Scout X4 flipping forward during takeoff.

Discussion in 'Walkera Scout X4' started by chase, Apr 13, 2016.

  1. chase
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    chase Member

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    Hey guys,

    I hate to say it, but I've run into an issue that has me scratching my head as to the cause. My Scout X4 is flipping forward during takeoff attempts.

    To help you help me figure out what could be causing this and a fix, here's some info.

    She's had her system recalibrated.
    I used a level to calibrate all points in Mission Planner.

    She had her Compass recalibrated next using true North.

    First battery was a matured but fairly new one... no issues. T&L's perfect. Hover, flight etc. Perfect.

    Second battery, New first time use, first takeoffs fine... then she flipped on take off. Battery use time, approximately 3-4 minutes. Still strong. Next takeoff - fine. Total flight time, 4:58 minutes. (I sheared a gimbal damper in flight) called it a day.

    Yesterday... New Battery #2.
    1st Takeoff - fine.
    2nd takeoff - she flipped forward.
    3rd takeoff - she wanted to flip but I corrected her and got her off the ground.
    4th, 5th, 6th, 7th and 8th attempts at takeoff with a total flight time of around 10-12 minutes to this point third bar flashing on the battery 3.4v on the tx, she keeps wanting to flip forward. Called it a day.

    Additional info.
    I'm not timid about taking off with her. Though I was watchful. If she showed signs of flipping I shut her down.

    The ground was level. The ground doesn't get much flatter than where I'm at. Additionally, my take off point was the driving green of a golf course. It's flat and fairly level. Grass well maintained and short.

    On the side of caution, I shut her down, pulled the battery, turned off the tx and rebooted and bound everything on a small table I bring to be sure it was level.

    She again tried to flip forward on takeoff.

    Wind was only 8-9 mph with maybe 12-14 mph gusts. I always takeoff facing her windward.

    Flight is great when she's flying. Though she's only had about 30 minutes total since her recent calibrations and firmware updates.

    All motors start at the same time. All props are balanced and new.

    She's only been in manual mode as she's "learning". And yes, I checked to make sure she wasn't in GPS mode during those last takeoff attempts.

    Speaking of which, a quick shout-out of thanks goes to bjr981s for mentioning she'll try to flip if you set it to GPS and attempt takeoff on anything but absolutely level ground. It was the first thing I checked due to his write up.

    She hasn't had a ton of flight time over all. She's a fairly new bird in regards to total flight hours.

    She doesn't have any trim added. No need. She hovers pretty true and solid. Though the wind will blow her like any bird.

    When she actually flipped on takeoff, I saw it about to happen and immediately cut the throttle and disarmed her. So there wasn't any run on to the motors after she went over.

    I could really use the input as her new leg servos just came in today...
    (picking them up and installing them tomorrow. Hurray! Finally after three weeks they'll be fixed!)

    Any thoughts here guys?

    tia
    - chase -

     
    Last edited: Apr 13, 2016
  2. bjr981s
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    bjr981s Moderator Staff Member

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    It sounds like the model is not calibrated correctly.

    You need to do the calibration dance and ensure it is completed before the LEDS stop flashing.

    You can't successfully calibrate using MP.

    MP is not 100% compatible with the Walkera FC implementations.

    This is a quick FAQ on the Tali. The X4 is the same.

    FAQ: Tali H500 Getting Started. Read Before Your First Flight

    Hope this helps.

    Cheers.
     
  3. chase
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    chase Member

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    Thanks for the link. I'll look into it.
    I did get info on first flights after calibration which was a response in reference to the Tali as well. Figured it'd work the Scout as well.

    And, no, calibration dance went well. Success before the lights stopped. Did it twice in fact only because I was off from True North a few degrees the first time I did it.

    The calibration I did in Mission Planner, you have to do in Mission Planner from what I understand. It's to set level. The first most calibration you're suppose to do after the firmware update... I forgot the exact name they call the calibration. I used a level add square on all points for that one. And like I said, she flies great when in the air after both were done.

    Takeoffs with the fist battery were spot on. Add that was in 18 mph winds.

    I have video from the last flight yesterday, in manual mode, as I'm not only letting her learn for the first five batteries as suggested, but I'm tweaking the gimbal as well.

