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UA 173 Crash Event Sequence and Context - Coggle Diagram
UA 173 Crash Event Sequence and Context
Probable Event Sequence
UA173 departed JFK, New York at approximately 1000 EST (NTSB 1979)
UA173 flew from JFK, New York to Denver, Colorado landing at approximately 1530 EST (NTSB 1979)
UA173 departed Denver, Colorado at 1647 EST to fly to Portland, Oregon with planned arrival of 2013 EST (NTSB 1979)
At approximately 2007 EST, UA173 approaching Portland Airport. During the approach the aircraft was configured for landing and a large bump was felt as well as asymmetric yawing of the aircraft (NTSB 1979)
At 2012 EST, UA173 advised they were going to discontinue their approach to troubleshoot a suspected landing gear issue (NTSB 1979)
At or around 0900 EST, the flight crew sign-on for duty to operate UA173 from JFK, New York to Portland, Oregon (NTSB 1979)
Between 2017 EST and 2043 EST, the flight crew completed their emergency checks and procedures and briefed the Cabin Crew on their intended approach to the situation (NTSB 1979)
At 2038 EST, the Flight Crew contacted United Airlines maintenance control centre via radio. The Pilots indicated during this conversation that they had 7,000 lbs of fuel onboard and were going to approach to land in 15-20 minutes (NTSB 1979)
At 2046 EST, the First Officer queried the amount of fuel remaining, the Flight Engineer advised 5,000 lbs was left. This was acknowledged by the First Officer. (NTSB 1979)
At 2048 EST, the First Officer again queried the amount of fuel remaining. The Captain advised 5,000 lbs still remained. (NTSB 1979)
At 2050 EST, the Captain asked the Flight Engineer to calculate the Landing Weight after a further 15 minute hold. The engineer advised that 15 minutes would leave them too low on fuel. (NTSB 1979)
At 2051 EST, the Captain asks the Flight Engineer to contact the company representatives at Portland to advise they'll be landing with approximately 4,000 lbs of fuel. (NTSB 1979)
At 2055 EST, the approach checklists were announced as complete and the Flight Engineer advised that 3,000 lbs of fuel remained. (NTSB 1979)
At 2057 EST, the Flight Engineer was sent to the Cabin to check on the emergency preparation. The Engineer returned to the Cockpit at 2101 EST. (NTSB 1979)
At 2102 EST, the Flight Engineer advised again that 3,000 lbs of fuel remained and the Captain advised of the after landing procedure to minimise fire in the event of a landing gear collapse. (NTSB 1979)
At 2103 EST, the Air Traffic Controllers requested an approximate time the UA173 expected to commence their approach. The Captain advised another 3-5 minutes and they had 3,000 lbs of fuel onboard. (NTSB 1979)
At 2106 EST, the Cabin Crew entered the cockpit and advised they were ready for landing. The Captain advised they'd be landing in about 5 minutes. (NTSB 1979)
Just after advising the Flight Crew that the cabin was ready, the First Officer advised they were about to lose an engine due to fuel exhaustion. (NTSB 1979)
Between 2106 and 2107 EST, conflicting and confused conversation was carried out by the Flight Crew regarding the aircraft's fuel state. (NTSB 1979)
At 2107 EST, the Flight Engineer advised they were about to lose Engine 3 as well due to fuel exhaustion. (NTSB 1979)
At 2107 EST, the Captain checked the fuel gauges and stated that either 1,000 lbs or 0 lbs remained. (NTSB 1979)
At 2110 EST, the Captain queried the status of the Gear lights again, requesting a reset of the circuit breaker to see if it resolved the issue. (NTSB 1979)
At 2113 EST, the Captain and First Officer identified they weren't going to make any airport and declared a Mayday. (NTSB 1979)
At 2115 EST, UA173 crashed into a wooded section of suburban Portland. (NTSB 1979)
2115 - 0000 EST Emergency Response to the crash commences with Police, Fire and Ambulance responding (NTSB 1979)
Context
3- Crew Operations for aircraft
Captain, First Officer, and Flight Engineer to operate the aircraft with Cabin Crew conducting safety tasks within the aircraft cabin. (NTSB 1979)
HF Issues
Management
Allocation of tasks and duties
Authority Gradient in the cockpit
Areas of responsibility and control
Very early days of Crew Resource Management, Captain still maintained ultimate command and responsibility for all aircraft systems and decisions (NTSB 1979)
Event occurred ~12 hours after crew signed on for duty
HF Issues
People
Potential for fatigue related cognitive function degradation.
Management
Procedures / Policies for operating during times of fatigue
Information transfer of the fuel state of the aircraft between the 3 crew wasn't urgent enough to prompt immediate landing
Cockpit designed with Flight Engineer as only person with visibility of Fuel Gauges
HF Issues
Workplace
Information transfer of the fuel state of the aircraft from Flight Engineer to Pilots (Fuel Gauges not visible to pilots)
DC-8 Aircraft
4-engine narrow body aircraft (NTSB 1979)
~269 passenger capacity (NTSB 1979)
Fuel gauge resolution changed from 100 lbs to 1,000 lbs (NTSB 1979)
HF Issues
Workplace
Comprehension of what the gauges and totaliser are displaying
Readability of the Gauges by the crew in high workload situations
Management
Reasoning for the change was to improve readability of the gauge but did not consider the change in the resolution of the gauges
Failure of Landing Gear Assembly (LGA)
Failure of the LGA occurred at high workload phase of flight (NTSB 1979)
HF Issues
Management
Workload of Flight Crew while troubleshooting, circling at low altitude, coordinating emergency procedures and completing emergency checks
Other Incidents of Crew Distraction
In 1963 an Aeroflot TU-174 (no flight number identified) ditched from fuel exhaustion following extended troubleshooting prior to landing (Aviation Safety Network 2020)
SAS933, a DC-8 crashed in 1969 when pilots were troubleshooting a gear indicator light not showing green, lost situational awareness and crashed into the ocean (NTSB 1970)
HF Issues
Management
Learning from other organisation's incidents
Monitoring and/or assessment of risks present in other operators vs. risks present in own operations
Eastern Airlines 401, a L-1011, crashed in 1972 following crew distraction with a failed landing gear indicator light. The autopilot had disconnected and the flight crashed following an unmonitored descent. (NTSB 1973)