On April 15, 1984, a Cessna 140 (registration N89984) was involved in an aviation accident near Aurora, CO. This summary draws on records from the U.S. National Transportation Safety Board (NTSB) historical archive.
An aircraft departed the runway after a sudden ground loop during landing. Investigation revealed the left gear leg had collapsed due to a sheared pin with signs of prior fatigue.
What happened
The pilot reported that the aircraft experienced a sudden ground loop while attempting to land. During this event, the airplane departed the paved surface of the runway.
The investigation
A physical examination of the wreckage indicated that the left landing gear leg had collapsed at some point during the accident sequence. Investigators located the pin associated with the left gear leg and found it to be sheared. Examination of the failed pin revealed a dark discoloration on the outer one-third of its diameter, indicating where the final failure occurred.
Findings
The evidence suggests that the structural integrity of the landing gear was compromised prior to or during the impact with the runway surface. The presence of discoloration on the shear pin points to a progressive failure mechanism rather than a sudden overload at the moment of touchdown.