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Teach me to control the turn indicator


ebabil
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Hi guys,

I have realized that i don't use turn indicator as much as it needed.

During the level flight, -as you know- helicopter doesn't always go where the nose points.

Most of the time it goes like a plane that is about to make a cross wind landing.

To correct this you need to apply pedals but for me , it is hard to determine pedal correction needs correctly. so i always use outside view for reference. Naturally, this is a very unrealistic method. You can not leave your ship and look around in real life :)

We need to use turn indicator ball to sort this problem out, am i right? ı have never seen it excatly centered.

if yes, please teach me how to use it on both huey and mi-8.

Pics are appreciated.

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Which typically means when turning right the ball should go to the right and when turning left the ball should go to the left. However in the Huey, I believe right turns specifically, the ball will often go opposite the direction of turn. This has been brought up many times but no one has determined if it is correct or incorrect behavior. I know in all other DCS aircraft I have flown: Mi-8, Su-25A, A-10C, P-51D, I have never experienced this behavior. Only in the Huey.

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Which typically means when turning right the ball should go to the right and when turning left the ball should go to the left. However in the Huey, I believe right turns specifically, the ball will often go opposite the direction of turn. This has been brought up many times but no one has determined if it is correct or incorrect behavior. I know in all other DCS aircraft I have flown: Mi-8, Su-25A, A-10C, P-51D, I have never experienced this behavior. Only in the Huey.

I would also love to hear someone explain this slip/skid indicator behaviour. When I make turns it initially moves the ball in the opposite direction of the turn? but after turn is established it will mostly center again though. Kinda like a pendulum effect? Pretty sure it's the same at least in the the ka-50. Recorded a quick video for reference when I didn't touch collective or pedals after I've put the ball centred in straight level attitude.


Edited by Penshoon

Otter

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I'm not sure whether it correct or not in the huey but I would imagine that comparing to fixed wings would be like comparing apples and oranges.

 

The reason you need to apply rudder into the turn on fixed wing aircrafts id due to adverse yaw. For example when you roll left your right aileron deflects down while your left deflects up. This increases the drag on the right side of the aircraft causing it to yaw to the right so to counteract it you will need to rudder to the left.

 

I'm not sure a helicopter would react the same but I don't know. Just thinking about it when you move the cyclic to the left it will cause the rotor to be at an increased pitch only while on the right side of the helo and a lesser pitch on the left. However the rotors are spinning freely from the fuselage of the helicopter so if there is increased drag on the right side how would this yaw the helicopter? I don't believe it would. But in theory, a roll to the left less power from the engine than a roll to the right because a roll to the right would need more pitch on the left to increase lift because the blade is retreating from your foward airspeed. With more power comes the need for more anti-torque or "rudder" to counteract the torque. I may be completely wrong on this though.

 

 

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I'm not sure whether it correct or not in the huey but I would imagine that comparing to fixed wings would be like comparing apples and oranges.

 

The reason you need to apply rudder into the turn on fixed wing aircrafts id due to adverse yaw. For example when you roll left your right aileron deflects down while your left deflects up. This increases the drag on the right side of the aircraft causing it to yaw to the right so to counteract it you will need to rudder to the left.

 

I'm not sure a helicopter would react the same but I don't know. Just thinking about it when you move the cyclic to the left it will cause the rotor to be at an increased pitch only while on the right side of the helo and a lesser pitch on the left. However the rotors are spinning freely from the fuselage of the helicopter so if there is increased drag on the right side how would this yaw the helicopter? I don't believe it would. But in theory, a roll to the left less power from the engine than a roll to the right because a roll to the right would need more pitch on the left to increase lift because the blade is retreating from your foward airspeed. With more power comes the need for more anti-torque or "rudder" to counteract the torque. I may be completely wrong on this though.

 

 

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So to compare apples to apples, in the Mi-8 the ball always slips in the direction of turn. In the Huey there are many occasions where it slips opposite the direction of turn. Why?

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So to compare apples to apples, in the Mi-8 the ball always slips in the direction of turn. In the Huey there are many occasions where it slips opposite the direction of turn. Why?

 

 

 

Like I said I'm not sure if the behavior is correct, just trying to think through it. After work tonight I'll play with both of them to see what I can find.

 

That being said I wouldn't imagine the slip indicator being accurate in violent maneuvers as shown in the video above. If I roll quickly to the left my body would go to the right and would expect the slip indicators ball to go to the right as well. Not due to yaw but centrifugal force rather. Just the same, if I was in a right bank and went rapidly from 100 fpm climb to a 500 fpm descent my body would feel light in the seat and I would expect the ball to go left not because of yaw but negative g's.

 

These are just thoughts and something to think about. Not saying this is correct.

 

 

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After some reading and testing the Huey tonight I believe that the direction of the turn is not relevant but the direction you pull or push the cyclic and how that effects the torque. I will attach this FAA guide on helicopter flight that I read before testing it in the Huey. In the section where it talks about turns it only states to apply anti-torque pedals in the direction needed to counteract the torque and not necessarily the direction of the turn.

