Poor UI design can
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Poor UI design led to two deadly plane crashes: 1. Air Inter Flight 148 crashed in 1992 when the pilots mistook the vertical speed mode for descent angle mode due to identical digital displays, causing the plane to descend too quickly. 2. The Kegworth air disaster in 1989 occurred when vibration in an engine was not visible to pilots on a new digital display, leading them to turn off the functioning engine. Both crashes showed that user interface changes intended to look modern instead prioritized readability, contributing to loss of life.
Poor UI design can
- 1. Poor UI Design Can KILL A SHORT PRESENTATION BY SANDESH BHETWAL 1
- 2. Air Inter Flight 148 CASE 1 : 2 On January 20, 1992, Air Inter Flight 148 crashed into the Vosges Mountains while approaching Strasbourg Airport in Strasbourg, France. 87 of the 96 crew and passengers on board were killed. The Airbus A320 had the most advanced cockpit in the world. The majority of the gauges and instruments in front of the pilots in this machine were digital.
- 3. The Accident Flight 148 crashed because the pilots inadvertently left the autopilot set in Vertical Speed mode (instead of Flight Path Angle mode) then entered "33" for "3.3° descent angle", which for the autopilot meant a descent rate of 3,300 feet per minute. When the aircraft was approaching the runway through thick clouds, the captain thought he had set a descent angle of a mild 3.3 degrees for a gentle descent above the Vosges Mountains. However, unbeknownst to him the plane was descending at a rate of 3,300 feet per minute, much faster than the descent would have been at 3.3°. The aircraft struck a mountain top and exploded. 3
- 4. The Cause The problem was that the airbus A320 used a single display for two different descent modes – Vertical Speed (VS) Mode and Flight Path Angle (FPA) mode. The display showed FPA as two digits separated by a decimal point, and VS as just two digits (and both had a minus sign where their values were negatives). This simple design error led the pilot to believe he was in one mode while he was in another. The crash almost certainly would not have happened had the aircraft’s user interface been more clear. This UI design error is one of a well-known class of errors called mode errors. 4
- 5. The Aftermath Airbus modified the interface of the autopilot so that a vertical speed setting would be displayed as a four- digit number, preventing confusion with the Flight Path Angle mode. The flight data recorder was upgraded so that it was able to withstand higher temperatures and for longer. Also recommended that pilot training for the A320 should be enhanced. The story of the disaster was featured on the ninth season of Cineflix television show Mayday in the episode entitled "The Final Blow" 5
- 6. The Kegworth Air Disaster CASE 2 : 6 In 1989, a Boeing 737 crashed into the side of the M1 motorway near Kegworth, England.
- 7. The Accident The problems started when the jet began vibrating, indicating that one of its two engines was malfunctioning. Unfortunately, the pilots got the impression that the good engine was at fault and turned it off. Without any functioning engines, the jet became a large piece of metal suspended in the air and did what large pieces of metal suspended in the air tend to do. It went down ! 7
- 8. The Cause Some months earlier, the cockpit instrumentation in this type of plane was updated to give them a slicker-looking digital design. At one point during the Kegworth flight, the dial indicating the vibration in the left engine rose to the maximum and stayed there for three minutes -- but the pilots never saw it, because it was too small. The dial itself was already hard to see, and on top of that it had a digital pointer that barely existed. Also the fact that the whole place was vibrating at the time. In the confusion, the pilots never saw the dials. 8
- 9. The Cause The older model had a large, clearly visible mechanical pointer that was pretty hard to miss and can read those dials. 9 The newer model had a slicker, small, digital dials. The dials were hard to see, and on top of that it had a digital pointer that barely existed. In a zoomed view we can see the pointers.
- 10. The Aftermath Many people died because of this silly dial error. Redesign of the dial was done to make it readable than look stylish. 10
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