At 19:13 EDT, the right wing assembly of a Cessna 501 suffered damage when the airplane landed with the right main landing gear partially extended. The private pilot and his passenger were not injured. The pilot said he silenced the landing gear warning horn while en route then forgot to lower the gear before landing. Just prior to touch down the pilot attempted to lower the landing gear. The airplane touched down with the landing gear in transit, and the right landing gear collapsed.