Originally Posted by olythom
Lots of good thoughts to probe. As followup to some of the questions/comments...
No jacket involved. Pretty darn sure that the elevator stick was not bumped.
Pull /spring on both rud and elev - servo pulls for up.
Clutching at straws here:
How stiff are your TX sticks? If the springs are loose, and you're jerking the TX during launch, then there is the - remote - potential for a stick flopping the wrong way.
Are the elevator servos secure - really secure? I grounded a plane where the elevator servo was covered with masking tape and glued to the inside bottom of the fuse. It slowly worked itself loose over time, waiting for the right moment ..
If you have a failsafe mode set for neutral control surface configuration, then a brown/blackout should not cause the plane to pitch downward.