Background
On a scheduled flight from Los Angeles, California, to Denver, Colorado, and Milwaukee, Wisconsin, a Boeing 727-22C, registration N7434U, was operating as Flight 266. The aircraft had been flying since January 15, 1969, with the No. 3 generator inoperative. This configuration was permitted under the Minimum Equipment List, provided that specific procedures were followed and electrical loads were monitored during flight.
Flight Sequence
The flight was scheduled to depart the gate at 17:55 but was delayed until 18:07 due to inclement weather and loading difficulties. The takeoff roll on runway 24 began at approximately 18:17. At 18:18:30, the engine fire warning bell sounded in the cockpit. The crew reported a No. 1 engine fire warning and expressed a desire to return to the airport.
Loss of Electrical Power
Shortly after the No. 1 engine was shut down, electrical power from the remaining generator (No. 2) was lost. Following the loss of all generator power, the standby electrical system either was not activated or failed to function. Approximately a minute and a half after the No. 2 generator was lost, electrical power at a voltage level of roughly 50 volts was restored, but only for 9 to 15 seconds. The Boeing subsequently descended and struck the sea 11.3 miles west of the airport, where the ocean depth is approximately 950 feet.
Probable Cause
The probable cause of the accident was determined to be the loss of attitude orientation during a night, instrument departure in which all attitude instruments were disabled by loss of electrical power. The Board was unable to determine why all generator power was lost or why the standby electrical power system either was not activated or failed to function.