Random Flip On Takeoff

I'm hoping for some help or ideas here. It appears I'm not the only one experiencing this. I've just started testing an R550 hexa frame (X configuration) with an APM2 ver. 2.5.5 . The very first couple of takeoffs were actually quite nice with the default parameters. I don't dare touch them until I've had more successful air time to evaluate performance and flight characteristics. A subsequesnt takeoff resulted in a flip. It was more like the copter wanted to fly but tipped over on its side at takeoff. After replacing props, I went to a larger field to test further but w/o the restriction of a yard full of trees. This is my first multirotor and many years of no RC stick time. I was in Stabilize mode. I ran the props up slowly and just as the thing got light (just under half throttle), it flipped over AGAIN!!! I know it has the ability to fly correctly with the current setup and parameters. It did well on its first couple of takeoffs. I did have to fish it out of the shrubs a couple of times but that was totally my fault from lack of experience. The setup is as follows:

R550 hex frame

2830 1000 KVA motors with 10X4.5 props and hobbywing 30A ESC's

APM2 w/ 2.5.5

Somewhere between 1720 and 1770 grams weight (I don't have a precision scale that goes above 2.2 pounds. I got a bath scale measurement of 3.8 lbs and ranges from 3.8 to 3.9.

I'm looking for some help and possible insight here. I'm not soliciting a lecture on open source code and the perils associated with it. I asked a simple question a few weeks back and got a condescending reply. I'm not looking for that again. I'm just don't want to play Russian Roulette everytime I run the props up.

Help is appreciated as I wait on more props.

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  • Update: After replacing all props with GEM FAM 10X4.5's. I rechecked all configuration settings. Actually I did a reset and redid everything. Had a good test flight Thursday. no hint of flip. ALT Hold worked well w/sonar. did not have RTL set up on six position switch. Went through on 3S 5AH battery and part of another.

    Went out again Friday after dropping the roll and pitch P from 4.5 to 4.25. It was a little twitchy. It did quite well with ALT hold. Yaw want to YAW around by itself sometimes. I tested POS Hold and it worked as aell as I would have excpected. RTL worked with AutoLand worked withing 13' from Arming/Takeoff. Decent enough for me. I tried to do a Position Hold and pull it away from it hold point and let it return. When I released it, it headed in an off course (10-15 degrees) direction and descending. My inexperience kept me from switching back to STABILIZE and recover. I broke two motor struts. Got more ordered from China. My fault for being too ambitious with the testing/verification process. I was about 1/3 of the wayinto the second battery. I should have quit while I was ahead. I've got a copy of Phoenix ordered. Hoping to build some reflexes and muscle memory. I used to fly fixed wing nitro in the 70's with no mixing. I guess when you're in your teens you're faster than when you're almost 53. Thanks to all for offering advice w/o telking down or telling me how "painfully obvious" something is. The Wiki site is full of info but no one can refute that it is scattered. Couple that with an old version and new version of the AMP and it was a bit confusing at first. Thanks again to all. I'm sure I'll have future issues to call upon the younger and more experienced with.

  • Thanks to all of you. The parameters are the default ones set when entering a hex X configuration. I've already thought about holding the machine over my head (securely) and having my RC friend ramp up the throttle to see if it want to list/flip. Also, I suppose I'm going to have to learn to download and interpret log files. I got to see when these are started/stopped and how you reference them to your particular event. Thanks again. I'll probably be needing some help with the logs. I could have also had some prop issues from the first flip and did not inspect closely enough. This could have cause the second flip. I understand this is a complicated and intricate machine with little room or tolerance for error or slack.

  • Not Sure if my problem is related, but I found that sometimes my copter flip on take off, I have learned to spot it by now before it happens. I Found that when this happens and I look at the log files on the mission planner the Y Gyro stays 0 and the X Gyro values stays below the 0 line, disconnecting and reconnecting the battery fixes it, I have no idea why this happens.

  • Moderator

    Hi Alvin,

    I have found most problems like this are due to some of the pids being wrong, and have experienced flipping during flight, in fact after months of flying with no problem and apparently stable flight just last Sunday I was flying and my Tricopter flipped several times from about 20m and into the ground, unfortunately I couldn`t view the log file as it wasn`t saved because the battery was torn off. But I have put it down to Stab p or I?

    Post your parameters here and it will be easier to see what may be the problem? and a log file if you have one?

  • I do think that punching it can be a problem.  With basic PIDs the multicopter will lift quite calmly off the ground.  A violent flip that breaks props is not an operator error, unless you are in manual mode and do not know how to fly.  Bad performance can be had if wrong PIDs were entered, such as misplacing a decimal point; or badly installed props.  But of course not random issues.

    There are methods to use to hold your 'copter safely as you experiment with takeoffs.  I would look to see what the APM is doing which causes the flip.  Learn how to view logs and see what told it to flip.

    You can hold it in a safe way under the 'copter and start it up, see if it happens again.  Maybe you can come to some conclusions. 

  • Well you know the issue can be in a number of places.  A flaky UBEC, wiring or a ESC maybe.  It would be of some interest to know after the flip if the APM is in a dis-armed state.  This might indicate that the APM has rebooted.  A brief power failure might cause this or a bad solder spot or something metal touching the board (ei: metal mounting screws).  A reboot will cause a quad to flip very quickly.  The increased vibration may cause a failure on the board or in the wiring.  With the props off maybe you can try simulating the problem on the bench and see if any light tapping or movement of wires will cause a APM reboot or other issue that you can see or hear.

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