By Eugene le Roux, mechanical engineer, one of his regular online articles on general project management principles.
Are specifications adopted from some literature source; derived from the System Engineering Process; or developed iteratively with the hardware?
Eugene le Roux, retired mechanical engineer.
© RACA Journal
May we discuss it, using a car’s radiator as an example?
Adopted specifications:
How sure are we that these specifications are representative of the exact environment in which, in this case, the radiator is to be used? Are the road vibrations similar, is the operating coolant pressure the same, is the mounting in the vehicle comparable? This method could have many hidden pitfalls unless one takes everything into account.
This process ostensibly seems fast and affordable.
Derived specifications:
As these are aligned with the true high-level requirements of the main product, would you agree that it should have a high probability of success?
It does, however, require expertise, and is costly, and time consuming.
Developed specifications:
This path where specifications are developed iteratively along with the hardware, could take too long, and costs too much, before the objective is reached.
It must be added that even derived specifications might be subject to some refining and updating as testing and application proceeds.
- Question 1 arises: Let us consider a component or subsystem which easily conformed to its specification by a wide margin, and successfully supported the system qualification of the main product. Later, an alternative to this component or subsystem is offered, which still conforms to the specification, but qualified with a narrow margin of performance. Could the successful implementation of this second component, or subsystem, be assumed safe in operation?
- Question 2 arises: Given that one might have an updated system specification, and may have reached the end of the development, must one now qualify the product against the original system requirement, or the updated system specification?
- Question 3 arises: If the performance of a specification changes significantly, are there any other documents on the project which must consequently be updated?
Would you like to help me understand this better? Please discuss, I’m learning from you all the time.
