On August 8, 1999, a Weatherly 201B (registration N197SK) operated by Richard E Shaw was involved in an aviation accident near Oberlin, KS. Investigators recorded the probable cause as: Engine failure due to an undertorqued carburetor fulcrum screw. Contributing factors were the muddy terrain and the low altitude of the aerial operation. This summary draws on records from the U.S. National Transportation Safety Board (NTSB) historical archive; 1 related events involving the same aircraft type or operator are linked below.
An airplane conducting an aerial application lost engine power and impacted a muddy field. Examination of the Bendix NA-R9B carburetor revealed chatter marks on the fulcrum screw and float pivot pin, with a broken safety wire and insufficient torque on the fulcrum screw.
Event
During an aerial application operation, the airplane experienced a loss of engine power and subsequently impacted a muddy field.
Carburetor Examination
Post-impact inspection of the Bendix NA-R9B carburetor revealed chatter marks on the fulcrum screw and the carburetor float pivot pin. The fulcrum screw was removed after being turned one-half of a turn. Additionally, the safety wire securing the fulcrum screw was found broken.
Maintenance Specifications
The technical overhaul manual for the NA-R9B float carburetor specifies that the fulcrum screw should be torqued to a value of 100–120 inch-pounds.