I am just getting the parts together. We changed some of them last year but this time we will do the rest.
However, doing some looking around, it seems clear that almost nobody does this.
There is no specification on the springs according to which they could be checked for stretch, etc.
OTOH isn’t there an argument to just leave them, because the new spring could be defective?
Which springs are we talking about ?
Metal springs have pretty good useful life, rubber & gas springs, not so good …
All of them, potentially.
Peter wrote:
However, doing some looking around, it seems clear that almost nobody does this.
And why would they? As long as there is no corrosion and the springs are not over-tensioned – which should not be possible inside the gear mechanism – they have near infinite life. Just think about the springs under the valves in your engine: They are actuated 50 times per second for thousands of hours. Your gear springs see less actuations over the life span of your plane than the springs inside the engine in five minutes of idling…
A metal spring is normally designed for infinite life. Bit it could be overloaded (stretched or compressed to much), corroded, worn by abrasion, high temp could destroy it. If there is no chance of it being overloaded and no corrosion or abrasion, why change them?
Actually this reminds me of the first year at the University in a course about metal structures. Metal springs do break from time to time, and the reason can be dislocations in the metal matrix. These dislocations are at an atomic level, and there are billions of them in any piece of metal, just part of nature. These dislocations wander around in the metal at random fashion when metal is stretched and compressed repeatedly. Statistically there is an incredibly small, but statistically proven chance that a whole bunch of them get at right position at the right time, thus the metal is weakened enough so it breaks. I have never heard about this since, so the problem is probably more of the academic funny kind than a practical one 
Interesting….
The advice to replace the landing gear springs periodically comes from the owner of the Socata owners’ group. There is possibly a little bit of evidence supporting such a policy, although it is IMHO more likely that practically all gear problems are caused by lack of maintenance which is a huge issue everywhere.
However if there is any corrosion then the spring should be replaced, because corrosion introduces surface defects which can propagate inwards.
I can’t find anything in the TB20 MM regarding spring replacement but then I don’t know where to look – it is a massive PDF and not properly searchable because the pages were scanned and then OCRd by ATP when they got it…
Peter wrote:
However if there is any corrosion then the spring should be replaced, because corrosion introduces surface defects which can propagate inwards.
Certainly. Some years ago a spring of my car’s suspension broke due to corrosion. Luckily while the car was parked, because the bottom end of the spring “speared” the tire below. That wouldn’t have been funny on the motorway…
Since the springs on your plane are probably rather inexpensive parts which are difficult to check for corrosion it is certainly no mistake to replace them from time to time.
what_next wrote:
on your plane […..] rather inexpensive parts
Somehow, I doubt that…
