It should be noted that SSP provisions will be incorporated into Annex 19 — Safety Management which was still under development at the time this third edition was published. This manual also provides guidance material for the establishment of safety management system SMS requirements by States as well as for SMS development and implementation by affected product and service providers. Summary The concept underlying the manual is that of a continuous loop. The manual initially presents basic safety concepts, as the foundation upon which to understand the need for both an SMS and an SSP.

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In essence, these documents reflect the safety practices of States, developed in the light of experience. It usually undertakes this by formulating regulations and procedures based on ICAO SARPs, tailored where necessary to meet local environmental or operational conditions.

Inspection and enforcement processes are then established to ensure that the aviation community complies with the national regulations. This is published by ICAO, and indicates to other States, and users, that their legislation differs from internationally agreed standards. Most States comply with this important practice. These procedures are usually well understood. On the other hand , there is much less documentation regarding accident prevention activities outside the regulatory safety field.

This manual attempts to overcome that deficiency. For example, a State controls the licences issued to its pilots, engineers and air traffic controllers.

Enforcement action may necessitate the revocation of a licence if the holder fails to comply with regulations or fails to maintain the required standards. This is an essential feature of regulatory control. However, if applied arbitrarily, enforcement can provide a definite obstruction to the full understanding of human failings.

Each new aircraft incorporates improvements based on the latest state of the art and operational experience. Manufacturers produce aircraft which comply with the airworthiness regulations of domestic and foreign governments, and meet the economic and performance requirements of purchasers. In some States these may be the only guidance material available for the operation of a specific aircraft type or piece of equipment. Thus the standard of documentation provided by the manufacturer is very important.

Additionally, through their responsibilities for providing product support, training, etc. These persons are available for the investigation of accidents or incidents to aircraft of their manufacture.

On the one hand, this is a spur to optimize safety, while on the other, it can act as a deterrent to the voluntary correction of faults when this could be regarded as an admission of design or manufacturing deficiencies. Where such activities do exist, they are usually carried out by a section which monitors over-all operating experience and provides independent advice to management on the preventive action needed to eliminate or avoid discovered hazards.

Such activities may also lead to economies in the airlines operation. Accident prevention programmes may tend to be oriented towards the flight operations side of the organization.

Safety, however, must embrace the total organization and it is essential that a close working relationship be maintained between all parts of the organization. As a consequence, substantial benefits are to be gained from accident prevention programmes aimed at this group. In addition, general aviation operators often share facilities such as aerodromes, air traffic services, etc. This mixing of operations with differing requirements and performance standards may introduce hazards.

It includes the growing areas of corporate or business flying, often operating sophisticated aeroplanes; helicopters flown by professional pilots, through to non-professional pilots who only fly occasionally for pleasure. Motivating an interest and awareness of safe aviation practices must be one of the first steps of an accident prevention programme aimed at this varied group.

Accidents are typically a combination of several different causes. When each such cause is viewed alone, it may often appear insignificant, but in combination with other causes it can complete a sequence of seemingly unrelated events that result in an accident.

Accident prevention therefore involves identifying and eliminating these causes before the chain of events is complete. This concept is illustrated in Figure 2. In this manual, these causes or factors may also be called hazards.

For simplicity, hazards have been categorized here into three groups: Man, Machine and Environment. Man 3. In its widest sense, the concept should include all human involvement in aviation, such as design, construction, maintenance, operation, and management. This is the meaning intended in this manual, since accident prevention must aim at all hazards, regardless of their origin. For example, during a pilots training he learns something of the mechanical aspects of the machine he flies, the hazards of the weather, the operating environment in which he flies, and so on.

However, usually very little information is provided concerning his own behaviour, limitations, vulnerabilities and motivations. See Figure 3. Because of this significant shift in the relationship between man and machine causes, a concensus has now emerged that accident prevention activities should be mainly directed towards the man. It is not surprising, therefore, that information on the human factor aspects of accidents or incidents is not readily forthcoming.

This is unfortunate, since it is often these areas that hold the key to the why of a mans actions or inactions. Successful accident prevention therefore necessitates probing beyond the human failure to determine the underlying factors which led to this behaviour.

