Upon entering the pattern, the pilot was given instructions by the tower controllers he had not anticipated. In complying with the instructions, he altered his normal landing procedures, and failed to complete his before landing checklist. He subsequently landed the airplane with the landing gear retracted. The airplane sustained substantial damage to fuselage stringers and skin.
The National Transportation Safety Board determines the probable cause(s) of this accident as follows:
The pilot's failure to complete his prelanding checklist, and a subsequent inadvertent wheels up landing.