Increasing the reliability of an expert’s initial hypothesis

Should half a dozen people riding an elevation 30 floors up – about 300 feet, expect the same standard of equipment maintenance as half a dozen people flying in a plane at 300 feet?  You would think so.  If the plane falls from the sky people are certain to be killed or seriously injured.  If the elevator free-falls in its shaft the same can be expected for the people on board.

What about a fun-filled Ferris wheel several 10s of feet high at a circus?  (There was one set up near my home recently)  What should the paying public expect?

What’s this got to do with an engineering expert formulating a reliable initial hypothesis on the cause of a building or bridge collapsing, or an elevator failing?  Actually quite a lot, if the reliability of a hypothesis is increased on knowing if maintenance of the structure included independent inspection.

I thought this after a reader told me about,

  • the strict maintenance procedures for military aircraft,
  • the independent inspectors who swoop in unannounced to check on maintenance, and,
  • the small profit margins for civilian companies who contract to do aircraft maintenance.

The Department of National Defence (DND) monitor and inspect the maintenance on military aircraft by private contractors.  Transport Canada do this in a similar way for civilian aircraft.

Who does the independent maintenance inspection for elevators?  Many are failing according to recent news reports. (Refs 1, 2)  We need to know if such a procedure exists if we are to formulate a reliable initial hypothesis on the cause of a failure.  We need to remember that maintenance is the Achilles’ heel of the built environment. (Ref. 3)

We can ask this question about any type of failure or accident in the built environment.  Who does the maintenance of structures – including Ferris wheels, used by the public and who independently ensures it’s done to an acceptable standard?  The owner of the structure?  He’s got his profit margins like the aircraft maintenance companies, and may also think of them as small.

I had these thoughts after Gary Bartlett, P. Eng., Halifax, a retired aircraft maintenance engineer, read a previous blog on the incidence of elevator failure in Canada and the suspect maintenance. (Ref. 2)  He commented on the exhaustive maintenance on military aircraft, the tight profit margins, and the independent government inspectors who would show up unannounced to check that maintenance had been done properly.

Gary and I were classmates in engineering at the University of New Brunswick; he did electrical engineering and I did civil.  He then joined the air force and flew on military aircraft as a radio officer for years.  After that my good friend joined a military aircraft overhaul company as an electrical and avionics engineer.  In time he became vice-president of an engineering design branch.

I subsequently spoke with an aircraft mechanic, Shaun Morin, Edmonton, who confirmed that independent inspectors might drop in on him doing his job, unannounced. They would want to know in detail what he was doing – right down to the toque he used to tighten a bolt.


What I’m realizing as I write this item – thinking on paper – is the need for independent maintenance inspection agencies for different structures used by the public, not just aircraft.  Agencies that ensure a maintenance program exists and is being carried out properly.

An engineering expert can increase the reliability of his initial hypothesis on the cause of a failure just by checking that such an agency exists for the structure involved in his investigation.


  1. Perkel, Colin, What goes up doesn’t always come down.  National Post, page 1, July 22, 2016 reporting on an investigation by The Canadian Press.
  2. Unusual data increases reliability in forensic investigation.  Posted July 29, 2015
  3. “Maintenance”: The Achilles’ heel of the built environment, and sometimes the cause of failures and accidents.  Posted June 12, 2014