NTSB Identification: CHI96IA125.
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Scheduled 14 CFR (D.B.A. SIMMONS AIRLINES )
Incident occurred Wednesday, April 03, 1996 in TRAVERSE CITY, MI
Probable Cause Approval Date: 12/15/1997
Aircraft: ATR 42, registration: N421MQ
Injuries: 36 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.

During landing rollout, the left main landing gear collapsed, and the aircraft skidded to a stop. Examination of the landing gear revealed that the barrel lugs (used to attach the swinging lever to the main landing gear barrel) had failed. The fracture of the outboard lower lug exhibited clam shell marks typical of a fatigue crack. The fatigue crack emanated from a corrosion pit in the bore of the lug. The four bushings for the lower lugs of the barrel (replaced during overhaul) did not have the proper interference fit. The bushings did not have the proper applications of corrosion preventative applied to the surface of the bushings. Primer paint had not been applied during overhaul, and Mastinox was used instead of the wet primer that the manufacturer's procedures specified. During the course of the investigation, nine landing gears (with various numbers of total cycles since overhaul or manufacture) were inspected. The inspections revealed torn or missing rubber sealant used on bushing flanges, corrosion in the lug bores, and corrosion on the lug faces.

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

improper use of procedures by maintenance personnel at an overhaul facility during overhaul of the landing gear, allowing corrosion to occur on the barrel lugs of the landing gear, which subsequently led to fatigue cracking of the lugs and eventual collapse of the gear.

Full narrative available

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