Aircraft Accidents and Lessons Unlearned XXXIX: United Airlines Flight 266

B727 Engineer’s Panel

On January 18, 1969, United Airlines flight 266 (UA266), a Boeing B727-22C, registration number N734U, crashed into Santa Monica Bay. The airliner took off from Los Angeles International Airport (LAX) four minutes earlier; they were attempting to return, following a number one engine fire warning, when the accident occurred (accident report number AAR-70/6). After impact, the sections of UA266 sank to a depth of 950 feet in the Pacific Ocean. The cockpit gauges were destroyed. All three engines were recovered on February 11th, the flight data recorder (FDR) and cockpit voice recorder (CVR) between February 21st through March 4th.

The National Transportation Safety Board (NTSB) determined that the Probable Cause, “… of this accident was loss of attitude orientation during a night, instrument departure in which all attitude instruments were disabled by loss of electrical power.” The NTSB’s probable cause went on to say, “The Board has been unable to determine (a) why all generator power was lost or (b) why the standby electrical power system either was not activated or failed to function.” But is that what happened or was it a simple case of confusion brought about by technical inexperience?

In 1972, almost four years later, Eastern flight 401’s pilots fixated on an indication light bulb inflight. Unknowingly, with attention diverted, they casually flew the L1011 airliner into the Florida Everglades. What if UA266’s “loss of attitude orientation” was not the result of a power loss, but was because the crew simply lost focus on the job at hand: flying the aircraft – like Eastern 401?

The B727 aircraft entered service in 1963. There were three flight crew members: Captain (CP), first officer (FO) and second officer (SO). The CP and the FO flew the aircraft; the SO monitored the various systems’ panels. The B727 had three generators, one on each engine. After engine start, each generator was synchronized, then manually tied to their bus; the SO had to purposely engage the generator. One engine generator could power the airplane and would have to be manually tied.

AAR-70/06’s probable cause consisted of opinion, not fact; for this, it was confusing. “… all attitude instruments were disabled by loss of electrical power.” Little evidence suggested a loss of electrical power; that was pure theory. Instead, the report demonstrated a mismanagement of the aircraft electrical system and a group of investigators who were unfamiliar with the B727.

AAR-70/06 also showed why maintenance-experienced investigators would not only have understood what happened with the electrical power, they would have realized what the SO was doing … or more importantly, not doing. Why? Because United SOs were pilots but their function on the 727 was as an onboard technician. Pilot or engineer investigators would not understand the technical issues with aircraft electrical systems. The accident SO logged only 40 hours on the 727 (Appendix B); his job was to run the systems panel, troubleshoot systems’ problems in flight. He received basic technical training. At 40 hours (maybe 12 to 20 flights), it was unlikely he ever worked many deferred systems, calculated a fuel load, swapped generators or manually adjusted cabin pressure. Certainly, never in a high stress situation.

Consider the SO’s last words: “I don’t know what’s going on.” Classic straightforward confusion. The CP and FO were flying in low visibility, high-stress conditions, possibly disoriented. A #1 engine fire; sporadic contact with LAX; a SO with systems panel problems. Both pilots would have divided attention from flying to help the SO – seated behind them – figure out the panel. They could have missed any directions by the air traffic (ATC) Departure Controller (DC). Did the pilots even realize ATC was calling? If power was out, Standby could have been selected, the battery used to transmit on the #2 radio.

The report AAR-70/06, stated in Finding 14: “The No. 2 and No. 3 engines were developing power at impact.” The post-accident engine tear downs showed number (#) 2 and #3 engines were producing thrust at impact; therefore, the #2 generator was providing electric power the whole time. Did the SO mistakenly disconnect the bus tie? Did the SO not close the bus tie? Did he fail to select ‘GEN 2’ on the Essential Power selector switch? Did he accidentally disconnect busses that powered the CVR and FDR?

The CVR transcript showed unorganized engine shutdown procedures between the fire warning bell (1818:30) and CVR cut-out (1819:13.5). In that 43.5 seconds, did the FO return controls to the CP? Who was flying the aircraft at takeoff? Why did the FO have to ask the CP if he should retard the #1 throttle? Were the #1 engine extinguisher agents used? At 1818:45, an out-of-configuration or takeoff warning horn sounded when the #1 throttle was retarded. The horn was the only indication the crew attempted to shut down the #1 engine and there was no evidence that #2 Generator was selected.

