What are you watching in YouTube?
- Thread starter 53' Stude
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Earlier I was watching why the FBI went back to 9mm over .40S&W. I still prefer 40 caliber over 9mm any day.
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GON
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Great video, thanks for posting.
GON
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Enjoyable video, thanks for posting. The flex/ flab in the wings is something I wish I better understood how that can happen without breaking and maintaining exact control of the aircraft forward movement. I also wonder in the super strong winds, once the back tires fit the ground, are engines still running at different rpms to keep the goal of getting the aircraft vertical with the runway.
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Paging @Astro14 lol. I would imagine he would know! If he wants to address your questions lol, I just totally had the first thought "He would know!"
The thrust on those engines is amazing I do wonder their limit for things like really high winds... I watch videos of wind turbines blowing up,
Water towers toppling over,
Things like that.
I feel like in a plane you have nowhere to go and too many have died in planes... yeah they are the safest form of travel but.. I have problems with.
I've flown as an adult I think 4 times in my life, most recently O'Hare to EWR earlier this year.
The wings flex with load. That load is created by lift (going up) and weight (going down) in level flight. All wings flex. To make them as rigid as a building would make them too heavy to work.
They‘re tested to well beyond design limit load (usually 2.5 G in an airliner).
Check out some of the video and explanation here:
https://www.popularmechanics.com/flight/g2428/7-airplane-wing-stress-tests/
For the landing, it’s complicated (as always). When the wheels touch the runway, the wing is still generating considerable lift, and, in an airliner, until the airplane is both de-rotated (nose lowered to the ground) and the spoilers extended, it’s making about as much lift as the airplane weighs.
So, at the moment when the back tires touch - it’s still very much a flying machine. Those tires have about zero weight on them (in a smooth landing) so, they can’t do anything to slow the airplane. Applying brakes would make them stop spinning, but so little weight is on them compared with the forward momentum of the entire airplane, that a couple locked up tires won’t slow it down, because a locked tire with no weight on it doesn’t really generate much force. Cars tires always have weight on them - so this doesn’t sound right but it’s basic physics.
The force of friction in Newtonian mechanics is mu times normal force where mu is the coefficient of friction (which is high for rubber on concrete or asphalt) and the normal force is the perpendicular force (in this case, weight) pressing the one object onto the other.
At touchdown, the normal force is about zero, because the weight is still borne by the wings. You have to get the weight off the wings and onto the wheels for the brakes to work effectively.
To stop the airplane, the pilot flying will select reverse thrust (which does slow the airplane) and extend the ground spoilers (which kill the wing‘s lift) as they de-rotate. The change in AOA as the airplane nose is lowered to the ground reduces lift. The spoilers reduce lift.
Now, with the weight of the airplane off the wings, there is enough weight on the landing gear for the tires to be able to generate braking force via friction as you normally feel it in a car.
It’s still flying though, even as it slows, because that big vertical tail is still affected by wind.
On a windy day, when the airplane is parked at the gate, you can feel the whole thing rocking back and forth as the wind hits the tail and creates lateral forces.
Finally, we don’t run engines at different RPM to control the airplane. We keep symmetric thrust if both engines are working. The control of the aircraft comes from the basic flight controls: pitch from elevator, yaw from rudder, roll from aileron, and sometimes, a bit of roll from flight spoilers.
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4WD
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GON
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Astro,
Significant paragraph from the article you linked reference a not well-known beneficiary of wing flex- passengers with weak stomachs:
"The 787's wing flexibility isn't just incredible to watch. Indeed, this aspect is also a massive benefit for passengers, and particularly welcome among those more prone to sickness caused by a bumpy ride. Analyzing various factors, including wing loading, gust alleviation, and wing flex, turbulence forecasting website Turbli crowned the Boeing 787-9 as the best aircraft to handle turbulence."
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