I noticed something potentially dangerous in the design of the electric aileron trim system.
The geometry is such that the C-606 linkages that connect the springs to the control column will experience rotational forces (i.e. torque) any time the stick is not centered laterally. There's nothing to oppose the rotational forces other than the friction/tightness of the one bolt that connects the C-606 linkage to the control column (that also connects the F-665 pushrod). So there's potential here for the bolt to loosen and the linkage to start rotating. Or worse, the bolt could eventually come completely loose and the F-665 pushrod would disconnect from the control column. Not a robust design, and failure here could be catastrophic (loss of aileron control).
I raised this issue to Van's. Initially they acknowledged my concern, but qualified it with the usual "[my paraphrase] but we've got hundreds flying and we haven't heard of it being a problem". Still, tech support passed it on to engineering. Next time I corresponded with them however, their message was CYA lawyer-ese, basically "no comment".
To cover my own "A", I won't make any recommendations here on how to fix it. But what I plan to do on my airplane is to redesign the C-606 linkage so that it connects to the control column through both bolts. That way the shear strength of the bolts opposes rotation, rather than relying on friction/tightness of one bolt.
I don't know if Van's is taking this issue seriously or not. But if they don't issue a service bulletin, I would suggest that anyone installing the electric aileron trim should study and evaluate the safety of the design for themselves.
The geometry is such that the C-606 linkages that connect the springs to the control column will experience rotational forces (i.e. torque) any time the stick is not centered laterally. There's nothing to oppose the rotational forces other than the friction/tightness of the one bolt that connects the C-606 linkage to the control column (that also connects the F-665 pushrod). So there's potential here for the bolt to loosen and the linkage to start rotating. Or worse, the bolt could eventually come completely loose and the F-665 pushrod would disconnect from the control column. Not a robust design, and failure here could be catastrophic (loss of aileron control).
I raised this issue to Van's. Initially they acknowledged my concern, but qualified it with the usual "[my paraphrase] but we've got hundreds flying and we haven't heard of it being a problem". Still, tech support passed it on to engineering. Next time I corresponded with them however, their message was CYA lawyer-ese, basically "no comment".
To cover my own "A", I won't make any recommendations here on how to fix it. But what I plan to do on my airplane is to redesign the C-606 linkage so that it connects to the control column through both bolts. That way the shear strength of the bolts opposes rotation, rather than relying on friction/tightness of one bolt.
I don't know if Van's is taking this issue seriously or not. But if they don't issue a service bulletin, I would suggest that anyone installing the electric aileron trim should study and evaluate the safety of the design for themselves.