1. Any circuit design must contain at least one part which is obsolete, two parts which are unobtainable and three parts which are still under development.
2. Nothing ever gets built on schedule or within budget.
3. A failure will not appear till a unit has passed final inspection.
4. If you can't fix it -- document it.
5. The primary function of the design engineer is to make things difficult for the fabricator and impossible for the serviceman.