Andrew Godwin - What can programmers learn from pilots?

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Andrew Godwin @andrewgodwin Programmers LEARN FROM WHAT CAN Pilots?

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Andrew Godwin Hi, I'm Author of 1.7 Django & South migrations Senior Software Engineer at Really likes cheese FAA & EASA PPL, working on IR

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ﬂickr.com/photos/russss/16735398019/

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Learning about aviation Applying lessons to coding 1 2

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Commercial ﬂying is very safe AIRLINES GA 0.2 11.2 CARS/TRUCKS 0.53 MOTORCYCLES 15.6 Source: 2005 Nall report, 2004 NHTSA stats, 1991-2000 FAA stats, 40mph avg. road speed (fatal accidents per million hours) General aviation is still not bad

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Pilot Source: 2005 Nall report Mechanical Other 76% 16% 9% GA ACCIDENT CAUSES

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COMMON CAUSES Controlled ﬂight into terrain (CFIT) Disorientation in clouds (VFR in IMC) Bad decision making (get-there-itis)

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WHY DO I KNOW THIS? Detailed investigation of every accident

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HOW DOES IT HELP US? Let's look at common problems

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Soft Failure Explicit disengage signals Covering inaccurate instruments Replacing parts at ﬁrst sign of issues

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Soft Failure Crash hard on any serious error Redundancy, not single system reliability Freedom to get rid of servers whenever

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Noisy Warnings Limited number of warning sounds Clear, unambiguous text & speech No constant low-level warnings

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Noisy Warnings Don't email/notify on every tiny error Choose 5 top errors, solve them ﬁrst If you ignore it for a week, delete the warning

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Poor Testing Every part tested to destruction Well known statistical limits Knowing when, not if, things fail

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Image: © Boeing 2010

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Poor Testing Test latency, memory issues, dodgy network and other unusual things Interactions are as important as individual units

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Automation Reliance Tested without autopilot/instruments Plane usually advises, rarely controls Easy to see what's happening and why

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ﬂickr.com/photos/wkharmon/4631001766

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Automation Reliance Don't rely on magical automatic failover Regularly practice manual recovery steps Know what your systems are doing

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People Reliance Checklists for everything Warnings built around common assumptions Reduce workload at critical times

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People Reliance Checklists for releases/testing/onboarding Automate common tasks Reduce workload at critical times

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Bad Priorities Aviate, Navigate, Communicate Minimum Equipment Lists Mayday priority

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Minimum Equipment Quiz Passenger video screens Lavatory ashtrays Air conditioning Fuel recepticle caps Seatbelt signs Weather radar

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Minimum Equipment Quiz Passenger video screens Lavatory ashtrays Air conditioning Fuel recepticle caps Seatbelt signs Weather radar

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Margaret Hamilton

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Bad Priorities What are your critical features? What can you do without? Know what you want to ﬁx ﬁrst and test most

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Unclear Responsibility Single person always in command Others are always listened to Clear, concise communication

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Unclear Responsibility Single person makes key decisions Others are always listened to Clear speciﬁcations and expectations

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Blame Culture There is never a single cause of an accident Individual problems identiﬁed and addressed Blaming someone solves nothing

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Blame Culture There is never a single cause of a problem Work back and ﬁnd all of the bad factors Blaming people makes things worse

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Deadlines Always carry extra fuel Always have an alternate Land safely rather than at the destination

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Deadlines Don't schedule everyone at maximum Always expect unknown problems Ship good code rather than to a deadline