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飛航安全與人為因素 行政院飛航安全委員會 報告人 王興中

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飛航安全與人為因素 行政院飛航安全委員會 報告人 王興中. 飛航安全 人為因素 飛航安全與人為因素 人為因素模組 飛航安全與人為因素調查 人為因素案件研討. 大綱. Flight Safety 飛航安全. Scheduled Air Carrier Accidents (1959-1997). 50. ___. U.S. and Canadian Operators. 40. - - -. Rest of World. 30. 20. 10. 0. 1960. 1970. 1980. 1990. Source: Boeing. - PowerPoint PPT Presentation

Text of 飛航安全與人為因素 行政院飛航安全委員會 報告人 王興中

Scheduled Air Carrier Accidents (1959-1997)
This graph shows the total scheduled carrier accidents, worldwide, that occurred between 1959 and 1983. As shown in the graph, the rate of accidents for all types of aircraft has dropped dramatically since their introduction into the fleet. By the late 1970s and early 1980s, accident rates had dropped to approximately 3 accidents per 1 million departures worldwide.
Note: The data exclude occurrences associated with sabotage, military operations, turbulence, and injuries sustained during evacuation. Second generation aircraft referred to in the figure include the 727, 737, DC-9, BAC 111, Trident, F-28, and VC-10 aircraft. Wide- body aircraft include the 747, DC-10, L-1011, and A300 aircraft. The graph was previously published in a book chapter by Nagel (1988); the source of the data comes from Boeing Commercial Airplane Company (1985).

Accidents/100,000 flight hours
U.S. Navy/Marine Corps
Source: U.S. Naval Safety Center
Improvements in aviation safety, however, are not unique to commercial carriers. General aviation deaths and fatal accident rates in the U.S. declined to a 15-year low in 1996, with only 1.51 accidents occurring per 100,000 flight hours (NTSB, 1997). Aviation accidents within the U.S. military (i.e., Army1, Navy, Air Force, and Marine Corps) have also decreased steadily over the past 2 decades. The rate of major accidents in the U.S. military, calculated as the number of accidents per 100,000 flying hours, declined from about 4.3 in 1975 to 1.5 in 1995.
In fact, if one were to examine any Service organization or even the civilian sector they would all look essentially the same (USN/USMC - upper right; USAF - upper left; commercial airlines - bottom). Specifically, they all reveal the same downward trend throughout the 50s, 60s and into the early 70s. Many have attributed this stark decline in the overall mishap rate to improved design, materials, training, and the implementation of standardized training programs. Notably, however, all the graphs show the same “flattening” of that positive downward trend in the mishap rate over the last couple decades.
1 The U.S. Army rates between 1950 and 1972 were unavailable at the time of publication.

The rate of improvement has slowed significantly and substantially during the last 10 years.
This has led some to conclude that further reductions in accident rates are improbable, if not impossible.
Still, worldwide air traffic is expected to double during the next 10 to 15 years.
Therefore, even if the current level of safety is maintained, the number of accidents will increase due to the increasing number of aircraft and hours flown.
Although the overall accident rate in civil and military aviation is very low, certain aspects of the data are unsettling. Specifically, the rate of improvement has slowed “significantly” and “substantially” during the last 10 years (Nagel, 1988). This plateau has led some to conclude that further reductions in the accident rate are improbable if not impossible. Still, worldwide air traffic is expected to double during the next 10 to 15 years (FSF, 1997). Therefore, even if the current level of safety is maintained, the number of aviation accidents will likely increase due to the increasing number aircraft and hours flown. Clearly, “accident-prevention steps must be taken now to stop the accident rate from exceeding its current level, and even greater effort must be taken to further reduce the current accident rate.” (FSF, 1997).

2 Based on industry estimates
3 Based on current accident rate
Number of Commercial Jet Accidents, Accident Rate
and Traffic Growth - Past, Present and Future
The red (bottom) line in this graph shows worldwide trends in aviation accident rates, as well as projected accident rates through the year 2010. The green (middle) line depicts the traffic growth which is expected to increase dramatically over the next 10 years. The blue (top) line shows the predicted increase in accident frequency due to the rapid industry expansion. Note that this predicted increase is based on the current accident rate; therefore, even if the accident rate stays the same over the next decade, the raw number of accidents will increase markedly. Furthermore, as can be seen from the graph, there may be as many as 52 accidents a year worldwide during the first decade of the new century. This translates into an astonishing one accident a week.
Note. Graph adapted from Flight Safety Foundation (1997). Values plotted in the graph are estimates based on industry statistics.

