On September 4, 2023, about 1610 Alaska daylight time, a DeHavilland DHC-2 float equipped-airplane, N97EL, and a Bell 206L-4 helicopter, N193AL, were involved in a midair collision near King Salmon, Alaska. The airplane sustained minor damage; the pilot and six passengers were not injured. The helicopter was substantially damaged; the pilot received minor injuries. The airplane was operated as a Title 14 Code of Federal Regulations Part 91 business flight. The helicopter was operated as a Title 14 Code of Federal Regulations Part 135 on-demand charter flight. The airplane departed from the Brooks River about 1600 and flew north to the mouth of the American Creek on a return flight to a lodge on Enchanted Lake. The pilot broadcast a position report over the common traffic advisory frequency while crossing over the mouth of the American Creek and proceeded to fly along the right side of the creek at an estimated altitude of 800 ft mean sea level (msl). About five miles past the reported position, the pilot noticed the passenger sitting next to him looking across the cockpit to the left with a startled look. The pilot looked left and saw a flash of white. He never saw the helicopter before impact. The airplane was traveling at about 90 miles per hour (mph). The airplane was not equipped with ADS-B, nor was it required. The helicopter departed from King Salmon Airport (PAKN) around 1600 en route to Homer, Alaska. The helicopter pilot reported that, after departure, he climbed the helicopter to about 1,000 ft above ground level (agl) and was flying direct to Homer Airport (PAHO). The helicopter was traveling about 115 mph. As the helicopter passed under the airplane, the airplane’s propeller made contact with the helicopter’s tail boom and tail rotor drive system, which severed the entire tail rotor gearbox assembly from the tail boom. The helicopter subsequently entered a spinning, uncontrolled descent into the tundra and tree-covered terrain below. The airplane began to shake and vibrate violently. The airplane pilot then realized that the airplane had collided with another aircraft and he turned the airplane 180°. The right seat passenger reported to the pilot that a helicopter had hit the airplane and he saw the tail of the helicopter separate and the helicopter crash. The airplane pilot broadcast the downed helicopter’s location over the common traffic advisory frequency and began to direct other aircraft in the area towards the helicopter wreckage. The airplane pilot then made an emergency landing in a nearby river. The airplane sustained minor damage to the floats and propeller. The helicopter pilot reported that he was monitoring the local traffic advisory frequency at the time of the accident. The helicopter was equipped with ADS-B in and out. The pilot was also using a Stratus that provided ADS-B data from other aircraft in the area on a moving map display on his tablet. He did not see any other aircraft along or near his route of flight on the display. He added that he never saw the airplane and was unaware that his helicopter had collided with the airplane until after the accident.   The nearest weather reporting station, located 34 nautical miles west of the accident site, reported 10 miles visibility with few clouds at 3,500 ft agl. Neither pilot reported any difficulty or restrictions with visibility.