Looking for Flap Cables
 

Anyone know of another source for flap cables besides Don Nieser or Cessna? Don is out and Cessna has them but, well you know.

Thanks Ed

You might check with your local FBO and see if they will do a search on ILS for you. That is usually pretty successful.

Or have your local FBO make up a new set for you - the hardware can be ordered (from Spruce, I think).

Thanks for the help. I ordered the cables through cessnaparts.com. They should be here in a day or two.

Ed

My shop removed the flap cables from one wing today. Here is what was found. The cables looked fine before they were removed. They looked fine when they were in our hands but you could clearly see a bend in the cable where they were running across the sharp turn on the pulley. Untwisting the cables in our hands revealed one broken strand and when my mechanic cut the cable and completely unraveled it, two or three more broken strands were apparent.

My mechanic was concerned enough about what he found that he mentioned he was going to file a "Service Difficulty Report." I'm not really sure what that all means but he did mention it. I did not get the impression that he felt the cables were anywhere near failure but he and I are happy they are out.

I am certainly no cable expert but two things were apparent to me today. The wear process in the cables was clearly underway and the process begins on the inside of cables.

Based on what I saw today, an external examination of the cables on the airplane could have never revealed what was found after the cables were removed, and twisting an intact cable after it is removed from the airplane makes it difficult at best to see the inside of the cable. Unraveling the cable after it was cut (and obviously destroyed) is when the best look could be had.

My airplane is a 1973 337G with 2480 hours total time.

When the other side comes off I will report the findings.


Ed Asmus

Ed
Photos would be a great help and maybe what is involved in accessing these cables would help the readers too.

Hey Herb,

I've been reading your signature line and as a helicopter pilot myself find it rather ridiculous.

BTW, there are several classic/vintage helicopter fly-ins held around the country, Rotorfest will be coming up soon in PA to name one.

Sorry for getting off topic.

I'll work on photos.....It will be a few days before I can get them.

Signiture changed, just having a little fun. I really do like helicopters :-)

I really like Herb's siglines - some of them are deceptively shallow, yet obviously deep - for the most part (some of them).

I have nothing major to report on the flap cables from the other wing. They looked just like the first set. There was nothing obvious from the outside and we did not bother to take the time to cut them open figuring the worst case would be a few broken strands like the first set.

I do have a photo of the first set that I will post here shortly but I left the camera somewhere else and will not have it back until this weekend. I have never posted a photo so if anyone has any advice I am all ears. I can say that I have seen pictures on this forum of other people's flap cables and some of them were very alarming looking to me. The cables that were removed from my airplane did not display wear patterns that looked anything nearly as bad as some of the scary pictures that were posted on this forum. My wear patterns were not nearly as advanced as some of the other photos but mine were in the same location as those photos revealed.

Thanks Ed

Here is the photo my flap cables.....

This thread interested me.

GUYS PLEASE DO CHECK THESE CABLES!

One of these snappped in exactly that spot at the tight corner it makes next to the pulley, invisible to usual inspections. I wasn't flying myself. The cable snapped while the pilot was turning onto finals from a left hand circuit. the RH flaps immediately popped up and Left side remained set on full. You can imagine a fairly good roll rate commenced to the Right. Luckily the plane started banked to the left, pilot guessed the problem, reached straight for the flap control and selcted up. Luckily the Left flaps retracted. result was a safe landing (with 5 scheduled traffic passengers on board).

I checked the one the other side which also had many broken strands and we replaced both.

Unfortunately we don't operate in the sort of environment where we file official service difficulty reports!

I will heartily second that recommedation: Check your flap cables at the next annual, if not before!! We just finished an extensive 100-hour inspection on2697S under the expert supervison of Aeromx (who comes on here occasionally). As a result of info he and I picked up at the final CPA 337 seminar in Santa Maria earlier this year, we wanted to specifically inspect this seldom looked at area. What we found was bad; one cable frayed and the other with completely broken strands.

Needless to say, they were replaced at the cost of a week or so of additional down time and a lot of hard work by Aeromx, but it was a find I was glad we made. And an SDR report is being made to the FAA. Maybe Tim (Aeromx will get on here with more info; he has some pics of the frayed/broken cables.

Joe

African 337,

Do you happen to know how many hours were on the plane, and if the flap cables have ever been removed for inspection (if so, how many hours ago?). What year and model 337 was it?

Hi Paul,

It is a 1969 Model C337D. Total time around 9000 hrs. Used to be N86439 if anyone out there knew it in USA! No idea on previous history of the cables. The problem is mainly a design one as the cable makes a sharp corner right my the long nipple and this is all around the back out of sight so only if your engineer uses a torch and missor and knows where to check will he see anything but in truth you'd be best to unmount that end of the cables and have the carefully inspected. We were lucky. Could easily have all ended in tears.

Flap Cables
 

I'm pretty certain there is a Cessna SB on these. The sharp bend around a smallish pulley is the culprit. The procedure for checking them is simple.

Take a rag, and wipe the cable. If it snags anywhere, you have a broken strand. If you have a broken strand on the outside, you undoubtedly have many on the inside. Waste no time, replace the cables. Both of them.

