4.1 General
Details of design and construction shall be such as to give
reasonable assurance that all aeroplane parts will function
effectively and reliably in the anticipated operating conditions.
They shall be based upon practices that experience has proven
to be satisfactory or that are substantiated by special tests or by
other appropriate investigations or both. They shall observe
Human Factors principles.
Note.— Guidance material on Human Factors principles can
be found in the Human Factors Training Manual (Doc 9683).
4.1.1 Substantiating tests
The functioning of all moving parts essential to the safe
operation of the aeroplane shall be demonstrated by suitable
tests in order to ensure that they will function correctly under
all operating conditions for such parts.