[HELP] My first tricopter won't fly!


Junior Member
Hi Guys,

I've been watching FliteTest for the last 2 and a half years or so and have finally decided to build my first real RC model.

I decided to build a tricopter using the X900 frame from Hobby King and the set of electronics that David recommended for his tricopter V3 frame. I would have gotten one of his frames but they were on back order and I didn't have long enough holidays to wait.

So I assembled it all, set up the KK2 via David's instructions, calibrated the ESCs and it won't take off. The props are spinning in the correct direction but it just shakes so wildly that I'm not confident to give it any more throttle, in the video it's just over 1/2 throttle. Also towards the end of the video one motor just stops working all together.
Not having a great first experience, any one got some advice for me?


NTM Propdrive 28-30 1200kv motors
30A afro ESCs
4000mah 3s lipo
KK2.1 HC
9x5 props
Turnigy 9x radio

Many thanks in advance! :)


Junior Member
Did you balance your props? I haven't built anything but from what I've heard prop balancing is pretty important.


Junior Member
No I haven't balanced props because I don't have a balance but I think the copter should still be able to get off the ground with unbalanced props, this one won't even do that.


Faster than a speeding face plant!
That howling sound says upside down prop.

Are you spinning the tail prop backwards or upside down?

The writing on a prop always faces forward (up).
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Junior Member
I never knew props could be placed upside down. What causes them to not function right after they are upside down?


Master Tinkerer
props are not like an angled flat plane that pushes air, but a flat plane that curves down at the back, which pushes air. When upside down, the props will be trying to push air with the "round" side of the prop, which will be less efficient.

Also, your tail servo is very wobbly. What servo are you using? I've tried two servos: A 9gram metal gear analog, and this one: http://www.hobbyking.com/hobbyking/store/__67049__Turnigy_380MAX_Micro_Servo_Metal_Gear_4_1kg_16sec_17_4g_AR_Warehouse_.html Only the second one worked, and even it stripped a bit on a hard "landing" and now wobbles a bit.

Before you fly your tricopter for the first time, and not just hovering, BE SURE THAT YOU HAVE ORIENTATION GUIDES OF SOME SORT. Whether it be different colored booms, props, LEDs, or something, make sure that you have something. I flew mine at sunset and a local field and it was VERY hard to keep orientation. I power drifted toward myself, and completely lost it. Hit the dirt level, but sill bent a prop and stripped the servo about 5 feet from my dad who was flying his Apprentice.


Junior Member
Props are definitely not upside down and I'm quite confident they're going the right way.
The servo you posted is the exact servo I'm using actually haha.
Is there anything else I can check to try and get this thing flying?


Senior Member
Do you realize that when a prop is on backward, it still pushes air in the proper direction, but poorly?

If "I'm sure the props are on right" == "The props are blowing air downwards" then you aren't sure.

If "I'm sure the props are on right" == "I checked and the writing on the prop hubs is on the top", then you are sure.

It's a common mistake. it explains the lack of thrust, and it *looks* like they are on backwards. When i say that is *looks* like they are on backward, I mean that when I Look at them, they seem backward.


Senior Member
If the props are on correct side up there is a chance that they are the wrong props.

Remove props and verify which direction each motor is spinning and that this is correct. Then mount the props and make sure the correct edge of the prop is the leading edge. It should be the high edge of the prop that is leading. This will cause lift.


Staff member
At 00:25 I don't see any markings on top of that prop. All other props I've seen have numbers on the blades on the side where the air is "sucked" from - with multirotors the numbers have to be on top.


Junior Member
Hey again guys,

I've confirmed that the props are on right by checking the directions of the motor and comparing with copters that work. I even swapped around the props to the wrong configuration and tested to confirm that they were on right.
I still have a heap of vibration which means the copter won't get off the ground at 2/3 throttle as shown in the video that's first in the post.
I've attached some photos close up to see if anyone can spot anything that could be the problem. One of the photos shows an arrow on the motor which points in the direction it spins.

