Deviation from Established Procedures
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Procedures are described in Aeroplane Flight Manuals, Company Operations Manuals, Quick Reference Handbooks, Checklists and Standard operating procedures to enable the pilot to respond correctly in most types of normal, emergency or abnormal situation.
These procedures are developed over a period of time after careful study of the situation, and are tested to ensure that they do not result in unintended consequences.
Where established procedures exist, they should be followed unless exceptional, overriding circumstances exist.
Where an established procedure does not exist, pilots should not attempt to find a procedure which resembles the one sought; following a procedure which was not designed for the existing situation may have unexpected and undesirable results.
In the absence of an established procedure, pilots should exercise their judgement based on experience and knowledge, even though this may result in unintentional inappropriate action.
When time allows, it may be possible to obtain assistance by reference to the company flight operations or maintenance department
Occasionally, pilots deliberately choose not to follow an established procedure, or to omit certain actions called for in a procedure. This inappropriate action may occur because of ignorance, complacency, overconfidence or even laziness.
Unintentional inappropriate action sometimes occurs because the pilot is unaware of or cannot identify an appropriate procedure for the situation, or because his/her judgement is faulty.