What happened
While climbing through 12,000 feet after takeoff, heavy black smoke entered the cockpit of the aircraft. In response to the smoke, the pilot declared an emergency and performed a successful landing at a nearby airport. The crew was not injured.
The investigation
A post-flight inspection identified that the left side turbocharger clamp had separated at the root of a spot weld through the tensioning band. Microscopic examination of the area surrounding the rim of the spot weld showed a crystalline appearance. Further analysis performed on a spot weld from the right turbo-charger clamp revealed the presence of small recrystallized austenitic grains.
Maintenance records indicated that the engine was installed in March 1991, and the turbochargers were replaced in June 1999. During the June 1999 replacement, the existing turbocharger clamps were reused. Under current regulations, the only requirement for replacing these clamps is a mandatory replacement during an engine overhaul.