Accident Summary
On May 21, 2010, about 1600 Pacific daylight time, a Schweizer G-164B AgCat, registration N3633C, operated by Sunrise Dusters, Inc., veered off the runway during landing and came to rest in an irrigation ditch near Robbins, California. The pilot, a certificated commercial pilot, sustained serious injuries. The airplane, used for agricultural aerial application, had departed Robbins about 1530. Visual meteorological conditions prevailed; no flight plan was filed.
Sequence of Events
During the flight, the pilot noticed that the right brake pedal was stiff. He observed what appeared to be hydraulic fluid leaking on his foot, possibly from the parking brake valve. Attempts to set and release the brake to correct the stiffness were unsuccessful. The pilot radioed ground personnel about the brake problems and indicated his intention to return to the airfield.
During landing, as the right wheel touched down, the airplane pulled to the right. The pilot attempted to steer back left, but during the correction felt a wind shift. The airplane veered left, departed the runway, and came to rest in an irrigation ditch.
Damage and Examination
The airplane sustained substantial damage to both wing spars, the propeller, and the main landing gear struts; a large quantity of soil entered the engine intake. The right brake calipers separated from the airplane and were found near the initial touchdown point of the right main landing gear tire.
Examination by an FAA accident coordinator revealed that the right wheel's inboard flange had separated from the inboard wheel half. The tire (a tube type) remained inflated; the expanded tire pushed broken flange pieces into the brake disc assembly. The brake disc attach points were bulged and stressed. The FAA inspector opined that the wheel flange failed in-flight, causing a locked brake pedal feel.
The installed tire was size 29x11.0-10, whereas the proper size for the wheel assembly (part number 40-101) was 8.50-10. The type certificate holder noted that some operators had obtained field approvals for oversized tires.
Regulatory Response
Following the accident, the FAA issued Special Airworthiness Information Bulletin SAIB CE-11-06 on December 15, 2010, recommending that operators using oversized tires acquire an STC or field approval with FAA-approved data, including flight test requirements and structural analysis. The bulletin referenced FAA Advisory Circular AC 23-17B and Safety Alert for Operations SAFO 10007 for guidance on installation, inspection, and maintenance of oversized tires.