RunRyder - Tail blades on left side of boom?

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Avant Aurora - EFX - FX > Tail blades on left side of boom?

alchemist
Senior Heliman
Location: London,UK

What is the reasoning for the tail blades on the Aurora being placed on the left side of the boom (looking from behind), given right thrust is required to counter torque?

I am sure there is a reason, I would just like to know why that design choice was made out of interest.

To every action there is always opposed an equal reaction

07-21-2008 01:36 PM

Jim Patterson
Senior Heliman
Location: AREA 51 Roswell

Depending on the gearing on a particular heli, which determines the direction of rotation of the tail blades, the tail unit is located on the side that allows the advancing blade to lead into the downwash of the main blades. I haven't finished my Aurora yet so i don't know if this is the case for this one or not, but it seems to hold true for all others i have built.

Highly addicted to carbon fiber.....

07-21-2008 02:06 PM

alchemist
Senior Heliman
Location: London,UK

Quote
Depending on the gearing on a particular heli

Of course, but the gearing is like most other direct drive model heli's around, nothing special going on.

The direction of rotation of the head is clockwise so the torque required is anti-clockwise, like most model heli's. That puts the tail blades on the opposite side than normal eg: the tail blows through the boom to counter torque generated by the head.

To every action there is always opposed an equal reaction

07-21-2008 02:32 PM

blade3d
Elite Veteran
Location: New Jersey

I wondered the same thing why on the left side ?

Blade3d

07-21-2008 03:09 PM

ZR2Chevy22
Senior Heliman
Location: Galveston, TX USA

The reason the tail needs to be on the left side of the heli is because of the output shaft in the front. IF the tail were a direct drive off the main gear (how MA has their's) then it would need to be on the right side to have the leading edge coming up into the downwash of the rotor.

You could in theory make it a right hand tail but you'd have to redo the location of the gears in the tail case to get the tail rotor rotation to be correct. The gear that drives the tail output shaft would have to be put towards the pitch slider if the tail were to be on the right hand side.

Andrew

It's Chevy's Fault!!!!

07-21-2008 04:57 PM

HOMEPAGE

alchemist
Senior Heliman
Location: London,UK

So it is preferable to have the leading edge of the tail coming up into the main rotor wash to avoid a canceling effect, analogous to a retreating blade stall - ok cool (although in 3D application one would assume not so important).

This is interesting, as the Trex600's for example have there tail out shaft on the right, and yet there gearing is the same?

To every action there is always opposed an equal reaction

07-21-2008 05:36 PM

creightoncarr
Veteran
Location: Missouri City, Texas - USA

MA tail rotors are on the left side too.

07-21-2008 05:50 PM

John Benario
Senior Heliman
Location: Atlanta

The tail pushing the air toward the tail fin (tractor) versus the tail rotor pushing the air into the uninterrupted airstream (pusher) is mostly a matter of designer preference. The drive shaft rotation doesn't matter since the bevel gears can be placed such that either rotation can be achieved. The important thing on full scale is to have the tail rotor blades rotating up into the main rotor downwash since full scale tail rotors are performance limited. On models the direction of rotation doesn't matter that much since the tails have so much excess thrust.

There is some thought (in full scale design) that pusher arrangements are more efficient since the airflow is not blocked by the vertical fin.

With regards to right tail rotor versus left the models over the decades have probably been split pretty evenly.

John Benario

07-21-2008 06:08 PM

alchemist
Senior Heliman
Location: London,UK

Thanks John that makes a lot of sense.

It seems that the Aurora could have been designed with the tail on the otherside (right), where the flow is not interupted by the tail/vert fin. Also the tail blade leading edge could be designed to rotate into the down wash of the main blades.

There must reason, it can't just be cosmetic

To every action there is always opposed an equal reaction

07-21-2008 08:51 PM

ckoelliker
Key Veteran
Location: St. Simons, GA

If having the tail rotating into the down wash is so important, why does the helicopter behave the same when it is inverted?

07-21-2008 10:22 PM

ZR2Chevy22
Senior Heliman
Location: Galveston, TX USA

Not all MA's are on the right side. The Fury Tempest FAI has the tail output on the left side like the Aurora.

Andrew

It's Chevy's Fault!!!!

07-21-2008 10:38 PM

HOMEPAGE

alchemist
Senior Heliman
Location: London,UK

Quote
If having the tail rotating into the down wash is so important, why does the helicopter behave the same when it is inverted?

Quote
On models the direction of rotation doesn't matter that much since the tails have so much excess thrust.

The point is why would you not have the tail rotating into the wash, if you want a machine max'ed out and optimised for performance?

It's the excessive nature and power to weight which makes these flying machines so amazing.

To every action there is always opposed an equal reaction

07-21-2008 11:16 PM

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Avant Aurora - EFX - FX > Tail blades on left side of boom?

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