Why Do Planes Crash?

Why do planes crash?

Michael Toppa
University of Pennsylvania
Perelman School of Medicine
Information Services
July 28, 2011

Why do planes crash?
 It'snot like the movies
 “The typical commercial jetliner is about as
dependable as a toaster”
 Poor weather

 Tired pilots, awake more than 12 hours

 Behind schedule, so the crew is hurrying

 Pilot and co-pilot have not flown together
before

The cumulative effect of small
errors
 Crashes
are the result, on average, of 7 consecutive
human errors
 No single error is disastrous, but the cumulative effect is
 Studies
show this is typical in disasters involving any
complex system
 The 3 Mile Island nuclear disaster was the result of 5 minor,
consecutive human errors
 I believe there are lessons here for our work as well
 Poor communication among the crew is a key factor

Mitigated speech
 Whenwe try to downplay or sugarcoat the
meaning of what we say, because we're
 Being polite
 Feeling embarrassed
 Being deferential to authority

Hypothetical scenario
 In a research study, pilots were presented
with a hypothetical scenario, and asked how
they would handle it
 They are in the role of co-pilot, they see bad
weather ahead, and they want to make sure
they don't fly into it.
 What do they say to the pilot?

6 possible responses
1.Command: “turn 30 degrees to the right”
2.Crew obligation statement: “I think we need to
deviate right about now”
3.Crew suggestion: “Let's go around the weather”
4.Query: “Which direction would you like to deviate?”
5.Preference: “I think it would be wise to turn left or
right”
6.Hint: “That return at 25 miles looks mean”

The responses
 Pilots with the rank of Captain
overwhelmingly chose the “command” option
 Pilots with the rank of First Officer
overwhelmingly chose the “hint” option
 This may seem alarming, because it is!

 “A hint is the hardest kind of request to
decode and the easiest to refuse”

1982 Air Florida Crash
 The plane had a problem with wing ice before takeoff
 First officer: “Look how the ice is just hanging on his,
ah, back, back there, see that?”
 First officer, again: “Boy, this is a, this is a losing battle
here on trying to de-ice those things, it gives you a
false sense of security, that's all it does.”
 The captain doesn't get the hint, and the plane plunges
into the Potomac river a few minutes after take off.

Avianca Flight 052
 The captain is exhausted
 Planes are normally very low on fuel when landing, but
this flight is literally running on empty
 First officer to ATC: “Climb and maintain three thousand
and, ah, we're running out of fuel, sir”
 ATC responds with a command to continue circling, and
asks for confirmation it's ok.
 First officer to ATC: “I guess so. Thank you very much”
A flight attendant enters the cockpit, and the engineer
makes a throat-cutting gesture to her
 Two engines flame out and the plane crashes

KAL Flight 801
 The captain is experienced, but exhausted,
it's night, and the weather is terrible
 The captain has flown to this airport several times
before
 He decides on a visual approach, using the
airport's beacon to navigate
 He's forgotten the beacon is on a mountain near
the airport

KAL Flight 801, continued
 First officer: “Don't you think it rains more? In
this area, here?”
 Engineer: “Captain, the weather radar has
helped a lot”
 They are trying to tell the captain they shouldn't
be making a visual approach
 Korean language and culture makes it more
difficult to speak directly
 The plane crashes into the mountain

Dealing with mitigated speech
 Crashes are more common with the Captain in the flying seat
 “Planes are safer when the least experienced pilot is flying,
because it means the second [more experienced] pilot isn't
going to be afraid to speak up”
 For 15 years the airline industry has trained flight crews on
reducing mitigated speech
 Standardized procedures for escalating communication
 If necessary, temporarily relieving the Captain of duty
 KAL switched to English-only in the cockpit

Example from The Clean Coder
 Mike: “Paula, I need the login page done by
tomorrow”
 Paula: “Oh, sorry Mike, but it's going to take
more time than that”
 Mike: “When do you think you can have it
done?”
 Paula: “How about two weeks from now?”

 Mike: (scribbles something in his daytimer)
“OK, thanks”

Passive Aggressiveness,
Saying No
 By not speaking more firmly, Paula is inviting
doubt about her estimate
 What if Mike went to his boss and blamed
Paula for the project being late?
 That's “morally reprehensible” passive
aggressiveness
 Saying no can be the first step in a
negotiation towards the best possible
outcome

Why Do Planes Crash?

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