Hovering issue

[cjcj1949]

It sounds like your roll trim is wrong. Model helis are not expected to roll (change their rate of roll) when the stick is centred. It is difficult with a full size pilot as sometimes full size and model size flying is different. I remember a RAF pilot who took about 6 months to learn to fly a model, then he was very good. It's probably best to find an experienced model pilot to fly it and then you'll know if it's you or the model.

[Westwind]

Re: Hovering issue

Ok so I've tried moving the cog aft and got a an aft slide but stol rolls. Gyro in HH or rate mode same effect. If I don't put in rudder input she moves left about 5 - 10 feet then rolls right on her own. If mucked around with the roll trim but it did not help. Think I have to take a close look at the swash plate set up

[tomatwalden]

I'm a bit confused ... you talk about rudder (yaw) input, but "roll" means aileron. If the heli is rolling (aileron) right, then either the swashplate isn't level (you can't really eyeball this, you need a swash levelling tool), or another possibility is the flybar. If the flybar paddles aren't true, then they can cause an aileron roll effect.

[Ruston]

It sounds like you need to do a complete head set-up.

This is the process I use on all my fly-barred helis and it has worked well for my Mini Titan:

The following assumes the helicopter is a two bladed fly-barred machine, built but with the rotor head not yet fitted.

The tx should be programmed in helicopter mode with, initially, a straight line pitch curve. A swash mix of 60:60:60 should be programmed in as a starting point (unless your helicopter’s manual suggests something different).

WARNING: For all setup, the motor must be disconnected. It is safest to use a separate rx battery to power the rx whilst setup takes place, ensuring that there is no chance that the ESC powers up and attempts to run the motor. Alternatively disconnect the motor from the ESC or remove the pinion gear from the motor shaft.

1. Install and set swash servo horns to be perpendicular (as close to 90 degrees as you can make them) to the main shaft with the servo at mid-point.

2. Install the swashplate and connect linkages to the servo arms, using the servo horn holes that allow the linkages to be as close to vertical (perpendicular to the servo arms) as possible.

3. Setup the swash mix and reversing on your tx so that the swashplate moves correctly with collective and cyclic inputs. If only one servo is moving incorrectly, then try changing the servo reversing of that servo. If more than one servo is moving incorrectly, then it is likely that you need to reverse the corresponding swash mix setting by changing the number to negative from positive (or vice versa) e.g. 60:-60:60 to reverse the aileron swash direction.

NOTE: Different helicopters use different head geometry (leading or lagging control arms) so, depending on your particular helicopter, the swashplate will either need to move up or down as the collective is raised – check the manual.

4. With the servos at their mid position (collective stick at its centre, you can enter the pitch curve menu on your tx to confirm the stick is exactly at its mid point) use a swashplate levelling tool to level the swashplate by adjusting the length of the linkage arms to the servos. If you cannot get the swashplate completely level via linkage adjustment alone, use the subtrim adjustment on your tx to adjust the servo(s) centre point.

5. Move the swashplate through its full range of movement and check:
a. The swashplate does not bind at the top or bottom of its range of travel. If it does bind you will either need to adjust the swashplate centre point (by adjusting the length of all three of the swashplate linkages) or reduce the amount of mechanical travel (by adjusting the position of the servo balls).
b. The swashplate moves freely with cyclic stick inputs at the top and bottom of its range of travel. Again, if it does bind you will either need to adjust the swashplate centre point or reduce the amount of mechanical travel.
c. With the swashplate levelling tool fitted, that the swash remains level at the top and bottom ends of its travel. If necessary, adjust the endpoint for the corresponding servo in your tx to achieve a level swashplate at the extremities. Some cheaper txs don’t have individual endpoint adjustment so both top and bottom endpoints will be adjusted at the same time – you will have to find a compromise position here.
d. With the swashplate levelling tool fitted, slowly move the swashplate through its full range of collective movement and closely observe the movement of the swashplate. If the swashplate is not level whilst it is moving, adjust the travel speed of the corresponding servo(s) in your tx (not available in cheaper txs).

6. Fit the rotor head and connect the pitch control linkages to the swashplate. Fit the blades (making sure they are the correct way around).

7. With the collective stick at mid position, measure the pitch on the blades using a pitch gauge. The pitch should be zero (i.e. the blade is perpendicular to the flybar). If the pitch is not zero, adjust the length of the pitch control linkages (from the swashplate to the blade grip) to achieve zero degrees. Repeat for the second blade.

