Saturday, December 10, 2011

Comments on the Crash of Air France 447

The Airbus's vertical stabilizer recovered

I just read a couple of articles about the crash of Air France 447. My take, (as a mariner, I am not an aviator)  is that the root cause of the crash was the  failure  to avoid bad weather.

The first article is from Popular Mechanics: Air France 447 Flight-Data Recorder Transcript - What Really Happened Aboard Air France 447 - Popular Mechanics

The factors which led to the crash were:

- The plane encountered bad weather
- An iced up  pitot tubes caused a loss of aircraft speed data
-With the loss of airspeed  data the computer  disconnected the autopilot
- The controls  switched modes from  "normal law" to "alternate law
- The junior most pilot panicked and stalled the plane.
- The yoke system averaged the input from the pilots and co-pilots yoke but without providing information that one pilot was pulling full back, this made it impossible  for the captain and other co-pilot to determine the cause of the plane's behavior.

Because of the unusual combination of factors above the crew flew a  perfectly good, highly sophisticated  plane with 228 passengers into the ocean.

The second article is from BoingBoing - the post is Disaster book club: What you need to read to understand the crash of Air France 447

This article points out that the crash is an example the type of incident described in the book Normal Accidents by Charles Perrow

I agree the accident could be viewed as a normal accident but my take is that the error made was the simple one of failing to avoid bad weather. The root cause can be found in the very first line from the synopsis in the  Popular Mechanics article.

At 1h 36m, the flight enters the outer extremities of a tropical storm system. Unlike other planes' crews flying through the region, AF447's flight crew has not changed the route to avoid the worst of the storms.
So it begins. It ends at 2h 11m when the plane hits the sea surface. 

Had the plane flown around the bad weather, the latent conditions and the weird, unexpected failure path never would have been revealed.

One other point,  you can't avoid heavy weather if you don't have or don't pay attention to the forecast. Typically, shipboard the mates will simply rip what ever comes off the INMARSAT printer and, regardless of it's relevancy,  post it without reading it. I don't allow that. On my ship I have a specific, written procedure that insures the correct weather forecast is read, understood and posted.

Knowing the weather forecast is not just a way to avoid disaster. It also should be part of routine on a well run ship as weather impacts almost all maritime operations.


Avoid heavy weather - that's a principle I've posted about twice before:  Parametric Rolling of a Car Carrier in a Head Sea 

In that post I wrote: "
- avoid heavy weather. Hidden flaws, the so-called latent condition, ..... are more likely to reveal themselves when the ship is being tossed about in bad weather, just when you can least afford to cope with it.
In the second post  Heavy weather encounter - The Satori. ,  I wrote:
It is not only the vessel that encounters heavy weather, it is the vessel, crew and cargo. Operating vessels, and their crews, near limits increases risks and chances of failure, - but the path of failure may not be the one expected.

 I've posted about normal accidents a couple of times: Normal Accidents and here "Thinking Like a Mariner - Managing the unexpected." 


The Antipodean Mariner said...

Thanks Kennebec Captain for the posting and link to the PM article. AM has followed the Air France 447 story with interest as a modern case study of the failure of the Cockpit Resource Management model under stress.

Aviation appears to be much more subservient to ATC instructions - a good thing that Masters can still largely determine their own routes, even with the provision of ocean routing services.


George Marikas said...

Avoid heavy weather.. That's a good advise & warning

George Marikas