Question for dual rotor heads

[East]

Took a ride last week in a helo with a tailrotor behind a dual rotor equipped one (CH-47). While hovering I understand how a helo with a tailrotor can maintain directional control, but how is that arranged with a dual rotor system?
Increase/decrease rpm's? ropeller

 

[Chubby]

Pretty sure yaw is controlled by tilting the rotors in opposite directions, thus creating a rotational moment about the axis. Could be mistaken though.

 

[ChunksJR]

Pretty sure yaw is controlled by tilting the rotors in opposite directions, thus creating a rotational moment about the axis. Could be mistaken though.

That is correct sir! ~Ed McMann

Blades work in same manner for cyclic/collective movement (with 90 deg phase lag) and opposite each other for the pedals movement.

Having the dual rotor system is amazing for powered limited situations/wind considerations...still you have to trust TWO jesus nuts AND a Sync-shaft...scary stuff...God bless the Marines/Army for still trusting it...but talking with hardcore Navy 46ers...they miss it.

Lovin' the .3 in the CH-46D in my logbook,
~D

 

[Road Program]

I may be way off here, so any -47 or -46 guys feel free to prove me wrong.

I'm pretty sure the rotors on the -46 are connected by a transmission shaft or something like that and spin in opposite directions at the same speed. This counter rotation of equal masses at the same speed eliminates the torque-spin effect (insert more technical term here) of the typical larger rotor on other helos.

Directional control is provided just like any other helo by the angle of the blades.

Well, that's my $.02...how'd I do?

 

[ChunksJR]

I'm not going to steal the thunder of the first proud PHROG to tell you how it works...they get so excited when they talk about the "good ole days" I was there for the transition of 46s to 60s and it was a lot like the new class at the end of "Officer and a Gentleman..."

~D

 

[East]

I'm not going to steal the thunder of the first proud PHROG to tell you how it works...they get so excited when they talk about the "good ole days" I was there for the transition of 46s to 60s and it was a lot like the new class at the end of "Officer and a Gentleman..."

~D

Saw that, great phrase

[U]"Where have you been all your lifes? Listening to Mick Jagger music and baaaaadmouthing you country....." Don't you eyeball me boy, gonna rip your eyes out and skullfvck you to death..[/U][/COLOR]

 

[ChuckMK23]

I may be way off here, so any -47 or -46 guys feel free to prove me wrong.

I'm pretty sure the rotors on the -46 are connected by a transmission shaft or something like that and spin in opposite directions at the same speed. This counter rotation of equal masses at the same speed eliminates the torque-spin effect (insert more technical term here) of the typical larger rotor on other helos.

Directional control is provided just like any other helo by the angle of the blades.

Well, that's my $.02...how'd I do?

There is indeed a "sync" shaft that connects the forward and aft transmissions. Thirteen and a half feet is the number that comes to mind on the overlap of forward and aft rotor blades.

The '46 was/is powered by a pair of T-58's wich connect to a mixing unit that evenly distributes torque to the forward and aft transmissions. It looks a little comlimplicated but in truth the frictional forces were no different than a single rotor drive system - just more spread out, etc.

Pich control (forward and aft cyclic)results in differential collective between the rotor heads. The individual swashplates on the heads were only capable of lateral cyclic movement. A seperate mechanism provided for slight forward and aft tilt (speed trim) to allow for level fuselage attitude over most cruise airspeeds.

Yaw was produced with differential cyclic (pedals). Moving the cyclic left pr right resulted in AOB and a normal turn.

AFCS was provided by a pair of Honeywell digital computers - and provided rate stabilization and dampening as well as attitude and heading hold. Altitude hold was all collective based.

The '46 was strong and easy to fly. Definetly a fun ride. Putting all your available power to lifting and not anti-torque was it's speciality. The Chinook is the platform of choice in the Afghan mountains. Heavy loads during hi DA was it's sweetspot.