8. Move the collective stick to the top and measure the pitch on the blades. It should be positive (leading edge of the blade higher than the trailing edge) and approximately 9 to 12 degrees (depending on the helicopter). Move the collective stick to the bottom and measure the pitch again. It should be negative and equal in magnitude to the measured positive pitch (-9 to -12) degrees. If the +/- pitch is not equal, this means that the swashpalte is not centralised, is binding at one extreme or the linkage geometry is poor - lengthen or shorten the servo to swashplate linkages as necessary and return to step 2. If the pitch is equal but not in the range specified, adjust the pitch swashmix on your tx. Increase from 60 to achieve more pitch or reduce from 60 to reduce the pitch. If the pitch swashmix is adjusted, return to step 5.

9. With the collective stick at its mid position (zero pitch), align the blades forward and aft (one blade directly over the boom). Move the cyclic stick and observe the blade. The pitch should only alter when an aileron (left to right) stick input is made. Move the cyclic stick fully right and measure the pitch on the blade. It should be positive and approximately 5 to 6 degrees. Move the cyclic stick fully to the left and measure the pitch. It should be negative and equal in magnitude to the previous measurement. If the pitch is equal but not in the range specified, adjust the aileron swashmix on your tx. Increase from 60 to achieve more pitch or reduce from 60 to reduce the pitch.

10. With the collective stick at its mid position (zero pitch), align the blades left and right (blades perpendicular to the boom). Move the cyclic stick and observe the blade. The pitch should only alter when an elevator (fwd and back) stick input is made. Move the cyclic stick fully back and measure the pitch on the blade. It should be positive and approximately 5 to 6 degrees. Move the cyclic stick fully forward and measure the pitch. It should be negative and equal in magnitude to the previous measurement. If the pitch is equal but not in the range specified, adjust the elevator swashmix on your tx. Increase from 60 to achieve more pitch or reduce from 60 to reduce the pitch.

That completes the basic mechanical setup and tx programming, you are now ready to start entering normal and stunt settings (pitch curves, throttle curves, dual rates and expo).

[Westwind]

Re: Hovering issue

Hey guys thanks for all your help, unfortunately the tail boom broke into three pieces in flight
uploadfromtaptalk1362862605523.jpg
It will be awhile before before I get it up again.

PS what tools would guys consider essential for setting up a helicopter

[Mike Sanders]

Thanks for that explanation Ruston. It accords with what I think I know already but I have a question. What if, having moved the cyclic stick, the left and right movements or the up and down movements are not equal? Is it because the swash is not at the correct height?

[Ruston]

Thanks for that explanation Ruston. It accords with what I think I know already but I have a question. What if, having moved the cyclic stick, the left and right movements or the up and down movements are not equal? Is it because the swash is not at the correct height?

It can only really be a result of a servo arm not being perpendicular giving a differential in the corresponding linkage movement (more movement one way than the other). I don't think that swash height would have this effect unless the height caused the swash to bind at one of its extremes.

EDIT: actually having thought about it, the swash height could cause the cyclic pitch to be different left to right and fwd and back if it is set up such that the mixing arms are non-perpendicular.

[Ruston]

Hovering issue

Hey guys thanks for all your help, unfortunately the tail boom broke into three pieces in flight
[ATTACH]56818[/ATTACH]
It will be awhile before before I get it up again.

PS what tools would guys consider essential for setting up a helicopter

Wow, was that a spontaneous failure or the result of some mishap?

When you do re-build I suggesting changing the green flybar paddles for the white ones used on the version 1 mini Titan. The green ones are light weight and designed for 3D. The white ones are heavier so give the heli more stability. I would also fit some cheap wood blades whilst learning to fly the model. They tend to brake first and therefore are much less likely to damage other parts of the helicopter in a crash

As for tools, all you really need other than your screwdriver and ball link pliers is a pitch gauge, swash leveller and a ruler/calipers for measuring. A servo tester is useful for centring the servos without the need to use a Tx, but it is not essential.

[Westwind]

Re: Hovering issue

Thanks R, yes it was spontaneous, fortunately I was only about a foot of the ground. I suspect the boom or tail assembly had some undetected crack and it finally let go. Got to do better pre fight checks