On July 11, 1998, a Let BLANIK L-13 (registration N49CC) was involved in an aviation accident near Hammonton, NJ. Investigators recorded the probable cause as: The shock absorber was improperly serviced, being full of fluid instead of the correct mixture of half fluid and half 468 psi nitrogen, which caused it to act as a rigid device and transfer landing loads directly to the airframe structures. This summary draws on records from the U.S. National Transportation Safety Board (NTSB) historical archive.
A glider pilot reported a firm landing with a bang and scraping noises. Post-landing inspection revealed structural damage around the nose landing gear, traced to a shock absorber overfilled with fluid, making it rigid.
Incident Overview
A glider pilot executed a landing to the runway, describing the touchdown as "firm" and noting a "bang" along with scraping noises during the landing and rollout. Following the event, an examination of the glider’s airframe disclosed significant structural damage in the vicinity of the nose landing gear.
Mechanic's Findings
A certificated airframe and powerplant mechanic who performed the subsequent repair work documented his observations in a written statement. According to the mechanic, the shock absorber was found to be "full of fluid instead of half fluid and half 468 psi nitrogen." He stated that this condition resulted in the shock absorber functioning as a rigid device. Because the device had been improperly serviced at some point in the past, it transmitted landing loads directly to the adjacent structures rather than dissipating them, leading to the observed damage.
Probable cause
The shock absorber was improperly serviced, being full of fluid instead of the correct mixture of half fluid and half 468 psi nitrogen, which caused it to act as a rigid device and transfer landing loads directly to the airframe structures.
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