Tuesday, July 20, 2010

Human Factors in Aircraft Maintenance

A survey designed to identify safety issues in maintenance, with a particular emphasis on human factors, were distributed to Licensed Aircraft Maintenance Engineers (LAMES) in Australia.
As a result the Australian Transport Safety Bureau has provided the following analysis, conclusions and recommendations.[7]

Table 1. Outcome of Safety Occurrences

System operated unsafely during maintenance18%7%
Towing event9%3%
Incomplete installation, all parts present8%9%
Person contacted hazard7%9%
Vehicle or equipment contacted aircraft7%1%
Incorrect assembly or orientation6%11%
Material left in aircraft4%5%
Part damaged during repair4%2%
Panel or cap not closed3%3%
Incorrect equipment/part installed3%4%
Part not installed3%6%
Required servicing not performed3%4%
Degradation not found3%5%

Table 2. Occurrences Factors

Unsafe Acts in OccurrencesAirlineNon-airline
Memory lapse21%20%
Procedure shortcut16%21%
Knowledge-based error11%18%
Trip or fumble9%11%
Failure to check6%2%
Unintended action3%6%
Failure to see5%6%
Occurrence factorsAirlineNon-airline
Lack of equipment8%3%
Poor documentation5%4%
Poor procedure4%4%

Definitions of Occurrence Outcomes

System operated unsafely during maintenance
Activating an aircraft system such as flaps or thrust reversers when it was not safe to do so, either because personnel or equipment were in the vicinity, or the system was not properly prepared for activation.
Towing event
A safety occurrence which occurred while an aircraft was under tow.
Incomplete installation, all parts present
Although all necessary parts were present, the installation procedure had not been completed. For example, a connection may have been left ‘finger tight’ rather than torqued.
Person contacted hazard
A worker came into contact with a hazard which caused, or had the potential to cause injury. Includes electric shocks, falls and exposure to aircraft fluids or other chemicals.
Vehicle or equipment contacted aircraft
A stationary aircraft was contacted by a vehicle or maintenance equipment such as stairs or moveable stands.
Incorrect assembly or orientation
A component was installed or assembled incorrectly.
Material left in aircraft
A maintenance related item such as a tool was inadvertently left behind by a maintenance worker.


The Australian Transport Safety Bureau considers that the issues identified in the survey are not specific to Australia but will be of use to safety agencies around the world, and has identified a number of recommendations: [8]
  • the need for refresher training for aircraft maintenance engineers
  • the need to remove barriers which discourage aircraft maintenance engineers from reporting incidents
  • the need for fatigue management programs
  • human factors training for management and engineers, and
  • program to address aircraft maintenance engineers concerning memory lapses, pressure, fatigue and coordination difficulties.
7. Aircraft Maintenance Safety Survey Retrieved on 16 Sep 2009 from Australian Transport Safety Bureau
8. ATSB Recommendation Retrieved on 16 Sep 2009 from Australian Transport Safety Bureau

Attention to Detail

Maintenance Resource Management

Maintenance Resource Management
What is Maintenance Resource Management aimed at?

Numerous safety studies have shown that the causes of aviation accidents and incidents are more likely to be related to human error than mechanical failure.  However, human error may occur both in flight and in ground operations.  Nearly a dozen recent aviation accidents have determined the probable cause to be maintenance related (including factors such as incorrect installation of components, fitting of wrong parts, loose objects (tools, etc.) left in the aircraft, inadequate lubrication, etc.).

Therefore, recognition of the importance of maintenance human factors and the need for operational research is growing.  Past accidents have dramatically demonstrated the potentialimpact of human error problems in maintenance areas such as: training for maintenance and inspection, tracking of maintenance responsibility, procedures and task documentation, work environment conditions, verbal and written communications, and leadership and teamwork. 

Thought Process has designed a tailored MRM Program for aircraft engineers that utilises both theoretical and case studies of past accidents to highlight the significant impact maintenance error(s) may have on the safe and efficient conduct of maintenance operations. 

MRM as an Error Prevention Tool

Training maintenance personnel in human factors and crew resource management can also help to avoid, trap or mitigate the consequences of human-related problems. Crew resource management for maintenance has already been successfully introduced by many aviation organisations across the world. Topics such as stress, shift work, and commercial pressures are taught during the course.  Participants will also receive the required skills to communicate clearly and assertively to supervisors when it is required.

Sadly, it sometimes takes an accident or serious incident before there is agreement on what needs to be changed within the organisation.  It is far better to identify the human factors and organisational failings before they have an opportunity to cause trouble, because reacting to disasters after the event is a costly and inefficient way of improving safety.

MRM Objectives 

a) To equip aviation maintenance technicians, supervisors and managers with the skills necessary to enhance safety, teamwork and efficiency in the workplace, and therefore, reduce aircraft maintenance errors;

b) To examine the human role in the chain of events that cause an aviation occurrence and develop ways to prevent or lessen the seriousness of the occurrence;

c) To provide aviation technicians with the tools necessary to understand human behaviour, address conflict, prioritise time and ensure integrity, and;

d) To explore the organisational role in error prevention by providing participants with problem solving, risk management, listening and teamwork strategies for the work place.


12 Human Factors in Aviation Errors