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Comment by blackflame7000 | Hacker News Reader

If you look at the Top 7 safest airplanes in terms of accidents per hours flown you get:

1) Airbus A340 - No crashes

2) Boeing 777 - 5 crashes, 2 intentional (Malaysia x2), 1 engine-related (Rolls-Royce problem), 2 pilot-error (Asiana/Dubai) - [Thanks fishywang]

3) Boeing 747-8

4) Boeing 737-NG

5) Boeing 767

6) Airbus A320

7) Boeing 757

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Also worth pointing out that there are 4 times as many 777s as there are A340s. Doesn’t mean A340 isn’t great, just that the odds of no accidents go up with fewer flight hours.

The popularity of A320 and 737-NG makes their safety records particularly impressive.

Also the A320/737NG typically fly more shorter segments so spend proportionally more time in the critical phases of flight.

It also speaks highly of the level of engineering and testing required to determine the limitations of each an every part that must be maintained for safe flight.

Did you miss the Asiana 777 at SFO? Or is that engine-related?

That one was stupidity-related.

I was always irrationally nervous flying into SFO, worried about precisely what ended up happening. We should all be glad the plane mostly held together through the cartwheel, saving many lives.

I can confidently assert that no airframe is designed with cartwheeling in mind. Nor hitting trees/buildings/cliffs.

True, it's not part of the certification process, but I do know that modern jets airframes are made to be as... um... "flexible"* (? searching for the word here...) as possible in catastrophic situations. An older airframe probably would have disintegrated under the same forces.

Luck and good fortune also played a huge role of course. What the pilots did was unconscionably neglectful. CFIT is often (usually?) fatal for all passengers.

*EDIT: It's similar to software that's written to be extremely robust that encounters an unexpected error (or set of errors). The software wasn't necessarily designed to handle it, but sometimes it can nonetheless.

> as possible in catastrophic situations

That isn't really something engineers can design to. What happens is the aerodynamics group calculates the maximum loads on the airplane. This is increased by 50% and called the "ultimate load", and the parts are all designed to not break up to that load.

Parts stronger than that are overweight, and weight is the enemy of all airplanes.

After parts are designed, they go through an independent "stress" group which verifies that the parts meet the strength requirements.

I think what he is referring to is the modern use of composites and carbon fiber which are both stronger and lighter than older aluminum or titanium components. Titanium, for example, is a very hard metal that will fracture more readily than a softer composite that is able to dissipate the stress better.

If a stronger and lighter material is used, that just means they use less of it.

There's a limit to that. People still need to fit, and parts need to connect so there are constraints in every dimension.

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