3D Page

So, I can loop and I can roll, and now I want to go on to 3D but what do I need to do to my helicopter set up? We are about to describe the standard 3D set up but first we would like stress to you that in this day and age a flight simulator is essential for 3D. Generally these manoeuvres demand constant practice, big gaps between your flying such as weeks or even months can slow your learning down but sometimes these gaps are unavoidable due to the weather, illness, lack of cash or even work! Hence the need for the simulator. However, when you are learning  new manoeuvres practice them on the simulator until you can do them perfectly and only then attempt to try it with the model, but before you can try 3D we need to set the helicopter up for it.

Follow this link for James Vincenti's review of the new Thunder Tiger Ultra lightweight 3D paddles.

A 3D set-up

A 3D set-up is really just a way of setting up your helicopters pitch and throttle curves.  Its much easier to show you in person BUT it is better in the long run to try yourself, so where to begin!!

Even a beginner will benefit from following these as follow these steps allows you to adjust the pitch to suit any style of flying you wish including beginner set-ups.

Rotor Head Set-up

Most manufactures boast of the machines having say 20 degrees of collective pitch movement.  What they mean by this is that with the rotor head correctly set up the blades will move from +10 degrees to –10 degrees, a total of 20 degrees in all.  This is usually more than enough for most machines, and with this amount of pitch at your disposal enables you to program the heli to do any style of flying you wish to do.

The programming bit means your pitch and throttle curves, but first we need to get your rotor head correctly set up.  The set-up process we are going to explain is not just for 3d.  If you have the head set-up ‘neutral’ then adjusting the pitch curves becomes much easier to do and understand.  Just trying to do it with a pitch gauge without paying attention to the complete head set-up will just involve complex calculations and non-linear curves.

So if we have 20 degrees, 10 each side, then zero degrees is going to be the centre point.  So for now put your transmitter aside, and leave you radio gear turned off.  (Now is a good time to make a cup of tea!!).  Attach one of the blades to the rotor head and slide your pitch gauge onto it.  Remove the link to the collective servo and manually rotate the blade until it reads zero degrees.

Now this next bit is very important, as this will make all the difference in achieving equal movement either side of zero degrees pitch.  All mixing arms, both upper and lower, and the swashplate must be level when the pitch is at zero.  Don’t be overly fussy about getting them exactly spot on; just ensure they are level by eye.  Also don’t be afraid of adjusting the links away from the manufacturers quoted lengths to achieve this.  With this done the final step in adjusting the head is to reattach the collective servo link.

Pick up your transmitter and turn it and the receiver on.  Move the throttle stick to the centre to centre the collective servo.  The arm needs to be positioned ideally so that its 90degrees to the pushrod, so adjust the link length until the arm can be positioned at neutral with the link as just described.  In theory now you should be able to move the throttle stick up and down and achieve equal amounts of pitch movement for top and bottom.  If it isn’t then you will need to adjust the link length and arm position until it is, whilst ensuring that its still a reading of zero degrees on the blade at centre stick.  In affect you are trying to achieve a linear result through a non-linear throw.

The reason for doing this rather than using the ATV’s to compensate for a non linear throw is you can now utilise the ATV’s do adjust the total amount of pitch on both sides by an equal amount which makes sorting out the pitch curves much easier.  So move the throttle stick to the to top and adjust the ATV until you get to the maximum pitch you can get without binding.  This may be reducing or increasing them, just remember though that it’s always better to increase the servo are length if you are having to drastically reduce the ATV’s.  Do the same for the bottom end.  Now if everything works out then the two ATV values will be within 5% of each other.  If not then go back and recheck everything until it is.

Pitch Curve explanation

To make it easier to understand when it comes to the number crunching bit, let us assume that your model can pull 10 degrees of pitch at full throttle and that 10 degrees also happens to be the maximum pitch your model mechanically allows (what a coincidence!!!)

So turn on your transmitter and enter the pitch curve menu.  You will be faced with 5 number positions usually called points, like these.  (Most normal helicopter transmitters have a 5-point curve with top of the range one's having 7-points).

