Beech spar carry-through woes.

Note:  To decrease your download time we have made these pictures thumbnails.  Just click on any picture to see a larger version of it.  Use your browsers back button to return.

AD 90-08-14 on Barons and Travel Air aircraft, as well as AD 95-04-03 on the Bonanza and Debonair, discusses inspecting for cracks on the main wing spar carry-through frame.  Once cracks are identified, they are classified for repair or re-inspection.  This time, we have a 55 Baron in the shop for repair per Beech Kit 58-4008.

This area is the left forward web.  The crack can be seen coming out of the upper large row, outboard huck bolt.  The size of the repair doubler is determined by the size and extent of the crack

The huck bolts are removed as needed, and several rivets are also removed.

The repair doubler is rough cut and initial holes located.  Extreme care is taken to ensure the doubler is well fit to the radius of the existing bulkhead.  We then mark the old huck bolt holes from the inside of the structure, remove the repair doubler, and drill pilot holes from those marks.

The repair is put back into position and secured, then we back-drill the holes to assure they are in the correct location.  After that, they are reamed to proper size.

Once all the attach holes have been located and sized, the adhesive is applied, then fasteners are installed.  High-strength close-tolerance bolts replace the huck bolts.  Where a hard rivet can be installed, it is.  There are some cherry rivets installed to the face of the bulkhead, as access is non-existent.  Up the side of the flange, cherry rivets can be used, but we find a much better repair is made by substituting in MS27039 screws with washers and lock nuts.  If the wing was off, we could use hard rivets, but wing removal would be overkill for this!

All repair fasteners are installed; floor structure, wiring, and other items removed for access are reinstalled.