Never heard of such a thing. What makes a welder “Aviation Certified”? Do they have a piece of plastic in their pocket similar to a Pilot Certificate?
In Canada, that's the way it is. The welder must have a ticket.
https://tc.canada.ca/en/aviation/re...section-57104-canadian-aviation-regulations-3
Those seats are regularly repaired by Acorn Welding in Edmonton, Alberta. I had several of that sort repaired. They cut off the old leg and weld on a new one made by them. They have Transport Canada certification for that repair.
The cracks have two causes: the slot was cut and left rough at the factory. Rough, sharp edges are prone to cracking, and in thin aluminum tubing it happens easily. The other cause is us big, heavy pilots and passengers sliding in and out of those seats, side-loading those legs and bending them a bit until they crack.
That seat has other weaknesses. The adjustable seat back has a couple of small clevis pins that ride on thin steel cams rotated by a hand crank through a threaded rod and bellcrank. Those clevis pins wear, and I have found them more than half-gone. Imagine them failing--if one goes, the other is getting all the load and could also fail immediately--and the seat back flops back just as you're accelerating in the takeoff roll. You will tend to haul back on the controls to pull yourself up. Crash.
The seat height adjustment uses another threaded rod through an aluminum nut. It seldom gets any attention or lubrication, so the nut's threads wear until they suddenly give out and drop you to the bottom of the range. Might be serious for a short person.
