In 1977, two fully loaded 747’s collided on the runway at Tenerife North Airport, killing 583 people. As of 2018, it remains the worst disaster in aviation history. As with any engineering failure, many factors had to align to defeat all the safeguards. The primary factor was heavy fog; as the KLM 747 was rolling down the runway for takeoff, visibility was only a few hundred meters. So they didn’t see the PanAm 747 — which was still on the runway — until it was too late. But why was the KLM 747 taking off when the PanAm 747 was blocking its path?
“Departure” versus “Takeoff”
Another factor that doomed the two planes was a communication problem. The KLM plane had lined up at the end of the runway, and was impatient to takeoff before the crew maxed out their on-duty time (which would have required a replacement crew). The KLM plane radioed to the tower “We are now at takeoff,” to which the tower replied “OK … {Stand by for takeoff, I will call you}.” The latter part of the tower’s response is in braces because it was inaudible to the KLM crew. Instead, they heard the SQUEAL of radio interference. This SQUEAL was caused by the PanAm 747 interjecting “No! Eh? We are still taxiing down the runway!" Fatefully, the KLM 747 interpreted “OK” as a takeoff clearance and began to roll.
The fire burned for several hours, but luckily the KLM’s cockpit voice recorder survived. It revealed that the KLM captain had begun takeoff unilaterally, even though his copilot thought the tower’s message was ambiguous. But the captain was KLM’s chief flight instructor, so instead of calling “Abort” to end the takeoff until a proper clearance had been received, the copilot deferred to his senior. This fact revolutionized the airline industry, leading to the formal development of Crew Resource Management (CRM), a discipline which studies how humans communicate and perform under stress, and the most efficient way to delineate tasks among the flight crew. One of the major changes was to radio procedures. The word “takeoff” is now only used by the control tower, and only when giving (or cancelling) a takeoff clearance. In all other situations, the word “departure” is used in in its place (e.g., “Line up for departure” or “We are ready for departure.”). This rule dramatically reduces ambiguity on a crackling, low-fidelity radio.
What does this have to do with chip cards?
If you’re like me, you’re also impatient to “take off” from the checkout line at the store. And if you’re like me, you pay for everything with a credit card, then kill off your balance after every statement. Enter the chip card, which must remain inserted in the point-of-sale reader … until the machine starts beeping loudly because it is time to remove it. I find this beeping extremely annoying, and am usually trying to put my wallet away so I can resume bagging, so I always try to rip my card from the reader as soon as possible. But sometimes I remove the card too soon, and doom myself to repeating the failed transaction. Clearly, this has happened to me often enough that I spent 30 minutes blogging about it. So what can be done?
The word remove should only appear when it is time to remove the card. I often see readers displaying messages like “Don’t remove card”, and these messages often inexplicably jump around the screen. My brain sees the word “remove” suddenly appear, and I yank the card out. If we learn from Tenerife, “remove” should be a reserved word, just like “takeoff”. In my opinion, the following rules will dramatically improve the user interface of chip card readers.
There should only be two messages when the card is inserted. “Keep card inserted.” and “Please remove card.” This reserves action words for their specific context, and intentionally avoids negation (i.e., “Don’t remove card”) which is another layer of complexity to parse.
Messages should always be in the same place/line on the screen, and should not jump around.
The two messages should emphasize their differences; the words “inserted” and “remove” should be bolded. Additionally, one message should be black on white, and the other white on black (or some similar change in background that indicates a time for action).
The beeping should start calmly (like a chime or ding), and only become really annoying when the card has not been removed after a few seconds.
An encyclopedia of failures
As a final though, the internet is an extremely powerful tool, and resources like Wikipedia make it extremely easy to disseminate humanity’s collective wisdom. However, a fundamental problem with the way knowledge is organized is that it often focuses on “what works” or “this is how you do it.” Little attention is paid to “what failed” or “don’t do it like this.” In the past, when all knowledge was printed (expensively) on paper, this strategy made sense, as there was only room for the winners. But now that information is cheap and plentiful, we have room for all those losers. Because humanity’s collective failures have an important purpose; to teach us what didn’t work, lest we make the same mistake again.