Even greater efforts must be taken to further reduce the accident rate
In order to achieve this goal
accident prevention measures must address the primary cause of accidents, which in most cases, is the HUMAN
“Although the global aviation safety record is admirable when compared with any other means of mass transportation, continuous effort must be exerted to maintain commercial aviation’s current level of safety” (Flight Safety Foundation, 1997).
In order to maintain the current level of safety, we must reduce the accident rates still further. In order to accomplish this goal, however, accident prevention measures must address the primary cause of accidents, which in most cases, is the human.

It is not surprising then, that human error has been implicated in 60-80% of accidents in aviation and other complex systems.
In fact, while accidents solely attributable to environmental and mechanical factors have been greatly reduced over the last several years, those attributable to human error continue to plague organizations.
“Human beings by their very nature make mistakes; therefore, it is unreasonable to expect error-free human performance.”
Human error has been implicated in 60-80% of accidents in complex, high technology systems. These systems include aviation, nuclear power, oil, medical, rail, and marine transport industries.
Although the overall rate of many industrial and transportation accidents has declined steadily during the past 20 years, reductions in human error-related accidents have not paralleled those related to mechanical/environmental factors. Indeed, humans have played a progressively more important causal role in both civil and military aviation accidents as aircraft equipment has become more reliable (Nagel, 1988).

This figure depicts the annual frequency of U.S. Navy/Marine Corps Class A, B, and C mishaps attributable, at least in part, to human error (top circles) and those solely attributed to mechanical/ catastrophic failures (bottom circles) between 1977 and 1992. While it is true that several mishaps attributed to human error in this figure were preceded by mechanical failure, in the opinion of the mishap board, the mishap might not have occurred, or been as severe, if the aircrew had not made an error.
Main Points:
- Aviation accidents attributable to human and mechanical/environmental factors were nearly equal in 1977. Yet by 1992, accidents solely attributable to mechanical/environmental factors had been virtually eliminated while those attributable to human error had been reduced by only 50%.
- If aviation accidents are to be reduced further, more needs to be done to prevent the occurrence of human error and/or to design more error-tolerant systems.
Note: This is a figure from our 1996 publication in Aviation, Space, and Environmental Medicine entitled “U.S. Naval Aviation Mishaps, 1977-92: Differences Between Single- and Dual-Piloted Aircraft.”

Pilot Error
Organizational Factors
Adding to the problem is the fact that “human factors” means different things to different people. These multiple definitions have led to confusion among safety professionals and, in some cases, have lead to extreme single-minded views of accident causation. There are at least 5 different terms frequently used synonymously with the term “human factors.” These include:
Pilot error - refers to the actions or inactions of pilots that are thought to directly cause the accident. Viewed from this perspective, the pilot is the “major cause of aircraft accidents” (Murray, 1997), and “the pilot and aircrew are the weak link in the aviation safety chain.” (Feggetter, 1985). As a result, pilots are more dangerous than the aircraft they fly (Mason, 1993).
Ergonomics - refers to errors caused by the design of knobs, dials and displays, or a mismatch between the anthropometric requirements of the task and that of the human. From this perspective, all accidents are design-induced and all errors can be engineered out of the system.
Aeromedical - refers to the physiological and psychological condition of aviators that cause accidents. From this perspective, accidents occur because aviators were not physically qualified or aeronautically adaptable.
CRM - refers to crew resource management (CRM), also known as aircrew coordination training (ACT), as well as other names. From this perspective, accidents are due to a breakdown in teamwork or the failure of the crew to work together properly.
Organizational factors -refers to errors committed by officials within the management hierarchy, such as line managers and supervisors, that initiate the sequence of events leading to an accident. From this perspective “Every accident, no matter how minor, is a failure of organization.” (Andrews, 1953). Furthermore, “ accident is a reflection on management’s ability to manage...Even minor incidents are symptoms of management incompetence that may result in a major loss” (Ferry, 1988).
How can all these pieces be put together into a coherent accident investigation and prevention program?

Pilot Error
A comprehensive Human Factors Analysis and Classification System (HFACS) has recently been developed to meet these needs. This system, which is based upon Reason’s (1990) model of latent and active failures (Shappell & Wiegmann, 1997a), encompasses all aspects of human error, including the conditions of operators and organizational failure.

