Elevator control cable termination

455 Bravo Uniform

455 Bravo Uniform

Final Approach
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455 Bravo Uniform
On a C152 (and other planes I suppose), the cable from the cockpit is connected to a bracket on the elevator by what looks like a ball on the end of the cable passing through a hole in the bracket, with the ball being bigger than the hole. How is the cable terminated (and what is it called) and can that sucker ever come loose from the cable?

Related question - when cables are rigged, I assume one end is fixed while the other is adjustable? How is the adjustment made (turnbuckle? Cable clamps? Other?).
 
The link (I'm not sure what the real name is) is stronger than the cable itself, so it won't come off.
 
455 Bravo Uniform said:
On a C152 (and other planes I suppose), the cable from the cockpit is connected to a bracket on the elevator by what looks like a ball on the end of the cable passing through a hole in the bracket, with the ball being bigger than the hole. How is the cable terminated (and what is it called) and can that sucker ever come loose from the cable?

Related question - when cables are rigged, I assume one end is fixed while the other is adjustable? How is the adjustment made (turnbuckle? Cable clamps? Other?).
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The terminal ball is swagged onto the cable. Yes, turnbuckles are usually used to tension cables. There may be centrally located turnbuckle(s) splitting the control cable into two (or more) segments, or turnbuckle(s) at one end of the cable using an eye end or fork end terminal. Cable terminal ends require proof-load testing after being assembled (swaged), to ensure integrity.
 
GlennAB1 said:
The terminal ball is swagged onto the cable. Yes, turnbuckles are usually used to tension cables. There may be centrally located turnbuckle(s) splitting the control cable into two (or more) segments, or turnbuckle(s) at one end of the cable using an eye end or fork end terminal. Cable terminal ends require proof-load testing after being assembled (swaged), to ensure integrity.
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Can the swagging degrade over time? Are they ever retested or replaced on a scheduled basis?

Gives me the chills (more than spiders) thinking of that tiny ball popping off...but I suppose that's uncommon?
 
I have never seen a terminal swag fail in service. I have seen them fail the proof-load test. I believe I commented about the need for proof-loading way back when TomD informed everyone he owned a cable swag tool. Cables are frequently replaced on airliners for discrepancies such as; rust, wear, broken wires and strands, found during routine inspections while installed. It is my understanding, all cables are removed and inspected at some heavy maintenance checks.
 
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Hope this helps
 
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I recently had a similar though during preflight when I saw the bracket, "that would suck if it gave way"

I would like to think I could land with trim alone if ever needed... hope I never have to try that out though!
 
Noun - swage.

Example: This type of connection is called a swage.

The swage tool has been checked for proper operation.

Verb - swage, swaging, swedged

Example:

Use the tool to swage the cable end.

He is swaging the cable end.

The cable end has been properly swaged.

Pronunciation: suh wedge

Hope this helps.
 
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Nicopress is a trade name for the process known as sleeve swaging. The type of swage used for aircraft control cable terminations is known as a ball swage. Both methods use a crimp tool that grasps the swage fitting and reduces its diameter to permanently affix it to the cable.

The sleeve swage, which can be made from steel, copper, cupronickel, aluminum, and alloys, is slipped over a cable and a tool is used to grip the sleeve circumferentially and crimp it to the cable. The sleeve can be a single barrel for one piece of cable or a double barrel, used to join two pieces together.
 
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Follow up question: we see planes advertised with "hangar rash repaired".

What happens when that hangar rash is on a control surface? Does the A&P doing the repair follow the control cables all the way around to look for cable and end damage? I'd imagine this would be a good idea, but maybe not necessary due to the strength of the cable and swaged ends as you guys clearly stated above (vs the crumpled thin aluminum control surface).

But...what about damage to the pulleys and their attachment points? That's the next weakest link?
 
455 Bravo Uniform said:
Follow up question: we see planes advertised with "hangar rash repaired".

What happens when that hangar rash is on a control surface? Does the A&P doing the repair follow the control cables all the way around to look for cable and end damage? I'd imagine this would be a good idea, but maybe not necessary due to the strength of the cable and swaged ends as you guys clearly stated above (vs the crumpled thin aluminum control surface).

But...what about damage to the pulleys and their attachment points? That's the next weakest link?
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Everything is up to the mechanic. You won't find any set rules on what needs to be looked at when it happens, no procedures in the manuals either.

Manuals may or may not even give enough details to determining if damage requires repair.
 
If the swage is done properly it should take the full rated strength of the cable. The swage is tested to 60% of the rating. If anyone needs to apply more than that in flight, there's something terribly wrong. Cable failures are rare, but if they happen it's normally because they've not been inspected properly and have been fraying or chafing or corroding for some time. I often find cables worn where they pass over rub strips or through fairleads; enough of that and the strands start breaking. I find corroded cables. I find pulleys seized way too often. Sometimes we find terminal hardware badly worn; think of the bolt that fastens that cable end to a bellcrank. Once in a while we'll find that someone has tightened that bolt so much that the cable end can't swivel on the bellcrank, and so it flexes the cable sharply at the cable's entry point into the fitting. That's a real good way to get a cable failure in short order.

The best insurance against cable failure is paying for thorough annual inspections by conscientious mechanics.
 
Thanks. Yeah, I was just talking about if a control surface is at the end of its travel and gets crunched in a bump against something, the elevator/aileron hinges, pulleys, etc may need to be looked at, but that's just a total guess from a total noob (depending on how tough or easy it is to crumple the end of an aileron that's already fully deflected vs the strength of the connected components).
 
455 Bravo Uniform said:
Thanks. Yeah, I was just talking about if a control surface is at the end of its travel and gets crunched in a bump against something, the elevator/aileron hinges, pulleys, etc may need to be looked at, but that's just a total guess from a total noob (depending on how tough or easy it is to crumple the end of an aileron that's already fully deflected vs the strength of the connected components).
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The control surface stops are found at the surface's bellcrank, usually. That prevents stress on the cables and the rest of the system if something gets hammered hard against the stop. It also allows full control surface deflection under flight loads; a stop at the control column would give up travel at the control surface due to cable stretch, pulley bracket movement, and so on. In most systems you can feel a certain amount of springiness once the control surface is at the stop and you keep turning or pushing the control.

On that 152 you fly, look at the elevator bellcrank--the thing that has the cables attached to it, right ahead of the rudder--and see how it contacts a couple of bolts. Those are the stops. Same for the rudder. The aileron stops are on the bellcrank inside the wing; just a push-pull rod connects the bellcrank and aileron. You can feel and hear the stops when moving the aileron.
 
455 Bravo Uniform said:
Follow up question: we see planes advertised with "hangar rash repaired".

What happens when that hangar rash is on a control surface? Does the A&P doing the repair follow the control cables all the way around to look for cable and end damage? I'd imagine this would be a good idea, but maybe not necessary due to the strength of the cable and swaged ends as you guys clearly stated above (vs the crumpled thin aluminum control surface).

But...what about damage to the pulleys and their attachment points? That's the next weakest link?
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Possibly, damage loads transfer through the system and structure. Got to know the aircraft you're dealing with.
 
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