    Though there's some wandering due to the wind gusts and the pilot, you can see, in flight, she's rock steady. Well, the gimbal adds to that of course, but, she's not flying erratically nor does she have a heavy forward drift.

    If compass calibration was off bad enough to make her want to attempt to flip on takeoff, wouldn't her fight be erratic and unstable? You mention it in your writing, about the flight of your un-calibrated Scout after the GPS upgrade.

    Btw, on a side note, I'm getting 12 SATS with mine consistently as is. I haven't checked, kinda wondering if mine was upgraded before I got it.. 12 SATs stock is pretty good. (7 blue flashes)

    I can do another compass calibration though just to be sure. I don't think that's it... but I'm not that far into her "learning" stages that it'll set me back that far.

    If it continues to try to flip, I'll give it another dance.

    We'll see..
     
    Last edited: Apr 13, 2016
  4. bjr981s
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    You have to complete on perfectly level ground before the blinking stops.

    You have me confused with your reference to true north? there is no requirement relating to true north?

    You cant calibrate the Scout with MP it is not compatible. None of the Advanced settings work. The IMU calibration in APM is for single one off calibration flight controllers.

    The Scout calibrates the IMU at every power up based on the calibration dance baseline.

    This is why you have to start on level ground for every flight. particularly in GPS auto takeoff.

    I see this as being a poor implementation and should only calibrate once under controlled conditions like the DJI phantom.

    The other issue I mention in another thread relating to my reluctance to test things is I have found the Calibration from the Calibration dance is often lost when just connecting the Scout to MP.

    Try a calibration dance. Do not connect to MP and do a manual flight to fine tune the compass.

    **********************
    True north calibration of a GPS/Compass module. (From DJI Documentation)

    This calibration is mechanical. Normally the GPS will face forward and the Compass is in the GPS module.

    Once you determine your latitude you can work out how many degrees magnetic north varies from true north.

    You can then offset the direction of the GPS mount, So the GPS points Magnetic North and the model points true north.
     
  5. chase
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    Not saying it was you or a requirement to point it true North when doing the dance.

    Simple logic to me was and is recommended by other birds for calibrating the compass is you start out pointing true North. Makes sense to me, as it is a compass your calibrating.

    And yes, the after calibration technique I'm using.. apparently you wrote on another site. Verbatim, what's in your link for after the calibration technique for the first few batteries is what I'm following. Just stretching it to the recommended 5 battery learn cycle is all.

    Anyway... your True North mechanical calibration you mention is different. Interesting...

    Now is the Scout GPS/ Compass layed out the same as the DJI ... are all gps/compass modules the same in that regard?

    True North of the GPS module would face which way for sure. It's there a way to test it and mark it? A half millimeter is probably a degree, and the tighter you get towards center, if that's where the compass module is, the smaller the increments get. How meticulous are the builders of these GPS modules...? Just saying...

    It works be nice to be able to test exactly were the module sees north.

    Did you do the mechanical to yours?

    As for the other calibration using Mission Planner, I just did as they instructed to do in the firmware update text...

    There seems to be conflicting views when it comes to using Mission Planner with Walkera products. Scout or otherwise.

    There's the guy that shows the "Compass Waltz" with the Scout and MP...

    I don't have enough experience with either to debate, argue or know the difference, or who's right or wrong on the subject. Just going by what I'm told or read on that end of things. lol

    But I do want to use MP for Mission Planning. That was something I liked about the Scout was the ability to use MP on my laptop. I prefer my laptop over a cell phone or tablet. I can Bluetooth into my laptop. WK-GCS and MP look the same gui wise. I don't know what to think on this one.

    Yeah, I'm surprised it recalibrates every time from what you're saying. Didn't make sense they would set it up that way. It should be set and forget as far as level is concerned.
    So I get what your saying as far as taking off from level ground every time.

    But understand... The whole area here is flat... Golf course driving pads pretty level. Humps are man made. And the table I bring along, certainly level. I rebooted on the table last time, and it just wouldn't take off without trying to flip.

    Ok I'll give it a whirl again, see what happens.

    Thanks.
     
  6. chase
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    I found the cause...

