TREX450 with APM2.5 setup problem

I have a TREX450 with a Spectrum DX7 transmitter and Spectrum AR7000 receiver.

Servo's are digital are Robbe FS61BB, and Align GP780 gyro.As a traditional heli without APM it flies fine with smooth servo movements and stable tail.

The APM have been set up as advised on the website. I have replaced the flybar propellor with a flybar-less version and have disconnected the gyro.

Connecting the APM to Mission Planner, programming the APM,arming the unit etc works fine and also the adjustments of all the stick movements in radio calibration are as required. Movement of the heli results in the correct response from the servo's and in Mission Planner the movement of all three axes are as they should be.

I have the following two problems:

- the servo response to movement of the stick on the transmitter for rudder, pitch and elevation is normal and equally smooth as without the APM, but the response to the roll is very nervous, fast and with large movement

- when I try to start flying the rudder is not keeping the heli in position and once the propellor gains speed the heli will rotate around it's axis.

Can anyone advise me wat to do.

Huib

Hello Huib,

I can only give advise with your last question - make sure your heli is placed on a lawn, or if you only have asphalt (concrete etc.) then apply rubber tubes/balls to the landing gear. They are available at (I believe) any store.

The obstacle here is: ideling up your heli results in a tremendous torque in to opposite direction of the main rotors movement. In the beginning of this process the tail-rotor doesn't have enough effect, yet, to conquer the movement the heli experiences.

If, however, your hell starts spinning after launch you might want to change the direction of action

of the gyro?

of the servo?

There's an easy trick to determine which direction the tail will move to, by looking at the tail-rotor-blades' nose. Take a look at it from the top, place the tail-rotor vertically. The blades' nose will either point to the left (then the tail will move to the left and thus the helis' nose to the right), or vice versa.

With this in mind move your transmitters stick to the left - the blades' nose now has to point to the right. If it doesn't then you need to reverse the servos' direction.
Now verify the gyro by turning the heli (viewed from top) to the right (clockwise) - the gyro should now steer to the left (the same thing you just did manually with the stick), thus the blades' nose has to point to the right, again - like before.

Hope that helps

Replies

Florian Cokl March 8, 2013 at 5:30pm
Hello Huib,

I can only give advise with your last question - make sure your heli is placed on a lawn, or if you only have asphalt (concrete etc.) then apply rubber tubes/balls to the landing gear. They are available at (I believe) any store.

The obstacle here is: ideling up your heli results in a tremendous torque in to opposite direction of the main rotors movement. In the beginning of this process the tail-rotor doesn't have enough effect, yet, to conquer the movement the heli experiences.

If, however, your hell starts spinning after launch you might want to change the direction of action

of the gyro?

of the servo?

There's an easy trick to determine which direction the tail will move to, by looking at the tail-rotor-blades' nose. Take a look at it from the top, place the tail-rotor vertically. The blades' nose will either point to the left (then the tail will move to the left and thus the helis' nose to the right), or vice versa.
- With this in mind move your transmitters stick to the left - the blades' nose now has to point to the right. If it doesn't then you need to reverse the servos' direction.
- Now verify the gyro by turning the heli (viewed from top) to the right (clockwise) - the gyro should now steer to the left (the same thing you just did manually with the stick), thus the blades' nose has to point to the right, again - like before.
Hope that helps
Alexandre Heitor Schmidt March 8, 2013 at 9:06am

Hi!

I'm not sure about the nervous movement on roll... Can't you set up some D/R on your controller to make it smooth? Or maybe mission planner has such feature.

I had the same issue of rotating around it's axis with my heli. I'm guessing it is related to magnetometer setup. Did you calibrate the magnetometer and set the north pole derivation correctly?

Regards,

Alex.

This reply was deleted.

ArduCopter User Group

Replies