We have experienced unrepairable damage to many aircraft transmission oil return lines. The suspected damage was created by the oil line making contact with the transmission oil filter housing drain plug.
The FIX
It was corrected by identifing a nutplate manufactured into the transmission deck located just below the drain plug. The nutplate was filled with proseal to prevent water intrusion and was not being utilized. After cleaning the nutplate, a common 1/4 inch panel screw was used to secure the oil line with a #10 hose clamp. A washer was also used between the clamp and transmission deck to prevent the oil line from contacting the deck.
