cable end failure - AD?

[flyboy1963]

I've searched, but can't find the reference to a recent post about crystalline failure of the 'rod end' of swaged cables ( like rudder cables)...or am I confusing this with the push-pull control cable advisory?
there were MS numbers to check for a bad batch.

anyone point me to the right place?

[Mike H]

The only recent AD I am familiar with regarding swaged cables is applicable to PA-28's. As I understand it in this scenario it is not so much about a crystaline failure due to impropery made terminal ends but corrosion and or failure of the galvanised cable strands in the swaged area adjacent to the terminal end.

[Alex Edwards]

There is an Australian AD for swaged cable fittings,rehabs that is what you are thinking of? refer to this thread:

http://www.vansairforce.com/communit...d.php?t=110632

[Mike H]

Looks like another regulatory knee jerk reaction to a problem that only exists in aircraft that are incorrectly inspected/maintained.

[CATPart]

Originally Posted by Mike H

Looks like another regulatory knee jerk reaction to a problem that only exists in aircraft that are incorrectly inspected/maintained.

How does one correctly inspect for this issue that cannot be seen? How does one correctly maintain against stress corrosion cracking?

[Mike H]

In this application I am not so sure this is "an issue that cannot be seen". The common factor in the reported failure of these cable terminal ends is corrosion. If the aircraft is taken care of properly (properly maintained) and the cable terminals are not allowed to severly corrode, then I don't feel there will be an issue.

Furthermore it preposterous to require a cable replacement due to calandar life only. Most life limited aeronautical products have a service life based on flight time or flight cycles which is determined through an engineering analysis. Usually the only parts that are calandar life limited are perishable items such as emergency batteries, explosive devices such as fire bottle squibbs, seals, O-rings etcetera. So will CASA require replacement when the cable reaches 15 years from date of manufacture, or date of installation? How does CASA conclude that replacing a cable when it reaches 15 years time in service for an aircraft that is not on an MSG-3 inspection program make sense, but if the aircraft is on a MSG-3 approved inspection program than a calandar life replacement is not necessary?

[CATPart]

Reading into the msg-3 methodology, I would conclude that since the cable is a critical flight system, it must be subjected to either some rigorous NDT at defined intervals, or perhaps even replacement at defined intervals. I am just making a guess here at how msg-3 could possibly cover this issue making it immune to the AD.

I guess my point is, SCC is a highly increased susceptibility to corrosion relating to material properties and sustained stress levels, like you would see in a swaged connection. Being an uncoated, unprotected (passivated?) surface, I just don't see how you maintain it other than looking at it. SCC can be visually undetectable at certain stages, and typically detected after the larger crack is found. Then material, environmental, and stress analysis usually aid to conclude the root cause SCC.

Either way, I am going to visually inspect my cables ends to the best of my ability, since they are at least 19 years old. I tend to agree with you that if a cable is progressively destroyed by corrosion and cracking, that you would expect some visual indicator. I have never heard of a cable failure on an old RV. Mine has lived in a dry environment its entire life, maybe that is a good thing.

[MarkW]

I do not remember seeing this in writing but it did effect one of our club planes just a couple of years ago.
I do not remember if it was the 172 or the Citabria.
We did replace the rudder cables at Annual due to this AD.