ANC93IA188

A 28 ounce duck was ingested into a JT9 turbofan engine of a B747 on takeoff, impacting and breaking the 10 ply fiberglass fan spinner. Downstream engine destruction followed. Engine manufacture and FAA was aware of a number of previous bird-strike failures with this spinner. New and stronger 20 ply spinners are being phased in; however, thin spinners are still in use on JT9 engines in commercial service.

On September 25, 1993, at 0835, Alaska daylight time, a Boeing 747-200, N629US, experienced a partial power loss after it had ingested 28 ounce Gadwell duck into its number one engine during takeoff rotation at Anchorage International Airport. The pilot in command shut down the affected engine, dumped fuel and landed without further incident at 0911. The airplane was operated by Northwest Airlines on a regularly scheduled cargo flight to Tokyo as NW Flight 905, under 14 CFR Part 121, on an international IFR flight plan. Visual meteorological conditions existed. A flight crew of 3 were the only persons on board, and they were uninjured. Damage was limited to the number one engine and the event was classified as incident damage.

The pilot told NTSB and FAA investigators that while he noticed waterfowl in the area on taxi out, he did not see birds at the time he experienced the engine failure. The airplane reportedly weighed 752,000 pounds at takeoff and dumped 84,300 pounds of fuel while orbiting at the direction of ATC. The landing gross weight was approximately 628,000 pounds. Investigators found blood and material resembling feather parts in the number one engine inlet. Damage was seen to the rotor blades of the fan, inside and outside of the inlet cowl. The fiberglass spinner cone was destroyed. No wing or fuselage damage was seen.

The engine damage was examined by Northwest Airlines with the assistance of Pratt & Whitney. The NTSB was advised that failure was due to downstream ingestion of fiberglass spinner parts and pieces of first stage fan blades.

The NTSB investigator contacted Pratt & Whitney at East Hartford Connecticut. The powerplant investigator at P&W told the NTSB that there "were a limited amount of 10 ply fiberglass spinners out there." He said that "P&W was aware of about one inflight failure per year with these thin spinners from bird strikes." He also said that he and the FAA had discussed it and didn't feel that an AD (Airworthiness Directive) was necessary, but that they were watching the numbers (as an in-house study). He also said that these were being replaced with a newer model spinner that had 20 plys, and there were no known instances of inflight failure known.

The findings of the investigation were forwarded to the NTSB's Engineering Division ((AS-40). On October 4, 1993, the NTSB NW Field Office was advised that the Engineering Division was reviewing the information for possible safety recommendation activity.