Why do planes crash?

Michael Toppa

University of Pennsylvania

Perelman School of Medicine

Information Services

July 28, 2011

Why do planes crash?

It's not 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

When we 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