More importantly, was the question of ‘indeterminate later time’, when the CVR and FDR were offline. Was it momentary? 30 seconds? One minute? At 1819:13.5, the CVR, the FDR and the transponder target cut out. The DC stated that UA266 did not respond to course directions. The ATC timer showed UA266 disappeared (impact) from the scope within two [radar] sweeps – four seconds each (Page 3, Note 4) at 1820:30. The CVR recorded nine seconds before impact, which was one second plus the two sweeps. The CVR had stopped for one minute and twenty-five seconds. The DC said he directed a right turn, but UA266 turned left and increased speed. Was UA266’s ‘increased speed’ the steep angled descent UA266 was found to hit the water at? Did UA266 even know they were descending?

At 0.5 seconds after CVR resumption, someone said, “… fields out.” Investigators believed the SO commented on the #2 generator’s electrical field, but if electrical power had been restored, why would the generator field be ‘out’? Besides, the “fields out,” speaker was unidentified. ‘Field’ could have been the airport or ‘field’. Investigators did not know. The “… field’s out” could have meant they had just discovered the communication problems with LAX. Was there stress in the crews’ speech? From the transcript, the SO never said that power had been restored. Did anyone notice the power returned or that power was even missed? The crew may not have known the radios, CVR, FDR or power were lost, because the FO or CP never commented about instrument recovery.

1.5 seconds after CVR returned, the SO stated, “We’re gonna get screwed up.” Two seconds later, the SO said, “I don’t know (what’s going on).” Question: If the SO failed to select Generator 2 on the Essential Power, would the instruments remain powered? Would the FDR and CVR have dropped offline? In his confusion with #2 generator, did he accidentally cut power to the busses powering the recorders?

In the last five seconds, the FO stated, “Keep it going up Arn [CP], you’re a thousand feet.” Two seconds later, the FO said, “Pull it up.” One second later: IMPACT. In those last five seconds, did the CP and FO return full attention to flying, like Eastern 401? The angle the aircraft hit the water suggested they were not aware of their attitude; the sudden call, “Pull it up,” suggested that neither pilot was focused on their rate of descent or pitch angle. The crew shut down the #1 engine without any procedures, no checklist. Could the crew have inadvertently put the aircraft out of configuration without realizing it? To answer the Standby system question, “(b) why the standby electrical power system either was not activated or failed to function”, if the crew did not know there was a power problem, they would not have select Essential Power to Standby. It was likely that the CP and FO focused attention on the young SO’s panel, then became disoriented when they looked back, just like Eastern 401.

Hindsight is 20/20; this is distinctly understood. However, accidents such as these should be reexamined and taught by/to investigatory agencies for the lessons unlearned, particularly mistakes made that could have prevented later accidents. UA266 represented lessons unlearned for investigatory agencies:

  1. Probable cause was useless in 1969 and is useless today. Root cause analysis should always have been pursued as the goal.
  2. Accident investigation reports have spiraled into opinions pieces, not factual analysis. Guessing may have saved time but what amateur opinions cost the aviation industry cannot be measured.
  3. The CVR and FDR data, analyzed while investigating accidents, must receive expert analysis by experienced aviation investigators.

UA266 represented lessons unlearned for the industry:

  1. An opportunity to improve cockpit resource management (CRM), a concept raised in the 1950s. The UA266 crew’s response to the #1 engine fire was disjointed, uncoordinated. CRM should have been a major focus.
  2. Better checklists and pilot-to-pilot challenges for flight crews to handle important events, such as terminating an engine fire or radio communication breakdowns.
  3. Enhanced ATC procedure reviews for communication losses with any aircraft in any stage of flight, whether takeoff, cruise and landing.
  4. Improved technical training for all pilots, specifically for the SO, whose real-life experience was as a pilot, not a technician.

Imagine what later accidents could have been avoided had some actual lessons been implemented in the UA266 accident report. As mentioned in Aircraft Accidents and Kobe Bryant, CVRs and FDRs are tools; if they are not used correctly, they are nothing more than paperweights. The post-tragedy of UA266 was that the data was not analyzed correctly by those who understood airline culture and training.

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