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Some days ago, I took a plane (Airbus A330) for a pretty long flight - around 8hrs. During the flight, we experienced some turbulences and I thought : what if the turbulences last the whole flight?

How would a plane react to 8+ hrs under mid to heavy turbulences during the whole flight?

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    $\begingroup$ Best asked on the aviation stack, but how severe? some wind shear can take wings off, other can just cause a mild sensation - and cause some to have motion sickness... $\endgroup$
    – Solar Mike
    Oct 9 '18 at 14:17
  • $\begingroup$ I'm thinking about the ones that you can feel inside the airplane, with 'up/down' bumps or lateral bumps. I'll also check the aviation stack (didn't know there is one) $\endgroup$
    – toto
    Oct 9 '18 at 14:19
  • $\begingroup$ It's tempting to state that aircraft can withstand turbulence for 105% of the time it takes you to get airsick. The simple answer is that the airframes are designed to withstand extreme storm conditions for the length of time it'd take to leave the storm area (plus a safety factor). $\endgroup$ Oct 9 '18 at 17:22
  • $\begingroup$ There was an incident back in the 1990s (but not caused by turbulence) where a B747 had continuous vibration levels in the passenger cabin which were so severe that the flight attendants couldn't walk around - and the plane survived about 90 minutes of that before landing - it couldn't land sooner, because the incident started when flying over the Pacific Ocean. $\endgroup$
    – alephzero
    Oct 9 '18 at 17:30
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You may want to look for aircraft fatigue loads, which are the typical loads that an airplane may experience during a fly (some sets include data for harsh conditions). They look like this (depending where are you measuring):

enter image description here

Or:

enter image description here

And note that airplanes are designed to withstand thousands of those cycles.

So, as long as the turbulence is not catastrophic (that one gust of wind is so strong that it causes immediate failure - which I think is unlikely) and you are not already near the end of the plane's life design, as Wasabi said, one long turbulent fly wont cause failure.

Source for the first image: Fatigue life prediction for aircraft structures and materials

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I can't point to a reference, but I'd say that, as long as you're not talking about catastrophic turbulence, the plane can resist for basically the entire flight.

So long as each of the "waves" of turbulence are individually safe, the entire turbulence is also safe. This is because the turbulence is unlikely to be at the plane's resonant frequency, and therefore you don't get magnifying effects over time.

The other relevant failstate would be fatigue, however that happens over countless cycles. So unless you have a very old plane (20+ years, which has consumed most of its safe cycles), fatigue also likely wouldn't be reached in a single very-turbulent flight.

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Duration of turbulence is not a factor, intensity is!

All modern airplanes have been designed with a flexible structure ready to take punishing weather and vibrate with the impact of the shock wave to dissipate the energy of turbulence.

They have been designed to vibrate longitudinally along the fuselage and rotationally to take in the torque induced by wing shock. The wings are designed to flex and vibrate to behave in a ductile mode.

Even the empennage, the end of the fuselage including the rudder and elevators, is designed to twist and shake safely.

However the pilot during an intense turbulence or even in the absence of it can subject the plane to stresses above the safe levels, do maneuvers that are not safe for that weather and cause damage to structure.

Fatigue which is the first culprit to look into happens mostly by the routine stresses of flight and engine vibration and has to be checked at routine service intervals.

FAA crash reports are a good source to start researching about effect of bad weather on flights, planes, and pilots' decision making.

I did some search on Youtube and found this on flutter of the airplanes in calm weather. Flutter

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