Human Error /accidents Flashcards
(13 cards)
Consequences of workplace death
Cost of human lives (4,764 in 2020, US)
Economic cost (163.7b in 2020)
Damage reputation
Majority can be attributed to human error and thus preventable
Introduction to HE
Important objective of HF is to reduce HE
2022/23 work related accidents stats - 135 killed, 561,000 sustained an injury at work
Majority can be attributed to HE and are therefore preventable
Major direct causes of injury
Exposure to harmful substances and environments
Over exertion and bodily reactions
Slips, trips and falls
Contact with objects and equipment
Major direct causes of deaths
Transportation incidents (eg motor vehicle accidents)
Slips trips and falls
Contact w objects and equipment
HE: aviation
In 1903 before ww1, 80% of aviation accidents caused by mechanical error, 20% by human error. The stars have now reversed
Eg of he In aviation - Tenerife disaster 1977
583 killed, worst aviation accident to date
HE: railway
During the period from 1900-1997, 70% of the 141 accidents on 4 main British railway lines occurred due to human error
Eg Ladbroke Grove 1999 head on collision, 30 fatalities 400 injured
Eg southall 1997 side collision, 7 fatalities, 150 injured
HE definition - indiv perspective
Error is an elusive concept - means diff things in diff contexts
Sometimes not clear if a human has made an error or not
Individual perspective: all those occasions in which a planned sequence of mental or physical activities fails to achieve its intended outcome, and when these failures cannot be attributed to some chance agency - reason, 1990
But…. Human intentions and the resulting actions may be correct from the performers point of view, from the goal he selects- which may be inappropriate judged from system output (Rasmussen et al 1991)
HE definition - systems perspective
Inappropriate human behaviour that lowers levels of system effectiveness or safety - Wickens et al 2004
Intentions/goals and human errors are inseparable
Whose fault was it? old view
In HF today, there are 2 different views of HE and human contribution to accidents.
Old view
System is mostly safe; its success is intrinsic
HE is the cause of most accidents.
It is unpredictable, unexpected and does not belong in the system. They are introduced to the system only through the inherent unreliability of humans.
Accidents are caused by erratic behaviour of a few unreliable humans (the bad apple theory)
Problems: 1) accident investigation stops with who instead of what. 2) if HE is unpredictable and random how do we develop interventions to mitigate them?
Who’s fault was it? New view
The System approach
HE is not the cause but the symptom of deeper trouble inside the system.
It is not random but predictable. It’s connected to the features of human cognitive landscape, the tools, tasks and the operating environment.
Accidents occur because of the interaction (misfit) between system components and the human
HE is not the conclusion of an accident investigation but only a starting point. Once identify HE, how do we improve it, implement interventions etc
Most of those involved in accident research and analyses are proponents of the new view
Eg simply writing off accidents merely to HE is overly simplistic, if not naive approach. It is well established that accidents cannot be attributed to a single cause or indiv.
Characteristics of HE
far less frequent than correct actions
Lack of variety - only take a limited number of forms
Share common cog mechanisms - so possible to generate theories about interventions
They are predictable (to some extent)
They can’t be eliminated
Slips and lapses examples
- Eastern air line flight 401 (1972). Cause = inattention due to preoccupation with burnt out landing gear indicator light during landing. Didn’t notice the automatic disconnected and weren’t keeping track of altitude. Slowly descended and crashed. 101 fatalities.
- Delta air line flight 1141 (1988). Cause - omission due to interruptions. Aircraft put on hold before lining up with the runway, during which time the flight crew engaged in extensive convo with the attendant (against regulations). Crew then forgot to extend the flaps, crashed shortly after take off due to insufficient lift.
- Air Inter Flight 148 (1992)
Cause - perceptual confusion.
During landing the pilot left autopilot mode in vertical speed mode instead of flight path angle mode and set 33 instead of 3.3 for descent angle. 87 fatalities
Mistakes examples
China airlines flight 006 (1985)
Misuse of automation!!
Lost thrust in engine 4, crew made several attempts to restart the engine but all fail
Captain should have manually exerted input on the rudder to counteract the plane from veering to the right but instead allowed autopilot to do it (but autopilot doesn’t use the rudder)
Plane started to roll, didn’t notice cause distracted with the engine, once noticed had already rolled 60 degrees. Disconnected the autopilot and violent roll to the right, dropped 30,000ft. Crew gained control again
