The Tybee Island B-47 crash was an incident on February 5, 1958, in which the United States Air Force lost a 7,600-pound (3,400 kg) Mark 15 hydrogen bomb in the waters off Tybee Island near Savannah, Georgia, USA. During a practice exercise the B-47 bomber carrying it collided in midair with an F-86 fighter plane. To protect the aircrew from a possible detonation in the event of a crash, the bomb was jettisoned. Following several unsuccessful searches, the bomb was presumed lost somewhere in Wassaw Sound off the shores of Tybee Island.
The B-47 bomber was on a simulated combat mission from Homestead Air Force Base in Florida. It was carrying a single 7,600-pound (3,400 kg) bomb. At about 2:00 AM, the B-47 collided with an F-86. The F-86 crashed after the pilot ejected from the plane, but the B-47, despite being damaged, remained airborne, albeit barely. The crew requested permission to jettison the bomb in order to reduce weight and prevent the bomb exploding during an emergency landing. Permission was granted and the bomb was jettisoned at 7,200 feet (2,200 m) while the bomber was traveling about 200 knots (370 km/h). The crew did not see an explosion when the bomb struck the sea. They managed to land the B-47 safely at Hunter Army Air Field. The pilot, Colonel Howard Richardson, was awarded the Distinguished Flying Cross after this incident for his role in piloting the B-47.
The risk of corrosion of the alloy casing of the bomb is less if it is completely covered in sand. But if, due to the shifting strata in which it is buried, part of the alloy casing of the bomb is exposed to seawater, rapid corrosion could occur, as demonstrated in simulation experiments. Eventually, the highly enriched uranium could be leached out of the device and enter the aquifer that surrounds the continental shelf in this area. Storms, hurricanes, and strong currents frequently change the sands of the continental shelf near Tybee Island.
To date, no undue levels of unnatural radioactive contamination (over and above the already high levels thought to be due to monazite, a locally occurring sand which is naturally high in radiation) have been detected in the regional Upper Floridian aquifer by the Georgia Department of Natural Resources.