Socata TB9 Tampico Loose Rivets In Vertical Stabilizer During the preflight inspection for a local training flight, blind rivets located halfway up the vertical stabilizer were found to be making aluminum oxide trails (smoking) on both sides of the vertical fin. This condition is indicative of a potentially loose rivet or cracked inner rib. Manufacturers service bulletin 10-083 requires this type of blind rivet at this location. The submitter suspects other aircraft may have the same issue. Part Total Time: Unknown Piper PA-31-350 Navajo Failed Starter Driver Gear The crew noted the number two engine starter would not engage. When the cowlings were removed, several pieces of metal were observed. On removing the starter, the Bendix drives engagement gear had disintegrated, damaging the drive housing. Part Total Time: 80 hours. BEECH Model B60 Duke Cracked Fuselage Stiffener During an annual inspection, a fuselage stiffener (p/n 60-410025-51)-located under the nose baggage floor on the right side at station 67 between the main and standby inverter-was found cracked around the Hi-Lok fastener holes. Removing the stiffener allowed further inspection of the keel (p/n 60-410025-601), revealing cracks in the web previously obscured by the installed stiffener. The mirror-image stiffener (p/n 60-410025-49) on the aircrafts left side revealed similar cracks with no damage to the keel. Part Total Time: 3004 hours BEECH Model V35 Bonanza Frayed Ruddervator Control Cable During inspection, a technician discovered a ruddervator cable with frayed and broken strands. The failure was located behind the instrument panel, about 10 inches above the bobweight, (p/n 35-521242-13). Part Total Time: 2801 hours BEECH Model 58 Baron Charred Cabin Heater Fuel Pump Smoke in the cockpit and an electrical burning smell were observed after the gear was retracted on takeoff. Inspection revealed a charred heater fuel pump (Facet model 70893). The heater had been operating for approximately 30 minutes before takeoff. This is at least the third burned pump in a fleet of 11 similar aircraft. Part Total Time: 1935 hours CESSNA 421 Golden Eagle Cracked Turbocharger Clamp During a scheduled progressive inspection, technicians found a four-inch crack along the left engine turbocharger-to-tailpipe clamps (p/n 227450) circumference. The same p/n clamp on the aircrafts right engine was found cracked seven hours earlier. Part Total Time: 1366 hours