Horses are wonderful but complex animals and hacking on the road can be unpredictable, causing even the most bomb-proof of horses to nap, buck, kick,…. As a keen road runner, I have lost count of the amount of times I have found myself surprised by the presence of an electric….
A NFCI is caused by long or recurrent periods of exposure to cold and wet weather conditions. It is a condition which mainly affects the…. Want to talk to one of our experienced lawyers? We can call when it suits you for a no-obligation, strictly confidential chat. Your browser is out of date. Please update your browser. This site and many others provides a limited experience on unsupported browsers and not all functionality will work correctly or look its best.
Military Claims. By Charlotte Jose. Charlotte's Recent Posts. Spinal Injury. See Charlotte Jose's profile. Preferred call time. Any Time Morning Afternoon Evening. What do you need help with? This site uses cookies to make sure you get the best browsing experience. In that case, the opportunity to take proactive safety measures before an accident happens would be lost. The challenge of aircraft safety management is identifying and focusing attention on truly hazardous conditions before a potential accident becomes a reality.
In the example described above, routine use of flight recorders or quick access recorders QARs to monitor stopping distance would provide operators with an independent means of detecting potentially hazardous abnormalities. In , accidents involving jet transport airplanes occurred in the United States at the rate of about 1. Except for a few, well publicized tragedies, most passengers involved in commercial aircraft accidents are not killed or injured. However, as shown in Figure , the rate for hull loss accidents involving large jet transports has improved only slightly in the last 20 years.
The same is true for fatal accidents. Accident rates can be computed in terms of accidents per passenger-trip, accidents per passenger-mile, or accidents per passenger-flight hour.
Depending upon the method chosen, the accident rates for Part operators, who commonly use turboprop aircraft, are about three to eight times higher than the accident rates for Part operators, who operate most of the large jet transports FAA, Rates for Part operators are declining, but slowly. Regulatory changes to establish more uniform safety standards for Part and operators are intended to address the disparity in accident rates. Analyses of the chains of events in accidents are generally useful just for preventing similar accidents.
Because there are so few accidents in the United States relative to the number of flights, focusing safety programs on accidents alone addresses only a small fraction of potential accidents and is reactive rather than proactive. A proactive approach that could eliminate risks before they cause accidents requires an effective means of tracking the chains of events in both incidents and accidents.
Preventive action not just remedial action could then be taken—based on how often individual links in the chain recur and their potential for contributing to future incidents and accidents.
Every abnormal event in the incident or accident chain could be examined to identify the cause factors that explain why it happened and to describe the underlying problems and deficiencies that should be corrected.
One approach for visualizing an incident or accident is as a chain of events that must occur in a certain sequence. Another is shown in Figure , which shows a system of disks spinning at random. Each disk contains a hole that must line up precisely with the holes in the other disks before a beam of light can pass through the entire system. The probability. The data depicted in all Chapter 3 figures cover commercial jet aircraft heavier than 60, pounds. Available data on aircraft manufactured by the states of the former Soviet Union are incomplete and are, therefore, excluded.
Data on accidents caused by sabotage, hijacking, military action, experimental test flying, or suicide are also excluded. This is why primary and backup hydraulic systems are physically separated as much as possible—so that a single damaging event will not disable all hydraulic systems.
Assuming that the disks represent events in a chain leading to an accident, corrective action to prevent one or more of the events i.
When an official investigator reports the "probable causes" of an accident or incident, consideration should be given to all of the events and cause factors. Cause factors can be grouped into the following categories:.
Identifying the precise cause factors for each event can be complicated, requiring good judgment and accurate interpretation of the facts. There could be more than one cause factor for each event, and some cause factors naturally overlap. Human factors include mistakes caused by voluntary acts, failure to act, and other factors associated with actions or inaction. Cause factors associated with aircraft, engines, and systems include deficiencies in the design, manufacture, maintenance, or operation of the aircraft or its systems.
Maintenance-related cause factors include improperly performed maintenance and inadequate maintenance procedures and plans.
Environmental cause factors include hazardous weather, volcanic ash, sand, dust, and birds. Cause factors associated with air traffic management include deficiencies in weather reporting, regulations, and the air traffic control system navigational aids; air traffic control directives; and airport facilities, runways, and taxiways. Combinations of factors and cascading cause-and-effect sequences must be carefully examined to understand all of the cause factors.
For example, to prevent accidents caused by system failure, the system that failed could be modified to prevent similar failures in the future. In addition, understanding if the failure was triggered by the failure of some other system, improper maintenance, abnormal operating environment, etc. The term "primary cause," defined as the most critical cause factor associated with a particular incident or accident, can be deceiving and is often subject to interpretation.