For example, was the individual physically and mentally capable of responding properly? If not why not? Did the failure derive from a self-induced state such as fatigue or alcohol intoxication? Had he been adequately trained to cope with the situation? If not, who was responsible for the training deficiency and why? Was he provided with adequate operational information on which to base his decisions?

If not, who failed to provide the information and why? Was he distracted so he could not give proper care and attention to his duties? If so, who or what created the distraction and why?

These are but a few of the many why questions which should be asked during a human factor investigation. The answers to these questions are vital for effective accident prevention. As a consequence, any other hazards revealed by an investigation were often not addressed.

Further, since the term tended to describe only what happened rather than why, it was of little value as a basis for preventive action. Fortunately, the term is now rarely used by investigation authorities. In fact, over the years the skill and performance of pilots have prevented many accidents when the aircraft or its systems failed, or when the environment posed a threat. Such occurrences usually do not receive the same attention and publicity as accidents, sometimes leading to an unbalanced perception of the skill and performance of pilots.

Machine 3. In fact a number of accidents can be traced to errors in the conceptual, design and development phases of an aircraft. Modern aircraft design therefore attempts to minimize the effect of any one hazard.

For instance, good design should not only seek to make system failure unlikely, but also ensure that should it nevertheless occur, a single failure will not result in an accident.

This is usually accomplished by so-called fail-safe features and redundancy in critical components or systems. A designer must also attempt to minimize the possibility of personnel using or working on the equipment from committing errors or mistakes in accordance with the inevitability of Murphys Law: If something can go wrong, it will. To meet these aims, some form of system safety programme is often used during the development of a new aircraft type.

An example of one manufacturers system safety programme is found at Appendix A. Modern design must also take into account the limitations inherent in man.

It thus includes systems which make mans task easier and which aim to prevent mistakes and errors. It has significantly reduced the number of accidents in which airworthy aircraft collide with the ground or water while under the control of the pilot.

Maintenance is then performed to ensure that an acceptable level of safety is achieved throughout the life of the aircraft. Manufacturing, maintenance and repair errors can negate design safety features and introduce hazards that may not be immediately apparent.

Some form of reporting system is thus required to ensure that component or system malfunctions and defects are assessed and corrected in a timely manner. Various methods can be used to express reliability. A common method for electronic components is the mean time between failure MTBF and the reliability of aircraft powerplants is usually expressed as the number of shutdowns per hundred thousand operating hours.

Initial failures, caused by inadequate design or manufacture, usually occur early in its life. Modifications to the component or its use usually reduce these to a minimum during the main or useful life period. Random failures may occur during this period. Near the end of the life of a component, increased failures occur as the result of its wearing out. Graphic representation of this failure pattern gives rise to the typical Bathtub shaped curve Figure 4.

Environment 3. From the accident prevention viewpoint, this manual considers the environment to comprise two parts; the natural environment and the man-made environment. Their manifestations, in forms such as temperature, wind, rain, ice, lightning, mountains and volcanic eruptions are all beyond the control of man.

These manifestations may be hazardous and since they cannot be eliminated they must be avoided or allowance made for them.

The physical portion includes those man-made objects that form part of the aviation environment. Air traffic control, airports, navigation aids, landing aids and airfield lighting are examples of the man-made physical environment. The man-made non-physical environment, sometimes called system software, includes those procedural components that determine how a system should or will function.

This includes national and international legislation, associated orders and regulations, standard operating procedures, training syllabi, etc. Obstructions near runways, malfunctioning or non-existent airport equipment, errors or omissions on aeronautical charts, faulty procedures, etc. Mission 3. Obviously the risks associated with different types of operation vary considerably.

For example, crop spraying with a heavily loaded aircraft close to the ground is considerably more hazardous than scheduled airline operations. The many crashworthy features built into most aircraft engaged in aerial work are proof of that. Each category of operation or mission therefore has certain intrinsic hazards which have to be accepted.

This fact is reflected in the accident rates of the different categories of operation and is the reason why such rates are usually calculated separately.

Man, machine and environment interaction 3. For example, a machine is designed, built and operated by man. Thus a failure of the machine is really a failure of man.


Doc 9422 Accident Prevention Manual



Accident prevention manual : (Doc 9422-AN/923)






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