    Inspection of the F12E TX I noticed the Manual/GPS/RTH switch had an ever so slight hang between 1st and 2nd position. (Manual mode and GPS mode)

    I sprayed some electronic contact cleaner in it and worked it a bit till she felt smooth and caught between the three positions.

    Just took the Scout out using the same battery, which I hadn't charged yet. Did three T&L's with out issue before the battery alarm went off.

    So it was the switch. And thankfully not the result of a low or faulty battery... (which was one possible cause suggested for another quad that was flipping on takeoff) Or ESC's... or calibration.

    Which means... I don't have to do the dance and start her learning over again. Yay!

    I want to point out the last owner hadn't flown this Scout or used the TX in a long while before I got it. It's been sitting. Stuff like this happens to things that just sit unused.

    So I'll spray all the contacts and switches with a little cleaner and that should take care of that.

    At least it's fixed, and I can relax a bit and think of better things like... tomorrow I get the new landing gear servos!

    Thanks for the replies and suggestions BJR981S. I want to hear more about the mechanical compass calibration now that you made me aware of it and how it worked out for you on your birds. Definitely peaked my interest there and learned something new, which is always a pleasure.

    Again thanx,
    - chase -

    PS - in thinking about it. If the bird is going to want to flip in GPS mode... on flat level ground even... How do you do execute an auto take off? Your suppose to have it in GPS mode before auto takeoff right?
     
    Last edited: Apr 13, 2016
  7. chase
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    @bjr981s - Hope you don't mind but I have some questions for you regarding this issue and your "after calibration procedure".

    First about the "after calibration procedure"

    You state:

    "Next battery. It should lift very stable, fly for 5 minutes in manual executing all manoeuvres."

    What exactly are "all maneuvers"?

    Next are about using gps mode and auto take off.

    I've watched just about every video posted on YouTube that I can find that the pilot uses auto takeoff or taking off with GPS enabled.

    It seems inherent to the F12E as those using the GCS didn't flip with a couple of exceptions which were using the TX.

    Most using the F12E however, including your vids and myself apparently, when gps is enabled, the bird tries to flip.

    Do you think it's a probability that in the TX parameter settings, when GPS is enabled there's the 30' diameter safety in place for takeoff as there is with the Smart mode?

    Just guessing here as it seems the bird is attempting to flip away from the TX.

    What are your thoughts on this?

    I'm going to try testing this possibility tonight just to see. As I'm curious. Not pushing it enough to actually flip my Scout of course... I'm not that curious!

    Thanks
    - chase -
     
    Last edited: Apr 14, 2016
  8. bjr981s
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    Great that you have found the cause.

    The Mechanical Calibration to True north is part of the DJI Wookong H and Ace One GPS setup. I have a couple of these (Wookong) for my Scale Helicopters. (2 metre Rotor span)

    This calibration is recommended if you have a gas powered heli and are going to fly a reasonable distance away. (gas increased flight range)

    The logic is the deviation from True north to Magnetic north is negligible if you are not flying a significant distance away. And only meaningful if you are flying with Ground Control to a Map.

    I have not bothered as they Club I fly with has constrained absolute boundaries and limits the distance away you can fly.

    Most GPS modules are combined GPS and Compass. (For RTF GPS models)

    Some exemptions are the DJI Phantoms 1,2,3 (Don't know about the 4 as I have not seen one yet.) And the Walkera G400 GPS Helicopter. These all have seperate Compasses.

    Autotakeoff in GPS mode should not flip on level ground. Only very non level ground.

    The Autotakeoff does a quick full throttle boost to about 5 Metres. If on sloping ground this can cause a flip.

    If the model has been "educated well", this even on sloping ground, is unlikely.

    To test if Autotakeoff works OK with your model. Do it manually in GPS mode. Accelerate slowly and see if the model starts to tilt. If OK land and do a quick boost takeoff.

    Remember any attempt to takeoff without a good solid GPS fix will result in a flip or worse. I would not Attempt this without at least 5 Sat blinks on the LEDs (10 sats in lock)

    I had major problems with my Scouts with the standard GPS module. It would drop lock constantly and the Scout would tear off in random directions.

    I upgraded my scouts to Dual GPS. Thread here. They perform perfectly now. And in Hover I can put the TX down and walk to the model. It does not move more that 2 inches in any direction. It consistently has 14 plus sats in the lock.