 

https://www.faa.gov/regulations_policies/handbooks_manuals/aviation/helicopter_flying_handbook/media/hfh_ch09.pdf

 

I tested the theory in the Huey:

I began a left hand bank, as I applied left cyclic I needed less left anti-torque.

As I applied aft cyclic I need less left anti-torque.

The more aft I pulled the cyclic the more right anti-torque I needed.

 

I began a right hand bank and needed drastically less left anti-torque.

As I applied more and more aft cyclic I needed more and more right anti-torque just as I did in the left hand bank.

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Bear in mind the Hip also has flight stabilization built into the system. So it may not be a fair comparison to the Huey.

 

I would also concur with the inertia in the ball theory. With all instruments, you shouldn't chase them, but let them settle before you interpret what they are telling you.

 

It's always a very good idea to study the aerodynamics of flight in detail, and helicopters in particular have some seemingly unfathomable quirks that make them do things that a fixed wing pilot would never expect.

 

It's always a minefield trying to pin down what should happen and what evidently does happen, and it is very easy to just blame the software, when it may well be that the prototype does exactly what you are seeing too, and it may have taken some poor pixelsmith ages to get it to misbehave just right. Remember, real pilots are consulted when it comes to flight modelling, so giving Belsimtek the benefit of the doubt might be the order of the day here too.

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After some reading and testing the Huey tonight I believe that the direction of the turn is not relevant but the direction you pull or push the cyclic and how that effects the torque. I will attach this FAA guide on helicopter flight that I read before testing it in the Huey. In the section where it talks about turns it only states to apply anti-torque pedals in the direction needed to counteract the torque and not necessarily the direction of the turn.

 

https://www.faa.gov/regulations_policies/handbooks_manuals/aviation/helicopter_flying_handbook/media/hfh_ch09.pdf

 

I tested the theory in the Huey:

I began a left hand bank, as I applied left cyclic I needed less left anti-torque.

As I applied aft cyclic I need less left anti-torque.

The more aft I pulled the cyclic the more right anti-torque I needed.

 

I began a right hand bank and needed drastically less left anti-torque.

As I applied more and more aft cyclic I needed more and more right anti-torque just as I did in the left hand bank.

Thanks for posting that, I think the effect of needing less and less left pedal as aft cyclic is applied in he turn is due to more air being forced though the rotor as you pull in the turn that's assisting the engine to keep up rotor rpm, governor tells engine to decrease throttle and less torque is generated. I bet that with emergency gov on we would see a decrease in rotor rpm as aft cyclic is applied in turn but with no need for right pedal instead unless throttle is manually rolled up. Look closely on the torque meter and you can see the drop and increase as ball moves.

Otter

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Do you know what "yaw" means?

On fixwings when acting pedals the planes rotate around "yaw" axis and the bullet needle moves.

On an helo it's the same,however it's also counteract (pedals)on main rotor overturning moment.At each time you act on collectiv or change attitude of helo with the cyclic,the overturning moment increases or decreases.

So you have to counteract with pedals(yaw).

In fact when you act on one of the three commands (collectiv,cyclic,pedals)of an helo you change the moments value and have to counteract.

Indeed the bullet needle points out all of these variations.Because on an helo each movement acts on lifting power and you have to react.

When collectiv goes down overturning moment decreases and when goes up increases.

So to get center of bullet needle you have to steady your helo on a perfect flat flight while keeping a direction.Once all moments are harmonized bullet is centered.

On the gazelle on the center of windshield you will see a string that show exactly when you are in a perfect rectilinear flight while she centered.Also that points out direction of wind when stationary ,but the main use is for show us the perfect positon of fuse relativ to airstream.

To resume:

bullet needle points out all moments changing and stills centered when all are stabilized.


Edited by cromhunt
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...

With all instruments, you shouldn't chase them, but let them settle before you interpret what they are telling you.

...

 

...

On an helo it's the same,however it's also counteract (pedals)on main rotor overturning moment.At each time you act on collectiv or change attitude of helo with the cyclic,the overturning moment increases or decreases.

So you have to counteract with pedals(yaw).

In fact when you act on one of the three commands (collectiv,cyclic,pedals)of an helo you change the moments value and have to counteract.

...

 

Indeed, as have been already been told, be gentle and patient. Flying straight and level first, fine-tune the ball ("step" on it) when settled.

Same in a turn, keep altitude and speed (need of collective), keep cyclic steady, then fine-tune the ball. Now you are flying a coordinated turn.

Tossing the helicopter around will not give you a good understanding of the forces involved.

 

And remember, all inputs have an impact on each other, small adjustment on one will necessitate small adjustments on the others, iteratively.

 

And a small note:

While investigating the behavior of the ball through coordinated turns, DON'T look on how the aircraft move relative the ground!

A perfect circle turn relative ground will need constant correction of all inputs and airspeed due to wind. But you already know that I guess.

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I used to work as a helicopter flight instructor, and while I only taught in small helicopters (R22, R44, and R66), the function of the slip/skid ball is identical to how it works in the Huey.

 

Doing normal turns, there is no need to add any pedal regardless of the direction you are turning. The only time you would do it is if you are also making a large change in power, by raising or lowering the collective during the turn. For small collective changes at airspeeds of 60+ kts the addition of any pedal is negligible, but the pedal input is only needed to counteract the increase or decrease in torque.

