First of all, thanks again for all your support.
Please, find here-attached the log and tlog files of my crash with ArduPlane 3.0.2, as I told you in Diydrones forum (diydrones.com/profiles/blogs/apm ... 3-released).
Resuming what I already posted there, I don't really know why my plane became to pitch down while I was flying in FBWA until it crashed. I didn't notice that odd behaviour until it was too late so I could not react so quickly to change it to Manual mode to save my air plane.
Checking my log I can see that there is a problem with Alt_error. I took off in FBWA without problems. Then I changed to RTL and changed Alt from 100 to 300 m AGL while I put my FPV googles. After that I changed again to FBWA and then my plane started to lose altitude, first in an smooth way but finally very steeply (that was when I worried and the crash happened).
The fact is that when it started to go down I had no response trying to pitch up the plane with or without throttle (in the contrary it went down and down). Mechanical failure? I don't think so because elevator works after the crash although now I can notice a great reduction in pitch response from MANUAL to FBWA (but I only can test it on ground with the airplane seriously damaged).
Two days before a performed some tuning in the plane and I was flying without problems (and a fairly good pitch response, although more fine tuning was required) and I think I didn't change anything before the last flight. Comparing with parameters of the previous flights few things have changed but compass_offset is the most different. In fact, Log Analysis give me the following results:
Log File //Tablet-pc/c/Program Files/Mission Planner/logs/2014-05-18 00-04-36 6_crash.log
Size (kb) 2942.3544921875
No of lines 48194
Firmware Version V3.0.2
Firmware Hash f233f957
Hardware Type APM 2
Free Mem 1342
Skipped Lines 0
Test: Brownout = PASS -
[color=#FF0000]Test: Compass = FAIL - Large compass off params (X:68.25, Y:176.92, Z:177.69)[/color]
No MAG data, unable to test mag_field interference
Test: Dupe Log Data = PASS -
Test: Empty = PASS -
Test: Event/Failsafe = PASS -
Test: GPS = UNKNOWN - No GPS log data
Test: Parameters = PASS -
Test: PM = NA -
Test: Pitch/Roll = NA -
Test: Underpowered = NA -
[color=#FF0000]Test: VCC = WARN - VCC min/max diff 0.335v, should be <0.3v[/color]
Could compass offset affect flight control?