1. Kegworth Air disaster Example of multiple levels of analysis What causes a plane to crash? [1 min.]

2. What causes a plane to crash? A laundry list is required, or, a swiss cheese loaf lined up A lot, in safety critical systems

3. Kegworth Air Disaster Why? –Near Ritter, Baxter & Churchill –A lovely example –Often used

4. Storyline Flight, jan 1989, Heathrow to Belfast, Midland 192 Experienced pilots, new plane (737) Part of one of the safest systems in the world Upon take-off, no problems Shuddering, fire in an engine at ~10 min. Shut off #2 engine, RHS (the good one!) This is the pilot error

5. Hardware and Mischance  badly designed new engine, failure at 3 months, approx. t=300 h, should be t=500,000 h, not tested at altitude  /  unlucky choice of diversion airport [BMI hub]

6. Auto throttle problem  poor mental model of plane [system] (turned off good engine, which disengaged autothrottled, solving the judder problem)  lack of engine feedback [interface design]

7. Vibration Dial 1  vibration dial harder to read [design]  vibration dial not required to fly [regulation]  dial and plane not trained with simulator  technology updated but not announced

8. Vibration Dial 2  vibration dial small [design]  Without range marking [design]

9. During descent  lots of interruptions  pilots can’t see the engines  no protocol: no checking/confirmation visually from cabin Passengers could see fire but explained it away, perhaps also flight attendants  diffusion of social responsibilities  Social distance between aircrew and pilots

10. crash 900 m short 43+4 out of 118+8 die

11. At crash  Not documented: noise abatement hillocks

12. Afterwards If any 13  or 3  missing, no loss of life What was the pilot error? Thus, systems require understanding people, technology, and systems and environment

13. References Wikipedia on kegworth BBC. (1991). Fatal error: Taking liberties [television series]. Youtube has videos as well