T/R usually only comes into play in a hover, low speeds, and certain flight maneuvers.

Makes perfect sense. Flying a largish RC in a smallish field I never really did a lot of fast forward flight.

 

[Nsconductor]

One of the many cool things I loved about flying the Chinook was its abilities to pivot at a hover. Pivot around either rotor head or about the center of the airframe. Of course you cal pivot a single rotor aircraft around different points as well, but just something cool about doing it in a Hook.


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[cgrab]

A tandem helo absorbs the torque in the spine of the copter. It literally wants to bend itself in half.

A tandem rotor helo can be rotated about the CG, the front or back rotor and allow a slung load to be positioned very precisely. Watching a CH-46 ship to ship unrep is like watching art in motion.

 

[catmandu]

Watching a CH-46 ship to ship unrep is like watching art in motion.

Huh. Guess I shoulda gotten out of the rack once to see that. Oh well.

If you sleep twelve hours a day, cruise is only half as long.