NTSB Identification: CHI05IA116.
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Scheduled 14 CFR operation of TRANS STATES AIRLINES INC (D.B.A. American Connection)
Incident occurred Thursday, May 19, 2005 in Kansas City, MO
Probable Cause Approval Date: 07/25/2007
Aircraft: Embraer EMB-145LR, registration: N814HK
Injuries: 54 Uninjured.

NTSB investigators used data provided by various sources and may not have traveled in support of this investigation to prepare this aircraft incident report.

The airplane sustained minor damage as a result of an uncontained failure of the left engine. Examination of the airplane revealed that the left engine's fan spinner was completely missing, and the forward fan blade retainer was missing a 90-degree section of the bolt flange. Several pieces of the fan spinner were recovered within the cowl. The NTSB's examination of the fan blade forward retaining ring revealed features indicative of overstress failure which originated on the forward face adjacent to a linear impression. The length and location of the linear impression corresponded to the corner on one of the bolt lugs on the aft side of the spinner. The linear impression contained evidence of fretting damage. The inside radius between the retaining ring's raised lip, and the flange was within the range specified by the manufacturer. The spinner's bolt lugs had a sharp outside corner where the spinner would interface with the radius on the retaining ring. The forging drawing for this part did not specify a radius; however, a manufacturer's representative indicated that an engineering drawing for the spinner specified that exterior corners have an edge break with a radius between 0.005 and 0.020 inches. The combination of the radius on the retaining ring, and the sharp edge on the aft side of the spinner, resulted in an interference when the parts were assembled. The manufacturer's examination of the retained parts indicated the presence of high cycle fatigue on both the spinner and the fan blade retaining ring. Three dimensional finite element analysis of the fan spinner, and forward fan blade retaining ring predicted a reduced low cycle fatigue life. As a result of this investigation, the manufacturer initiated a one-time, on-wing eddy current inspection of all the one-piece fan spinners to be accomplished within 18 months or 2,000 hours. The manufacturer also initiated a re-design of the fan spinner, and indicated that the one-piece fan spinners will be removed from service by the end of 2010.

The National Transportation Safety Board determines the probable cause(s) of this incident to be:

The fatigue failure during cruise flight of the fan spinner and forward fan retaining ring due to an interference between the mating parts resulting from the inadequate design by the manufacturer.

Full narrative available

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