On August 9, 1984, an Aeronca 7AC (registration N83233) was involved in an aviation accident near Prineville, OR. Investigators recorded the probable cause as: The improper grinding of the crankshaft journal, which resulted in a fracture near the number two crankthrow. This summary draws on records from the U.S. National Transportation Safety Board (NTSB) historical archive.
A pilot experienced a sudden loss of power and heard engine chatter while maneuvering, forcing a landing in a field. Investigation found the crankshaft broke due to improper grinding.
What happened
While the aircraft was being maneuvered, the pilot reported hearing a loud chattering noise originating from the engine, which was immediately followed by a significant loss of power. In response to the mechanical failure, the pilot reduced the remaining available power and initiated an emergency forced landing in a rough barley field.
The investigation
A post-accident examination of the aircraft revealed that the engine crankshaft had fractured near the number two crankthrow. Further technical analysis determined that the journal surface was improperly ground, which likely contributed to the structural failure.
Probable cause
The improper grinding of the crankshaft journal, which resulted in a fracture near the number two crankthrow.
Frequently asked questions
What happened in the 9 Aug 1984 Aeronca 7AC accident near Prineville, OR?
A pilot experienced a sudden loss of power and heard engine chatter while maneuvering, forcing a landing in a field. Investigation found the crankshaft broke due to improper grinding.
What aircraft was involved and where did it happen?
The accident on 9 Aug 1984 involved an Aeronca 7AC, registration N83233, at Prineville, OR.
What was the probable cause of the accident?
The improper grinding of the crankshaft journal, which resulted in a fracture near the number two crankthrow.
A SkyWalk Join't 3 paraglider crashed into the ground near Las Vizcachas, Chile, on September 1, 2024. The pilot and passenger sustained serious spinal…
PARAPENTE (ULTRALIVIANO NO MOTORIZADO)·2024-09-01DGAC Chile
A Cessna 172N struck electrical cables while on final approach to land at Aucó Aerodrome in Chile. The pilot was uninjured, but the aircraft sustained damage…
A Bombardier DHC-8-402 suffered a tail strike during landing at Puerto Williams on September 9, 2024. All 76 occupants were unharmed, but the aircraft…
A MYD JS-MD 3 glider veered off the runway and struck a wall at Vitacura Aerodrome on January 6, 2025. The pilot was uninjured, but the aircraft sustained…
A recreational paraglider flight in Puchuncaví, Chile, ended with the pilot sustaining serious injuries after a rapid descent and impact with a hillside on…
PARAPENTE (ULTRALIVIANO NO MOTORIZADO)·2025-03-29DGAC Chile
A Tecnam P2006T landed on its belly at an aerodrome in Poland after the crew failed to confirm landing gear deployment. The incident resulted in no injuries…