reported Trim with slip indicator always nose left?

[MstrCmdr]

Maybe someone with more helo experience than I can help answer the idea of a yaw-trimmed helo.

In the MI8 and the MI24 I prefer to trim yaw to zero the drift (i have no idea if this is accurate to RL).  This means I'll inevitably have an unlevel helo as it will slightly dip in the direction the wind is coming from.

In the apache rockets video wags put out the centered ball still results in some weather cocking/crabbing.  Is this normal procedure in all helos or just the apache or what?

Asking for a friend......

[Wags]

With rockets, you'll want to be in aerodynamic trim such that the rockets fly true.

If not, you can fly in nose-to-tail trim, which may feel more natural, and safer for NOE flying.

Kind regards,

Matt

[Eldur]

The thing I don't understand (and it affects all helos, including the Ka-50 at higher speeds) is that the ball indicates no sideslip while the thing still does sideslip. Why is that?

[Sinclair_76]

2 hours ago, Eldur said:

The thing I don't understand (and it affects all helos, including the Ka-50 at higher speeds) is that the ball indicates no sideslip while the thing still does sideslip. Why is that?

It has to do with wind. When the ball is centered you're flying with no sideslip realtime to the air. In no wind conditions this would result in aerodynamic trim (ball centered) is the same as nose to tail trim (velocity vector straight up). With wind added, a.t. and n.t.t. are not necessarily the same. 

When flying NOE, it's advisable to fly n.t.t. since the tail is always right behind the aircraft and you are less prone to whack a tree with it. But with wind you're not flying in aerodynamic trim when flying n.t.t.

Also this applies to all aircraft not just spin wings. It just so happens that the wind vector in slow moving aircraft is more apparent.

 

[Lurker]

 

It's not just wind. Even in 0 wind, a helicopter will still drift due to tailrotor downwash. This is how I understand it at least. 

Edited February 22, 2022 by Lurker

[MstrCmdr]

15 hours ago, Wags said:

With rockets, you'll want to be in aerodynamic trim such that the rockets fly true.

If not, you can fly in nose-to-tail trim, which may feel more natural, and safer for NOE flying.

Kind regards,

Matt

 

8 hours ago, Sinclair_76 said:

It has to do with wind. When the ball is centered you're flying with no sideslip realtime to the air. In no wind conditions this would result in aerodynamic trim (ball centered) is the same as nose to tail trim (velocity vector straight up). With wind added, a.t. and n.t.t. are not necessarily the same. 

When flying NOE, it's advisable to fly n.t.t. since the tail is always right behind the aircraft and you are less prone to whack a tree with it. But with wind you're not flying in aerodynamic trim when flying n.t.t.

Also this applies to all aircraft not just spin wings. It just so happens that the wind vector in slow moving aircraft is more apparent.

 

 

37 minutes ago, Lurker said:

 

It's not just wind. Even in 0 wind, a helicopter will still drift due to tailrotor downwash. This is how I understand it at least. 

 

This is all really good information on trim guys.  So basically the answer is it depends.  And I like that answer actually.

All this research on helo dynamics like gyro precession and transient torque makes me think "spin wing" pilots are a lot better than us straight wingers.  I mean not to derail my own thread but the whole rockets employment fiasco lately is also clearly evidence of how good we have it in jet planes.

Two weeks ago I would have told you I'm proficient in helo simming but I now realize that I did not know what I did not know.  I think that's called the Dunning-Kruger effect.

[Sinclair_76]

1 hour ago, Lurker said:

 

It's not just wind. Even in 0 wind, a helicopter will still drift due to tailrotor downwash. This is how I understand it at least. 

 

With helicopters you will never deal with absolutes. You're right. In a hover the tail rotor will create a side slip which in turn is cancelled by tilting the main rotor. Hence CCW turning spin wings hover left side low en CW turning spin wings the right side. In forward flight due to translational lift and vertical stabilizer the amount of anti torque needed by the tail rotor is not much, cancelling out the drift all together.

