The advent of SI units makes it necessary to revise many standard constants and numerical values which are familiar to a generation of aeronautical engineers whose education and practical experience have been solely with the British system of units.

Most affected by these changes are not so much those who spend all their time carrying out (computer-aided) calculations, but those who direct such work and whose personal calculations are limited to the backs of envelopes. The task, for the latter, of assessing and communicating data presented in unfamiliar units is very daunting, and the possibility, for them, of ever being able to think in the new units may seem remote.