Throttle Failsafe not functioning as expected

Hello all, today I had some decent weather, although a bit windy, so I decided to test my throttle failsafe settings on my quad in x mode running AC 2.8.1.

Failsafe settings:

RC3_MIN 1034

RC3_MAX 2073

THR_FAILSAFE 1

THR_FS_ACTION 0

THR_FS_VALUE 1013

So I started flying and switched to ALT HOLD for a few mins then I turned off my TX. At this point the log shows that it changed to stabilize mode.  When this happened the quad started to flip and fell to the ground and continued to spin one of the motors.  I couldn't regain control when I switched my TX back on and I had to disconnect the battery to shut off the motor.  According to the tlog when the TX was turned off the value of RC3 fell to 1007 and should have triggered THR_FAILSAFE.  There was no GPS at the time so I was expecting it to just land.  Any insight as to why it switched to stabilize mode, and was very unstable, and not RTL would be appreciated. 

The event happens at 92% in the tlog.   

2013-01-17 17-14 9.log

2013-01-17 16-46-37.tlog

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  • If I read correctly, in Arducopter an ACTION of zero means do nothing.  The description of THR_FAILSAFE_ACTION is also different in the Mission Planner

    This is from the German version of the Wiki, but it doesn't show anywhere in the English version:

    There are two options for failsafe. If you are in Auto and prefer to continue your mission, the parameter THR_FS_ACTION should be set to 1. If you prefer to have the copter RTL even if it is flying under autopilot, set THR_FS_ACTION to 2.

    And from the same (German) translation: 

    For safety, Failsafe RTL will NOT engage unless you are Armed and at least 10m from GPS home

    And then, there's the Mission Planner.  Failsafe is enabled or disabled in the "Standard Params" page, but the Failsafe Action is simply "On or Off".  The popup for "Throttle Failsafe Action" says:

    Arducopter Auto: Off, No Action, On, RTL

    Arducopter other: if have GPS, RTL, Otherwise Land

    Confused yet?  I certainly am.  Testing Failsafe will indeed be a test of faith.  But I think setting your FAILSAFE_ACTION to zero means to do nothing.

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