DSC_6588.JPG DSC_6589.JPG DSC_6590.JPG DSC_6592.JPG


Senior Member
I know you said you're sure the props are on correctly, but just for peace of mind, are there any numbers imprinted on the prop anywhere? Most usually have the prop size on them somewhere.

I've had my props on backwards before and it's definitely a no-go. And one other thing, do you have the prop nut tightened all the way? It looks like you do, but just to be safe. I think it would've spun off if you ran it up that high and they weren't tightened, but it's worth double checking.


Faster than a speeding face plant!
You state that one photo shows an arrow on the motor that points in the direction it spins...

Brushless motors don't have a set direction. You can reverse direction on any brushless I have ever seen (seen lots of NTMs) simply by swapping two of the motor leads on the ESC. The threads might have a direction but not likely on those motors with those prop adapters.

Watching the video again, your tail rotor is pushing air up, not down.

Put the copter on the ground and gently raise the throttle. Carefully place your hand over the rotors about a foot above them. If any rotors are blowing up, that is the problem.


Winter is coming
Yeah, it's hard to tell, even after slowing your video to .25 speed, but when the props are still, it looks like you have the following configuration:

Front Right: CCW
Front Left: CW
Rear: CW

I actually have mine setup with all motors spinning CCW with the standard CCW props on all of them for simplicity, but most diagrams I've seen of tricopters with counter rotating motors have two CCW motors, and one CW (usually the left front):


I don't think that's necessarily your problem, if you have the motors wired correctly, but if you don't (again, hard to see with a CMOS type camera recording it even with the video slowed down), that could be your problem.

You might want to make another video with the props loosely placed on top of the motors, NO spinner/nut, and slowly move the throttle up with all the props in clear view. Then pan closeups of all the props when they're still so everyone can see either the numbers or the shape of the prop.

All the advice posted above is great.


Winter is coming
By the looks of it, at least one of those props is on upside down.

I'm not so sure that of that on closer inspection of those pictures posted above... They're not properly focused on the props, but you can almost sort of make out smudges that look like the prop size etchings on the tops of all three blades... of course, it could just be reflections, dirt or scuff marks because the photos aren't focused on them... again, the angles are also bad, so it's hard to tell how they're curved, but they look like they're curved upward... thankfully, those props have a big enough pitch to more easily tell...

I'm leaning towards wrong motor direction... looks like you have bullets on the motor wires, so it should be easy to correct if that's the case!
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"That guy"
I'm not so sure that of that on closer inspection of those pictures posted above...

Here's why I believe it's upside down. Based on the shadow of the prop on the floor, the light source is coming from the direction of the red arrow. If that's the case, and the curved part of the prop was facing up like it should be, the glare on the prop itself should be where the yellow line is, not at th very edge of the propellor. Also, the area at the blue arrow is higher than the area under the green arrow, showing that the hollow of the prop is facing up.

The prop is on upside down. :)

Or it's so horribly warped that it would be rendered ineffective.

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Junior Member
Thanks for all the help guys but I have done a lot of research about multirotors before I built this.
I'm certain the props are not on upside down, the numbers saying "9x5" and "9x5R" are on the top and each blade is spinning the right direction.
I know brushless motors can change direction if the leads are switched, I just drew that arrow to remind me which way I had soldered it.
I have already checked that the air is blowing in the right direction, it is.
Sometimes the one of the copters blades even gets a little bit off the ground.
I've calibrated the ESCs.
As I said before, I've put the props on the wrong motors and upside down and compared with what I have and I've definitely got it on right.

When I hold it in the air and power up the motors I notice that the top of the motor seems to oscillate left and right due to the huge amount of vibrations. The problem is that I'm too scared to give it any more power because it's already vibrating so much before it's off the ground on it's own power.
I just need to work out some way of significantly reducing the current levels of vibration.
The motors and props are not currently balanced but I don't believe that having unbalanced props/motors would render this thing unable to get off the ground.


Please try to power your motors without props on. When it is also vibrating violently, you have at least one bad motor.
Also: If you have less vibration and your tilt servo still goes back and forth so quickly, try to take away some sensitivity on the servo (in the flight controller configuration). It should not wiggle that hard/at all when just turning the motors and not flying.