ship flexing in storm

This would make me uneasy....

https://www.youtube.com/watch?v=PmlTk_3NN_g

 

Does the flexing of an aeroplane's wing make you uneasy?

 

You get use to it, but think about what would happen if it was so rigid it didn't flex, particularly as the ship crested a swell on the bow and stern at the same time, leaving the midship area unsupported. Being flexible is good, just ask your wife . . .

 

Well said.

 

Well, since ya brung up airplanes...

http://old.seattletimes.com/html/boeingaerospace/2011468264_boeing29.html

So in this test, the wing broke at 54% more than it was designed for. A brand new wing, not one that has been in service for x amount of years with x amount of take off and landing cycles.

If I buy a hoist that's rated for a maximum of 1000#, and can assume it will explosively shatter at 1540#, I'd be a little leery of it. But it's not like you would fall 30,000 feet or sink in the ocean if it happened.

https://www.quora.com/What-is-the-typical-lifecycle-of-a-passenger-airliner

So, it would be interesting to see them bend that wing after 60,000 pressurization cycles, being as how it has only been tested to 50% past it's design strength to begin with. Actually, I'd like to see them bend it as far as they did fast, maybe 2 or 3 times, in 50 degree below zero temps, like in a real situation, and not just once over a two hour time frame in a heated hanger.

https://www.quora.com/When-does-an-airliner-get-retired-from-use

That sounds a little like the bean counters getting involved in the engineering, which is often interesting.

Anyway, it would make me uneasy to be on that ship and I don't particularly like it when the wings start flopping up and down either.

Here's another ship situation, it has some off color language so if that makes you uneasy, plug your ears or something....



https://www.youtube.com/watch?v=YL2XL17z8Fs

 

Don't worry, it is all comprised in that "design strength" term - which is actually called "limit load" according to aeronautical terminology. It includes the maneuvering effects, the wind gust effects, the severe dive speed effects, high-lift devices effect, the fatigue and others, and is a statistically very conservative number.
That limit load is than multiplied by a safety factor of 1.5 in order to obtain the so-called "ultimate load", which is the one the wing has to be tested and proven against.

Modern wings routinely fail within +/-3% of the ultimate load. This is an indicator of both the accuracy of modern tools for structural design and analysis, and the fact that this load is so conservative that designers feel extremely confident that they do not need to add anything more in order to meet the safety goals.

See that wing-bending animation in my previous post? Well, compare it to a typical wing flexing in a severe turbulence:
https://www.youtube.com/watch?v=i9IhQxmt08U
(I guess only Russians would take-off a passenger plane in such weather conditions - that's why you really don't want to make war on Russia )

Or this one:
https://www.youtube.com/watch?v=IQ7hLToojUg

As you see, the load test brings the wing structure way, way beyond the stress which the plane will likely ever encounter over it's life span, as much as it can be extended.

 

How much do you want to increase the safety margin by? To 200% to 300% it's always possible to make something safer, but at some point you just have to stop and say X is safe enough then implement a testing regime to ensure continued reliability.

Rough numbers are that a 737 burns about $100 of fuel per year per pound of weight. If you start with the base empty weight of the plane of 120,000lbs and add 10% more mass to increase the safety factor that's an increase in weight of 12,000lbs. And an increase in fuel cost of $1.2m. At the same time you have reduced the usable payload from 35,000lbs to 25,000lbs.

So at the same time you increase the fuel cost for an empty plane you also reduce the number of pounds available to pay off that fuel bill. Skyrocketing ticket prices, and increasing the number of planes needed in order to carry the same amount of cargo.

All to acomplish what? Airline travel, even in tertiary markets and carriers is incredibly safe. Even old worn out planes have close to zero in air failure rates. So why force an industry to design to a higher standard when they current one is so immensely safe?

 

Stumble,
that, too, is very well and correctly said.

 

Fatigue is an extremely complex subject.

It depends upon, the design the manufacture and the in-service monitoring.
The design side has more inputs than i can shake a stick at, but suffice to say, are you referring to constant amplitude loading or variable...are you referring to a stress ratio of R = 0 or 0.1 or what...and so on and so on. Similarly with the manufacturing. But then is the last, the in-service monitoring. Knowing locations that are prone or suspect, a program of monitoring is employed to ensure such regions do not become critical. Just like general servicing of your car..after XXX miles, check the brake pads or brake hoses etc...just because one must replace them does not mean it is a poor design!

Sadly that's nowt compared to several flights I've had. One in which the bad turbulence lasted over 10hours...there was no escape. No food drinks etc for over 10hours as the crew were ordered to remain sitting.!

 

If at all possible,avoid domestic planes and carriers in Russia.

You don't want to know....