One cause factor may contribute more to the consequences of an accident or incident than the others, but making this determination may also depend on one's point of view. Take the case of an accident involving an uncontained engine failure that severed all of the aircraft's hydraulic lines.
The aircraft crash landed, broke apart, and caught fire. The flight crew and some of the passengers survived the accident. The official investigation found that the original material from which a large rotating part of the engine was fabricated contained a defect that ultimately resulted in a crack.
The crack grew over the life of the part and finally fractured, resulting in shrapnel damage to the aircraft and its hydraulic systems. The investigation further disclosed that the part had undergone numerous inspections designed to locate defects like the one that ultimately resulted in the part failure.
Inspections were made at the part's material manufacturer, the forging manufacturer, the engine manufacturer, and during routine maintenance of the engine by the operator. The official report on this accident determined that the probable cause was inadequate consideration given to human factors limitations in the inspection and quality control procedures.
An expanded list of cause factors appears in Appendix D. In an uncontained engine failure, a piece of the engine, such as a rotor disk, is ejected from the engine. Commercial jet engines are designed to contain blade failures but not disk failures. The danger of disk failures is, therefore, addressed through stringent manufacturing and inspection procedures.
As a result, a fatigue crack originating from a previously undetected metallurgical defect was not detected. The subsequent catastrophic disintegration of the part produced debris with a pattern of distribution and with energy levels that exceeded the level of protection provided by design features of the hydraulic systems that operated the aircraft's flight controls.
In this example, one link in the chain was singled out as being more significant than the others, which included the processes used to produce the basic material for the rotating part, numerous inspections designed to detect the defect before it became a crack, and the susceptibility of the aircraft design to damage by the distribution of debris in this particular failure. The committee believes that a safety management program should have an inclusive view of what constitutes a significant cause to ensure that corrective action addresses multiple cause factors and provides multiple assurances that a similar accident or incident will not occur in the future.
For the purposes of analyzing the most common causes of accidents, the committee reviewed official accident reports and various summaries of those reports. Figures and show the primary cause factors cited in official reports of accidents resulting in the loss of aircraft. Data from both the U. Figure shows that there were 50 hull loss accidents worldwide between and in which the airplane was a primary cause factor.
Figure shows that 15 of these accidents took place in the United States. For the 50 accidents worldwide, Figure shows the breakdown by aircraft system.
FIGURE Airplane system cause factors for hull loss accidents involving large commercial jet airplanes worldwide, through For example, Figure might lead one to believe that maintenance is a growing problem.
The percentage of maintenance-related accidents during the year period ending with is more than three times higher than for the entire year period to However, when dealing with small numbers, small changes can produce large changes in percentages.
In fact, only three accidents during the year period were attributed primarily to maintenance. As already discussed, the attribution of primary causes is sometimes problematic. If the primary cause of two of those accidents had been attributed to one of the other cause factors associated with those accidents, there would have been no percentage increase in maintenance-related accidents.
One manufacturer examined a large number of past accidents and identified all actions that could have broken the chain of events leading up to the accidents. This examination indicated that operators could significantly reduce accident risks by taking the following measures:.
An accident prevention strategy that considers all cause factors involved in incidents and accidents—not just primary cause factors—has a greater potential to prevent accidents by eliminating factors that are common in many incidents and accidents. These common factors serve as "traps" that may be easier to identify and eliminate than a unique, extremely rare factor that may be labeled the "primary cause" in a given accident.
For example, if a series of accidents appears to be unrelated, corrective action might focus on the specific circumstances of each accident. A comprehensive review, however, might reveal a fundamental deficiency, such as poor pilot training, safety management, or aircraft maintenance, that is common to the entire series of accidents.
Identifying and correcting these fundamental deficiencies is important because they can lead to many types of incidents and accidents. Trend analysis based on reliability, or mean time between failure, could add another dimension to the safety management process. One could theoretically do trend analyses of aircraft components, structures, etc. However, because of the redundancies built into the design of aircraft structures and systems, the failure of any single component does not pose a threat to continued safe operation.
In fact, FAA-approved minimum equipment fists allow aircraft operation with some equipment out of commission. Also, for economic reasons, airlines and manufacturers already use component reliability analyses to keep their aircraft in the air. For at least the timeframe of this study—the next 10 years—the committee believes that a focused effort to determine mean times between failure, which would require collecting and analyzing vast amounts of data, might not identify specific safety trends and would bog down the safety.
Data on incidents involving jet transport airplanes provide a slightly different picture. To begin with, many organizations do not have adequate incident reporting systems, and it is very difficult to obtain complete and consistent records of incidents.
0コメント