NTSB Factual Report

On February 27, 2002, at 0601 central standard time, a Canadair CL-600-2B19, N991CA, operated by Comair, Inc. (d.b.a. Comair Airlines) as flight 5266, received minor damage during a failure of the number two engine during climbout from runway 29 (6,501 feet by 150 feet, concrete) at the Outagamie County Regional Airport (ATW), Appleton, Wisconsin. Visual meteorological conditions prevailed at the time of the accident. The 14 CFR Part 121 passenger flight was operating on an instrument rules flight plan. No injuries were reported. The flight was en route to the Cincinnati/Northern Kentucky International Airport, Covington, Kentucky.

The flight crew reported that there was a vibration while in a climbing turn through 3,000 feet msl and 4 nm from the departure end of runway 29. The flight crew shut down the number two engine and returned to land without further incident at ATW five minutes later.

On-site investigation of the airplane in Appleton, Wisconsin, revealed that the low pressure turbine (LPT) module had separated from the engine and departed the airplane. The LPT module was later recovered in a farm field about 4 miles from the airport. Airframe damage was limited to some scratches on the vertical stabilizer and a small puncture in the right hand stabilizer leading edge. The engine was removed from the airplane and shipped along with the LPT module to the Comair maintenance facility in Cincinnati, Ohio.

The airplane was powered by two General Electric CF34-3A1 dual spool, high-bypass turbofan engines incorporating a single-stage fan and fourteen-stage high-pressure compressor (HPC), which are driven by a 4-stage LPT and 2-stage high-pressure turbine (HPT), respectively. The engines have a normal takeoff thrust rating of 8,729 lbs and a maximum takeoff thrust of 9,220 lbs.

According to company maintenance records, the engine was received new in May 1997 and had not been overhauled. The engine accumulated 9,121.6 hours since new (TSN) and 9,317 cycles since new (CSN). The last shop visit occurred on December 27, 2001, at Comair's Cincinnati facility.

General Electric has issued two Service Bulletins (SBs), CF34-AL SB 79-A0014 revision 1 dated August 23, 2001, and CF34-BJ SB 79-0015 revision 1, dated August 23, 2001, which introduced an initial and repetitive inspection program to prevent potential B-sump oil events due to B-sump scavenge screen blockage. The Federal Aviation Administration (FAA) issued Airworthiness Directive 2001-19-02, dated September 10, 2001, that mandated the B-sump scavenge screen inspection and cleaning procedures. According to Comair records, the inspection required by the AD was last complied with on December 27, 2001, during a 500-hour inspection at a TSN of 8,714 hours and a CSN 8,885 cycles.

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.

Since the incident, General Electric Aircraft Engines has issued two additional Alert SBs, CF34-AL SB 79-A0016 and CF34-AL SB 79-A0017. These SBs provide instructions to either replace or rework the B-sump scavenge screen fittings located at the forward and aft end of the lube and scavenge pump assembly. The rework will remove the screens to prevent B-sump oil release events that result from coke blockage of the screens. The new replacement fittings do not have screens. These new SBs are being mandated by the FAA and will provide a terminating action to the repetitive inspection requirements of AD 2001-19-02.

Documentation of the engine was performed by the Powerplant Group Chairman's report which is included in the docket of this report.

The FAA, Bombardier, Comair, and General Electric were parties to the investigation. The Canadian Transportation Safety Board was the designated representative to the investigation.

NTSB Probable Cause

The separation of the low pressure turbine module due to coke resulting in the blockage of the oil system.