Help please, instability when descending..??

[andytee]

Hi,
I wonder if anyone can help..
I have a Droidworks AD4 V3 heavy lift, with Wookong m flight controller.
It flies absolutely fine.. until you start to descend from altitude.. at which point the motor/propellor tone starts to sound like a swarm of angry wasps, and the quad starts to rock in all directions... as it descends this motion becomes more and more violent, and unless I slow the descent rate right down it gets to the point of nearly flipping... this happens in GPS and Atti mode, I haven't tried manual (I'm very new to flying quads, so I avoid manual)
Many thanks
Andy

 

[multi-prop-chop]

Whats your all up weight and payload weight?

My skyjib wobbles if I try to descend faster than it would like. Its much better with a heavy payload, shot with a red recently and it was great on the descent. Adding a little aileron or elevator helps...

Paul

 

[andytee]

Many thanks for the reply..
Take off weight is about 3450g... There is quite a bit of kit onboard..! Wookong M, Spektrum AR8000 receiver (flight control from DX8), AR6200 receiver (for gimbal and camera control from DX6i) , DJI OSD mk 2, Freefly HDMI converter, DJI 5.8Ghz Video TX, AV130 gimbal, Nex5n with 10-18 lens, gopro 3 black, and a 5000Ma 4s lipo, 2x 5v becs for nav lights and powering HDMI converter, and charging Gopro... Flying with 40amp tmotor esc's and unidentified torxpower motors with 12 x 3.8 carbon props. ( I bought the basic quad second hand so I don't have all the details, and can't find any ID on the motors, think it may have been built by quadcopters)
Motors get just noticeably warm after a couple of 6 min flights, which is what I get off a 5000mah 4s lipo.. (strangely I get identical flight times with the one 4000mah battery I have.. same make..!!)

 

[Benjamin Kenobi]

My Naza did this at first. Adjust gains. A little forward motion (or any direction) also removes the wobble as Paul said.

 

[dazzab]

I think this is quite common with MRs. They don't like descending through their own prop wash which is turbulent. As others have said all you need to do is add movement in any direction so you aren't coming straight down and it should be much more stable. I'm no expert so take this comment with a grain of salt. There are others here with a lot more experience than me.

 

[andytee]

Thank you all very much for your help.. Adding some forward movement appears to stabilise things greatly...
I am gradually learning.... but I'm only just graduating to using combinations of stick inputs, rather than one movement at a time..!!!

 

[ProPilotWannaBe]

I think this is quite common with MRs. They don't like descending through their own prop wash which is turbulent. As others have said all you need to do is add movement in any direction so you aren't coming straight down and it should be much more stable. I'm no expert so take this comment with a grain of salt. There are others here with a lot more experience than me.

Actually, all helicopters. That's why in "real world" (big people carrying birds) pilots avoid descending straight down if at all possible, and always descend at a slant.

 

[maxwelltub]

It's true with all helis to an extent, but collective pitch helis don't really have the same issue because of the ability to create negative pitch while maintaining head spead. When you bring your MR down you enter your prop wash as well as lower your Rpms which provide most of your stability. If I start to wobble I goose the throttle a little or give it some yaw which spins some of the motors back up to speed.