Toilet Bowl only on auto land, anyone else experienced this?

[tailspnr]

Okay, so this is my first post and I'll admit that I'm a little new to the Naza-GPS unit, but so far it's been awesome. I own a LHS and I've just built my first Flamewheel 450 ARF with NAZA-GPS combo for a customer and I think I've got everything dialed in good with the exception of consistent Return Home-Auto Land.

I've done a little reading and come across the spreadsheet of setups. I'm using the basic gain numbers of 145,145,140,145 and altitude gain numbers of 120,120.

What I've noticed is the quad holds impressively in GPS mode and the RTH feature tends to work well approximately 60% of the time, but some times when I test the RTH feature I get a nasty 25'+ toilet bowl effect. The bird, on occasion, tends to start it's final decent before re-establishing a stable hover and never loses the toilet bowl effect. I seem to notice that on the first RTH activation it might work well, but on subsequent RTH activations I get a nasty, unstable decent.

Anyone else familiar with this issue, or have any recommendations?

thanks,
the new guy, Tailspnr........aka Scott Kimball, Hobby World, Louisville KY

 

[tailspnr]

BTW, the initial RTH activation after taking off usually results in a smooth and straight line decent on final. It's just subsequent RTH's after the initial RTH that result in scary decents. The last attempt resulted in a bailed FS and almost caused me to loose orientation. Once that happened I lost orientation and sent the craft almost out of site. As a last attempt to save the craft I hit the FS switch and she did as programmed and returned to her original position in the sky and started a normal decent. Once she was in good view I resumed flight in ATT mode and executed a safe landing.

While I'm not 100% comfortable on continuous usage of RTH/FS on the same flight, I have learned to trust the RTH/FS function in that emergency situation.

Just wondering if it's normal to get normal functionality on initial activation of FS while subsequent activations within the same flight may result in poor performance.....ie, unstable and toilet bowl decents.

 

[Tomstoy2]

Just taking a wild stab at it here, but I'm thinking that if you bail out and then re-enter fs you have lost the original home lock, thus the toilet bowl.
It's extremely important to ensure you have gps home lock before take off.

I'm not exactly a big advocate of rth use. I view it as a last ditch effort and treat it as such. Might be a good idea to enforce that thought to your customers.
I do applaud you for making sure every function does work.

Like I said,,, I really don't know, just a w.a.g..

 

[Benjamin Kenobi]

Have you offset for magnetic declination? North is different depending on your location. A common cause of TBE as the Naza's corrections are slightly off.

 

[Dewster]

I experienced the toilet bowl effect on one of my landings when I installed the WKM on my quad for testing. It worked as advertised until one day when a gust of wind disturbed it's landing. The craft kept hunting and pecking for an exact spot to land and that caused a wild toilet bowl effect. It was so bad that that I was worried that it would fly into a light pole or a tree. I didn't know how to regain control of the craft (change flight modes to interrupt it's automated sequence) so I just watched helplessly as my craft eventually landed in a bush.

I've had success on flights afterward using RTH without the toilet bowl effect. I primarily use the RTH just to bring the craft back and then I'll land it myself (I have a Y6 with Graupners and don't want to ruin the blades if I have a tip over during landing). I trust that it'll work, but don't feel the need to let itself land.

 

[tailspnr]

Have you offset for magnetic declination? North is different depending on your location. A common cause of TBE as the Naza's corrections are slightly off.

I have not done any compensations for magnetic declination, nor am I aware of how to do so. I'm starting to wonder if after the first time you use RTH if you shouldn't reboot the system.

One other thing that I've noticed is that when it begins the RTH sequence occasionally it will begin it's decent while in route to it's overhead home position as opposed to pausing to reestablish a stationary hover prior to descending.

So here's a basic question. How does the "attitude" pitch/roll gains differ from the "basic"? And honestly, up until just now, I thought I was reading "altitude gains" and I just realized it's "attitude gains". But I'm still curious as to your opinions of the difference between the two.

And thanks for the replies.

 

[Benjamin Kenobi]

I believe basic is how it responds to your commands and the other how it responds to un-commanded inputs (the wind etc).

I'm glad you noticed the difference between attitude and altitude. People are often getting it wrong and it becomes confusing. Altitude = Height. Attitude = Horizontal stability. At least that's how I think of it. Google probably says something a bit more intelligent.

 

[Benjamin Kenobi]

Ps - Read up on Magnetic Declination. The manual states its importance. The US has quite a deviation in parts. In London it's just over 1degree so very small.

 

[tailspnr]

Ps - Read up on Magnetic Declination. The manual states its importance. The US has quite a deviation in parts. In London it's just over 1degree so very small.

I just spent a little time talking with a full scale pilot and he explained magnetic deviation to me. Where I'm located we have appx 5 degrees of deviation. I'm assuming
it has to do with the way you mount the GPS direction.

The customer picked up the quad today and is thrilled with it. As far as I can tell by my research it's functioning properly.

I appreciate all the feedback and I'm looking forward to my next build which is likely a F550.........

 

[tailspnr]

BTW, the full scale pilot that explained magnetic deviation is also the customer of the quad. He's aware of the need to compensate for it at the GPS and is going to let me know his findings. And I also thought that 5 degrees was quite a bit in terms of being off of your heading......... Good info!!!

 

[Benjamin Kenobi]

Nice! Another step up the ladder we go!

 

[tailspnr]

Nice! Another step up the ladder we go!

Yes sir.........and having lot's of fun while I climb!