inspected mine and the push tubes showed signs of scraping on the inspection plate screw (only on the outter end) cables were ok. there is additional clearance on the inner push tube end and with shorter screws it has over an inch of clearance; however the otter push tube end there is very little clearance. the inner inspection cover on mine has the top center and top right screw holes adandones and small strips of alum. are riveterd in place to clamp on both sides were the tinnerman fitting were, so no rubbing is possible. however the otter cover does not and uses all screws. if you swap cover and use the inner on the otter you will have clearance (also swap the unused tinnerman clips on the otter area and place them in the abandon holes on the inner area. also make sure the screw are short enough to give clearance but ennough to hold. also i spray ac150 corrosion all over the interior every year so all cables and pulleys are always lubericated (two benefits in one application)
thank you for the pictures submitted it made it very easy to locate the areas, great job!!!!!!!!!!

Flap Cables
 

I've been changing cables on our 337's and thought ya'll would be interested in the results.
One with 3200 hrs 4 of the 6 were frayed -@ 6 to 8 strands
One with 2000 hrs 3 of the 6
One with 3000 hrs 1 of the 6
Kim

So what do you think, guys? If one were going to pre-emptively replace the flap cables, would one only replace the 2 inboard cables (which run from the motor to the inboard belcranks), or all six?

Paul

From the condition of the cables I've removed from our planes, I would change them all at @ 3000 hrs. You have to take them out to inspect them. When removing the cables I found it much easer to remove the pullies and leaving the cotter pins that keep the cable on the pully in place.
Hope this helps
Kim

Perhaps the cable strands are breaking because of the extra drag caused by the push rods rubbing on the inspection panel screws? Or, is there any extra stress on the cables for lowering the flaps at 140mph vs 100mph?

Personally, I think it is good to visually inspect. But wear items like this should be time/cycle limited. Aviation is only 100 years old. This is the first time in its history that 40-50 year old metal airplanes are flying with no manditory parts replacement times -- i.e., no contiued airworthiness instructions as newer airplanes have. I don't think Mr. Cessna ever envisioned that his airplanes would fly for 30, 40, 50, 60 + years, but they are. I asked Cessna, thru an email, what was the designed service hours/life of a 172; they never answered back. My guess is because they never considered it during its design.

This forum, and others like it, is a God's send. We are our own tech support, and are sitting at an historic aviation crossroad. That crossroad is: "How long can you fly an airplane before it just falls out of the sky?"

Old thread, new broken cable.
 

All, during my 337 refurb project, we just put the wings on and were routing the flap cables when I discovered my inboard flap cables (specifically called out in the above) also showed broken strands exactly where this issue was identified. I strongly recommend folks look at this area next time their aircraft is opened up or has the rigging touched.

1460100-7 is the part number.

Guys this is a really old thread but all good

I replaced my flap cables back in 2010 and found several with broken strands that could not be seen until you removed them and bent the cable back.

The reason for broken strands is not load related, but has everything to do with the bell cranks. There is a sharp 90 degree bend in the cable when the flaps are actuated and this continued bending to this extreme force will eventually break the strands. I don't know if these cables would ever fail because there are so many strands that are still attached. However I had my cables out for inspection and had new ones in stock so why not put the new cables in the wings. Personally I think it would take a long time for the good stainless cables to fail. The failures in the field have been on older 336 and early 337 that had the non stainless steel cables and were in high humid environments. It's just peace of mind to check these but be sure to have new ones on the shelf so once you take the originals out you can replace with new, don't put the old ones back in service.

P337 stainless flap cables
 

I'm trying to find as much info on this issue but can't really find it. Does the stainless flap cables have less of a chance for for strands breaking over regular steel cables? Have almost 5000 hours on this P and thinking about at least replacing the two. We have stainless already.

Most cables today are Stainless Steel and that is because of corrosion not broken wires or strands. I would venture to guess that every Skymaster out there has probably got a broken strand or wire and this is not from stainless steel cables but from the design. Because of the radical bend in the design this is what breaks the wires or strands. Back in the day of 336 and maybe early 337 some failures of flap cables could have been from corrosion. With the stainless cables this should be eliminated. For my own peace of mind, I replaced mine just to know for sure what kind of shape they were in. Just have new cables ready to install because you won't want to put the old cables back in once you see the broken wires or strands