Waddington Effect… contd…

Ref the earlier post on Waddington Effect here…

Waddington and his team were trying to figure out the right timings for scheduled and unscheduled maintenance performed on aircrafts. In those times, the bombers underwent scheduled “preventive” maintenance (PM) services every 50 flight hours.

So, they collected data and plotted those as histogram. The result went against their general expectation. Waddington and his team discovered that unscheduled repairs dramatically went up after each scheduled 50 hours service. and then declined steadily over time until the next scheduled 50 hour service was due. Once done, the pattern just repeated over and over again — shooting up unexpectedly just after a scheduled PM and then tapering off when the aircraft neared its scheduled PM time.

It looked something like this:

Histogram of repairs undertaken after scheduled PM

On examining the pattern, Waddington commented that scheduled maintenance “tends to increase breakdowns, and this can only be because it is doing positive harm by disturbing a relatively satisfactory state of affairs. Secondly, there is no sign that the rate of breakdown is beginning to increase again after the 40 - 50 flying hours, when the aircraft is coming due for its next scheduled ‘preventive’ maintenance event.”

Now the question is — do industrial machines also follow patterns similar to that observed for the bombers?

Not surprisingly, the answer is a big yes.