On February 27, 2005, about 1543 Alaska standard time, N6174D, a ski-equipped Piper PA-22 airplane, converted from a nose wheel to a tailwheel configuration, sustained substantial damage when the left main landing gear collapsed while landing on the frozen Lake Hood Seaplane Base airstrip, Anchorage, Alaska. The private pilot/airplane owner and the sole passenger were not injured. The 14 CFR Part 91 local personal flight operated in visual meteorological conditions without a flight plan. The operator of the airplane was the pilot/owner. During a telephone conversation with the NTSB investigator-in-charge on March 1, the pilot related he had landed on the ice to the east, and was turning the airplane to the right to taxi to his parking spot, when the left ski dug in and the right wing came up. The left main landing gear subsequently collapsed, and the left wing struck the ice. The pilot related that there were no preaccident mechanical problems with the airplane. The extent of the damage to the airplane could not be determined until April 1, when the airplane was partially disassembled for repairs. Two NTSB investigators examined the airplane, and discovered substantial damage to the fuselage crossover tube near the left main landing gear attachment cluster. The aviation mechanic repairing the airplane noted that he had to cut a portion of the steel tubing from the crossover tube, and make repairs by welding a thicker tube piece into the void. Other portions of the gear attachment cluster had strengthening steel splices added by welding. The mechanic noted that an FAA Form 337, Major Repair or Alteration, would be completed for the repair work.