A2 losing height in forward flight

H

hs_foto

Member
Hi guys,

I just finished a new built: a coax x8 octo with the A2 [FONT=Open Sans, Helvetica, Arial, Verdana, sans-serif]v2.1 and it flies great except that in loses height when flying forward or backward.
I tried vertical gain and IMU/GPS location adjustments and it doesn´t make a difference.

Anyone got any idea?

Thanks a lot

David[/FONT]
 

ary

ary

Member
Vibration on center plate can cause it. Check vibration on each arm.
In my case : I have several bad motor bearing, cause severe vibration through center plate. After I change those bearing, it flew normal again
 

Carapau

Carapau

Tek care, lambs ont road, MRF Moderator
Dare I say it, it could just be an optical illusion if you are flying away from yourself. Just a thought.
 

H

hs_foto

Member
unfortunately the phenomenon is pretty strong: about 1m height loss every 10m or so depending on speed and i can see it clearly when flying towards myself as well as away...
 

Carapau

Carapau

Tek care, lambs ont road, MRF Moderator
Perhaps it is where you have mounted the IMU. Air passing over the IMU will could cause a drop in pressure around the IMU hence a drop in height. I am purely guessing here.
 


fdproductions

fdproductions

FD Productions
Yes totally agree with Car, on the A2 I suggest mounting the IMU in the center frame and mounting everything else outside of central airframe, more similar to the s1000 set up
 

P

plexus

Member
On that video you can see the problem . Only action on the roll.
I am in atti/gps mode.
My A2 is 2.0 Kg with Basic pitch roll Yaw
170 170 150

Atti pitch roll Vertical
160 160 150

http://youtu.be/NvbTM_78QcU
 
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kloner

kloner

Aerial DP
from my experience aside from any gain tuning, that airframe size vs. cg looks really low to be banging it around so hard..... if you do the same move at say 1/4 that fast does it do the same thing? all aircraft because there defying gravity have envelopes they need to stay within to maintain safety and a predictable behaviour to the pilot..... i know we all wish it wasn't, but to fly that aggresively would require more than just holding the stick at 50%...... on any controller

If i flew a red that hard under my jib i'd be standing in the unemployement line..... this is what heros and discos do, if need this might look into more power, bigger arms, same payload and it'll get better but not go away
 
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gtranquilla

gtranquilla

RadioActive
hs_foto,
I suspect a coax would have much more prop wash issues that could affect the baro sensor on your MR.
And the baro sensor is the prime method for the MR to determine its altitude.
I had similar issues with my WKM on a flat 6.... put some cotton gauze on the sensor hole which seemed to help.
But later I repositioned the IMU and the issues disappeared.
While the A2 has added a 2nd baro sensor hole in an attempt to improve altitude accuracy that might also create an additional challenge in some situations.
 

P

plexus

Member
Hi,
Just returning to fly, and with a vertical gain = 200 it dont loose the altitude, only some cm.
But you are wright, may be with a biggest frame that would be better: to try !!!

Anyway thanks for your help.
 

R

R_Lefebvre

Arducopter Developer
There are a lot of issues that can cause this. Not enough power, vibration, etc.


But some amount of altitude loss is unavoidable, even on a perfect setup. It just the basic Venturi Principle. Airflow past the barometer causes a drop in pressure, which causes a flight controller to think it is too high, and descend.

from my experience aside from any gain tuning, that airframe size vs. cg looks really low to be banging it around so hard..... if you do the same move at say 1/4 that fast does it do the same thing? all aircraft because there defying gravity have envelopes they need to stay within to maintain safety and a predictable behaviour to the pilot..... i know we all wish it wasn't, but to fly that aggresively would require more than just holding the stick at 50%...... on any controller
Click to expand...

You could fly a Red at mach 1 with the right setup. ;) But seriously, there's no reason why you couldn't set up a multirotor that could do this. You just need enough power.
 

kloner

kloner

Aerial DP
and a big enough footprint to leverage it all

i've taken reds 40mph for a half mile as it it now, but it's a slow gradual thing getting it all going, stickbanging is for 3d, slow smooth deliberate movements are for a/v. To put that movement i saw in laymans terms, that's like throwing a ball as hard as you can to a little kid then scolding them cause they didn't catch it, gotta give the rig a chance and know the limitations or this rig is going down.....

this is naza, but it's the same thing.... atti
that's a few feet off the deck holding the elevator to full forward for a half mile or more...i rarely ever have to move throttle, but time to time i'll hit something that changes it up... gusty wind is the worst, has pressure changes within it
 
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