Looking for Flap Cables

[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

[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.

[Gord Tessier]

Hi All, My guy Bob Evans at Eaglerock Aviation can make up these cables. He is an AMO (Aircraft Maintenance Organization) up here in Canada and he does all the work on my aircraft. He also has over 500 hours on Skymaster's and knows the a/c really well.
Bob has all the specialized equipment to make these cables up.
He can be reached at 905 684 4612.

[hharney]

I have removed and replaced the cables that connect inboard bell crank to the outboard bell crank. This is cable -8 or -308 for stainless. When the visual inspection was performed while the cables were still on the aircraft, there were no concerns found with the cables. Using a mirror, camera and q-tips the cables appeared to be in good shape with no indications of concern.

Removing the right wing side first and never have performing this task took about 2 hours. Being as careful as possible not to damage the cable during removal proved to be challenging. Although when the left side was removed it was much easier having done the right and knowing what to expect and what position the flaps should be in.

Upon inspecting the cable once it was on the bench the inboard side of the cable did not indicate any concerns but the outboard end did have a broken strand on the outside of the cable where the cable made the sharp bend around the bell crank. This broken strand was on the inside of the bend or the portion of the cable that touched the bell crank. It was detected by touch, as a finger glides along the cable in only one direction. Feeling the cable toward the fitting at the sharp bend there was a broken stand detected. See first photo.

Then on the inboard end of the same cable, where no detection of concern was felt or seen, the cable was twisted and opened to view inside. After vigorously bending and twisting a single strand was found broken. The question is, did the aggressive inspection cause the strand to break? See second photo.

Then the cable was cut and unraveled to reveal the broken strand inside on the inboard end. See third photo.

The cable on the left side once removed, revealed the same exterior strand broken on the outboard sharp bend. This strand could be felt by gliding a finger toward the fitting at the inside exterior of the sharp bend. No concerns were recognized from the inboard side of the left cable. The forth photo shows the left outboard end of the cable with the strand detectable by finger.

The last photo is the left cable, inboard end, that looks and feels clean with no worries. No other cables have been cut or twisted to inspect inside. More on that later.

The original (1968) cables that were removed appear to be stainless type. The only method of determination performed was using a magnet to detect the differences of the old cables vs. the new cables that were purchased stainless (-308). With this information would there have been concern that these cables could have had a catastrophic failure? This is the 6 million dollar question that really can't be answered but I have to believe that these cables removed would have provided many years of service without failure. This is my own opinion and only goes that far. This aircraft has 3000 hours total time and has spent the largest part of it's life in the desert west. It has no visible corrosion inside the wing areas. All other flap components look and work fine. If and when the cables are cut and there are any discrepancies found I will post them here.