Good day,
Tried my first test flight today without success.
My goal for today was to hover in stabilized mode perhaps move around a little.

HT-FPV frame
10-47 props
APM 2.5 with GPS and sonar
25 amp plush ESC

Did the setup and calibration during the week.

Gently applied throttle and either the back or front would rise, one end on the ground. Definitely not level so I thought it was not balanced correctly. Added weight to either end but the same results. Either the front or back would lift off, then would attempt to flip before I cut the throttle. Actually flipped once.

I'm missing something here.

I also noticed a spike in the throttle on the bench and during my test flight. Brief increase in speed before retuning to normal. This happen consistently.

Any suggestions?

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Are your props spinning the right way?  Are they plugged into the correct channels as per the wiki?  Do the hand test!  Hold on tight and clear to the underbelly and apply throttle - you'll soon see where the drive isn't coming from.

I did check the motor rotation during setup. The motors respond immediately to the throttle but I did check against the wiki during setup. I will try the hand test.
Tried the hand test.
Bring the throttle up and I can feel more pull from the rear. Throttle back down and up again then I can feel it from the front.
Exact behavior as during my test. The thrust (is that the correct term) not equal and it changes between the front and back motors.

Is your throttle on the right channel?  That sounds like your throttle stick is moving your pitch, maybe...  Don't know how experienced with transmitters you are.

 ESCs individually calibrated with Tx?  Correct orientation selection during set-up?  Motors all on the right channel as per wiki?  I made all of these mistakes.  Dig through the archives and everything has been answered somewhere.  

If you have not already, remove the weight for balancing.. unless it is extremely out of balance. That is not the problem.

But with a 'flying man' type frame, it will come into play once loaded up with the camera. How much? You are not there yet.

Can you suspend the aircraft somewhere near the CG by a means that will not be fouled by the props? If so, you can determine if the controls are correct. When I started flying my 3DR based frame (home brew) Aruducotper, Elevator was reversed. Even in stabilzed mode it was evident.

Is your DX8 new? Mine DX6i was used and had a glitchy Airleron pots. I could see it on the 'Monitor' setting. You might check the same thing on yours. It should also be evident in Mission Planner during radio calibration if such a thing exists on your system.

Oh, I have to fly my AC in ACRO (fixed wing) mode on the DX6i  NOT Heli. Heli slaves Chan 5 with Throttle (inversely). Not sure about how the DX8 functions in Heli. You only want Throttle changing the ESC drive.

Do your ESCs have a soft start function? They don't need that with a quad usually.

Also try disabling/disconnectng the sonar input.. simplify the installation as much a possible.

I used a servo tester to determine if the motor rotations were correct on my quad.

Another idea is a short leash type of tether. Twine about 6 -8 inches in length connected one to each arm. The other end is secured to a large flat board or heavy items that the quad cannot possibly lift. This way you can get up off the ground but control how much it can 'get away'.

Good Luck


Thanks for the comments.
I will go through the setup again. Perhaps I have over looked something.

The DX8 is new.
I will suspend it from string and make sure it is balanced but I agree that I don't think this is the current issue. In my hands I can feel the front and rear motors are not equal.
I will check the soft start on the ESC.

This is my first quad so I will go through the setup again but suggestions are always welcome.


Best make sure you are using an aeroplane model on the DX8 and not a helo model.  Are you also sure that the assigned motors are on the correct pins?  

 You can check the control outputs from the dx8 on both the monitor on the rx8 and on the AP Planner. Take your props off when testing this bit. 

As a matter of interest, if you turn the whole quad 90 degrees and then try, does anything different happen?  If so, check you're really in stable mode with the simple box unchecked.

DX8 is set for aeroplane model.
I went through the motor test in MP and each motor spun correctly and in order.
Checked the input pins again.
Thro connected to input pin 3 (pin 1 being left most pin)
Aile connected to input pin 1
Elev connected to input pin 2
Rudd connected to input pin 4
Gear connected to input pin 5
Aux 1-3 are connected to pin 6-8 respectively.

Check Stablize in MP and the simple mode is not checked.
Output from the radio looks good. Throttle low give 1124 and 925 when it is off.
I notice the throttle in MP spikes to about 1600 and radio 7 spikes also. I don't see a pattern. The DX8 is off. Notice it when it when I was in the field. Wonder if it is caused by being to close to the receiver?

I will continue to troubleshoot.

Thanks for the comments.

Thanks for the reply. Not sure what to check next.
I have recallibrated the ESC and leveled and made sure it was on the X configuration.
Made sure it was balanced.

Still either the back or front rises first as I give it throttle.
If I try and adjust the yaw when lifting off then it helps but I lose control immediately once in leaves the ground.(Yaw and throttle are on the same stick. I thought it would have been pitch for forward and back)

Could my problem be the PID settings?


I don't think the PIDs are at issue (though I have been wrong before ;) ).

Just for the sake of complete information, how is your APM mounted in the frame/body?

There is a 'forward' orientation between 'X' and '+' styles. It is a long shot but I'm just eliminating variables.

For you 2.5 board THIS. The front of the aircraft is to the right.

Your inputs as listed above sound correct. How about confirming the outputs? Is the below the way they are configured? I am assuming that from the HT site I am looking at the top of the chassis.


So the overshoot is either the front lifting or the back lifting? After throttle down it alternates? Wow.



Are you using the adapter board that James Y was showing on his HT-FPV build?


Yes, I did buy the adapter board from James.
The orientation is exactly the way you have it your post.
The GPS points in the correct direction and it moves as I turn the quad.
I did the motor test several times. Starts with motor one and goes clockwise.
Motors all start at the same time and looks good, just the front or back rises first. Doesn't ascend evenly.
Perhaps I have to adjust the trim at the transmitter?

Should I expect the quad to ascend evenly as I apply throttle?
What do you think?

Thanks for your comments.



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