An airplane is a system, it is made of
components
That are interconnected and have a behavior. Thus as a system, an airplane:
- It is composed of dissimilar elements/parts/components
- Parts are interrelated:
- What happens to one part may affect the others.
- What happens to one part may affect the outcome (output) of the whole system.
- While performing processes transform inputs into outputs, it has a behavior, derived from how it is formed (its structure) and the interrelation of its components.
The most important consequence is that to have control of what an
airplane does, it is necessary to control its components and the interrelations
between them.
When we put together this system, we have to assure the parts are right and
the connections and processes between the parts are working right, to obtain
the desired results.
How is this accomplished? By formally:
- Describe the structure (specify the components).
- Define the inputs and outputs (specify performance).
- Describe the processes that transform inputs into outputs (define procedures).
The word formally means with a form, following some order, that have a material permanent form, so it is not just an idea or immaterial thing.
That's why it is necessary to have the drawings and construction manuals, have a specifications sheet, and finally the Pilot Operating Handbook or POH.
These are considered to be so important, that are required by regulations as an input to grant the airworthiness or permission to fly.
As a system -it is the widespread strategy- the safest way to operate (fly) an airplane is following checklists. It is adhering to formal procedures.
