When Uruguayan Air Force Flight 571 crashed in the remote Andes mountains on October 13, 1972, the thirty-three initial survivors faced unfathomable odds. While battling sub-zero temperatures and starvation, a glimmer of hope emerged when survivors discovered the detached tail section of the Fairchild FH-227D aircraft miles down the glacier. Inside was the aircraft high-frequency communications system, which appeared completely intact.
Survivor Roy Harley, who had rudimentary knowledge of electronics, joined efforts with others to trek back and forth to the tail, hoping to hook up the radio and transmit an SOS signal to search teams. They successfully retrieved the heavy radio set and attempted to wire it up using batteries scavenged from the aircraft. However, their desperate attempt met a devastating technical roadblock: the aircraft radio required a 115-volt alternating current (AC) power supply generated by the plane running engines, whereas the storage batteries they recovered only provided direct current (DC) at 24 volts.
Without an inverter to convert DC to AC power, the radio remained completely useless. This agonizing technical realization forced the group to abandon hopes of radio rescue, leaving them with no choice but to undertake the heroic, harrowing foot trek across the mountains that eventually saved the remaining sixteen survivors.