Looking for Flap Cables

[Ernie Martin]

I see only 3 part numbers in the 1965 IPC figure and parts table (relevant parts shown below). Note that in the table the penultimate column is "units per assy" and it shows 2 inboard actuator cables (item 8), 2 outboard actuator cables (item 9) and one return cable (item 27). This is confusing to me, because I interpret "assy" to mean wing and I only see one of each actuator cable per wing. And if "assy" means "aircraft", I'm still confused because it looks as if each wing has its own return cable, so 2 should be listed per aircraft (not one), unless the return cable is super-long and reaches out to both wings. Anyhow, if you're working in this area, the number of cables should be evident.

Ernie

[billsheila]

Thanks Ernie. Here is a real basic question...looking at this parts sheet, seems like there were two choices (?) either standard cables which I presume are regular steel or stainless steel. I wonder, is stainless stronger in straight tensile strength...just my assumption...but maybe more brittle and likely to fail in the application here of an extreme bend. If my basic metallurgic assumptions are right, would regular steel maybe be better choice than stainless in this application? Anyone know what would drive the choice between whether to use the stainless versus regular steel -- why are both in the parts manual choices?

Thanks

[Ernie Martin]

Based on discussions on this forum, I believe the consensus is to go with stainless. I believe that the principal cause of failures is corrosion. In later models, although the IPC still shows both regular and stainless, I think the factory installed stainless and there has been either no failures or far fewer failures than with regular cables. But this is my recollection and I could be wrong. Hopefully others will jump in here and elaborate.

Ernie

[billsheila]

Thanks Ernie...probably while you were typing your reply I was on the phone with a fellow at Beechhurst, who was quite helpful. He was crystal clear in his advice that given a choice, go with regular steel cables over stainless. He said the failure mode of these cables is "work hardening" and not corrosion typically (unless in some very specific and unusual applications) and there is no question that regular steel is the way to go. He quoted all kinds of examples (different aircraft) where fleets were having exactly this issue with stainless cables (he kept calling it "CRES" cable for Corrosion Resistant Steel) and where the fleet operator switched to regular steel and solved their ongoing maintenance issues. He mentioned Cessna Caravans as one that came to mind, but he had others. In doing a little more research via my good friend google, came upon this:

http://www.mechanicsupport.com/aircr...able_wear.html

[Ernie Martin]

Both pieces of information are excellent. I think this seals it: choose standard steel, which I assume is galvanized.

Ernie