control cable inspection

[Frank]

How difficult is it to do a thorough inspection of control cables during annual? I'm sure my IA looks at them, but are there suspect areas which might be hard to get to, and likely missed? The Aussie 15 year replacement AD doesn't apply to U.S. airplanes, but it does make one want to be sure...

[N3322G]

Have not had a failure but did have the cables speaking to me - hard to open cowl flaps, props that wouldn't stay synced, harder to move throttle etc
Replaced them all and had the power quadrant disassembled and cleaned - wow, what a difference! Props stayed synced, cowl flaps became a one-hand operation again and smooth throttles during landing. Nice and money well spent if you like to fly.

[Clarence Beintema]

I'm guessing that you're referring to flight control cables? The only way to be 100% sure is to remove them one at a time for inspection.

When I bought my 400, I replaced them all, some were corroded, but none had broken strands. The aileron cables which pass through the back of wheel well are prone to corrosion.

Clarence

[Ed Asmus]

Hi Frank,

My 59' 250 just came out of annual last month at Heritage Aero in Rockford, IL. I had a 10 minute conversation with Clint (the IA who performed the inspection on my plane) about exactly this topic. Though I agree that the only certainty would be replacement, as the last post indicated, Clint stated that thorough inspection of the flight control cable system is not difficult. After the conversation, I did feel confident that a failure in this system is very unlikely.

The statistics seem to support this conclusion. I do not recall reading any accident reports or articles stating a failure in this area as the cause. The Australian AD is quite interesting on this topic. I would be interested to know exactly why they instated it. The fact they require replacement on ALL aircraft at 15 years leads me to believe this was done as an abundance of caution as opposed to any specific safety threat. Anytime a government agency "paints with such a broad paintbrush," I become quite suspicious. That's just my opinion.

I would worry about the possibility of doing more harm then good attempting to comply with an AD of this nature. There is no system in any airplane more critical then the flight controls. Nothing else matters if they don't work right. I always fear after compliance, bigger problems when there were none before compliance.

I have complete faith in my shop at Heritage. If they tell me thorough inspection yielded no issues, that's good enough for me. Time will tell if they are right and time will tell if I'm right about doing more harm then good as the Australians start replacing all their cables.

Hopefully we hear more opinions about this thread from people on this forum, especially the Australians!

Thanks

Ed

[Frank]

Thanks, Ed... That's a very reasonable approach, I think. Since some airplanes have have had some corrosion and/or frayed cables, a comprehensive check seems in order. My local IA is good, but doesn't work on lots of Comanches, so I'd like to find some guidance in being sure to do a thorough check. I agree that doing more than necessary - i.e. total replacement - is likely to induce more problems than it solves.

[Clarence Beintema]

I respectfully disagree, there are areas in the wings which you can not see the cables. When was the last time the pilots side floor of your aircraft was removed? The back seat? The baggage compartment floor? All the flight control cables are run under the floor in this area. When I took the floor out of my plane I found a large nest surrounding the cables, many had areas of corrosion from mouse urine, hence replacement with new.

Clarence

[N3322G]

Agree with Clarence.

Flight control cables are 'easy' to inspect in the wing via the inspection panels and attach points however, unless the floor is up, you won't know. Be sure the IA looks up behind the panel. For 8 years a cross control cable was rubbing and cutting a corner off a radio. No damage to the cable fortunately, only the empty corner of the radio was sawed.

Taking out the interior is time consuming but something you can accomplish on your own if you pay attention to how to put it back together - if you are looking to save $. Taking extensive photos is also helpful for the next time. Look for metal shavings, metal powder, metal rubs - obviously, any frayed cable.

Hope this helps ... I'm a big trust but verify kind of owner.

[Ed Asmus]

HI folks,

Thanks for your comments and opinions. I hope we receive many more. It would be interesting to know the opinions of as many "maintenance experts" as possible regarding the Australian flight control cable AD.

