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Wobbling in Hover - Compass or Just Winds?

Discussion in 'Phantom 2 Discussion' started by Fink, Mar 14, 2014.

  1. Fink

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    Real quick back story...

    I've had my P2 since 3/1, I have flown it five times - each and every flight was perfect. This thing was insanely stable, reliable and a blast to fly. I figure after five flights I'd plug it in to the Assistant software and just check everything out to make sure I was in the green. I was, but went ahead and did a few calibrations and checked the IMU and it indicated there was no need to calibrate. Unplugged it, charged it and went out for my sixth flight this afternoon.

    Now, I had read on here that most people recommend (and some passionately insist :p ) that you let the Phantom go through all of its pre-flight checks and locking before you do the compass calibration. I had not been doing it this way. I assumed that once you entered the Phantom into compass calibration mode, indicated by the solid amber LEDs, it would know what you were up to. But, given that one guy said I ran the risk of getting an error with abnormal IMU values, I decided that on my sixth flight, I'd start doing it this way. So...on to my question...

    Phantom comes out of the case, I put it on the grass about 15 feet away from the case and transmitter (which is already powered on) and power it on. Given how bright it was today, I had to cup my hand under the LEDs to see them so I hung out for a minute and waited for both sets of rapid green flashes to occur. I then went to the transmitter, flipped the S1 switch about eight times and went back to the Phantom, confirmed the LEDs were amber and rotated it horizontally 360*, LEDs turned green, flipped it on its edge, rotated it 360*, LEDs go back to flashing steady green and I'm ready to go. CSC, Phantom is in the air and I'm letting it just hover for about 30-45 seconds. Now, the winds today were between 8-12mph - not sure what the gusts were but it wasn't anything that immediately alarmed me. The Phantom was wobbling fairly substantially - enough that I was not comfortable getting it more than 10' off the ground or so. I've seen this behavior a little bit at higher altitudes when the winds picked up, but I have yet to see it at lower altitudes on what I would consider only a moderately windy day.

    I fly it around in about a 30' circle after it hovered for about a minute or so and while in motion, it didn't wobble very much - flew fairly steadily, but then I noticed the severe J hook that others have talked about. Ironically, I just posted in the "Compass and the J Hook" thread that I had never had this happen - I deserve this, I guess!! :lol:

    So I figure, alright, let's land it, power everything off and start over. Run through all of the steps the exact same way and same behavior - rather wobbly (you know when you can hear it wobbling around a little bit, the different sounds the props make through the air and such), and the J hook was present. So I figure, ok, maybe something is just weird with this location, let's go to another spot.

    Fast forward an hour due to 4:30pm Orlando traffic (UGH)...

    Arrive at my usual spot, where I've flown the majority of my flights with ZERO issues. This time, I decide I'll go back to my usual sequence (power on, compass calibration, Phantom pre-flight GPS lock, etc.). Go through all of the steps, LEDs are all displaying perfectly normally, wait for LEDs to flash green rapidly twice and then let it sit another 45 seconds or so and go for the CSC. Now this time, it was noticeably more stable - I wasn't as nervous as I was before so I got it up to about 20' or so and went in the straight line and sure enough, it was much better, only hooked maybe 1.5-2' out of line at the very end. Still slightly wobbly, more than I'm used to, but better.

    So...finally...my question. Does this sound like anything you have experienced before? Is this just some funky compass action, maybe stronger winds than I thought just cause it to move around as it adjusts to the winds, interference?

    I'm likely making a much bigger deal about this than I should be, but given that this is my first time experiencing this, I am hypersensitive.

    Thanks for hearing me out - if nothing else, it's nice to vent to people that understand me, versus my lovely girlfriend who just nods and keeps her face buried in her iPad watching Vampire Diaries. :roll:

    Cheers!

    Fink[​IMG]
     
  2. UFOwithaGoPro

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    I believe no matter how thourogh our preflight checks and procedures are...every once in a while, there is going to be flights like you described simply because we cannot control other unseen interference and signals in the airwaves. Also, satellite signal quality (not quantity) could also vary. Don't know much about satellites but its possible.
     
  3. Fink

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    Good perspective and it seems to be the case.

    I flew it today at the same field where I had the issues yesterday and everything went perfectly fine. I did go back to my old ways of doing the compass calibration immediately following powering it on and everything seemed to go fine. I tested Home Lock as usual and it worked perfectly.

    Thanks for the response, UFO! Hopefully it was just a fluke, but the way I see it, it's a sign that I am getting to be in-tune with how the Phantom flies and its behavior, which is reassuring to me.

    Cheers,

    Fink[​IMG]
     
  4. Big Ben

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    Was it less windy today? You didn't mention that. If you want to find a cause (if there is one) change one thing and fly again. Don't change two things simultaneously because that way if you notice some difference you don't know which one of the two changes might have caused this.

    If you want to check a possible effect of the procedure you follow, do both right after each other in the same location with the same wind.

    More wobble with more wind doesn't sound too strange. You could try a higher Basic Gain setting for the right stick controls. This could make it more stable in hover. On my P1 (FC40) I have those set at 150%.
     
  5. Fink

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    Thanks for the response, Ben!

    Great point. I did sort of go to an extreme the day I had the issues because I immediately wanted to make sure something wasn't wrong.

    Flew it twice today - first flight this morning was smooth as glass. Second flight had some wobble, but the winds did seem slightly breezier. Both times the winds had to be lower than 8mph. For now, given that I am have no other issues, I have it chalked up as just normal wobble from the winds as it tries to correct in hover.

