An Airworthiness Concern Sheet was filed on June 29th by the FAA concerning cracks at the tail post. I spoke with the FAA representative Keith Noles who is the contact person on this ACS and deals with issues with Piper aircraft. The subject aircraft was a PA18-135 in the Netherlands, you can read the report below. Seems there were several cracks found during a tear down for recover. I asked about evidence of corrosion, when it was last recovered, year model and if it was stored outside. I suspect this is an L21B that was built in the 1950s. Will post when I find out ore details. Having repaired a lot of fuselages I have seen a lot of corrosion in this area and some cracks, most that corrosion were a major contributor. Will be interesting to hear other's comments on this subject.