A proper language comparison...

[Walter Bright]

On 7/26/2013 3:03 PM, Joseph Rushton Wakeling wrote:
> I hope I'm not being unfair, but my impression was that the very impressive
> modern safety record of air travel is at least partly down to lessons learned
> from some major historical catastrophes.

Designers make mistakes even in redundant systems - sometimes they turn out to 
be coupled so a failure in one causes a failure in the backup. Sometimes certain 
failure modes are not anticipated.

But one thing they do NOT do is assume that component X cannot fail.


> The one that always springs to mind is
> the De Havilland jets breaking apart mid-flight due to metal fatigue.

Boeing's fix for that not only involved fixing the particular fatigue problem, 
but designing the structure so WHEN IT DOES CRACK the crack will not bring the 
airplane down.

This design has been proven through a handful of incidents where an airliner has 
lost whole panels due to cracking and yet the structure remained sound.


> The number of flights and resulting near misses surely helps to battle test
> safely procedures and designs. That volume of learning opportunities can't
> readily be matched in many other industries.

The most important lesson learned from aviation accidents is that all components 
can and will fail, so you need layers of redundancy. The airplane is far too 
complicated to rely on crash investigations to identify problems.

I watched a show on the Concorde the other day, and was shocked to learn that 
there'd been an earlier incident where a tire burst on takeoff, the tire parts 
had penetrated the wing fuel tank, and the fuel drained away. The industry 
decided to ignore fixing it - and a few years later, it happened again, but this 
time the leak caught fire and killed everybody.