APM2 Code 2.4 - Throttle problems

Hi all,

I really could use some help here....

As of today, the throttle is not working on either APM2 boards.

I shall refer to them as B1 and B2 for simplicity....

Before today, i have flown both boards, but with serious GPS problems, navigation was vague, ok got to the bottom of that issue and today i thought i would try to fly, now knowing that the GPS is playing ball as it should.

Ok...B1, hooked it into my test ship, (known airframe that up to today i have been flying the original AP in with no issues.

got all servos going the right way..checked 'STAB' & FBW-A on the bench, throttle working as expected.....loaded a couple of WP's...

hit auto on the bench again, just to make sure its attempting to navigate. Servos go over as expected, no throttle!

Checked  the outputs from the planner, Ch3 is not being increased on the output.

So, plugged in B2, checked that, no throttle.....

The planner wanted an update, so I let it...

Reloaded the firmawre 2.4 on B1, B2 i didnt update anything....

The only change is the update in the planner, and reloading B1, so why would B2 be playing games also..? Also, how can the planner affect the operation of the AP itself!?

I have to say that my patience is wearing thin, 2+ weeks of trying to get to the bottom of the GPs problem, and finally i think we can go test the unit, and now no throttle...

Did the usual checks to see if by some wierd chance there was an issue with the ESC's, so plugged in a servo in its place, behaved normaly in in all but AUTO, FWB_B, RTL, basically all modes that control the throttle....

Now, i apologise if there is a 'enable motors' setting i have missed, as its possible that i have been staring at it for too long, and not seeing the obvious.

3 months i have had both these boards and not yet had a successful flight, doing as it should....

again, if i have missed something i would be greatful, if someone could shed some light...its about a hair away from being airbourne with NO airframe, it shouldnt be this hard!

I look forward to anyones thoughts.

Kind regards,


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  • Dr. Mike,  This is from the Attitude.pde file line 336.


              // We want to supress the throttle if we think we are on the ground and in an autopilot controlled throttle mode. 
                            /* Disable throttle if following conditions are met: 
                                    1 - We are in Circle mode (which we use for short term failsafe), or in FBW-B or higher 
                                    2 - Our reported altitude is within 10 meters of the home altitude. 
                                    3 - Our reported speed is under 5 meters per second. 
                                    4 - We are not performing a takeoff in Auto mode 
                                    5 - Home location is not set 
                            if ( 
                                            (control_mode == CIRCLE || control_mode >= FLY_BY_WIRE_B) && 
                                            (abs(home.alt - current_loc.alt) < 1000) && 
                                            ((airspeed.use()? airspeed.get_airspeed_cm() : g_gps->ground_speed) < 500 ) && 
                                            !(control_mode==AUTO && takeoff_complete == false) 
                                    ) { 
                                    g.channel_throttle.servo_out = 0; 


    Take off in manual and go fly!

  • You need to go fly mate, the frustration just builds up otherwise, until something flies ok. Having also just gone through gps-lock failures (Xbee too close to the gps, everything too cramped in the easyglider cockpit), I understand how you feel....

    Fortunately, this one is easy: its an RTFM problem - as Isaac says the motor only works in manual or stabilise until the plane is in motion. Its in the Wiki. The idea seems to be for safety reasons - so that the motor doesn't fire up if you switch into one of the autopiloted modes while the plane is on the bench.

  • Reason your throttle is not working is because your plane must be moving, throttle will not arm in auto mode when standing still. Hope this helps
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