On April 10, 2006, at approximately 0800 mountain daylight time, a Cessna 170B, N2831C, was substantially damaged when the airplane taxied into a hangar without an occupant on board at Havre City Airport, Havre, Montana. The commercial pilot was not injured. The pilot/owner discovered the airplane's battery had discharged over the winter months, and was attempting to start the airplane by hand propping it. The pilot reported that he had set the parking brake, and that the right brake failed during the starting procedure. The outboard two feet of the right wing was bent and wrinkled, and the right flap was pushed into the fuselage. The Cessna 170B maintenance manual states that a discharged battery should be charged on the ground before attempting flight. The Federal Aviation Administration’s Flight Training Handbook, AC 61-21A, states: "It is recommended that an engine never be 'hand propped' unless a qualified person thoroughly familiar with the operation of all the controls is seated at the controls and the brakes set."