Midair collisions: limitations of the see-and-avoid concept in civil aviation

INTRODUCTION

Midair collisions cause loss of life and property and undermine general aviation; they also represent failures of the see-and-avoid concept in air traffic control. This study identifies limitations of the see-and-avoid concept.

METHODS

Analysis of National Transportation Safety Board data on 159 U.S. civil aviation midair collisions and limitations of the see-and-avoid concept.

RESULTS

On average, there were 15.6 midair collisions annually from 1991 through 2000. At least one aircraft was maneuvering in 88% of collisions, and both in 70%. There were 77% that involved arrival to, departure from, or flight over an airport, with 61% in the traffic pattern. Head-tail collisions were more frequent in the traffic pattern than out (28.3%, 2.8%, p < 0.05). Other horizontal convergence angles were equally frequent in or out of the pattern: head-on (8.3%, 11.0%), obtuse (11.0%, 8.3%), and acute (13.8%, 16.6%).

DISCUSSION

Because the relative bearing to each aircraft on an unaccelerated collision course is constant, pilots sometimes cannot see converging aircraft when climbing, descending, or level. Even if a converging aircraft is unobstructed, it appears small, motionless, camouflaged, and inconspicuous until imminent impact. A statistical model reveals that the probabilities of seeing and avoiding a converging 40-ft aircraft, for an optimal observer or theoretical pilot scanning 2/3 or 1/3 of the time, respectively, are less than 0.91, 0.60, 0.30 at 200 kn; 0.49, 0.32, 0.16 at 300 kn; 0.28, 0.18, 0.09 at 400 kn; and 0.15, 0.10, 0.05 at 500 kn. The see-and-avoid concept has striking physical and behavioral limitations.

[Malfunction simulation by spaceflight training simulator]

OBJECTIVE

To implement malfunction simulation in spaceflight training simulator.

METHOD

The principle of malfunction simulation was defined according to spacecraft malfunction predict and its countermeasures. The malfunction patterns were classified, and malfunction type was confirmed. A malfunction simulation model was established, and the malfunction simulation was realized by math simulation.

RESULT

According to the requirement of astronaut training, a spacecraft subsystem malfunction simulation model was established and realized, such as environment control and life support, GNC, push, power supply, heat control, data management, measure control and communication, structure and so on.

CONCLUSION

The malfunction simulation function implemented in the spaceflight training simulator satisfied the requirements for astronaut training.

Safety of emergency medical service helicopters

Robust safety specifications and funding arrangements are needed.

Work domain analysis for air traffic controller weather displays

INTRODUCTION

Adverse weather conditions have a major impact on National Airspace System (NAS) operations. They create safety hazards for pilots, constrain the usable airspace for air traffic control (ATC), and reduce the overall capacity of the NAS. A system-wide dissemination of weather information to controllers could theoretically improve safety and efficiency.

PROBLEM

However, it is currently unclear what weather information would be beneficial for tactical operations. Furthermore, no previous research has empirically evaluated optimal presentation designs for ATC weather displays. Ill-designed weather displays can cause safety hazards by presenting redundant information (i.e., by increasing the cognitive load) and display clutter (e.g., by interfering with the visual extraction of traffic data).

METHOD

In the present paper, we outline our use of cognitive work analysis (CWA) techniques for the assessment of weather information needs for terminal controllers.

RESULTS

Specifically, we describe how the CWA modeling tools helped us reveal instances in the terminal domain where weather information is lacking or insufficiently disseminated. We used our CWA results to drive the development of weather display concepts and to set up a high-fidelity simulation capability.

IMPACT ON INDUSTRY

By means of high-fidelity simulations, we can empirically evaluate controller weather information needs in order to propose weather displays for increased aircraft safety and efficiency of terminal operations.

Flight safety in Alaska: comparing attitudes and practices of high- and low-risk air carriers

INTRODUCTION

Aircraft operations are a vital component of the transportation system in Alaska. Between 1990-2002, a total of 481 people died in Alaska in aviation accidents. The purpose of this study was to examine the practices and attitudes of Alaska commuter and air taxi operators and their pilots as they relate to company fatal accident rates.

METHODS

A case-control analysis based on accident statistics was performed, grouping operators and their pilots into cases and controls, based on operator fatal accident rates, during January 1990 to June 2001. Responses from two aviation safety surveys-one of air carrier operators and one of active commercial pilots-were compared between cases and controls.

RESULTS

The average case pilot had less career flight experience than control pilots and worked 13 h x d(-1) and 81 h x wk(-10; that is, 1 h x d(-1) and 10 h wk-1 more than controls. Case operators were less likely to consider pilot fatigue a problem when scheduling flights (p = 0.05) and more likely to depend financially on timely delivery of bypass mail (p = 0.04). Case pilots were three times as likely as controls to fly daily into unknown weather conditions. Nearly 90% of case pilots reported that they never flew when so fatigued that they wanted to decline the flight, compared with 64% of control pilots (p = 0.01).