L          1            2            3            H

On some transmitters this is displayed as a graph with the five points at the bottom.  This graphical way of displaying it is actually the best way of explaining it, so we will use it also and is shown in fig 1 below.   Why the radio manufacturers use L and H instead of 1 and 5 is beyond us, but let us use 1 to 5 to make it easier to understand.

The golden role for a 3D set up is quite simple really, keep all push rods at 90 degrees to their servo arms, keep any mixing arms the model might have in their neutral positions, keep the swash plate in the centre of its travel and make sure it's level, and then set the blades at zero degrees. Generally the pitch range for a 3D heli is +10 degrees to – 10 degrees,  although 60 size helicopters use a bit less. At this zero degree point on the helicopter, the pitch stick should be in the centre of its travel.

Which brings us to the next point, the throttle. This is where most people get confused, with the pitch stick in the centre of its travel we need to set the throttle so that the head speed of the heli is around say, 1800rpm, now we need to maintain this head speed all the way up to +10degrees pitch, using the throttle curve section in your transmitter. Now repeat the process so that when you pull the throttle stick back to –10degrees pitch the head speed remains at 1800rpm.
Your rotor is now set up, most people who fly 3D always have their own preference to how they set their helicopters up but as a rule this is the standard way.

The curve points are at the bottom on the x-axis and are really just five points in the throttle sticks movement, which is what the x-axis represents.  The y-axis is the pitch curve value.  This represents the blade pitch in a percentage form and is why we said we would use 10 degrees as the maximum blade pitch at the extremes.  It makes it much easier to understand if +10 is 100% and –10 is 0%.

Now if +10 is 100% and –10 is 0%, then 0 (degrees) must be 50%.  You can see this by placing one finger on position 3, which corresponds to centre stick, on the x-axis, and another on 50% on the y-axis.  Now draw them together and they should meet in the middle as shown in fig 2:

You can see now why the mechanical set-up is so important as you have already achieved the basic ‘building block’ for your desired pitch curve (to be chosen later) without actually having to input any numbers!!

Now before we start to adjust the curve you need to understand a bit about the ‘flight modes’ available to you on your transmitter.

Flight mode explanation

Somewhere on you transmitter you will have a 3-way switch labelled ‘flight modes’ are ‘idle-up’.  Check your manual to find out where it is if it’s labelled with just a letter.  This switch enables you to use three different flight modes and it used to enable to fly in different styles all in the one flight.  It does this by enabling you to use different curves for each position on the switch.

More commonly these positions are known as:

Idle up curves are usually used to have the engine at a position above idle (hence idle-up) at bottom stick and is used to perform aerobatics and 3D flying.  The normal position is used for hovering and learning on.  In your transmitters pitch curves menu, briefly flick though all the flight modes and ensure that all three curves are reset in the default positions of:

1(L)       2             3              4             5(H)

0          25            50            75            100

Pitch Curve Adjustment

The ‘normal’ pitch curve is used to enable you to start your model, take off into a hover, fly circuits if you wish, land and shut down the engine.  This curve is also what a beginner would want to use.  Ignore the idle up curves for now. If you want a little insight though, you’ve actually already done them!! 

Now this bit is the most important bit of all:

Most beginners, and we would encourage them to do this as it makes the flight less jumpy, learn to hover with the stick at the centre position.  Now a helicopter hovers at +5 degrees and to achieve this at half stick all you have to do is follow the helicopters instructions and you are there – simple.  This is just as it should be, as a beginner needs it to be simple, so they can get on with learning to fly!!  HOWEVER if you tried then to make a 3D curve from the set-up of 5 degrees at half stick it would get very confusing as you would have a very non-linear curve – i.e. 5 degrees above half stick and 15 degrees below half stick.  The percentage numbers would get out of hand and ATV values would be small one side and large the other.  Which is what all this setting up we have made you do is all about.  It all rests on this 5-degree hovering pitch value:

