Investigation Summary
The aircraft, a nearly new Boeing 727-22C, was dispatched with the #3 generator inoperative, a condition permitted by the Minimum Equipment List (MEL). Approximately two minutes after takeoff from Los Angeles, a fire warning light illuminated for engine #1. Although post-crash investigation found no evidence of an actual fire, the crew followed emergency procedures and shut down the engine, which also removed the #1 generator from the electrical bus. This left the #2 generator as the sole source of power. Seconds later, the #2 generator failed, likely due to an electrical overload or a fault in the control panel that had a history of malfunctions. The standby electrical system, which should have provided emergency power to critical flight instruments, either failed to activate or was not properly engaged by the crew. In the instrument meteorological conditions (IMC) of a rainy night over the ocean, the pilots had no visual horizon and no working attitude indicators, leading to a rapid loss of control.
Final Conclusions
The NTSB determined the probable cause was the loss of attitude orientation during a night, instrument departure after attitude instruments were disabled by a total loss of electrical power. The investigation could not definitively establish why the #2 generator failed or why the standby power system was not utilized. Contributing factors included a lack of independent backup power for flight instruments and a cockpit layout where the battery switch was located adjacent to the galley power switch, potentially leading to an accidental disconnection of the battery during the emergency.
Photographic Evidence (1)
Video Analysis
Unsolved To This Day : United Airlines 266 — A detailed look at the electrical failure and subsequent crash of United 266, exploring the mystery of why the backup systems failed to save the aircraft.
If playback is blocked, the owner has disabled embedding — use the link above.
Airframe & Maintenance
Crew Experience
Captain
Leonard Leverson, 49. 22 years with United Airlines.
First Officer
Walter Schlemmer, 33.
Flight Engineer
Keith Ostrander, 29.
Systems & Failure Modes
Electrical Generation System
Consisted of three engine-driven generators; the loss of all three led to the total loss of cockpit instrumentation.
Standby Electrical System
A battery-powered backup intended to provide power to essential instruments, which failed to function or was not activated.
Engine Fire Detection
A single-loop system that triggered a false fire warning on engine #1, initiating the emergency sequence.
Interesting Facts
- 01The aircraft had been operating with the #3 generator inoperative since January 15, 1969.
- 02Post-crash inspection of engine #1 showed no evidence of fire or heat damage despite the cockpit warning.
- 03The wreckage was located in approximately 950 feet of water and was highly fragmented.
- 04The #2 and #3 engines showed evidence of high RPM at impact, while #1 showed almost no rotational damage.
- 05The aircraft was only four months old with less than 1,100 total airframe hours at the time of the accident.
Safety Actions & Advisories
Mandatory Backup Instrumentation
Source ↗The FAA required all transport-category aircraft to carry backup flight instruments powered by a source independent of the main generators.
Automatic Standby Power Switching
Source ↗NTSB recommended mandatory automatic switching of essential systems to standby power in the event of a total generator loss.
Switch Guarding and Separation
Source ↗Recommendations were made to guard the battery switch and separate it from similar-looking switches like galley power to prevent accidental disconnection.
Known Controversies & Unanswered Questions
Witness Reports of Engine Fire
Reference ↗Several ground witnesses reported seeing sparks or fire emanating from engine #1 or the rear of the fuselage during takeoff. However, post-crash investigation of the recovered #1 engine showed no evidence of fire or heat damage, leading investigators to conclude the fire warning was false and the visual sparks were likely caused by a compressor stall or electrical fault.