CONCLUSIONS

Pilots of high-risk operators differed from those working for the other operators, both in experience and working conditions. The combination of pilot inexperience and longer work hours and workweeks may contribute to Alaska's high aviation crash rate.

Automation in future air traffic management: effects of decision aid reliability on controller performance and mental workload

Future air traffic management concepts envisage shared decision-making responsibilities between controllers and pilots, necessitating that controllers be supported by automated decision aids. Even as automation tools are being introduced, however, their impact on the air traffic controller is not well understood. The present experiments examined the effects of an aircraft-to-aircraft conflict decision aid on performance and mental workload of experienced, full-performance level controllers in a simulated Free Flight environment. Performance was examined with both reliable (Experiment 1) and inaccurate automation (Experiment 2). The aid improved controller performance and reduced mental workload when it functioned reliably. However, detection of a particular conflict was better under manual conditions than under automated conditions when the automation was imperfect. Potential or actual applications of the results include the design of automation and procedures for future air traffic control systems.

The IFR bullet: can it kill our accident rate?

The helicopter air ambulance community has been very consistent lately: about once a month, we crash. A fifth of those crashes involve weather, the biggest category by far. Suppose we had a silver bullet, aiming all our safety emphasis on this one area; could we blow a hole in our accident rate?

How can ergonomics influence design? Moving from research findings to future systems

Ergonomics design is about the creation of future work. So how can ergonomics research support and inform design if its findings are cast in a language oriented towards current work derived from field observations or laboratory settings? In this paper we assess instances of three different strands (experimental, ethnomethodological, and surveys) of ergonomics research on paper flight strips in air traffic control, for how they analytically confront future work and how they make the findings relevant or credible with respect to future work. How these justifications come about, or how valid (or well argued for) they are, is rarely considered in the ergonomics literature. All three strands appear to rely on rhetoric and argument as well as method and analysis, to justify findings in terms of their future applicability. Closing the gap between research results and future work is an important aim of the ergonomic enterprise. Better understanding of the processes necessary to bridge this gap may be critical for progress in ergonomics research and for the use of its findings in actual design processes.

Human performance breakdowns are rarely accidents: they are usually very poor choices with disastrous results

When human error is involved in the error chain of accidents in complex systems, the causes of the errors are very seldom the result of: a random slip, one inadvertent oversight, a single unintended action, one mis-perceived event, simple mal-performance of a complex action, or a poor training program for the human operators. Invariably, the cause of the break down is in a very poor conscious choice by someone from the operator back through system designer, the supervision, management and leadership through the entire organization. Usually the operator bears the burden of the blame and is either rebuked, retrained or replaced. In systems such as commercial aviation, complex manufacturing systems, power plants, process control systems, information-processing systems and communications networks, the replacement or retraining of individuals or even classes of individuals usually does not result in any long-term improvement of the safety or effectiveness of the system. What is needed is a system that identifies the reasons why the operators made the errors. Further a system is needed that can recommend what can be done to improve the future performance within the system. The professional performance analysis system (PPAS) has been developed and applied to more than 50 major aircraft accidents in the past 30 years. The PPAS is a direct outgrowth of the human performance analysis system developed by Robert Mager over 45 years ago. The PPAS system is applied after a complete and unbiased definition and description of the events of the accident or incident has been developed by the teams of accident investigation and accident reconstruction professionals. The PPAS then uses a systematic protocol and algorithm to determine the reasons as to why the humans committed the errors or why they performed at subnormal performance levels. This process is based on quantitative behavioral science principles and findings that have been demonstrated valid for many generations. The PPAS looks at five attributes of human performance to identify the factors that can be changed to improve performance in the future. The result is a series of objective definitions of changes that have been demonstrated to be the attributes that influence human performance. The PPAS provides a tool to the analyst, who lacks sophistication or experience in quantitative behavioral sciences, to arrive at recommendations that are based on validated human performance principles.

Alaska air carrier operator and pilot safety practices and attitudes: a statewide survey

INTRODUCTION

Aviation crashes are a leading cause of occupational fatalities in Alaska, with Alaskan pilots having nearly 100 times the fatality rate of U.S. workers overall. A survey was designed to study pilot and company practices and attitudes in order to develop intervention strategies that would reduce aviation fatalities.

METHODS

Two surveys were administered: one of air carrier operators and one of active commercial pilots. Surveys from 153 air taxi and public-use operators were received at a 79% response rate.