It is important to also take note of the fact that a model helicopter hovers at +5 degrees; therefore it naturally hovers inverted at –5 degrees.  Also remember that the most important pitch position during 3D is not –5 but 0 degrees.  Why??  Well because 3D flight nearly always has the helicopter intentionally pointing either vertically up or down or knife-edge sideways at some point during a manoeuvre.  It is vitally important for the pilot to know exactly where 0 degrees pitch is as only at zero degrees pitch is the helicopter going to have no forces applied to it to ‘pull’ or ‘push’ it away from the desired line of flight.  So most 3D pilots set 0 degrees at centre stick so they can easily find it. 

So we now need to go back to our curve diagram, as we need to show you something very important.  You have come to a point in your flying where you need to make a decision!!  Do you wish to do 3D??

If yes then you need to be aware that your hover position on your transmitter stick will change and you will need to relearn this position.  It’s not all that hard; in fact half a flight and you probably won’t even notice the difference, especially with a flight simulator to practice on first!!

The reason for this is that if as we said earlier if 50% is 0 degrees then it is no longer half stick for 5 degrees which is what you have been using up to now.  So at what position is 5 degrees??  Well if 100% is 10 degrees and 50% is 0 the 5 degrees must be 75%.  Refer to figure 3 and place your finger on the 75% point on the y-axis.  Move across till you reach the pitch curve (diagonal line) and then drop down and notice it corresponds to the number 4, which is point 4 of your 5-point pitch curve.

So your hover point from now on will be at the three quarter stick position.  Notice therefore, again see fig 3, that your inverted hover position will be at the quarter stick position, which is –5 degrees.

So now as we said earlier this ‘default’ setting of your pitch curves is already an idle-up curve ready to use for 3D flight!! 

So turning back to the ‘normal’ pitch curve requirements we want to be able to take off hover, land and shut down the engine.  We don’t want to use this flight mode for 3D, therefore we don’t need –10 degrees pitch at the bottom.  –4 is a good low end for normal as it allows you to descend under powered control rather than a ‘floaty’ descent with 0 degrees which you may have used whilst learning to fly.  As the engine is at idle at –4 degrees it will mean that the actual descent will be made at –1 to –2 with the engine still engaging the clutch (about 20% throttle).  Combine this with the models weight and believe us when we say that if you wanted to, bringing the model down in normal mode will present no problem!!!

Form + degrees onwards the curve is left as it is.  We only need to adjust the points below the hover point.  So if –4 degrees is 30% the curve will look something like fig 4.  Notice how, since we are not using this flight mode for 3D, half stick does not need to be 0 degrees.

A point worth mentioning is that from now on you will have to remember that above the hover point the curve is much steeper.  This will result in the collective being that little bit more sensitive.  This is why a beginner should learn with the hover point at the centre, as it will flatten the curve.

So to show this in the way your transmitter might show it, the values are:

Curve points                 1              2             3              4               5

Curve values                 30           45           60            75            100

Pitch values                  -4            -1            +2           +5            +10

Idle-up Pitch Curve Adjustment

As previously mentioned idle-up 1 and 2 will be correctly set up in their default states once the head is centred around 0 degrees – simple!!!!

Idle-up 2 is not often used anymore as most people once into 3D, fly in Idle-up all the time.  They fly their model the most in this flight mode and consequently feel happiest flying with it engaged.  You then land in idle up and flick the switch back into normal mode to turn the engine off.   As a safety feature set idle-up 2 to be the same as idle-up 1 so that if you inadvertently knock the switch to far it won’t cause any harm.

So when we say ‘to turn the engine off’ what do we mean?  For that we will need to explain the other half of a 3D set-up, the throttle curve.

Throttle Curve Explanation

For 3D flight you will be spending half your time inverted.  This requires your blade to be in the negative value, but its no use applying negative if there is no engine power to back it up!

