Canadair CL-600-2B19Comair, Inc.

The scheduled commercial passenger flight returned to the departure airport after the number two engine's low pressure turbine module separated from the engine and departed the airplane while climbing through 3,000 mean sea level and 4 nautical miles from the airport. Examination of the B-sump forward scavenge screen revealed that the entire screen area was blocked with coke including several metallic flakes, the largest of which was 1/3 inch by 1/3 inch. The screen was also partially collapsed. An oil sample from the B-sump forward scavenge line was black and contained black particles. The B-sump aft scavenge screen was estimated to have been approximately 90 percent blocked and contained some metallic flakes. An oil sample from the B-sump aft scavenge line was black and contained black particles. The C-sump forward scavenge screen contained a block of about 75 percent with coke. The center portion of the screen was clear. The C-sump aft screen was 5 percent blocked. The oil filter contained black particles and black oil. The impending bypass button on the oil filter was popped.