[Sobakopes]

With centered ball you fly sideways. The rockets will fly into this direction resulting in lateral miss. You can compensate for this using a little roll angle. You fly straight but ball will not be centered

Edited February 23, 2022 by Sobakopes

[Eldur]

On 2/22/2022 at 2:32 PM, Lurker said:

 

It's not just wind. Even in 0 wind, a helicopter will still drift due to tailrotor downwash. This is how I understand it at least. 

 

Shouldn't the ball show that though?

(And yes, wind irrelevant. In Wags' video the 64 always pulls to the right, regardless of his heading and that's what I see on my end as well with other helos, except, of course, for the ones that pull to the left. I mean even the tail rotor induced drift (or in the more complex case of coaxial rotors at speed), which basically is sideslipping, should be indicated on the ball and the fact that it isn't is what makes me wonder.

[Dragon1-1]

It's not indicated on the ball because the ball is a gyroscopic instrument, and it doesn't actually show airflow. It'd show on a yaw string, which does, but not on a gyroscopic slip indicator.

[Sobakopes]

Ball shows lateral acceleration or gravity

[Dannyvandelft]

Shouldn't the ball show that though?
(And yes, wind irrelevant. In Wags' video the 64 always pulls to the right, regardless of his heading and that's what I see on my end as well with other helos, except, of course, for the ones that pull to the left. I mean even the tail rotor induced drift (or in the more complex case of coaxial rotors at speed), which basically is sideslipping, should be indicated on the ball and the fact that it isn't is what makes me wonder.

Look at it as driving a car. If you'd drift a corner, with the back stepping out, you'd see the ball move to the side the back stepped out on.

Now if you'd make a lane change, the ball wouldn't move. Even though you moved sideways, the orientation of the car never changed, so neither would the ball.

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[MstrCmdr]

1 hour ago, Eldur said:

Shouldn't the ball show that though?

(And yes, wind irrelevant. In Wags' video the 64 always pulls to the right, regardless of his heading and that's what I see on my end as well with other helos, except, of course, for the ones that pull to the left. I mean even the tail rotor induced drift (or in the more complex case of coaxial rotors at speed), which basically is sideslipping, should be indicated on the ball and the fact that it isn't is what makes me wonder.

You also have more lift in the front 180 degrees of the rotor when airspeed is above ETL which translates to left side lift due to the gyro precession manifesting at 90 degrees later.

[Sinclair_76]

2 hours ago, Sobakopes said:

With centered ball you fly sideways.

No Depends. A centered ball means either straight or in a coordinated turn. A coordinated turn implies no slip or sideway flight, relative to the air. The exception being a small right side slip in slow flight for CCW rotating blades.

Furthermore to aid in level flight (roll wise) at higher velocity the trailing edge of horizontal stabalizer is different on the right and left side. One side bent up and the other down.

Edited February 23, 2022 by Sinclair_76

[jaylw314]

2 hours ago, Eldur said:

Shouldn't the ball show that though?

(And yes, wind irrelevant. In Wags' video the 64 always pulls to the right, regardless of his heading and that's what I see on my end as well with other helos, except, of course, for the ones that pull to the left. I mean even the tail rotor induced drift (or in the more complex case of coaxial rotors at speed), which basically is sideslipping, should be indicated on the ball and the fact that it isn't is what makes me wonder.

A wings level crab is still coordinated flight, and the ball will reflect that.

"slipping" means you're drifting one way through the air and banked, so not wings level.

 

Edited February 23, 2022 by jaylw314

[Dannyvandelft]

A wings level crab is still coordinated flight, and the ball will reflect that.
"slipping" means you're drifting one way through the air and banked, so not wings level.
 

Yawed, not banked.

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[jaylw314]

25 minutes ago, Dannyvandelft said:

Yawed, not banked.

Sent from my SM-G960U using Tapatalk
 

??  a slip (sideslip) by definition is a constant heading, not a turn.