As others have pointed out, this should be part of the annual inspection that your IA performs.

The only way you can check these cables is to remove them at the bell crank. A flashlight and mirror doesn't usually show the frayed cable. I've attached a picture of where they fray. Hope this helps.

African 337,

Thanks! We have similar aircraft - we're flying a T337C. You are correct in that the only way to inspect the cables is to remove them. There are two per side which hold the flaps DOWN - these, of course, are the critical ones. There is also one cable per side to hold the flaps UP - these are much less of an airworthiness concern where a cable breaks in flight.

Once the four important DOWN cables have been removed for inspection, one might as well replace them. The cable and end connectors can be easily had, and then the only thing one needs is an A&P with a big swedger, and voila! four new fabricated cables for not much money.

I've heard of one operator of several 337s in Australia who does this routinely every year with his fleet of 337s.

I agree as well. Removal is the only way to inspect these cables. A visual inspection tells only a small portion of the story. It is better than nothing but probably not adequate.

Ed

Pics of JChronic's 1969 337D Inboard Flap Cable damage (x2) as found at 100hr/Annual Inspection - See attached.

As has already been noted by others you CANNOT see the affected areas of these cables with REMOVING them from the bellcrank. You MUST remove them for proper inspection. We replaced all 6 flap cables with new stainless cables and re-rigged the entire system per the service manual. The cables were tough to find but managed to find 5 out of the 6 we needed from 5 different sources. Had to have the last cable made/fabricated by Beechhurst Industries in NY (Ph: 718-468-1565). They can make most flight control cables under a Mil-Spec part number thereby eliminating the need for an STC or field approval....log entry only needed. The cost of the fabricated cable from Beechhusrt was the same as if I could purchase it from Cessna or other sources if it was available.

Let me know if anybody has any questions or needs any help.

- Tim/Aeromx

Great job!

Excellent photo's.

Ed

Thankyou to all who have contributed to this issue, I spent time with Don Nieser a couple of months ago in which he took me through the flap cable issue.

The photo's are a great help and add completion to understanding the issue at hand, will replace all wing cables regardless over Christmas.

Regards
David

If this was previously reported, please forgive the repetition. I talked with a missionary flyer last Sunday who reported a 337 crashing during this last year in Copan Guatemala (if I recall the location correctly). This was described as a fairly short, up-sloping runway - sounded challenging. It was probably a short field landing. Upon flap extension, only one flap extended but the other didn't. The aircraft commenced roll and impacted a deep crevasse just short of the runway. There were six souls on board; all survived, apparently un-injured or with only minor injuries.

The missionary, an extremely experienced bush pilot, blamed himself for not reacting faster in retracting the flap(s) to restore control.

The account I heard may have been in error regarding the failure sequence - perhaps the flaps were already extended when one snapped up.

A semi-happy ending for all except the unfortunate airplane. And a reminder for us all to be primed to quickly retract the flaps and add full power in case of un-commanded roll. This makes it important to have props forward and mixtures full rich when turning final, before extending full flaps.

Should we have the props forward and mixtures full rich whenever we extend any flaps at all? Or maybe do this turning base, instead of on final? This assuming we're close to sea-level flying a normally aspirated Skymaster.

Because some of the info on this thread did not conform with earlier knowledge, I spoke to Don Nieser about checking the cables.

It's true that a thorough visual and cotton swab/rag inspection may not detect a cable that may have a few broken strands, but we believe that it will allow you to make a determination on whether the cable is sound or should be replaced.

The fact that there are 100 or more strands and the typical design margin lead us to believe that a cable inspected thoroughly (visual and cotton swab/rag) and found to have no broken strands is good for continued service until the next annual.

I would add that it's not a bad idea to include this in your landing checklist: Flaps up immediately if aircraft rolls.

Ernie

For what it's worth, the reason I made my comment is because I've changed flap cables myself, I'm an AME here in Canada,. On one Skymaster, visually inspecting the cables before they were removed showed nothing. Once removed one cable had around 40-50% of the cable strands broken. There was no way of seeing this. With half the cable strands broken I question how much strength is left in the rest of the cable.

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.

Ernie

just a thought - i would think that cycles induce wear, base on that theroy low time and
less cycles would produce less wear. with one exception, some a/c had sheet metal screws that were too long and rubbing on the cable. year back i checked that and mine were. just replace the screw with a shorter one. it did not indicate any wear or broken strands; but that
was with 800.0 now it's 2000.0.

one could always drop the flaps well below the 160 maybe at the low end to reduce cable
tension and you really don't need them on takeoff, just a thought.

cost of the flap cables?
 

Thanks for this great info everyone. N2125X is just going in for annual and I will likely ask them to remove the flap cables for inspection based on this. Curious as to what the cost was for replacement cables?
Brian

As best I can tell, I spent $1,200.00 for all the cables and 10 hours of labor to do the job. Labor was another $770.00. So about $2000.00 for the entire job in September of 2009.

Ed

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.

Flap Cable Replacement - Broken Internal Wires
 

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

Flap Cables Needed
 

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???

Flap Cable Source
 

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

Good Luck,
Tim / Aeromx

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

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

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

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

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

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

Ernie