We should now have two pitch curves programmed into the two main flight modes normal and idle-up1.  The final step is to sort out the power requirements for each.  Once again we turn to the graphical method of representing the curves as the throttle curve is based upon similar lines as the pitch curves.  Fig 5 shows a typical throttle curve.  Along the bottom, x-axis, we have the familiar 5 points on the throttle stick travel.  The Y-axis is the amount of throttle applied:

Thankfully the throttle curve is fairly easy to understand as the y-axis percentage amount is no longer ‘representing’ anything other than a percentage – i.e. no pitch values to work out.  The difficulty comes in matching the throttle curve to the pitch curve to achieve the right head speed.

Throttle Curve Adjustment

Lets do the normal flight mode throttle curve first.  We know that out helicopter hovers at +5 degrees and the amount of throttle required to achieve this, with a head speed of about 1600, is 50% or half power.  Now if we refer back to fig 4 we know that +5 degree's of pitch is at point 4 (3/4 open on the throttle stick).  We therefore need to make this 50% engine power.  See fig 6.  Naturally maximum pitch will require maximum power so this is set at 100%.  The bottom point (1) needs to be idle.  This is so we can use the normal flight mode to carry the model out to the flight line, spool up the blades for flight and lastly stop the engine upon landing.  This is set at 0%.  You won’t need to set this value at say 5% to work around the trim; your radio will do this calculation for you.  The trim should still work as normal and this is used to adjust the idle speed and as the engine kill.

Points 2 and 3 are simply filled in as the values between 50% and 0% to the nearest half percent.  Below are the final values shown corresponding to the amount pf pitch for each throttle setting

Curve points                 1              2              3              4               5

Throttle value(%)          0            16.5         33.5          50            100

Pitch Value                   -4            -1            +2            +5            +10

Now the ultimate goal with any helicopter set-up is to achieve a constant head speed.  For a normal flight mode since we don’t want to do any aerobatics in it, we want a head speed of about 1600.  These values should result in a head speed around this figure, but it will require fine-tuning of the values to achieve a constant figure across the whole curve.   Once again we should point out that the above value of +10 degrees is purely there to aid with the understanding of the curves.  Most helicopters, especially the 30 classes will struggle with 10.  8 or 9 are more usual.

Idle-up Throttle Curve Adjustment

To hover the heli inverted we require the exact opposite value of pitch as the upright hover.  We will also want a slightly higher head speed to enable the 3D style of flying to be executed in order to get to the inverted.  However it’s no use utilising the normal flight mode throttle curve for a pitch range of +10 to –10.  An idling engine is not going to pull –10 degrees for very long!!  So we will have to program the idle-up throttle curve to do what is called a ‘V’ curve.

Before we continue we must point out that there is an increase in danger with the use of idle-up functions utilising a V throttle curve.  In normal mode if the throttle stick is knocked to the bottom the engine will die down to idle.  In Idle-up, the engine will never drop below half at any point on the sticks travel, so always, and we repeat, always check what mode you are in before starting the engine.  Second you really now need to be moving away from wooden blades.  Not only do they flex more in flight which can be disastrous in 3D, there is the danger of them failing due to the high head speeds of 3D set-ups.  As a general rule never exceed 1700rpm with wooden blades.

So for a V curve we need 100% throttle for both +10 and –10 degrees pitch, and at least 50% throttle for –5 degrees to enable us to hover inverted and show off!!  In fact to maintain the higher head speed we are really looking at 75% at the hover points and 50% at 0 degrees.  This will result in a healthy 1900–2000 rpm for a 30/50 class and 1750-1850 for a 60/90. Fig 7.

From now on it is possible to check your engines settings before actually lifting of.  Once the head has been spooled up flick over to idle-up and gradually reduce the collective to bottom.  Providing you have carbon/glass blades fitted there will be no problems in reaching –9/-10 with 100% throttle.  It will simply sit pressed to the ground with a lot more noise and smoke.  Since –10 puts the same loads on the engine as +10, there is no longer any need to risk a full power climb out to check the engines settings.

Once you have mastered setting up your helicopter for 3D it will only be a matter of time before your helicopter looks like this....