Traditional Helicopter – Configuration using Mission Planner¶
Setup using AP Mission Planner¶
Connect your APM to your computer using the USB, set the COM port and the baud rate and then press “Connect” and wait for the parameters on the APM to be transferred to your computer. Now, from the Firmware screen, push the “APM Setup (Plane and Quad)” button, then click on the Radio Calibration tab.
When it comes to calibrating your radio in Mission Planner, all the physical sticks should move in the same direction as the green bars on the Radio Calibration Screen with the exception of Pitch which should move in the opposite direction to the physical sticks.
To get the bars moving in the right direction you may need to reverse a channel in your radio but you really shouldn’t have to with the exception of throttle/collective for Futaba radios.
Before you attach your APM to the heli I would recommend you do an accelerometer calibration which is well described here. It’s easier to do if the APM is not mounted in the heli and it’s essential when running firmware 2.9 or higher.
Configuring the Servos¶
1. Ensure the Collective pitch bar moves up as you move your collective pitch up. If it does not, repeat the Radio Calibration. You may need to reverse the collective pitch setting on your radio.
2. Check that all your servos are moving in the correct direction as you move your collective pitch up and down. If any move in the opposite direction, click the rev check box beside the appropriate servo. Don’t be surprised or concerned if one or two of the servos move in the wrong direction just click the rev check box. I sure to be needed on at least one servo.
3. Type in the correct positions of each servo around the swash plate in degrees. 0 = at the front of the swash. Refer to the compass image on the set-up screen if necessary. Note: after updating one of the position values you must leave the field (or click on the compass) and you should then notice the swash twitches momentary as it is reinitialised.
Capturing the Swash Plate Range¶
4. Push the Manual button. This will momentarily allow the servos to move freely and input from the radio will directly control the servos.
Change the collective pitch on your radio to move the swash to it’s upper and lower limits. If you accidentally move the swash too far so the servos bind, manually set the Top and Bottom of the range in the field provided.
Push the Zero button after making sure your main blade’s pitch is zero. If you want to tune your heli even better, set the pitch at hover pitch, say 3 or 4 degrees, and your heli won’t climb when you switch modes but this is a refinement that you may want to come back to after your initial set-up.
Push the Save button.
If you want to re-do this step, close the setup window and re-open it.
5. Update the maximum roll and pitch values into the fields provided as a number of degrees. Default is 45 degrees which is what most people use.
Avoid reversing the collective pitch channel (RC_3) in Mission Planner because it will affect the way the arming system works. Instead, reverse your servos in Mission Planner OR reverse the channel in your radio.
Configuring the Rudder¶
6. Tick the Rev check box if you find the tail moves in the wrong direction. Again, its not atypical to have to reverse this function. Remember, stick to the right, heli should rotate clockwise, Stick to the left, heli should rotate anti-clockwise (when viewed from above).
7. Push the Manual button and move the rudder channel on your radio to it’s full range to capture the min and max rudder range while avoiding any binding.
Push the Save button.
As with the collective pitch you can update the Min and Max manually if necessary.
8. If you have an external gyro, click the Gyro Enable button. Enter the Gain manually. This is a value from 1000~2000. this servo value is simply output on Channel 7 which should be connected to your external gyro’s gain channel (thus freeing up a radio channel for other purposes). An external gyro really is not needed and this is a legacy option. The APM2.5+ will lock the tail beautifully.
Rotor Speed Control (RSC) using Output Channel 8 on APM2.5¶
To use the APM to control the rotor speed (ie.throttle/ESC), all you have to do is send whatever throttle signal you want in on Ch8(in) and then plug the throttle servo or ESC into Ch8(out) on the APM. Ch8 throttle control is important because it forces you to arm the APM before you can fly. Without arming, the motor will not start nor will the collective servos work. So Ch8 is used for switching the motor/collective on and off something like a throttle-hold.
RCS can be set on the Heli Setup Tab of Mission Planner
There are three settings to control how the APM sets up Ch8 control:
Note the following error on Mission Planner: Mode 1 is a direct pass through of the throttle input signal and Mode 2 is for an ESC with built in governor. MP asks you for the “Mode 1 Setpoint” This is a typo and it should ask for the “Mode 2 Setpoint”. Please test with caution. Hopefully this will be rectified in the next release.
Disable (H_RSC_MODE set to 0)¶
If you don’t want to use Ch8 control then set H_RSC_MODE to 0. Now you can arm the APM without Ch8 but the collective will only work once armed. Hopefully you can live with that and it achieves the important step of insuring that you do not fly unarmed.
Mode_1 (H_RSC_MODE set to 1)¶
With H_RSC_Mode set to 1, you have a direct Ch8 pass-through; however it is still set low when disarmed. The motor will ramp-up subject to H_RSC_RAMP which can be set to 0 if you want to rely solely on your ESC’s start-up characteristics. Once ramped up Ch8(out) it is slaved to the Ch8(in) so you can pass through a variable throttle signal if you want.
All H_RSC_RAMP does is, after arming, when you first engage the throttle in Mode 1 or 2, it ramps up the output slowly. It’s like a super-soft-start.
RSC_Ramp set to 1000 = 10 seconds.
Also note the APM won’t arm in Mode 1 or 2 unless Ch8 is within 10 of RC8_Min.
