Rusty,
All prebuys raise additional questions. That's why we do them! The airplanes value is determined by how easily and accurately these questions are answered. Unfortunately, Your question cannot be easily answered, because of incomplete aircraft records, and this significantly lowers the aircrafts market value.
To answer your question, you must realize that none of the internal structure on 150's/152's was primered with Zinc Chromate (green paint) at the factory. The green primered components you found in the internal wing structures are proof positive that at least one wing skin was removed for access to these components. "Plane rebuilt" is insufficient in the extreme to answer any questions about this work, may indicate other repairs were made to other areas, and may even be intentionally deceptive. It is common practice for technicians to primer replacement sheet metal components, or modifications, before installation. It is arguable that these components may have been replaced due to corrosion, but it is more likely there was improperly documented damage history. In this case, it is unlikely that just the spars were replaced or repaired. A detailed inspection should reveal other replaced components, probably also primered, such as leading edge skins, ribs, rib caps, stringers, strut attach points, etc.
Are you sure you meant spars? Did you mean ribs? The only time I ever saw just the spars replaced on a 152 was following an extremely hard landing that actually flexed the wings enough to bend the spars at the strut attachment points. There were damaged rivets at the upper skin overlap areas, but the rivets were replaced and the skin was re-useable. There was also a detailed inspection of the gear mounting, which required partial dissassembly and repair of that structure. Did 'your' student pilot land hard? Did he take out a couple of small trees? Who knows?
All that said, this may still be a good solid airplane now, but the logs have to be considered incomplete at this point, and that diminishes the worth of the aircraft as far as resale goes. I'd get my $500 back and walk away. There are too many good airplanes (with good records) at this price. If he wants to knock a bunch off the price (at least as much as you stand to loose at resale time) You can still enjoy this plane as much as any other, at lower initial cost. You will have to plan on replacing the radios at some point in the future!
If you proceed, I would make the sale contingent on your mechanic completing an annual inspection, with emphasis on determining the extent and quality of previous repairs. You are just paying for the inspection phase. The owner pays for additional repairs that affect airworthiness. If he declines, he pays for the inspection and you walk away! You both agree to this in writing beforehand. You can negotiate minor discrepancies that you want repaired. Your technician's evaluation of the previous repairs should be fully documented in the aircraft logs, and 337's filed documenting any major repairs missing from the FAA records you ordered. Your tech may not be willing to do this, if he feels he cannot verify the completeness, quality, or airworthiness of the repairs. He may require partial disassembly as necessary for access, or even redoing the repair himself. You should talk to your tech about this now, before pursuing the purchase further. If your tech can't or won't sign off on the next annual, making the logbooks right in the process, or it becomes cost prohibitive, the whole deal is dead!
Carl
