LAX97IA209

The aircraft experienced an uncontained left engine failure during the initial climb after takeoff. The flight returned to the airport, and an uneventful landing was made. The engine was removed and returned to the repair facility that performed major repairs just 76.9 flight hours prior. During the teardown examination, the No. 5 bearing inner race retaining nut oil supply holes were found plugged. According to the Pratt and Whitney Standard Practices Manual, the procedure for the plating of silver over steel specified that the No. 5 bearing race should have been grit blasted to remove old plating per Service Process Operations Procedure (SPOP) 10, which specified use of PMC 3052-9 aluminum oxide grit. The SPOP consumable materials list identified PMC 3052-9 as 500 aluminum oxide grit. The actual processing of the nut included grit blasting with 120 grit aluminum oxide, contrary to P&W recommendation to use 200 to 500 aluminum grit oxide media or glass beads. The nut was to be cleaned and flushed after the blasting.

History of flight

On June 17, 1997, about 1701 hours Pacific daylight time, a McDonnell Douglas MD-83, N875RA, operated by Reno Airlines of Reno, Nevada, experienced an uncontained left engine failure during the initial climb from Las Vegas, Nevada. The flight was operating as flight 516, a scheduled flight to Colorado Springs, Colorado. The aircraft received minor damage, and there were no injuries to the 140 passengers and crew of 5. Visual meteorological conditions prevailed for the departure and an IFR flight plan was filed.

During departure from runway 25R at 1,000 feet agl, the crew heard a loud noise followed by a left engine vibration and subsequent shutdown. An emergency was declared and the aircraft returned for an uneventful landing.

Postincident inspection of the engine revealed that the engine had experienced an uncontained internal failure with penetration to the cowling and minor damage to the fuselage.

Engine information

The No. 1 (left) engine was a Pratt and Whitney JT8D-219 turbofan. At the time of the incident the engine had accumulated 20,039.0 total hours and 16,057 cycles.

The engine had accumulated 76.9 hours and 56 cycles since it was repaired at American Airlines Maintenance and Engineering Center, Tulsa, Oklahoma, following an ice ingestion incident on March 14,1997.

A postincident examination of the engine was conducted again at the American facility. An external examination revealed that the engine had four holes in the combustion chamber fan ducts just forward of the High Pressure Turbine (HPT) plane of rotation.

An internal inspection revealed that the HPT shaft had separated at the No. 4 1/2 bearing hole scavenge oil holes, which were elongated away from the direction of rotation.

The oil holes in the No. 5 bearing inner race retaining nut were found plugged with a hard, black colored material. The assembly sheets for the No. 5 bearing area do not have specific instructions to check the holes in the inner race retaining nut. The sheet has a general instruction at the top of the sheet that states, "NOTE: BEFORE ASSEMBLY BE SURE PARTS ARE CLEAN AND BLOW OUT OIL PASSAGES. OIL MOVING PARTS BEFORE ASSEMBLY."

The No. 5 bearing inner race retaining nuts in the American inventory were examined. Of 17 nuts awaiting assembly, one had several oil supply holes plugged.

The Pratt and Whitney (P&W) standard practice manual for overhaul plating (SPOP) of silver over steel specifies that the No. 5 bearing race should be grit blasted to remove old plating per SPOP 10, which specifies using PMC 3052-9 aluminum oxide grit. The P&W standard practice manual of consumable materials list identifies PMC 3052-9 as 500 aluminum oxide grit.

The actual processing of the incident nut consisted of grit blasting with 120 aluminum oxide grit, contrary to P&W recommendation to use 200 to 500 aluminum oxide grit media or glass beads. The nut is to be cleaned and flushed after the blasting.