Need help to diagnosis my crash upon taking off. My maiden flight…
My quadcopter is H4, very alike X, and I set the frame to X schedule, diagonal 690mm, front arms a bit shorter than rear arms.
Motors are sunnsky V3508 380kV,
ESCs are hobbywing, X rotor 40A
Battery 4S 5200mAh
Propellers 1238 genuine APC SF
Test in mission planner is ok, it armed normally.
However, it seems a bit lack of power to rise. I pushed the throttle up and it ascended but flipped forward. I don’t know what’s wrong. Tried to take off again in Althold mode, rather than Stablize mode in the first trial, same crash happened again. Flip forwards.
I checked it many times before my testing flight. Motor orientation and propellers are set in right direction as Frame X, with the front right motor running anticlockwise.
Hope that someone can point out my problem.
Any help is appreciated.
Check your radio configuration. It looks like you pitched the copter down to cause the crash.
Pitch went to 1000 at the point of the crash so either the control is backwards or miss configured.
Mike
Thank you Mike, I will check it again. Is there any other abnormality you can figure out? From auto analysis, it shows
Log File C:/Users/RiceHouse/Desktop/Crash2.log
Size (kb) 602.76953125
No of lines 8333
Duration 0:01:01
Vehicletype ArduCopter
Firmware Version V3.2
Firmware Hash c8e0f3e1
Hardware Type
Free Mem 0
Skipped Lines 0
Test: Autotune = UNKNOWN - No ATUN log data
Test: Balance/Twist = GOOD -
Test: Brownout = GOOD -
Test: Compass = FAIL - Large compass off params (X:-101.00, Y:55.00, Z:-199.00)
Large compass offset in MAG data:
Z: -199.00
mag_field interference within limits (7.00%)
Test: Dupe Log Data = GOOD -
Test: Empty = GOOD -
Test: Event/Failsafe = FAIL - ERR found: CRASH
Test: GPS = GOOD -
Test: IMU Mismatch = GOOD - (Mismatch: 0.30, WARN: 0.75, FAIL: 1.50)
Test: Parameters = GOOD -
Test: PM = GOOD -
Test: Pitch/Roll = GOOD -
Test: Thrust = GOOD -
Test: VCC = GOOD -
Is there anything wrong truly related to compass failure? or it’s just a reading upon crash.
Mike, really appreciated your comment
Joe
That should be fixed as well but you were in ALT Hold mode which just relies on the barometer for height.
Later when you use Loiter or Position Hold you will need that working.
Also try flying in Stabilize mode and see what happens.
Don’t know why your pitch from the radio went all the way forward at the point when the copter went down.
Mike
really appreciated, Mike
would you please tell me how could you figure out the pitch is running high in the log. Sorry, I am newbie to Pixhawk/APM. I try to read the data in RCIN and RCOUT but figure out the finding. My RC setting channels are AETR, pitch should be E as Ch2.
Thanks,
Joe 
First I filtered on ATT and graphed the Pitch. Then I filtered on RCIN and graphed C2.
Mike
[attachment=0]Crash2.png[/attachment]
Thanks very much,I will try it again after repair. Indeed strange, upon taking off, Pitch and Roll (A & E, CH1, 2)are self centered, not touching it. Why will it surge without stick movement 
It does look like you pushed the stick forward, and the copter did exactly what you commanded. The pitch input movement looks like a human input, not any kind of program error, etc. You might have moved the stick instinctually. It’s common for people to have the pitch control reversed, I’ve done it myself.
Thanks much, Rob
I will check it again and try to do some simulation without propellers on, after collecting my repair parts.
Jos