flying a correct coordinated turn

[newbie2k]

Hey guys,

I am somehow not able to fly a coordinated turn correctly. :-)

What do I have to do to fly a 90 or 180 or whatever degrees turn without gaining or loosing to much height and/or speed?

 

The way I do it right now is while flying a turn I add as much pedal input as required to keep that little black ball in the middle. But when doing so whether the height or the speed changes dramatically.

 

Any hints on that? How would one fly that procedure in real life?

 

Thanks in advance!

[-MadCat-]

In forward flight a helicopter shares a lot of characteristics with a fixed wing.

So a good start is to pull back on the stick to prevent a loss of altitude and of course correct with the pedals.

 

The more you bank, the more you need to pull which in return reduces the amount of forward propulsion, meaning greater speed loss.

You could compensate with more collective, thereby less cyclic pull needed and so on.

Yet that often just makes the turn more aggressive as needed.

 

Keep the turns coordinated and turn as wide as possible and only as sharp as needed.

Keep the collective put and if you do very gentle turns you'll see the loss will be very small.

Hope that helps a bit for the beginning!

 

Greetings

MadCat

[159th_Falcon]

In forward flight a helicopter shares a lot of characteristics with a fixed wing.

No it doesn't

And as such you should not fly it as an fixed wing.

 

Two totally different things.

 

To turn in a helicopter;

Move cyclic left/right to initiate the turn

Use pedals to prevent side slipping

Move cyclic forward to keep the speed you were flying

Move collective up to compensate for the extra thrust required by the new attitude of the helicopter.

 

Please note that in certain parts of the helicopters performance envelope it may not be possible to keep both speed and altitude while making a given turn.

[leafer]

If you're using twist grip for rudder then forget it. It's just can't cope with that kind of precision flying for both plane and helo. You'll have to build one or get a set of Simped pedals.

[-MadCat-]

Sorry to disagree, but:

Pulling the cyclic back, lifts the helicopter's nose, reducing speed and gaining altitude.

Pushing cyclic forward, lowers the helicopter's nose, increasing speed and losing altitude.

Deflecting cyclic to either side banks the helicopter in the same direction, the helicopter drops the nose and starts to swing in that direction.

In what way does this differ from fixed wing ?

 

I'm not talking about hover or speeds close to the transition between forward flight and hover.

I'm just talking about forward flight, and in that flight regime you can for the most part fly a helicopter just like you do a fixed wing.

In case not, I'm doing something wrong and still it magically works out just perfectly fine.

For turns with reasonable forward speed and say less than 20° bank, I add so few collective it isn't worth mentioning if any at all.

I bank to the direction I want to turn and pull on the cyclic while correcting with pedals to not slip the tail.

Speed or altitude loss is negligible.

So I stick to my point to mostly treat it like a fixed wing in forward flight.

 

I'd like to hear flyer49's opinion about this too, from what I gathered he has significant hours on the UH-1 and can sure tell 100% how to turn correctly.

 

Greetings

MadCat

[159th_Falcon]

It's different in the fact that a co-ordinated turn, at least the way i understand it is;

A turn at the same speed and altitude as you started and no side slipping.

 

To achieve this in a helicopter you need to do the exact opposite then in a airplane.

 

ie, pushing the cyclic forward instead of pulling it aft.

And where you pull the helicopters collective to compensate for the extra power requirement you need to push the throttles in an airplane.

 

So yes, from a straight and level flight pulling aft will result in similar behavior, what you have to do to keep flying in co-ordinated manner is quite different though.

 

(not to mention the rudder pedals)

[Suchacz]

The effect, that is spoiling your effort for nice, smooth and coordinated turn is called "gyroscopic precession". You should learn something about it and about its influence on the helo in left and in right turn. Anticipating this with cyclic stick is the key to the turns as you want them to be :thumbup:

 

http://www.copters.com/aero/gyro.html

http://helicopterflight.net/gyroscopic%20P.htm

 

Edited August 1, 2013 by Suchacz

[lorenzoj]

Excellent video series from Getting Smarter. Thanks

[159th_Falcon]

Please not the gyroscopic precession again.

I know its being thought in schools, and even official manuals.

But its wrong.

 

Though, when explained it does work out. But not because of physics.

The effect is aerodynamic in nature.

(and as such has nothing to do whit gyroscopic precession, which is an physical effect, not an aerodynamic one)

 

And now its time to duck for cover as everyone will start saying i am wrong.

[jay43]

Flying and turning a helicopter is totally different from a fixed wing aircraft it is by no means the same not even forward flight.

 

When making turns you have to be aware of unloading the blades as they are what provides lift and thrust, unnecessary unloading of the blades will result in mast bumping causing a catastrophic separation of the rotors from the mast.

 

Everything you learnt about flying fixed wing is not applied the same in a helicopter.

 

For example you approaching a hill and need to climb in fixed wing this is achieved by a slight increase in throttle together with a slight pull back on the stick.

 

That example can not be applied to a helicopter forward flight requires the cyclic to be pushed forward so the rotor can pull you along do that in a fixed wing and you are going down to the ground so its clearly nothing like fixed wing.

 

To get over the hill you would think pull on the cyclic wrong that unloads the blades and can cause mast bumping and will reduce your forward speed resulting in loss of lift.

 

There are to many variables to go into in a post or topic this video will help those that think flying a helicopter is the same as flying a fixed aircraft clearly showing it is not as released by the USarmy http://www.youtube.com/watch?v=nm8iV_uiBsI&feature=fvwrel&nomobile=1

 

I would suggest watching it a few times so you fully understand whats going on.

[-MadCat-]

Unloading the disk in a turn ? !

