Tag: normal accidents

The Dropped Washer Effect

One of these buildings can melt your car down. Can you identify the culprit?

Have you ever come across a situation where something, utterly negligible and minor, had become a cause for a major disruption or even an accident? Such as a small crack in an underground water pipe, dripping inconspicuously for a couple of years, and eventually causing a landslide after accumulating a critical mass of water? Or a seemingly common glass building capable of focusing the sunlight so that it melts the bodywork of cars parked nearby?

If so, chances are high that you observed an example of the Dropped Washer effect. Named after a Boeing 737 accident in Okinawa, Japan, the dropped washer effect describes large-scale adverse events that happened because of the cause of an incomparably lower significance. The unfortunate Boeing ended up burning out completely because of a missing slat mechanism washer, 0.625 inches wide, that the engineering crew forgot to replace after the aircraft’s last service.

One characteristic of the potential dropped-washer features that makes them particularly naughty is their zero perceived value for the business. Offering no added opportunities and presenting no apparent risks for the product, they often do not even exist in the minds of the product stakeholders. This important peculiarity makes it all too easy for them to slip every safety measure employed in modern production flows – from risk assessment to quality control.

Happily, in many cases there are techniques that can help increase our chances of spotting and eliminating the dropped washers from our projects.

Check out my new paper here.

Picture credit: Reuters

7 Security Mistakes Boeing Made

The story of the two recent Boeing 737 MAX crashes is packed with questions we are yet to find answers to, yet it is already clear that the distinctive feature of the double tragedy is overwhelming number of gross blunders – a lot more than you would expect in a field so extremely attentive to security and safety as commercial aviation.

While we don’t know all the details of the crashes so far, what we do know points out a number of grievous security flaws:

  • security feature as a paid option, not by default: Boeing charged airlines extra for sensor discrepancy detectors; neither LionAir nor Ethiopian aircraft had them installed;
  • hiding information: Boeing hid from 737 pilots that their new aircraft featured a new MCAS system, which could quietly intervene and override the pilots’ control of the aircraft;
  • ignoring feedback: MAX pilots complained to FAA about issues with the aircraft’s in-flight performance, but those were largely silenced/ignored;
  • no safeguards for MCAS failure: this has not been officially confirmed, but it looks like pilots wouldn’t be able to switch off MCAS if they needed to, effectively being unable to fly the aircraft fully manually to recover from MCAS or sensor failure;
  • creating workarounds rather than fixing bugs: the MCAS system was introduced to balance the MAX’s tendency to raise its nose up due to changes in the aircraft’s aerodynamics as a result of its bigger engines. In other words, the essence of MCAS is effectively adding a ton of BBQ sauce on to your overpeppered steak, rather than cooking a well-peppered steak from the very start.
  • conflict of interest: it appears that a great deal of safety tests of the new aircraft were performed by its very creators;
  • trust compromise: this is by far the grossest mistake made by Boeing and FAA; something that might well affect the success of the whole MAX family and of its freshest 777X machine, which was quietly (guess why) introduced two days ago. Whereas the whole world had been grounding their MAX fleets, Boeing chose the tactics of silencing the matter, denying any allegations, and refusing to admit similarities between LionAir and Ethiopian crashes. The only statement that made sense from them was about introducing a vague ‘software update.’ A matter of uttermost importance is that, as per Boeing’s own words, the prospective change was in the works well before the second crash.

I feel incredibly sorry for those who lost their friends and relatives in the crashes, and I feel sorry for the designers of the MAX, which is without doubt a great aircraft. I only hope that the investigation goes smoothly (with Boeing bosses apparently being quite reluctant for it to), and discovers the full truth about the crashes. Being sensible humans, the best we can do for those who gave up their lives to the tragedy, is to learn our lessons and write down all the mistakes we made, and then do everything in our power to prevent anything similar from happening in future.

Picture credit: Boeing