Looking for Flap Cables

Originally Posted by Ernie Martin

Tony, that changes everything. Question: it was a thorough visual, with flashlight and cotton swab/rag? And showed nothing, no fraying of the cotton? If that is the case, then I retract my prior message, and I'm sure Don would too.

In this particular case we were changing the cables on spec. It was a few years ago so I can't remember the exact details. If I recall correctly, I gave them a visual inspection and ran my finger over what I could access and didn't find any problem. Once the cables were removed we were quite surprised to see them as bad as they were.

When I did my skymaster it was pretty much the same thing. Although the cables weren't frayed as bad.

[SkyMac]

Hi Everyone

Just keeping you all informed on what I find as we continue with the project, there has been a lot of information recently regarding flap cables and replacement.

Having just removed cables and bell cranks from L/H wing in preparation for replacing the cables. Even though the flap cables functioned and showed little signs of wear prior to aircraft dissasembly, a small number of internal wires were broken - TTAF 1958hrs. No record of previous replacement.

Regards
Dave

[hharney]

I cannot find any part #1460100-307 flap cable. Don has none and all the Cessna sites are out of stock. Does anyone know of any available???

[Aeromx]

Try Beechhurst Industries in Whitehurst, NY. They can legally fabricate the cables you need. Talk to Frank. www.beechhurst.com

Good Luck,
Tim / Aeromx

[billsheila]

Would someone with access to a parts manual happen to have the part numbers for all 4 cables? If it matters my machine is 1965 serial number 0031. Thanks. I am intending to contact these guys in NY as well...I wonder if we can get into some group buy opportunity where they come off a bit against Cessna prices?

Thanks,
Bill

[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

[hharney]

Originally Posted by hharney

I cannot find any part #1460100-307 flap cable. Don has none and all the Cessna sites are out of stock. Does anyone know of any available???

Checking the steel part number it is available. The stainless steel is out of stock but steel is available.

[billsheila]

Herb; Do you know when they say "carbon steel" if that is by default a galvanized steel cable (like the article on wear differences discusses?). I found some early failure reports from a Canadian website that discuss failures on 336's (per what you mentioned to me before) and these were the carbon steel variety not the stainless steel, so it would seem that perhaps either one will fail? Here is one way to look at it, that if these are simply high wear items that have a known failure mode (apparently with either type of steel) then one might as well just replace them often and use the cheaper part! On that point, I seem to be getting odd price data, even on the carbon steel variety. I had one quote where the
"-8" variety were like $175 and the "-7" were multiples of that at $534 both apparently available. This doesn't make sense because perhaps other than length they have the same fittings on them etc. I can't imagine it costs hundreds of dollars more for 50 inches of longer carbon steel cable? When I spoke to Beechhurst, they claimed there was nothing wrong legally with using their replacement cables (and they had appropriate paperwork to verify proper mil-spec construction) and they are made to order in either carbon steel or stainless steel, but you can't order them directly they basically make them to match what you send them as replacements. If you end up ordering from Beechhurst let me know and I will order a carbon steel set alongside yours. Thanks. Bill

[hharney]

While doing the inspection on the flap cables the idea came up to photograph the cable and then take the opportunity to zoom in on the photo for a closer detailed look. Anyone have any thoughts on this method?

I am having a very difficult time trying to find a visible issue that indicates the cables are compromised. I understand that it is difficult to detect the possible broken strand without removing the cable. I question if once the cable is removed and inspected could the strands break while inspecting? With the cable in such a tight bend for so many years does the opposite bending for inspection break the strands?

Did the known failures of these flap cables give any indication of problems before they failed? Was the maintenance documented and were the cables inspected to the degree that these photos reveal? Do the cable just fail or is there visible compromising of the material before it happens?

[hharney]

[quote=billsheila;18169]Herb; Do you know when they say "carbon steel" if that is by default a galvanized steel cable

Label "Carbon Steel" does not indicate that the material is galvanized. Galvanizing is a process of applying a coating not the type of steel.

[billsheila]

Herb; Agreed galvanizing is applied. I wonder though if all aviation grade carbon steel cables are by default (or spec)' galvanized? The previous link I attached certainly seems to indicate that galvanizing reduces wear of the type that leads to failure.