On July 18, 1993, approximately 1132 hours central daylight time, a Champion 7KCAB, N11AT, piloted by the owner/operator, crashed while maneuvering in the traffic pattern at Hill City Municipal Airport, Hill City, Kansas. The airplane was destroyed. The commercial pilot (front seat occupant) and private pilot (rear seat occupant) received fatal injuries. Visual meteorological conditions prevailed for the local flight, no flight plan was filed. The banner towing flight operated under 14 CFR Part 91, and originated from Hill City, exact time unknown. The commercial pilot and his private pilot-certificated wife had travelled from their hometown of Russell, Kansas to celebrate his father's 80th birthday. The morning of the accident the pilots flew the airplane locally, towing a banner which read "Happy Birthday Max Super." Police records indicate the pilots were airborne towing the banner at least 22 minutes before the accident. Witnesses reported the airplane made a low pass (estimated 10 feet above the ground) along Runway 17 at the Hill City airport, and dropped the "birthday" banner. They stated the power increased and the airplane began a climbing left turn. One witness estimated the airplane reached about 50 feet above the ground when the engine "stalled." Witnesses stated the airplane banked further left, then nosed down steeply into the ground. The airplane impacted terrain on airport property, approximately 150 feet south-southeast of the runway. Several witness statements were obtained from participants in a golf tournament held at the Hill City Golf Course the morning of the accident. The golf course is located south of the Hill City airport. One tournament participant stated: "The pilot banked hard left as if to avoid...the golf course." Other witnesses speculated the pilot may have been trying to return to the runway. A commercial pilot/witness reported he assisted the couple with the banner tow operation the morning of the accident. He indicated the pilot successfully picked up the banner on the third attempt. He stated: "Each...pass was made by reducing the throttle (power) to the...poles, then adding power at the anticipated pick-up point. Each time the power was added, the engine coughed or sputtered slightly." Other witnesses reported the airplane engine had been running rough, intermittently coughing and sputtering, throughout the day. Witness statements and police records are appended. Postaccident examination revealed no evidence of preimpact mechanical malfunction. The engine was removed from the airframe and installed on a test stand for a run-up. The FAA Inspector stated "...the engine turned over twice, fired and began running. It ran rough, but exhaust and intake manifold pipes were crushed...the engine was run up to 1800 RPM and it seemed...it could have run...higher, but this was not done due to unknown engine conditions." An Inspector's statement is appended. An autopsy was conducted on July 18, 1993, by Dr. Daniel G. Odom, M. D., Staff Pathologist at Hays Pathology Laboratories, 1300 E. 13th Street, Hays, Kansas, 67601. The autopsy report is number A-21 1993. A copy of the Toxicological Report is appended.