I helped assemble an Alon A2A which had been shipped over from England about
2 years ago. Everything looked fine. A recent AD required a center section
inspection. During this AD I found a couple of suspicious bulges in the
lower spar cap. Upon probing them intergranular corrosion that had
penetrated the spar cap and progressed to exfoliation was discovered.

The elapsed time from assembly from the shipping container when everything
looked fine, to discovery of the corrosion was 1-1/2 years.

So this corrosion had been festering in the internal grain structure for
nearly 40 years before it came to the surface. When it did appear, the spar
cap had already been penetrated through and through.

The plane was beyond economical repair.

Cheers:

Paul
NC2273H