MTBF warranty/guarantee for multiple user avionics

A MTBF (mean time between failures) warranty/guarantee situation is modeled for an avionics unit installed on different platforms and subjected to varying levels of operational stress. The demand for warranty repairs is approached by structuring submodels and solving these submodels using linked spreadsheets. The spares guarantee is modeled using the MTBF parameter and the expected number of units installed in the various platforms. The spreadsheets contain the essence of the mathematical models/calculations and are a form of self-documentation