The integrated accident causation model (IACM) is a wide-ranging structure,and offers a particular awareness of the factors which are involved in an accident. The accident causation model is beneficial in an aviation industry focused on improving safety within its progressions. Several protections within the industry have been demonstrated after theses frameworks and their efficiency is obvious in the industry’s safety record. Heinrich’s Accident Pyramid developed in 1931 by H.W Heinrich is one of the first accident causation models in the aviation history. Afterwards, Edwards demonstrated that an aviation safety record could fail in one of four places: Software, Hardware, Environment or Liveware (SHEL). This model was modified in many places, including 5M model Man, Machine, Mission, Medium and management. However, Reason’s Swiss Cheese Model is one of the most widely used in the aviation safety record, which proposes that failures within functioning procedures cumulate to form a situation where an accident become more likely. The IACM combines the four accident causation models to deliver a safety record to the operator with a wide-ranging structure.

Safety is a principal task in the aviation industry, an element that is revealed in the planned goals of the International Civil Aviation Organization ICAO. According to Aviation safety coordinator’s manual (2008) aircraft accident not only contain the cost of damaged aircrafts, but also create extra costs such as insurance, fines, etc. Moreover, an aircraft accident could possibly affect an airline financially; unlike a car taxi company, which any suffers short-term loss in profit when their car is involved in the accident.

The accident causation model simplifies the supervision of safety within the aviation industry. The method of developing safety platforms, not only includes the operation of events or action, but also examining or studying about the past accidents, recognizing parts of weakness in a system which generates chances for error. Accident causation models were not only changed the way accidents are exterminated, but also offer valuable and benefit data for system improvement (Aviation safety coordinator’s manual 2008).


Heinrich created the first safety causation model for the aviation industry well-known as the accident triangle. According to Roughton, (July 2008) there were 29 minor injuries and 300 near misses. These incidents and near misses begun with similar circumstances that created one perfect accident. The pyramid model shows that situations of accidents can be present and their attendance is recognised by the several minor, but alike incidents that happen. However, the pyramid model does not give the reasons involved in an accident or the connection between those reasons.


SHEL is described in four areas; Software comprises all procedure, plans, manuals and paperwork. Liveware is human associated with the tool equipment, which can be directly or indirectly involved in the procedure. Hardware and Environment are factors involving temperature, vibrations, and weather (Perezgonazalez, & Perry,2010). These elements are always contemporary and have emotional impact the efficiency value of a progression result.


The 5M model covers the five factors, which are well known to be present if an accident occurs. The five factors contribute to a process which includes Man, Machine, Mission and Media and links to the SHEL. As a result, management operates all the five factors and handles a situation should it occur (Lee. Attan, & Witwiki. 2012).
However, the SHEL and 5M model do not obviously prove the change or improvement of an accident. They demonstrate the reasons contribute to an accident; one party's failure can change the conditions for an accident.


James Reason also known as the Swiss Cheese Model contains covering layers, and demonstrates safeguards with holes, which shows that all precautions have condition for failure. According to Tong (2012) due to the uncertainty of these structure errors, one error often disturbs another. Moreover, an accidental association by holes, shown by the characteristics of Swiss cheese demonstrates that multiple errors can let a dangerous threat go through all safeguards, finally causing damage.

The Swiss cheese model layer characterises for different types of error that are associated with an accident. The last layer is the dynamic error; the action outcomes in an accident. These errors are passing through by individuals functioning on a structure. The layer previously to the dynamic error is the covert error. Covert errors bring up actions which can lead to situations for accidents, but do not really cause an accident, for example, unsuitable actions or procedure aberrations. The Swiss cheese model has a significantly affect on the aviation safety; but there are concerns about its cogency. The model is too guileless to be applied to a real world situation. It does not have more explanations for the connection between issues which contribute to the change of a dangerous situation (Tong , 2012).


The IACM was developed carefully to demonstrate the process and factors that are associated to the accident. They are involved with four accident causation models as mentioned above.
Accidents are caused by a series of events especially in the aviation industry, when a chance of an accident breaks into the system safeguards. To demonstrate this, the pyramid contains a lot of layers; each layer characterises a safeguard in the process action. Developed from the Swiss cheese Model, the holes in the layers represent the delay in the process.

The pyramid figure of the IACM was resulted from Heinrich’s model. The parts of each layer in the model are reduced towards the top of the model. The modifications in areas show the number of incidents leads to the single accident at the angle of the pyramid model. The aim of these results is to improve the safety, as each layer acts as part of the safety net.

The four parts of the IACM are modified from the SHEL model and combined with the 5M model. The 5M model shows that human output has been involved directly or indirectly . This factor contains the several management styles, related to different tasks. “Machines” contains all mechanical matters and tools used to achieve a task. The “Medium” is involved with environmental features such as vibration, which includes cooperation with the quality of a task being performed. “Mission” involves operation rules and processes by guiding a task.
The IACM is beneficial for accident investigation. For example, in the case of a fatal aircraft crash, the pyramid figure of the model demonstrates that many incidents led to the crash. However, different from other models which recommend that the chance of error can be stopped by a perfect safeguard, the IACM demonstrated that while a process can be a tool to address one part of error management. In addition, there is some other part which may have contributed to the expansion of an accident.

In conclusion, the IACM combines four structures model to provide a detailed account of accident causation. The Heinrich (pyramid) figure demonstrates that small incidents can be happen over again. The 5M model based on man, machine, medium and missions, contributes to the user in defining the factors which can lead to the accident happening. The Swiss cheese model defines the course of the error by classifying the events that lead to the accident. Overall, the IACM is valuable in accident investigation, as well as procedure development, which is supreme in sustaining quality standards in the aviation safety industry.

Aviation safety coordinator’s manual (2008). CAA, civil aviation authority of NZ
Roughton, J. (July 2008). The accident pyramid. Retrieved 10 Oct 2012 from http://emeetingplace.com/safetyblog/2008/07/22/the-accident-pyramid/
Perezgonazalez, J. D. & Perry, M.D. (2010). Shell model. Retireved 10 Cot 2012 from http://aviationknowledge.wikidot.com/aviation:shell-model
Lee.C , Attan, M & Witwiki. L. (2012) 5 M model approach to accident investigation. Retrieved 10 Oct 2012 from http://aviationknowledge.wikidot.com/aviation:5-m-model
Tong, H.K. (2012). Risk management: Swiss cheese model. Retrieved 10 Oct 2012fromhttp://www.hkcem.com/html/training/files/Risk%20Management.pdf

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