When UI is a Life or Death Affair

John Gruber highlights the Telegraph’s Damn it, we’re going to crash account of the Air France Flight 447 tragedy – “User-interface design is, in some cases, life or death.”

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The whole account is mixture of bad design decisions mixed with human error so easily brought about by panic and stress, which is exactly what happens in a crash, of course. Gruber quotes this section, which is the biggest indictment:

A minute after the autopilot disconnected, Bonin muttered something odd: “I’m in TOGA, huh?” TOGA stands for Take Off, Go Around. Bonin was apparently so disorientated that he believed he was operating at low altitude, in a similar situation to a pilot having to abort a landing approach before circling for a second attempt. Standard procedure on abandoning a landing is to set engines to full power and tilt the aircraft upwards at 15 degrees. But Flight AF447 was not a few hundred feet above a runway. Within a minute it had soared to 38,000 feet in air so thin that it could climb no more. As forward thrust was lost, downward momentum was gathering. Instead of the wings slicing neatly through the air, their increasing angle of attack meant they were in effect damming it. In the next 40 seconds AF447 fell 3,000 feet, losing more and more speed as the angle of attack increased to 40 degrees. The wings were now like bulldozer blades against the sky. Bonin failed to grasp this fact, and though angle of attack readings are sent to onboard computers, there are no displays in modern jets to convey this critical information to the crews. One of the provisional recommendations of the BEA inquiry has been to challenge this absence.

But there are other interface problems too, including the shift from analogue to digital in which the natural affordances of dual controls are lost:

Like all other aircraft in the modern Airbus range the A330 is controlled by side sticks beside pilots’ seats, which resemble those on computer game consoles. These side sticks are not connected to the aircraft control surfaces by levers and pulleys, as in older aircraft. Instead commands are fed to computers, which in turn send signals to the engines and hydraulics. This so-called fly-by-wire technology has huge advantages. Doing away with mechanical connections saves weight, and therefore fuel. There are fewer moving components to go wrong, the slender electronic wiring and computers all have multiple back‑ups, and the onboard processors take much of the workload off pilots. Better still, they are programmed to compensate for human error.

The side sticks are also wonderfully clever. Once a command is given, say a 10-degree left turn, the pilot can let the stick go and concentrate on other issues while the 10-degree turn is perfectly maintained. According to Stephen King of the British Airline Pilots’ Association, it’s an admired and popular design. “Most Airbus pilots I know love it because of the reliable automation that allows you to manage situations and not be so fatigued by the mechanics of flying.”

But the fact that the second pilot’s stick stays in neutral whatever the input to the other is not a good thing. As King concedes: “It’s not immediately apparent to one pilot what the other may be doing with the control stick, unless he makes a big effort to look across to the other side of the flight deck, which is not easy. In any case, the side stick is held back for only a few seconds, so you have to see the action being taken.”

Read the full account on the Telegraph’s website here.

Andy Polaine

Interaction and Service Designer, Writer, Lecturer, Researcher. Follow him on @apolaine.

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