A Grumman HU-16 amphibian airplane, N7026Y, was destroyed following a loss of control during the turn from base to final approach near Chetumal, State of Quintana Roo, in the Republic of Mexico. The instrument rated private pilot and his 2 passengers were fatally injured. The airplane was owned and operated by the pilot. Visual meteorological conditions prevailed for the personal flight for which a visual flight rules (VFR) flight plan was filed. The flight originated from Tulum at 17:30 with Chetumal (CTM) as its intended destination. Local authorities reported the airplane had been cleared to land on runway 10 at the Chetumal International Airport. Witnesses reported that the airplane rolled and nosed over during the turn from left base to final approach. The airplane came to rest about 4 miles from the threshold of runway 10. A post-impact fire consumed the airframe.