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UA173 Potential Human Factors Issues - Coggle Diagram
UA173 Potential Human Factors Issues
People
Captain
Expectations
That the other crew members would directly outline their concern about the fuel state
Analysis of how flight crew communicate safety critical information
That the other crew are aware of and monitoring the fuel state
Analysis of flight crew understanding of areas of responsibility in the cockpit
Perceived mismatch in fuel-quantity indicators may have led to expectation of more fuel in tanks than indicated
Analysis of how pilots consider the fuel state of the aircraft
Attention
Drawn by mismatch in landing gear indicators and the physical sensation felt during gear extension
Troubleshooting popping circuitbreaker for anti-skid system
Analysis of Flight Crew attention model during troubleshooting and normal operations
Competency
27,638 total hours, 5,517 hours as Captain of DC-8s
Successfully passed last proficiency check in Sep 1978 & enroute check in October 1978
Holder of Air Transport Pilot Licence
Type Rated on DC-8 and B727
Fatigue
210 hours flight time in previous 90 days
18h 4m flight time in previous 7 days
3h 38m flight time in previous 24 hours
Analysis of Fatigue Related Error Likelihood
14h 40m free time prior to signing on for flight
First Officer
Expectations
Captain is aware of and monitoring fuel state for the flight
Analysis of flight crew understanding of areas of responsibility in the cockpit
That the captain would understand their concern regarding the fuel state
Analysis of how flight crew communicate safety critical information
Perceived mismatch in fuel-quantity indicators may have led to expectation of more fuel in tanks than indicated
Analysis of how pilots consider the fuel state of the aircraft
Competency
Type Rated on DC-8
Holder of Commercial Pilot Licence
5,209 total hours, 247 as First Officer of DC-8s
Successfully passed last proficiency check in June 1978 & enroute check in August 1978
Fatigue
182 hours flight time in previous 90 days
18h 4m flight time in previous 7 days
14h 40m free time prior to signing on for flight
3h 38m flight time in previous 24 hours
Analysis of Fatigue Related Error Likelihood
Attention
Troubleshooting circuitbreaker for antiskid system
Analysis of Flight Crew attention model during troubleshooting and normal operations
Flight Engineer
Expectations
Captain is aware of and monitoring fuel state for the flight
Analysis of flight crew understanding of areas of responsibility in the cockpit
That the captain would understand their concern regarding the fuel state
Analysis of how flight crew communicate safety critical information
Perceived mismatch in fuel-quantity indicators may have led to expectation of more fuel in tanks than indicated
Analysis of how pilots consider the fuel state of the aircraft
Competency
3,895 total hours, 2,263 as Flight Engineer of DC-8s
Successfully passed last proficiency check in February 1978 & enroute check in December 1978
Holder of Flight Engineer Certificate
Type Rated on DC-8
Fatigue
179 hours flight time in previous 90 days
14h 40m free time prior to signing on for flight
18h 4m flight time in previous 7 days
3h 38m flight time in previous 24 hours
Analysis of Fatigue Related Error Likelihood
Attention
Troubleshooting popping circuitbreaker for anti-skid system
Analysis of Flight Crew attention model during troubleshooting and normal operations
Management
Organisational / System Factors
Resourcing
Captain
3 Crew Flight Decks were Common, Crew Resource Management / Coordination was not
Assessment of 3-crew operation effectiveness and/or viability
First Officer
Flight Engineer
Organisation of Work
Clear areas of responsibility were identified, however ultimate decision making landed with the Captain
Cabin preparation delegated to Cabin Crew
Communications about timeframe for cabin preparation unclear
Assessment of procedural clarity and delegation of tasks
Procedures
Specific procedures existed for suspected Landing Gear issues
Landing Gear Lever Down & Gear Unsafe Light On Procedure
Assessment of procedural clarity / suitability
Landing Gear Apparently But Not Conclusively Down Procedure
Management Decisions
Flaps and Gear left in the 'down' position while troubleshooting
Increased fuel burn while at low altitude with 'dirty' aerodynamics
Decision to continue delaying landing following consultation with Company Maintenance determined landing could proceed in accordance with procedure
Assessment of Communications between Maintenance and Flight Crew regarding clearance to proceed to land
Organisational decision to change Fuel-Quantity indicators to a 1,000lb resolution
Assessment of Organisational decision making and change management
Assessment of Equipment Design
Maintenance
Main Landing Gear Retract Assembly found to be corroded
Corroded Assembly failed leading to the 'quick' gear lowering and vibration and noise detected by flight crew
Contact with Company Maintenance made per procedure and concluded ~30 minutes prior to crash.
Job Design
Workload
Initial abnormal handling & noise occurred during final approach to airport runway
High workload time in Flight Operations
Assessment of Cognitive workload during approach, landing and troubleshooting
Troubleshooting of popping anti-skid circuit breaker became sole focus while preparing to land
Task Design
Procedures designed for 3 crew operations
Assessment of Cognitive workload during normal operations
Aircraft Operations Manual identified specific procedures for many aircraft states
Information Transfer
Communication (Written & Oral)
Communication between FO and Engineer to Captain didn't convey low fuel state with sufficient urgency
Assessment of Cockpit Authority Gradient and Crew Management
Changes made to fuel quantity indicator reduced the resolution available (smallest resolution was 1,000lb)
Assessment of Equipment Design
Communication between Captain and Cabin Attendant didn't outline timeframe for readiness of the Cabin for abnormal landing
Assessment of procedure for suitability in event context
Instructions
Company procedures clearly outlined steps to take in the event of suspected abnormal gear indications
Assessment of procedural clarity / suitability in event context
Workplace
Work Environment
Noise
Loud bang heard by pilots formed part of their mental model when troubleshooting
Vibration
Unusual vibration & change in aircraft handling characteristics prompted pilots to investigate potential landing gear issue
Assessment of Decision Making Model of Pilots
Visibility
Weather reports indicate clear visibility at time of crash
Workplace Factors
Site Design
3 Crew Cockpit (Captain, First Officer, Flight Engineer)
Assessment of communication flow in 3-crew cockpit
Equipment Design
Feedback
Failure of the Main Landing Gear Retract Assembly disabled the microswitch for the gear position indicator leading to the system to show an unsafe gear state
Assessment of Decision Making Model of Pilots
Main Landing Gear Retract Assembly failing led to asymmetric extension of the Landing Gear which may have caused yawing of the aircraft
Warning Systems
Landing Gear Warning Horn
Ease of Use
Fuel tank indicators displayed 8 separate levels for each tank but combined into 1 'totaliser' for ease of reference
Both displays showed 3 numbers which were to be multiplied by the applicable multiplier (100 for individual tank, 1000 for totaliser) to determine the amount being displayed
Assessment of Equipment Design
Fuel display wasn't directly visible to the pilots and was relayed from the Engineer
Displays
'Totaliser' fuel display resolution was 1,000lb of fuel, reduced from 100lb resolution
Assessment of Equipment Design
Green Lights used to show 'down & locked' position of Landing Gear
Individual tank fuel display required to be multiplied by 100 to gain fuel remaining
'Totaliser' fuel display required to be multiplied by 1000 to read the total fuel display remaining