Help! What's the problem with my flying wing?

[erfan_m14]

Hello everyone.
I made a flying wing, at the first flight, it hit the ground right after the launch, then I made a little up thrust angle and it seems that the problem is solved, now here is the second flight, as you see, it rolls to left then it seems sth like stall and then crash. At first I thought its left is heavier, and it is actually a little heavier and I have to fix it, but after watching the video a few times, I see it flys well at first and suddenly rolls to left, so I started to think maybe there's sth wrong with flight controller? Or maybe I should change PID settings? I use multiwii as FC. Do you recommend me to put it in "thru" mode so that will be like without flight controller and no gyro?
So I think one (or more) of these are the problem (s) but can't guess which one:
1. Left is heavier
2. PID settings
3. Flight controller doesn't work well
So please tell me what do you think based on your experience
Thank you so much for your help.

 

[Merv]

.....Do you recommend me to put it in "thru" mode so that will be like without flight controller and no gyro?.....
3. Flight controller doesn't work well.....

It looks to me like the gyro or Tx may need to be reversed.

With the gyro, when the plane rolls to the left, the left aileron should go down and the right aileron should go up. When the plane pitches up the ailerons should go down.

With the Tx, when you move the stick to the left, the left aileron should go up and the right down. When you pull back on the stick the ailerons should go up.

I always put the plane in through mode for the first few flights, to get the plane trimmed out. The plane will fly much better when trimmed.

 

[Hai-Lee]

Just ensure that your controls are not overdriving the servos. I set my mix with flying wings to 50% elevator mixed with 50% aileron. If you mix 100% with 100% you cannot expect any more than 100% output so the handling will be horrible.

Also disable any stabiliser and get the bird balanced and gliding properly first.
Then fit the stabilizer and ensure that the stabiliser drives the control surfaces in the correct direction, (the same as your stick inputs would generate for the same amount of upset.

A properly set up wing should not ever be capable of a stall in normal flight. I land mine at full "UP" elevator for minimum flying speed and they never stall. A little nose heavy is far better than a little tail heavy. Tail heavy WILL stall.

When on stabiliser you need to ensure that the stabiliser has a true idea of where down actually is - recalibrate if necessary.

Have fun!

 

[FoamyDM]

Good advice @Hai-Lee
Glider fly success first.

 

[kilroy07]

That multiwii looks like a cool project! Which software package are you running on it?

I'm with @Merv thinking maybe the controls/gryo were reversed.

I have a couple different flight controllers and they all seem to have different setup procedures.
It's always a good investment in time to thoroughly go through all flight modes you have set up, Before taking it to the field.

Like @Hai-Lee suggested I always (well, NOW... after a bad crash) launch the plane with a new stabilizer on it with the gryos OFF.
Get it up to a nice high altitude THEN try flipping the stabilization/gryos on... with the finger on the switch if the plane subbenly does something like this (the crash I spoke of earlier was with one of the $10 gliders and it litterally shattered in a thousand pieces because I had one gyro backwards... LOL)

 

[erfan_m14]

Hello everyone and thank you so much for your reply.

With the Tx, when you move the stick to the left, the left aileron should go up and the right down. When you pull back on the stick the ailerons should go up.

I always put the plane in through mode for the first few flights, to get the plane trimmed out. The plane will fly much better when trimmed.

Just ensure that your controls are not overdriving the servos.
Also disable any stabiliser and get the bird balanced and gliding properly first.

I'm with @Merv thinking maybe the controls/gryo were reversed.
launch the plane with a new stabilizer on it with the gryos OFF.

Well I made sure that elevons were going the right direction and the servos reacted well to both pitch and roll , I also turned off stabiliser.
So I went for the next flights.

Here is the first one, I think the launch was horrible and it was the cause of the crash (but maybe you can get an important point from the video or any useful advice that helps so I uploaded it).

This one is the second flight, it’s the third or forth time that the wing rolls to the LEFT and then crashes (it has never rolled to right yet!)

I checked that the wing is balanced with high precision, but I’m now thinking that maybe its P factor? Propeller rotates clockwise when viewed from behind. So what do you think, should I make the right wing a little heavier? Or make some right thrust angle? Or maybe this can’t be the main problem?

Thanks a lot for your great help.

Which software package are you running on it?

I run a modified version of multiwii 2.4 on an arduino pro mini + nRF24L01 + GY521.

 

[JasonK]

why multiwii instead of iNAV, Ardupilot, or one of the other 'current' FC setups?

Your second flight were it rolled to the left, your release was to 'up' and the wing was going to slow, so there wasn't enough airflow over the control surfaces for the stabilization to do anything. When launching like that, you want the motor to be running to the point were the wing feels like it is going to jump out of your hand on its own and your really just guiding it for the first 1/2 second or so to get it going the correct direction.

 

[Merv]

I agree with @JasonK, the second video looked under powered. Try a higher throttle setting.

 

[Tench745]

Yeah, most of those launches look like the plane is pretty nose-high and struggling to get up to flying speed.
I would surmise that what you are seeing is a stall or the start of a stall. The roll left is probably from p-factor because the plane doesn't have enough speed to fight it yet.
I think it's definitely worth trying some glide testing to see if the plane rolls left the motor isn't running.

 

[kilroy07]

It could be P-factor, or a torque roll (that would depend on which way the prop is spinning.)
P-factor most likely; http://ffden-2.phys.uaf.edu/webproj/211_fall_2016/Collin_Lasley/collin_lasley/PFactor.html

 

[Hai-Lee]

In the video clip of the second flight I see a major issue!
The launch speed is far to slow for flight and I wonder why the wing is launched vertical.
After the release the plane does not climb under motor power and as there is no tail there can be no "P" factor.

The roll could be simply the torque effects of the motor. The reason the controls are unable ot correct the roll is the simple fact that without sufficient forward airspeed the aerodynamic control surfaces will not function.

Try the glide test first and this can be done without the motor being powered on and horizontally. It will give you soe idea of what airspeed you need for it to fly.

After the glide is done and the flying speed is determined then you can power up the motor and see if the motor has sufficient thrust to sustain flight. The motor power does not seem that great currently.

Have fun!

 

[kilroy07]

and as there is no tail there can be no "P" factor.

http://ffden-2.phys.uaf.edu/webproj...Lasley/collin_lasley/SpiralingSlipstream.html
Might be what you were thinking about.

 

[Hai-Lee]

It started rolling straight from release.

 

[L Edge]

Another factor maybe the prop is not mounted and rotating properly? Dia and pitch label should be in front and rotating correctly.