On May 29, 1999, about 1520 Alaska daylight time, an amphibious float equipped DeHavilland DHC-2 airplane, N30CC, sustained substantial damage while landing at the Lake Hood airstrip, Anchorage, Alaska. The airplane was being operated as a visual flight rules (VFR) instructional flight under Title 14, CFR Part 91, when the accident occurred. The first pilot, seated in the right seat, the second pilot, seated in the left seat, and the two passengers aboard were not injured. Visual meteorological conditions prevailed, and VFR company flight following procedures were in effect. During a telephone conversation with the National Transportation Safety Board investigator-in-charge on May 29, the first pilot, a certificated flight instructor, reported that he was providing turbine transition instruction to the second pilot. The accident airplane has been modified by the installation of a Pratt & Whitney PT6 turbine engine. The first pilot stated that during a previous flight that day the propeller governor control was causing "the engine to surge." The airplane returned to a maintenance facility where repairs were performed, and the airplane was returned to service. He added that about 45 minutes into the second flight, the engine again began to surge, and both pilots elected to once again return to the maintenance facility. The first pilot reported that just prior to touchdown on runway 31, while the second pilot was manipulating the controls, the engine again surged, and the airplane landed hard. In the Pilot/Operator report (NTSB form 6120.1/2) filed by the pilot-in-command, and during a later telephone conversation, he reported that during the previous landings, the second pilot failed to "carry power so as not to land hard again." The first pilot said that he then instructed the second pilot as to the differences of a turbine engine vs. a piston engine. He wrote: "I watched very closely until we were over the runway, and once again, quick as a cat, we stalled and hit hard." The airplane's fuselage sustained substantial damage. Wind conditions at the time of the accident were reported to be 120 degrees at 4 knots.