RESULTS

There are almost 2000 pilots employed in Alaska during peak season by air taxi operators and public agencies. Surveyed operators and pilots generally agreed that improved weather information and regional hazards training would be effective ways to prevent crashes. Operators were more in favor of operator financial incentives (p < 0.05) and better pre-employment hiring checks on pilots (p < 0.05) compared with pilots' survey responses. There were 48% of pilots of large operators and 73% of pilots of small operators who considered their jobs to be at least as safe as other jobs.

CONCLUSIONS

The results of operator-pilot comparisons suggest that financial pressures on operators may influence their views on what measures would be effective in preventing crashes, and that Alaskan pilots underestimate their occupational fatality risk.

A classification on human factor accident/incident of China civil aviation in recent twelve years

OBJECTIVE

To study human factor accident/incident occurred during 1990-2001 using new classification standard.

METHOD

The human factor accident/incident classification standard is developed on the basis of Reason's Model, combining with CAAC's traditional classifying method, and applied to the classified statistical analysis for 361 flying incidents and 35 flight accidents of China civil aviation, which is induced by human factors and occurred from 1990 to 2001.

RESULT

1) the incident percentage of taxi and cruise is higher than that of takeoff, climb and descent. 2) The dominating type of flight incidents is diverging of runway, overrunning, near-miss, tail/wingtip/engine strike and ground obstacle impacting. 3) The top three accidents are out of control caused by crew, mountain collision and over runway. 4) Crew's basic operating skill is lower than what we imagined, the mostly representation is poor correcting ability when flight error happened. 5) Crew errors can be represented by incorrect control, regulation and procedure violation, disorientation and diverging percentage of correct flight level.

CONCLUSION

The poor CRM skill is the dominant factor impacting China civil aviation safety, this result has a coincidence with previous study, but there is much difference and distinct characteristic in top incident phase, the type of crew error and behavior performance compared with that of advanced countries. We should strengthen CRM training for all of pilots aiming at the Chinese pilot behavior characteristic in order to improve the safety level of China civil aviation.

CAPPS II: the foundation of aviation security?

A new computer system is being developed to classify U.S. air travelers by the degree of terrorist threat they might pose. Reports indicate that the system--called CAPPS II--would use large amounts of information about each passenger, perhaps including such personal details as his or her magazine-subscription behavior. We argue that what is publicly known about CAPPS II raises questions about how substantially the system would improve aviation security. We discuss conditions under which CAPPS II could yield safety benefits, but suggest that it might be more prudent to view the system as one component of future security arrangements rather than the centerpiece of these arrangements.

Credible investigation of air accidents

Within the United Kingdom the Air Accidents Investigation Branch (AAIB) has been used as a model for the other transport modes accident investigation bodies. Government Ministers considered that the AAIB's approach had established the trust of the public and the aviation industry in its ability to conduct independent and objective investigations. The paper will examine the factors that are involved in establishing this trust. They include: the investigation framework; the actual and perceived independence of the accident investigating body; the aviation industry's safety culture; the qualities of the investigators and the quality of their liaison with bereaved families those directly affected by the accidents they investigate.

Human factors in maintenance: impact on aircraft mishap frequency and severity

INTRODUCTION

Aviation mishaps caused by maintenance factors vary in severity, but can cost untold sums in lives and equipment lost. This study proposes to demonstrate that certain specific maintenance-related human factors are significantly correlated with both mishap frequency and severity.

METHODS

Using information from the Maintenance Error Information Management System (MEIMS), 1,016 aircraft mishaps caused by human factors in maintenance were examined. These mishaps were previously categorized using the Human Factors Analysis and Classification System-Maintenance Extension (HFACS-ME). Frequency analysis was used to determine the most common HFACS-ME factors seen in aircraft mishaps. Logistic regression techniques were used to describe the relationship between the dichotomized outcome of mishap severity and the human factors found in the HFACS-ME.

RESULTS

Inadequate supervision, attention/memory errors, and judgment/decision errors were the factors found most often in aircraft mishaps. The factors of inadequate design, inadequate adaptability/flexibility, inadequate lighting/light, confining workspace, and attention/memory error increased odds of being associated with a higher severity mishap.

DISCUSSION

Emphasis in training and education placed in the first three factors mentioned may reduce overall number of mishaps. Concentrating resources on the final five factors may decrease the number of severe mishaps.

Mental workload in air traffic control: an index constructed from field tests

BACKGROUND

Mental workload assessment is a recurrent issue in air traffic control (ATC). Studies of ATC have used either objective aspects, i.e., numbers and distribution of aircraft, or subjective factors, such as self-imposed performance and stress levels, with mixed results. This is partly due to the difficulty in bringing together comparable data pertaining to both air traffic, with its ever-changing distribution, and judgement or quickly fluctuating psychophysiological variables.