    Also had some slight hook on the second flight but that seemed to go away a few minutes into flight. I will say I fly around some metal soccer goals most of the time. The best spot to fly is at a park near my condo where they have two soccer fields together lengthwise and then two smaller fields on each end of that. When nobody is there, I have a good 200yds or so to fly, albeit with two sets of metal soccer goals to watch out for.

    I've gone back to doing the preflight stuff my old way - power on, compass calibration, then let it do its GPS locking. Did that on both flights today so that did remain constant at least today.

    I finally broke down and got a second battery - I should be able to do some good testing now whereas before I was having to do multiple takeoffs and landings on the same battery and that was just kind of annoying. :p

    Thanks for the replies, guys - I appreciate the input!

    Fink[​IMG]
     
  6. ianwood

    ianwood Taco Wrangler
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    My Phantom definitely dances when the winds gets going. You can hear the adjustments in motor speed being made when close up and you can hear it encounter turbulence from time to time when it's further away. The nature of the wind is important to understand. Sometimes you can have smooth steady wind and other times you can have blustery turbulent air. The closer to the ground, the more likely the air will be blustery depending on terrain. If you're still concerned about unusual Phantom moves in the air, post a video of it.
     
  7. Fink

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    Thanks for your response, Ian.

    I've done some flying since the first flight that had me freaked me out and up until last night's flight, it seemed to just be wind or environmental anomalies.

    Last night, though, I seemed to have some GPS problems. I decided to change the sequence I do at power-on, moving the compass calibration to last. Powered-on, let it go through all of its GPS communication, got both sets of rapid green flashes, flipped the S1 switch initiating compass calibration mode, calibrated, LEDs go back to steady green and I take off. Even in hover, the thing was wandering pretty substantially. Winds were maybe 2-6mph. It seemed to level out after it hovered for about a minute or two, minor drift when flying forward but my guess was the winds, as they were going in the direction in which the Phantom was drifting.

    Then came my Home Lock test. It started to come back home, but seemed to do the little "bump" it does when it reaches home about 15 feet away from where home actually was. So I tried it again, this time, the Phantom refused to go into Course Lock or Home Lock, no LED changes, just steady green. Then I got freaked out and landed it.

    Next flight, same location, I did the entire process over again, but going back to my old sequence doing compass calibration immediately following the end of the beeps at power-on. Took off, hover was better, didn't drift as much and Home Lock worked just fine.

    In short...no clue what was going on last night, but I do plan on going for at least one more flight today at the same spot and then hopefully another later this afternoon at a different spot just to see how she behaves.

    Fink[​IMG]
     
  8. Shrimpfarmer

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    I own 2 Phantoms. Each has only ever been calibrated once. I have flown them at multiple flying sites and they have flown the same at each. Every time you carry out a compass calibration you run the risk of introducing errors and if your unlucky enough to calibrate where there is underground cables or metal reinforcement you risk losing your quad.

    Only calibrate when you get a calibration error message on the lights or the quad is behaving in an unusual manner. This does not include if its being buffeted by wind gusts.
     
  9. Fink

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    Ya know...I had thought this entire time that I was overdoing the compass calibrations. I appreciate the affirmation confirming that. I'll be more comfortable omitting that the next few flights to see how it goes.

    One question, though. Is the compass calibration generally blamed for losing control of the Phantoms? I figured that would be more interference with the radio system or a GPS mishap than the compass - is that a fair assumption?

    Thanks again for the response!

    Fink[​IMG]
     
  10. Shrimpfarmer

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    I don't think anybody knows what causes a Phantom to fly away. Some people say its radio masts, electric rail lines and a myriad other things. By all means look for those types of hazards before takeoff but I have flown in the presence of both on several occaisions.

    There are quite a few posts where the Phantom has flown off and failed to respond but very few state that they tried activating ATTI mode. That mode ignores the GPS and the compass, it just holds altitude. So if they are at fault ATTI mode should allow you to recover control and land safely. Thats why you should ensure its been enabled by switching to Naza mode. Then learn how to fly in ATTI mode and how to reliably switch it on and off.

    Flying in the out of the box Phantom mode does not give you access to ATTI or HOMELOCK which are both essential modes for recovering a quad thats not behaving.
     
  11. Fink

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    All good points - I appreciate the insight.

    My concern wasn't necessarily with a full-on flyaway, I think that's 90% pilot error and 10% mechanical/software failure or an issue with GPS.

    I would think the compass calibrations would be more to ensure you have a smooth flying experience and the Phantom doesn't drift/float all over the place. I can't imagine the compass data could actually tell the Phantom to change the throttle of specific rotors or anything, ya know?

    Thanks again for advice. I will fly today without calibrating, given that my flight last night went well after doing my calibration and wait to see how it does.

    Cheers,

    Fink[​IMG]
     
  12. Fink

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    Have to say, your advice really helped. I know attempting to fly in ATTI was probably a newb thing I overlooked, but doing that has really put things in perspective for me. Gives me an entirely new appreciation of just how awesome the GPS is in the Phantoms. In ATTI mode, I could definitely tell that the wobbling in hover was in fact the GPS keeping it there. Out of GPS mode, I could easily tell just how much the winds were affecting the Phantom, even when my perception of the winds didn't indicate that they were really doing anything.

    I now plan on flying in ATTI mode a ton more and really getting to know how the craft itself works, with the help of the NAZA in keeping my altitude relatively constant for me.

    Again, thanks for the advice everyone - for those of you that just aren't used to the Phantom and how it reacts to winds and might be thinking something is strange, flip it to ATTI and fly for 10-15 minutes. You will immediately appreciate all of the little gyrations it is doing in the wobbly hover to keep you doing just that...hovering.

    Fink[​IMG]