 

A standard practice for turning in cruise flight (using maximum continuous power/torque at approximately 110kts) would be to roll the helicopter with the cyclic, and then apply a little aft cyclic to maintain altitude, while still holding the same collective setting. At no point is any pedal input required in this situation, regardless of how shallow or steep the turn is.

 

Pedal inputs are normally only made during power changes and for turning at slow airspeeds.

 

We never actually used the slip/skid ball for anything other than practice instrument flight, because the trim strings are inherently superior at telling if the helicopter is flying in trim. The reason for this is that while flying in trim, the ball may not necessarily be centered. The trim strings are affected by the airflow over them, where as the slip/skid ball is affected by gravity and g-forces.

 

If your helicopter is loaded in a way to have its lateral center of gravity left of the rotor mast, then in a hover the slip/skid ball will be left of center. This is the indication you would also want to maintain during forward flight to stay in trim. In this situation, the trim strings would be straight up and down (outside the cockpit, affected by airflow) and the ball would be slightly left of center (inside the cockpit, affected by g-forces). The same would be true with a right side heavy CG (ball would be slightly to the right while in trim or in a hover), and a centered lateral CG (ball sits in the middle while in trim or in a hover).

 

For this reason, we would always do an instrument check before takeoff for a practice instrument flight, and one of those checks would be to check the slip/skid ball's location in a stable hover so we knew what to look for in flight (you couldn't see the trim strings while wearing a view limiter).

 

I'll admit, I'm not quite sure what to make of the slip/skid ball in the Huey. It will stay centered during a hover, but in forward flight I need excessively left pedal to keep it anywhere near center. It's my understanding that most helicopters are designed so that the pedals will be in a neutral position during cruise flight. The ball in the Huey seems to kind of do its own thing so I mostly just ignore it and fly what looks right, but that only really works in a no wind/direct headwind/direct tailwind situation.

 

Sorry if that was a bit of a ramble, I did not proof read this before submitting.

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Just my 2 pence worth. When your flying in correct trim with level flight and ball centred irrespective of speed don't use rudder inputs during the turn. The ball is a slip indicator and the bank angle is denoted by the pointer above the ball. If you use rudder inputs while turning you will either rise or descend.

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I used to work as a helicopter flight instructor, and while I only taught in small helicopters (R22, R44, and R66), the function of the slip/skid ball is identical to how it works in the Huey.

 

Doing normal turns, there is no need to add any pedal regardless of the direction you are turning. The only time you would do it is if you are also making a large change in power, by raising or lowering the collective during the turn. For small collective changes at airspeeds of 60+ kts the addition of any pedal is negligible, but the pedal input is only needed to counteract the increase or decrease in torque.

 

A standard practice for turning in cruise flight (using maximum continuous power/torque at approximately 110kts) would be to roll the helicopter with the cyclic, and then apply a little aft cyclic to maintain altitude, while still holding the same collective setting. At no point is any pedal input required in this situation, regardless of how shallow or steep the turn is.

 

Pedal inputs are normally only made during power changes and for turning at slow airspeeds.

 

We never actually used the slip/skid ball for anything other than practice instrument flight, because the trim strings are inherently superior at telling if the helicopter is flying in trim. The reason for this is that while flying in trim, the ball may not necessarily be centered. The trim strings are affected by the airflow over them, where as the slip/skid ball is affected by gravity and g-forces.

 

If your helicopter is loaded in a way to have its lateral center of gravity left of the rotor mast, then in a hover the slip/skid ball will be left of center. This is the indication you would also want to maintain during forward flight to stay in trim. In this situation, the trim strings would be straight up and down (outside the cockpit, affected by airflow) and the ball would be slightly left of center (inside the cockpit, affected by g-forces). The same would be true with a right side heavy CG (ball would be slightly to the right while in trim or in a hover), and a centered lateral CG (ball sits in the middle while in trim or in a hover).

 

For this reason, we would always do an instrument check before takeoff for a practice instrument flight, and one of those checks would be to check the slip/skid ball's location in a stable hover so we knew what to look for in flight (you couldn't see the trim strings while wearing a view limiter).

 

I'll admit, I'm not quite sure what to make of the slip/skid ball in the Huey. It will stay centered during a hover, but in forward flight I need excessively left pedal to keep it anywhere near center. It's my understanding that most helicopters are designed so that the pedals will be in a neutral position during cruise flight. The ball in the Huey seems to kind of do its own thing so I mostly just ignore it and fly what looks right, but that only really works in a no wind/direct headwind/direct tailwind situation.

 

Sorry if that was a bit of a ramble, I did not proof read this before submitting.

 

 

 

Thank you for the detailed post and insight.

 

I have found that in a light huey you can be at more or less nuetral pedal in forward straight and level flight and the ball be centered because it takes so little collective to maintain. But as you load her up with fuel or weapons or fly at higher altitude or even high airspeeds and increase collective to maintain that configuration, it needs left pedal to keep the ball centered. Which this is really how we all fly her right, loaded to max .

 

 

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