METHODS

We propose a method of mental load estimation devised to take into account both objective traffic variables and the additional load imposed by subjective effects, including the seriousness of conflicts and the time-pressure for their resolution. First, we developed a traffic load index (TLI) to identify time boundaries during which additional load may occur. Then we quantified the additional load according to the air traffic situation.

RESULTS

TLI was developed from analysis of 25 h of recordings of radar control sessions involving 25 professional air traffic controllers at a major airport. Results were then compared with a simple objective index (number of aircraft) and subjective workload ratings (NASA-TLX test). The whole population (intersubjects analysis) showed a better correlation between the TLI and the self-rated workload than for the number of aircraft alone. Among the controllers who rated more than one level of workload through the TLX-test, 77.8% showed better correlation between TLI and TLX than between N and TLX (intrasubjects analysis).

CONCLUSION

Workload estimation should integrate both objective task variables and subjective evaluations associated with them.

Flight safety and medical incapacitation risk of airline pilots

BACKGROUND

This paper examines the use of quantitative incapacitation risk assessment for aeromedical decision-making in determining the medical fitness of multicrew airline pilots, and estimates the effect on flight safety should medical standards be relaxed. The use of the "1% rule" for setting limits for aircrew incapacitation risk is re-examined. Human failure (medical incapacitation) is compared with acceptable failure rates in another safety-critical system, the aircraft engines.

METHODS

The expected number of cardiovascular incapacitations occurring in flight was modeled by applying an age-related cardiovascular incapacitation risk to the pilot population. The effect on flight safety of relaxing the maximum acceptable incapacitation risk on estimated incapacitation rates in two-pilot operations was also modeled, taking into account a likely increase in the number of pilots who would be allowed to continue to fly with a known medical condition.

RESULTS

The model overestimates cardiovascular incapacitation risk and, therefore, provides a cautious estimate. If the maximum acceptable cardiovascular risk is increased, the model predicts a disproportionately small increase in the number of such incapacitations in flight.

CONCLUSIONS

The evidence suggests that the incapacitation risk limits used by some states, particularly for cardiovascular disease, may be too restrictive when compared with other aircraft systems, and may adversely affect flight safety if experienced pilots are retired on overly stringent medical grounds. States using the 1% rule should consider relaxing the maximum acceptable sudden incapacitation risk to 2% per year.

Challenges of assuring crew safety in space shuttle missions with international cargoes

The top priority in America's manned space flight program is the assurance of crew and vehicle safety. This priority gained greater focus during and after the Space Shuttle return-to-flight mission (STS-26). One of the interesting challenges has been to assure crew safety and adequate protection of the Space Shuttle, as a national resource, from increasingly diverse cargoes and operations. The control of hazards associated with the deployment of complex payloads and cargoes has involved many international participants. These challenges are examined in some detail along with examples of how crew safety has evolved in the manned space program and how the international partners have addressed various scenarios involving control and mitigation of potential hazards to crew and vehicle safety.

Pilot ability to anticipate the consequences of flight actions as a function of expertise

The study offers insights into pilot ability to anticipate consequences of actions and how this ability changes with experience. Novice and expert pilots completed trials in which 3 screens depicted a control movement (or control movements), a cockpit flight situation, or a change in flight situation. Changes depicted in the 3rd screen of each trial were consistent, inconsistent with the mental model of the effect of the control movement or movements, or inconsistent with the application of the control movement(s) to the current flight situation. Pilots indicated whether the depicted change was inconsistent or consistent with their expectations, and accuracy of consistency judgments was greater for mental-model than for situation-model inconsistent statements. Experts are more accurate than novices, particularly for trials that involve multiple, meaningfully related control movements. Expert ability to organize information into meaningful units appears to facilitate future flight state projections, and projection failures appear to result from situation- rather than mental-model failures. Actual or potential applications of this research include analysis of flight situation awareness and flight performance errors.

Parachute use to prevent death and major trauma related to gravitational challenge: systematic review of randomised controlled trials

OBJECTIVES

To determine whether parachutes are effective in preventing major trauma related to gravitational challenge.

DESIGN

Systematic review of randomised controlled trials.

DATA SOURCES

Medline, Web of Science, Embase, and the Cochrane Library databases; appropriate internet sites and citation lists.

STUDY SELECTION

Studies showing the effects of using a parachute during free fall.

MAIN OUTCOME MEASURE

Death or major trauma, defined as an injury severity score > 15.

RESULTS

We were unable to identify any randomised controlled trials of parachute intervention.

CONCLUSIONS

As with many interventions intended to prevent ill health, the effectiveness of parachutes has not been subjected to rigorous evaluation by using randomised controlled trials. Advocates of evidence based medicine have criticised the adoption of interventions evaluated by using only observational data. We think that everyone might benefit if the most radical protagonists of evidence based medicine organised and participated in a double blind, randomised, placebo controlled, crossover trial of the parachute.