How bad design kills people

This article about the plane collision above the amazon reads like a novel, and details the “long, thin thread of acts and omissions [that] brought the two airplanes together”. The accident could have been avoided if the pilots of the smaller plane – the one who cut the left wing of a Boeing 737 carrying 154 people – had noticed a chain reaction: losing their transponder (some sort of identifier) took down the anti collision system. The warnings were “in view but unseen”.

At that moment, 4:02 p.m., the transponder quit. No chime sounded in the cockpit. Instead, a small warning silently appeared on each of the two Radio Management Units, showing an abbreviation for “Standby.” The understated warnings must have made good sense to Honeywell’s engineers, who inhabit offices in Arizona, but they were not helpful to the pilots far away in flight, who were drowning in their products. For the next 500 miles the “Standby” warnings remained in view but unseen [...]

with their attention again focused on the cockpit, the pilots still did not notice that the transponder was on Standby. Another warning they missed was a small sign saying tcas off, shown at the bottom of each pilot’s Primary Flight Display, the screens they would have referenced for basic flight control had the autopilot not by law been handling that chore. tcas stands for Traffic Collision Avoidance System. It is a nested safety device independent of Air Traffic Control that converses electronically with other airplanes in flight, and in the case of imminent collision alerts the pilots of both airplanes and negotiates a solution—typically instructing one crew to descend and the other to climb. It is required equipment in almost all airliners and jets, and is considered to be so reliable that its instructions supersede those of air-traffic controllers. It works, however, only between airplanes with active transponders. In the Legacy cockpit, therefore, the tcas necessarily dropped out when the transponder switched to Standby. Again, there were no warning chimes. But as a consequence the Legacy was now flying blind to the presence of other airplanes, and was itself invisible to their otherwise functional tcas displays.

Link

How small moments of inattention can become diabolic. Routine is a pilot’s worth enemy I guess.