Wednesday, December 11, 2013

SMS, NDT And Human Errors

After major airplane accidents pilot error is often determined as the only cause, and calls for more automation is immediately on the list of demands. Automation is necessary and helpful. The days are gone when a pilot must leave the flight controls and manually and mechanically lower the landing gears in an emergency situation, which is necessary on the WWII veteran airplane PBY-5A.  


However, when pilot error is determined to be the root cause, safety is compromised and doors are closed to apply human error as an operational link to organizational factors. 

When rolling down a runway pilots are the first in line to discover automation errors.
Making flying critical dependant on automation may at first impression appear to be the right thing to do. On the other side of the coin, removing authority of human factors from the processes may lead to unexpected consequences.

In the aircraft production line human factors are applied in testing of material quality.
Non Destructive Testing (NDT) is a process to improve aviation safety as quality control of material defects or material fatigue. This method of testing does not destroy the product and tested components are used in the production line. NDT is used in almost any industry where there is a material performance quality control system in place. 

There are different types of NDT applications. Some of these are x-ray, ultrasound, fluorescent penetrant, magnetic particle, isotopes and acid inspections. Each one of these processes is applicable to specific parameters of the quality control process. X-ray is used to check for internal errors, ultrasound is non-precession inspection of material flaws, fluorescent penetrant is to inspect for surface pores or cracks, magnetic particle for defects in ferrous material, isotopes for coating thickness and acid for material temperature variances.

An example of the fluorescent penetrant process is to inspect for pores and cracks on a compressor-disk for assembly in jet engine. By applying a fluid which is visible under fluorescent light, any pores or cracks will show up when applying fluorescent light in a dark room.
Another example is the inspection of temperature control in production of a turbine engine rotor shaft. A rotor shaft in production must be exposed evenly and within tolerances of temperatures. After production a quality control test is conducted by submerging the shaft into a tub of acid for a period of time. When lifted out, discoloring on the surface will indicate if the material has experienced variations in temperatures.

When pores are found and discolouring identified, the investigation review the possibility of inspector’s human errors and the inspection and manufacturing processes are investigated. By identifying segments of the processes, it becomes possible to investigate human factors, inspection processes and the manufacturing processes without ambiguity.

If automation replaces humans in critical stages of a process, the human-error factor is not eliminated, but transferred into an automation package. 

When humans are erased from the process and automation fails there is no one to manage errors.
When human errors are concealed in automation, these errors may not be correctable due to automation lack of performance resilience.
People are resilient with the ability to recover from mistakes. In an SMS world, it is people who make the difference in how errors are managed. 

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