    Walkera Scout Improvement Program.

    All manoeuvres means fly to the extend of all controls. Full forward, Full sideways, Full rudder. lets the self learning experience the extremes of flight control.

    I guess a likeness to how you calibrate the TX sticks.

    Lastly I have lost calibration a number of times by connecting my models to APM. Not always but often. I do not know why. This is without trying to change any settings.

    It has been documented on this site and others that Walkera's implementation of the APM code ignores a number of settings and overwrites others in its own specific code.

    I have not found yet a definitive What does and doesn't work across the various models that use APM. e.g. Scout, Tali and Voyager. Plus I guess the new Runner 250 APM FC model.

    I am not sure how the Scout allows or Inhibits Auto takeoff. I suspect as with most Walkera code they leave that to the operator. (DJI does the opposite.)

    Even if it does restrict the GPS drift to 30' this would impose a significant chance of tilting on liftoff.

    In suspect that if you attempt an Auto take of with no lock it will still try. I have not tested for obvious reasons.

    Cheers.

    Brian
     
  9. chase
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    @ Brian - Hey thanx for taking the time and your input on this. It better explains things I had questions on.

    I'm going to side note for a second...

    I installed the new landing gear servos and though it was touch and go for a while till I figured out what the apparent procedure was, all is operational again. Tested it out several times on the bench, landing gear working smooth. Aside from some re-tweaking the gimbal now that the servos are in, she's 100% operational again.

    Back on topic...

    Though, as I mentioned, I'd like to use MP as the ground station. I haven't connected to MP since the first time (as per firmware update instructions). So I wouldn't have lost calibration that way if it's off in anyway... i(n thinking out loud.)

    How do you know if you lost compass calibration when connected to MP? Is there a place to look in MP so you know? Or is something you find out during flight by how she flies?

    I'm timid about using the Auto Takeoff with the TX till I get the takeoff in GPS mode smoothed out.

    I got back to late yesterday to test if there's a possible 30' safety distance being picked up when gps is on prior to take off or not.

    There shouldn't be any real difference between having just GPS enabled takeoff, and Auto Takeoff (which has GPS enabled).

    The tendency to want to flip seems primarily in GPS mode enabled only.

    Something is off there for sure.
    My thought is it's a software based issue.
    It's either picking up a parameter it shouldn't or disregarding a parameter it should. (Like level or whatever that first calibration is called). There's a glitch in the software somewhere I feel. I could be wrong but, the signs are there it's a good possibility.

    I talked to someone about it yesterday, hopefully he'll take a look at the code as he said he would and I'll know more soon. He's majoring in computer science so if there's a glitch, hopefully he'll catch it.

    I'll report back my findings on the GPS enabled 30' test as soon as possible.
    If weather holds, maybe this weekend or even tonight if I get back in time.

    And... I re-tune the gimbal... (one of the gimbal motors is humming every now add again since the new landing gear servos were installed.) I wave that tuned first before taking her out again.

    Oh yeah... I get a consistent 12 SATs with the GPS module I have installed. Though I have looked into the dual GPS module.
    Carolina Drones is out of stock and in trying to get one direct from Walkera, neither I nor the local rep are sure of the exact part number. The language barrier I think is preventing us from getting a solid aha correct answer from the Walkera rep in China.. so for now, I've held off getting one.
    That's if this bird want previously upgraded... (?) I'm not sure as I haven't opened up the GPS housing to find out yet. But that's on the to do list.

    Again thanks....

    Love to see those 2 meter span heli's you mentioned btw... 550 is my largest heli to date. I've never even seen a heli that big in person... must be a show stopper for sure!

    - chase -
     
  10. bjr981s
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    By how it flies. It will not hold in GPS and Takeoff in manual is very shaky.

    The only difference is Auto does it at an apparent full throttle.

    The upgraded GPS for the Scout is the same GPS for the Voyager and Runner.

    If you buy the Runner version then you don't get a spare cable for the scout. Same GPS different cable.

    Walkera Runner 250 Advance Spare Part GPS Module Runner 250(R)-Z-14

    I dont have a video of mine yet. But here is the same Roban Air Wolf Model in a german video.

     

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