Human Factors discovers and applies information about human behavior, abilities, limitations, and other characteristics to the design of tools, machines, systems, tasks, jobs, and environments for productive, safe comfortable, and effective human use

Hull Loss Accidents – Worldwide Commercial Jet Fleet – 1990 Through 1999
10% 20% 30% 40% 50% 60% 70% 80%

1978 DC-8 Portland
583 people

Issues in Human Performance Assessment
Issues in Human-Centered Automation

Information displays
Communications processes
Human Information Processing
Human actively process information, we do not just passively receive, store, and retrieve information
We construct what we see
We construct what we remember


Human visual system is particularly sensitive to the orientation of stimuli

US Civil Aeronautics Board Report
Two commercial aircraft were approaching New York city at 11,000 feet and 10,000 feet respectively. At the time, clouds were protruding above a height of 10,000 feet, forming an upward sloping bar of white against the blue sky.
The crew of the lower aircraft misperceived the planes to be on a collision course and increased altitude quickly. The two aircraft then collided at approximately 11,000 feet.

Human capabilities and limitations
Methods for measurement
Sensory store
Here are two main forms of sensory store
Iconic for information we see
Visual information is held for about 0.5 to 1 second
Echoic for information we hear
Aural information is held for about 2 to 8 second

Information is forgotten in seconds without rehearsal
Extremely limited capacity
Capacity is for all intents limitless
Information can potentially be stored forever
Distributed and associative by nature
Three type of information are stored in LTM
General knowledge, our understanding of the world
Memory of past events

Develop internal mental models with experience
Generating projection of future system states
Pattern matched to elements in the mental model to achieve situation awareness
Pattern-recognition sequence can become automaticity
Direct limited attention in efficient ways
Situation awareness can be negatively impacted by automaticity

Automation dependencies and skill retention
Interface alternatives

Accident-related cause
Captain conducted unauthorized troubleshooting
Faulty fuel management
Auto switching and load shedding – no crew action required
Auto fuel management with alert of low fuel, wrong configuration and imbalance
Improved takeoff warning with digital computer
Dual electric spoiler control
New equipment training strategies
Selection criteria and methods

Few qualified pilots
As mentioned earlier, we have incorporated Reason’s (1990) model of how humans contribute to the breakdown of safe flight operations into our HFACS model. In this model, system failures are classified as either active or latent conditions. However, the exact nature of these failures or “holes” in the cheese have yet to identified and described. In this section, we provide a framework or taxonomy for identifying, classifying, and organizing active and latent failures with in the system. As previously stated, the framework is based upon the “The Taxonomy of Unsafe Operations” (Shappell & Wiegmann, 1997) which was developed for, and has recently been adopted by, the U.S. Navy/Marine Corps and U.S. Coast Guard for use in aviation accident investigation and analysis. The taxonomy describes four levels of failure within the system which include: (a) organizational factors, (b) unsafe supervisory practices, (c) unsafe conditions of operators, and (d) the unsafe acts operators commit. Each level is described in detail, beginning with the level most closely tied to the accident itself, unsafe acts.

Where do we usually look to prevent accidents?
System failures are like dominos, with the failure of one “domino” effecting the toppling of the next. The end result is the accident or injury. When this happens, however, we often forget that the accident itself is the last “domino” in this sequence, and that many dominos fell well before the accident occurred. As a result, we tend to focus almost exclusively on the people responsible for front line operations (i.e., the aircrew). Unfortunately, this has lead accident pilots (if they survive the accident) to feel severely scrutinized, as if they are being placed under a microscope or interrogated for a crime.

Organizational Failures
Unsafe Supervision
Unsafe Acts
Operating Environment
Rather than scrutinizing the failure of a single system component, we must take a step back and look at the entire sequence of events that lead to the accident. A systems perspective requires that we examine blemishes or faults throughout the entire system. After all, it is often the failure of multiple components that combined together to produce an accident.
Some people may raise the question, “Why stop at the organizational or even industry level?” Does the system’s boundary really end there? Presumably everything has a prior cause. Therefore, we could potentially trace the cause of an accident all the way back to the Big Bang. Stopping at the organizational level is just arbitrary.
Theoretically this may be true. But we need to be practical. In seeking the reasons for an accident, we should search far enough back to identify factors that, if corrected, would render the system more tolerant to, or even prevent, subsequent encounters with conditions that produced the original accident. The people most concerned and best equipped to do this are those within the organization (Reason, 1990).

According to the International Civil Aviation Organization (ICAO) Annex 13, Chapter 3, Section 3.1;
The sole purpose of the investigation of an accident or incident shall be the prevention of accidents and incidents. It is not the purpose of this activity to apportion blame or liability.

Total Command Hours on B747-400 2,017 hrs
CM-2 Male, age 36
Total Flying Hours 2,442 hrs
Total Command Hours on B747-400 552 hrs 
CM-3 Male, age 38
Total Flying Hours 5,508 hrs
Total Hours on B747-400 4,518 hrs
Aligned with centerline



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