help understanding why cyclic is not centered when a helicopter hovers

[skypickle]

I can understand why you need left boot - to counter the torque of the main rotor

But why do you need to put the cyclic to the left of center and a little back if the weight is balanced (center of gravity=center of lift)?

[G.J.S]

45 minutes ago, skypickle said:

I can understand why you need left boot - to counter the torque of the main rotor

But why do you need to put the cyclic to the left of center and a little back if the weight is balanced (center of gravity=center of lift)?

To counteract the tendency of the tail rotor to push the aircraft sideways, "Translating tendency". And the direction can be dependent on type.

Edited April 2, 2022 by G.J.S

[skypickle]

duh. how could I miss that. Is the aft pull needed because the center of gravity is forward of the center of lift?

[G.J.S]

7 hours ago, skypickle said:

duh. how could I miss that. Is the aft pull needed because the center of gravity is forward of the center of lift?

More than likely - don’t know which heli you are using, but if armed there’s a chance that unarmed may show less rearward pull is needed. 

[SUBS17]

With FLY BY WIRE and AUTO PILOT TAKE OFF/CRUISE/TRANSITION and LANDING the Navigation system compensates for Torque and it maintains its heading Automatically. This is an upgrade for many aircraft in the near future where they can fly on Autopilot the whole journey. The RED BULL BO105 was fitted with FLY BY WIRE and it is the same as the Apache FLY BY WIRE but with a few extras on the Apache. So future versions will have the full Autopilot. There is other devices in development that prevent VRS which creates a positive pressure under the rotors which prevents the VORTEX RING STATE from forming because of NEGATIVE AIR PRESSURE. It is possible to develop AUTO-TORQUE CONTROL for Helicopters.

[Mars Exulte]

On 4/2/2022 at 6:13 PM, skypickle said:

I can understand why you need left boot - to counter the torque of the main rotor

But why do you need to put the cyclic to the left of center and a little back if the weight is balanced (center of gravity=center of lift)?

  The Ka-50 manual has a lengthy section on rotor dynamics, if you care for a more detailed read.

 

On 4/4/2022 at 3:28 PM, SUBS17 said:

Stuff

....... *sigh*

[G.J.S]

7 hours ago, Mars Exulte said:

  The Ka-50 manual has a lengthy section on rotor dynamics, if you care for a more detailed read.

 

....... *sigh*

Being a contra twin whisk the -50 will behave differently to a conventional heli layout.

 

Love the ‘sigh’ 

[Mars Exulte]

5 hours ago, G.J.S said:

Being a contra twin whisk the -50 will behave differently to a conventional heli layout.

 

Love the ‘sigh’ 

  Yeah, of course, but it's still a general breakdown on rotor dynamics and very detailed.

[SUBS17]

8 hours ago, G.J.S said:

Being a contra twin whisk the -50 will behave differently to a conventional heli layout.

 

Love the ‘sigh’ 

The KA50 has Torque but not as much as a UH1. You still have to trim for flight with FLY BY WIRE. A future version of the KA50/52 or AH64 might not require as much trim with an upgraded FLY BY WIRE.

Edited April 6, 2022 by SUBS17

[skypickle]

but even Hueys empty need aft cyclic to hover.   The center of gravity is under the mast so no aft cyclic should be needed.

The wiki (https://en.wikipedia.org/wiki/Bell_UH-1_Iroquois) says:

'The UH-1H also features a synchronized elevator on the tail boom, which is linked to the cyclic control and allows a wider center of gravity range. '

how does the elevator affect the cg?  do they mean center of lift?

 

[G.J.S]

39 minutes ago, skypickle said:

but even Hueys empty need aft cyclic to hover.   The center of gravity is under the mast so no aft cyclic should be needed.

The wiki (https://en.wikipedia.org/wiki/Bell_UH-1_Iroquois) says:

'The UH-1H also features a synchronized elevator on the tail boom, which is linked to the cyclic control and allows a wider center of gravity range. '

how does the elevator affect the cg?  do they mean center of lift?

 

Think it’s referencing the elevator offsetting a slightly forward CofG by going elevator leading edge down, and vice versa for a slightly aft CofG. Only would be effective in forward flight however. At minimal speeds or at the hover, then you would just push or pull to maintain a hover.

[Alicatt]

Which way is the wind blowing?

[Hiob]

On 4/3/2022 at 1:13 AM, skypickle said:

 and a little back if the weight is balanced (center of gravity=center of lift)?

...from my understanding, in most helicopters - especially when they are designed to transport personnel - the main rotor boom is tilted slightly forward, so that the fuselage is level, when in cruise trim. (the rotor disc needs to be tilted forward in forward flight). So when you don't go forward, you need to counter this by aft stick.

In a fully commited attack helicopter like the Apache, this is probably less relevant, therefore you need a lot less aft stick for hover (in comparison)

Edited April 13, 2022 by Hiob