[Dannyvandelft]

??  a slip (sideslip) by definition is a constant heading, not a turn.

Yes. If you're flying in a straight heading, but you're crabbing, you need to step on the ball, with the rudder. To correct yaw. Banking is roll.

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[Sinclair_76]

12 hours ago, jaylw314 said:

??  a slip (sideslip) by definition is a constant heading, not a turn.

No.

https://skybrary.aero/articles/slip

What is an aircraft slip?
Definition. Slip is an aerodynamic condition of uncoordinated flight in which an aeroplane moves towards the inside of a turn or is moving somewhat sideways as well as forward relative to the oncoming airflow.

 

So it can happen in a turn as well.

 

[jaylw314]

3 hours ago, Sinclair_76 said:

No.

https://skybrary.aero/articles/slip

What is an aircraft slip?
Definition. Slip is an aerodynamic condition of uncoordinated flight in which an aeroplane moves towards the inside of a turn or is moving somewhat sideways as well as forward relative to the oncoming airflow.

 

So it can happen in a turn as well.

 

That's why I clarified "sideslip", which is straight uncoordinated flight, which is what people seemed to be confusing with "crabbing"

A "slipping turn" is uncoordinated flight during a turn, with too little rudder

A "slip" can be any uncoordinated flight

[Dannyvandelft]

That's why I clarified "sideslip", which is straight uncoordinated flight, which is what people seemed to be confusing with "crabbing"
A "slipping turn" is uncoordinated flight during a turn, with too little rudder
A "slip" can be any uncoordinated flight

Only one confusing here is you bud. The rest of us are right. Slip or crabbing is adjusted by yaw. Not roll. Doesnt matter if it's straight flight, or on a turn. If you're heading 180 and your nose is pointing at 170, you need to adjust yaw to get the nose pointed on the right heading. Start flying warbirds, and you'll learn this real quick.

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[Raptor9]

18 minutes ago, Dannyvandelft said:

Only one confusing here is you bud. The rest of us are right. Slip or crabbing is adjusted by yaw. Not roll. Doesnt matter if it's straight flight, or on a turn. If you're heading 180 and your nose is pointing at 170, you need to adjust yaw to get the nose pointed on the right heading. Start flying warbirds, and you'll learn this real quick.

It's not just about yaw.  To fly a "slip", you need to bank slightly (roll), otherwise your ground track will shift.  The whole point of a crab is that you are flying a ground track, not a direct heading.  If you want to align your heading to your ground track but keep flying that same ground track, you will need to roll into the direction your nose was crabbing, otherwise the ground track will shift.

Edited February 24, 2022 by Raptor9

[frostycab]

On 2/22/2022 at 1:32 PM, Lurker said:

 

It's not just wind. Even in 0 wind, a helicopter will still drift due to tailrotor downwash. This is how I understand it at least. 

 

I believe I've heard this referred to as "translational tendency." In a stable hover my understanding is that the main rotor disc needs to be angled slightly left or right to counter the pull from the tail rotor.

[kgillers3]

On 2/24/2022 at 7:15 PM, frostycab said:

I believe I've heard this referred to as "translational tendency." In a stable hover my understanding is that the main rotor disc needs to be angled slightly left or right to counter the pull from the tail rotor.

You are correct, It absolutely is translating tendency.  It isn't the same as what's being referred to as crabbing in forward flight. 

Fixed wing in forward flight "crab" pending what the winds are doing as well. 

Edited February 26, 2022 by kgillers3

[jaylw314]

4 hours ago, Dannyvandelft said:

Only one confusing here is you bud. The rest of us are right. Slip or crabbing is adjusted by yaw. Not roll. Doesnt matter if it's straight flight, or on a turn. If you're heading 180 and your nose is pointing at 170, you need to adjust yaw to get the nose pointed on the right heading. Start flying warbirds, and you'll learn this real quick.

Sent from my SM-G960U using Tapatalk
 

I do, and you've managed to confuse yourself.  Good luck!