Please read up on "centripetal force" !

The only thing you could possibly mean with unloading the disk is doing the push over on the peak when crossing a ridgeline, having nothing to to with turning.

Unloaded blades are only present when there is no acceleration present.

Turning in fact is an accelerated condition.

 

Think I'll quit here, this seems to be going in a direction bringing up theories defying more and more laws of physics...

 

MadCat

[VanjaB]

Dont give up MadCat, you are the only one that is actually making sense here. :) Can you explain 'unloaded blades' to me? Im not really sure I understand the concept, what exactly is it and what are the conditions necessary for this to occur?

[Wokka]

Madcat is totally wrong about pulling back on the stick though. In a turn with a helicopter, you just pull a little bit of collective, NOT cyclic. You adjust your cyclic and pedals as necessary to maintain a coordinated turn. Pulling on your cyclic would decrease speed and decrease turn radius until you come to a hover... That wouldn't look much like a coordinated turn :-)

[159th_Falcon]

This thread is just to funny. Anyone figured out yet why centrifugal forces have nothing to do whit the 90 degrees controls offset?:D

EDIT....................................................................^^^^^^^^^^^^ should read "gyroscopic precession"

Edited August 1, 2013 by 159th_Falcon

[Wokka]

Falcon, centrifugal forces have nothing to do with the 90 degrees offset, it's just gyroscopic precession.

[159th_Falcon]

Falcon, centrifugal forces have nothing to do with the 90 degrees offset, it's just gyroscopic precession.

Oops, i ment gyroscopic precession. Other posts trew me off.

[Wokka]

But... gyroscopic precession has everything to do with the 90 degrees offset.

Why do you think otherwise?

[ARM505]

Ah, the typical 'descending spiral of physics arguments' fail thread, hello again :)

[VanjaB]

So will someone post a video or .trk of a correctly performed coordinated turn or what?

[jay43]

Unloading the disk in a turn ? !

Please read up on "centripetal force" !

The only thing you could possibly mean with unloading the disk is doing the push over on the peak when crossing a ridgeline, having nothing to to with turning.

Unloaded blades are only present when there is no acceleration present.

Turning in fact is an accelerated condition.

 

Think I'll quit here, this seems to be going in a direction bringing up theories defying more and more laws of physics...

 

MadCat

 

 

Ok so please explain how you would perform a turn then.

 

To follow I have asked our instructor pilot to explain the correct turning procedure, he has over 2000hrs in the Huey and a lot more in the UH-64.

Edited August 1, 2013 by jay43

[newbie2k]

Well, thanks for that constructive discussion. :-)

 

Let's se if I got things right.... when flying a coordinated turn, let's say a right turn, I would add right pedal to prevent slip (or release left pedal when flying with a lot of torque), afterwards pushing the cyclic right and forward and adding collective at the same time to stay at flight level. Would that be the correct way?

 

By the way, right now I am flying without rudder pedals, because my CH Pro Pedals annoying me. I hate that self-centering and the fact that you have to put your whole feet on it. After 10 minutes of flying it's getting very uncomfortable. I pendered about modifying them, but then I decided to build my own pedals and when doing so, I will also assemble some kind of collective.

 

I have nothing to do, anyway :-)

I'm eager to see how flying "feels" with the new stuff ;-)

 

by the way, jay43, those US Army films are nice ;-) Do you have some more links to valuable ressources like this one?

[Griffin]

But... gyroscopic precession has everything to do with the 90 degrees offset.

Why do you think otherwise?

 

Google "pprune gyroscopic". I can't really explain it. :)

[Thomasew]

Hi,

 

 

Rather than everyone playing guessing games, .. as most are, .. read this:-

 

In a gentle turn, the position of the nose in relation to the horizon, which is the visual reference for pitch attitude, will remain relatively the same as in straight and level flight. However, as the angle of bank is increased, the attitude of the disc must be altered by backward pressure on the cyclic. This is to compensate for the added load factor imposed by centrifugal force as the turn steepens. The loss in airspeed, or the need for an increase in collective to maintain airspeed, becomes more apparent as the angle of bank increases.

 

Taken from:- http://www.tc.gc.ca/eng/civilaviation/publications/tp9982-exercise6-975.htm

 

 

I've highlighted one part in bold, .. for those that said that back pressure on the cyclic is not used.

 

.. just as you would use back pressure on the Yoke/Control stick of an airplane .. in a coordinated turn. :)

 

 

Some of the comments here are too funny. :megalol:

 

 

Cheers

Tom

[lorenzoj]

That Canadian site Thomasew linked to has many excellent flight manuals available for purchase or free PDF download. Thanks. I grabbed a couple for helis

[159th_Falcon]

From the same site;

In a level turn, lift must be sufficient both to support the helicopter and to provide the inward force. Therefore, it must be greater than during straight and level flight. This additional lift can be acquired by increasing power or by sacrificing some airspeed to maintain your altitude.

Guess what happens when applying back pressure on the cyclic?

That's right, you sacrifice airspeed.

 

So in an co-ordinated turn, keeping the same altitude and airspeed you need to;

push cyclic left/right and FORWARD

pull collective to compensate for the extra power requirement

use pedals to keep the ball centered.

The above all at the same time by the way, not after each other.

 

Also, i never said physics failed, only that physics are not at play in the 90 degrees controls input off-set.

 

Hint, study some aerodynamics and follow the input rod (pitch link, whatever other names you wanna use) round the swashplate to see what it does and what happens to the rotor blade at the same time.

 

If you do this you should be able to discover all on your own why there is an 90 degrees conrol input offset.

And also why its an aerodynamic effect that has nothing to do whit physics.