On August 29, 2019, at about 1900 Alaska daylight time, a tundra tire and tailwheel-equipped Piper PA-22 airplane, N7236D, sustained substantial damage following a partial separation of the left main landing gear near Talkeetna, Alaska. The certificated flight instructor and certificated private pilot receiving instruction were not injured. The airplane was registered to Christianson Lake Rentals Maintenance LLC and operated by Alaska Floats and Skis, under the provisions of Title 14 Code of Federal Regulations Part 91 when the accident occurred. Visual meteorological conditions prevailed, and a company flight plan had been filed. The flight departed Talkeetna Airport (PATK), Talkeetna, Alaska. According to the operator, while dragging an off-airport landing site, the flight instructor heard an audible "pop" and noticed a partial separation of the left main landing gear. They returned to Talkeetna, conducted a fly by and were informed that the left main landing gear was loose. During the ensuing emergency landing, the airplane ground looped and sustained substantial damage to the fuselage. An initial examination of the airplane revealed that the aft left weld-on fuselage landing gear fitting had separated at the weld area from the fuselage. A photographic visual examination of the fractured weld surfaces by the National Transportation Safety Board (NTSB) Materials Laboratory revealed an unacceptable weld filet profile, which included incomplete fusion, a lack of penetration, and gross porosity in the weld deposit. The NTSB Materials Laboratory examination report is in the public docket for this accident. The closest weather reporting facility is Talkeetna Airport, (PATK), Talkeetna, Alaska. At 1853, a METAR from PATK was reporting in part: wind, 200° at 4 knots; visibility, 5 statute miles, smoke, haze; sky condition, overcast clouds, 4,600 ft; temperature, 66° F; dew point 45° F; and an altimeter setting of 30.08 inches of mercury.