Mode_2 (H_RSC_MODE set to 2)¶
When H_RSC_MODE is set to 2 the APM now only sets Ch8(out) to be high or low and, when high, it sends out H_RSC_SETPOINT (this is the setpoint in MP) while when low it sends out RC8_Min.
Plug the ESC into Ch8 on the APM and put it in governor mode.
Ch8 can be driven by a 2 position switch. When the switch is down, it outputs whatever the minimum is (endpoint is set to -100%) and when the switch is up it sends the maximum signal, so endpoint +100%.
The only trick is to “calibrate” the ESC to the signal which is easily done if you can plug the ESC into the Rx.
To calibrate it using the APM, take the blades off or loosen off the pinion. First make sure you have done a radio calibration in APM using the 100%/100% endpoint on Ch8. Unplug the ESC from the APM. Boot the system up, the ESC should be beeping at you because no signal. Now, make sure the Ch8 switch is low or you can’t arm the APM. Now arm it, set the collective stick to the middle (this prevents it disarming due to inactivity) and then switch the Ch8 switch high and wait about 15 seconds. It should now be outputting a high signal on Ch8. Plug the ESC in. It should give you a confirmation that it has gotten a high signal and waiting for low. Now, turn Ch8 off. The PWM output will immediately drop to the minimum. Your ESC should beep to tell you it has read the minimum, and is ready to go. Now, if you switch Ch8 high again, the motor should go to full power. It will ramp slowly over 10 seconds if you have left the R_RSC_RAMP at 1000. You could set this to 0 if you have a good soft-start on your ESC. Or you could change it to 500 for 5 seconds, 2000 for 20 seconds, whatever you want.
Then after all this is done, go into the endpoints and I change the high endpoint so that it is outputting only 80% throttle when it’s switched on. Now the governor gets an 80% signal when running and you get a nice even head speed while flying.
Now it’s really easy to use. Put Ch8 off, collective down. Arm the heli, switch Ch8, the motor starts and gets to the target speed. Now you can take off.
The only catch here is that if you arm and leave the collective at full negative it will disarm after 10 to 15 seconds. When this happens the APM will immediately shut down the motor. So it’s safe but it can be a nuisance. To avoid this, while waiting for spool up, move the collective up just off the bottom, not enough to fly and this will prevent the disarming.
The APM will always arm with the stick down/right and disarm with down/left.
Getting to your First Flight¶
So here is what you need to do to get to your first flight.
What flight mode should you have your radio set to while tuning the servos?
Usually Stab mode but sometimes it’s worth looking at Acro mode too, depending on what you’re doing. But NEVER in auto mode. If you are trying to adjust the collective you should be using the button for that in the Mission Planner Heli tab. If you are trying to do it the manual way, by just twiddling the settings in the Advanced Param tab, then you should use Acro for collective adjustments. This ensures that the STAB_COL params are not in play. So you would set your ABSOLUTE min and max in Acro mode. Then set the STAB_COL in Stab mode.
Remember, any time you change any of the numbers in the Advanced Parameter list you must got to H_SV_MAN, set it to 1, then “write”, back to 0, then “write”. This resets the swash calculations. If you don’t do that, it messes things up. If you modify the swash through Mission Planner this is done automatically by the Mission Planner software.
Set your heli up with +/-10° pitch. Then, you will need to go to Configuration>Advanced Parameters>Parameters List and find H_STAB_COL_MIN and H_STAB_COL_MAX and set these to 30 and 90 respectively. This will give you a collective pitch range of about -2° to +8° in Stabilisation mode.
Now, any time you change these numbers (ie: change them in Mission Planner and “Write” to the APM), they won’t take effect right away. There’s a number that gets calculated and it is only recalculated when you reset the swash. The swash is reset any time you reboot, however, you can force it by finding H_SV_MAN in the Parameter List and setting it to 1, “write” and then set it back to 0, and “write”. This forces it to reset the swash and you’ll see the effect of the H_STAB_COL changes immediately. Hopefully this will be changed in a future version of Mission Planner with all of this in the heli setup tab.
You should be able to switch between Acro and Stab, move your throttle and see the difference in the swash plate movement.
We do recommend setting up the swash with lots of negative pitch and then set the H_STAB_COL_MIN for whatever negative pitch you are comfortable with. Even if you never use negative pitch, this still allows the Alt_Hold controller to have access to full negative pitch will sometimes be needed.
Set H_COL_MID to be hover point rather than 0° pitch to avoid having the heli ascend when you switch to Loiter or Alt Hold Mode. So that covers the swash plate setup.
So here’s what Flybar_Mode does.
First, in Acro mode, it skips ALL stabilization/rate controllers. Your stick inputs go DIRECTLY to the servos. The only thing the APM does is the CCPM mixing. It becomes completely dumb. So Acro = Full Manual. The only real issue with this is that there is basically no trim. If you are trying to hover, and the swash isn’t setup right mechanically, it’ll roll. The only way you could stop that is by adjusting your swash linkages, or using radio trim. Using radio trim is not good, because then that will mess up all your other modes because the APM will think you are holding the sticks.
So the second big thing Flybar_Mode does is that it makes the Rate I term only “active” near zero rate command. It won’t move whenever you’re asking the heli to move. It will only move the Integrator, basically in a hover. So it’s sort of like an auto-trim for hover. Whenever you are moving the sticks, it’s frozen. Again, I did that because I didn’t want the Integrator doing whacky things to the flybar, because the flybar and the rate integrator do the exact same thing, but neither one of them knows what the other is doing!