Not being a mechanic myself, it is difficult for me as an owner to decide what maintenance is appropriate and what may not be. My profession is an air traffic controller in Chicago Center which I have been doing for nearly 25 years now. Suffice it to say, there are very few people who agree in the profession on what would be the "best" way to handle air traffic in Chicago. If you want to witness a spirited debate, put controllers in the same room, and pose this very question. Because of all my controlling experience, I have my own opinions. I feel I can logically explain (with science and math) why I feel this way, and I can confidently disregard the opinions of the folks who are just "way off" and have no ability to support their conclusions using "science and math."

Because I lack the same maintenance experience that I possess in air traffic control, I have no choice but to either obtain the same level of experience myself to develop my own opinions that I have confidence in (not likely to happen) or find people who earn my faith (Heritage Aero), and trust them. (Trusting people is not something that comes naturally to me. I'm a cynic at heart.) Though I have not been working with Heritage too long (about two years now), all the folks I meet there give me a good feeling on their judgments and opinions about maintenance and most importantly, why they feel the way they do. The "WHY" is the most important part. Having the backing of the ICS helps too.

Based on the conversation I had with Heritage about flight controls, my extreme hope is that they are correct. My life depends on it. I hope the ICS gets heavily involved in this potential issue as they did with the tail horn AD. We desperately need "science" to back the answer to this question. I personally need to be convinced there is an unacceptable level of risk continuing with the current cables (don't feel that way yet as I don't hear of our Comanches falling from the sky as a result of this issue) because I definitely feel there is substantial risk in messing with such a critical system if its not absolutely necessary. The Australians, in my little opinion, are not off to a good start applying the AD universally. That seems like the easy way out to me.

Clarence and Pat, to answer your questions, the few times I stopped to see the inspection of my plane in progress, the seats were out, at least portions of the the flooring was removed though I cannot recall exactly which portions, and they did inspect behind the panel and even made some adjustments there. I do recall everything being exposed under the back seat and aft of the baggage area. Unfortunately, I can't recall if the baggage floor itself was removed or the pilots side floor. Next time I'm there though, I will ask for sure. This is why I want the opinions to keep coming!

Thanks,

Ed

[Clarence Beintema]

As I stated earlier, if you want 100% assurance that your flight control cables are good you have to remove them for inspection. The aileron cables in the wing have areas which can be seen and just as many which can not.
Our control cables are mostly 7X19 steel cables meaning there are 7 bundles made up of 19 individual wires, other than the rudder cable which are 7X7.

Visual inspection while installed is really not sufficient, broken cable strands are not really visible unless the strand has left the bundle. Cessna maintenance manuals as well as the AC43 show inspection criteria which involves bending the cable into a loop to expose broken strands. Unless the cable is removed I don't know how you'll bend it into a loop?

I'm not sure what is in the Australian AD but I do recal something a few years back concerning broken brass turn barrels, Piper has a fairly recent SB calling for inspection of cable terminal ends as well as the brass turn barrel.

Clarence

[William Hughes]

I had the exact same issue as Clarence with my 250. It had sat for 10 years in a shed and the wings were full of mouse nests. Those critters secrete acid, apparently, as the aileron cables were corroded and frayed where-ever they went through the nests. All replaced.

[Ben Ayalon]

Many years ago, while I was an air-force engineer inspecting the cables was one of the 100h inspection. We had to remove all floors and panels and then to clean the cable with a cloth dipped with white spirit. While doing this we could feel if there are any broken strands as they would catch on the cloth. once this was done a visual check for corrosion was carried out. If none was found, the cable was checked for correct tension and then re-coated with some sort of a black paste that stops rust. We found damaged cables from time to time but there was no need to replace every time because the number of broken strands and the distance between them was a factor.

Regardless of what other people say and my own experience If I would have bought a 60 years old aircraft I would have replace all control cables.

Fly safe

Ben

[Phillip Graybar]

I just saw December Flyer mag:

I just completed my 12th owner assisted annual. One of my jobs is to remove the interior which means the front seats, seat rails, carpet, inspection covers. The the rear seat is removed and the tarp under the rear seat and the the rear hatch of the tail cone and finally the rear baggage compartment floor.

I have done this 12 times now. I thought this was standard for all annuals. Every year I get to see the cables front to back and side to side since I also remove all inspection covers under the wings. I have a 1960 pa24-180 and cables are fine. I looked and clean the cockpit floors and wells and cables every year.