As flap cables seem to be a hot topic I can affer the following (my CPA post)
Just had a 337 arrive at the door with a broken left hand flap operating cable. The cable snapped just at the bellcrank and resulted in one flap up and one fully down on final, nearly causing a serious accident.
At the flap bellcrank in a 337 the cable takes a very sharp bend. We pulled the opposing operating cable even though it looked ok in situ, this cable when bent revealed that the heart strands were broken and also heading for a failure.
Cables look as if they have been there for a long time, dont have the logs at the moment so cant confirm that.
Suggest that operators of higher time 337's look at this area by undoing the operating cable at the bellcrank.
Would be interested if anyone else has experienced this in a 337, cable was gal and does not show signs of corrosion. As a precaution we have replaced all of the flap cables, removed and greased the bellcrank bushes, rod ends and flap rollers.
The picture on 337 site of Freds flap cable show that it is worn and could be heading for a failure. I strongly suggest that 337 owners of higher time (5k+) undo the cable at this location and inspect it. Because of the bend in the cable the wear is in the heart strand and inside of the cable and not visible in situ. Freds pic shows that the cable is not wound as tight in one location indicating that the heart strand could have serious wear and possible break. For those not up on cables these are 7x19 superflex 1/8 cable, this means the cable is made up of 7 bundles of 19 strands. At a sharp bend like this the middle or heart strand cops most of the wear and will eventually break, this accelerates the wear on the bellcrank side as now only 6 of the 7 bundles takes the load.
I can send photos that I sent to the CPA to show the cables if you are interested.
Fred if you are out there please e mail me to discuss your cable as I believe it is defective.
Aircraft Engineers Associates