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In the question Is there any emergency situation in which jet engines would not be shut down before passenger evacuation of a transport aircraft comment says:

At full engine power, those vortices are quite capable of lifting something the size of a 1-foot cube of concrete from the ground into the engine!

Incredible! Did it really happened? I guess it did not ended up well for the engine. Any links/images?

I found this:

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  • $\begingroup$ Concrete is 2.4x as dense as water, so 1 foot of concrete is about 0.7 meters of water, which is like 0.07atm. Yeah if you managed to suck a vacuum above the entire run way you can lift the entire run way easily, theoretically. $\endgroup$ – user3528438 Jan 2 '18 at 23:48
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    $\begingroup$ Is a one foot cube of balsa wood "the size of a 1-foot cube of concrete"? $\endgroup$ – DJohnM Jan 3 '18 at 5:32
  • $\begingroup$ I hope very few runways have loose chunks of concrete sitting around. Maybe after a major earthquake, or a bombing run... $\endgroup$ – jamesqf Jan 3 '18 at 6:59
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Small, loose pieces, it sure could. But those are small flakes which would fit in your hands. Large chunks, it’s doubtful that the suction could lift them to ingest them off the runway. Now there’s a chance such a piece could get kicked up by the nosewheel of an airplane during a ground roll and thrown into the intake of an engine. Airports generally have surface crews which periodically do FOD sweeps of the runways and taxiways looking for debris like that.

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Basically, atmospheric pressure is 14.7 psi and a jet engine functions as a vacuum. Given somebody else's postulate that a cubic foot of concrete weighs 150 pound per cubic foot and that an absolute vacuum exerts 14.7 * 122 == 2,116.8 pounds of pressure per cubic foot, it will blend... and fly... if it gets close enough to the jet intake.

A jet engine won't exert a full vacuum, but even a household vacuum cleaner tends to exert about 3psi, which if it scaled up to jet engine intake size would also lift said concrete block.

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  • $\begingroup$ If anybody can share the suction / distance formula for say the GE-90 engine, I'd appreciate it. 2 million CF/M consumed in a 128 inch diameter. $\endgroup$ – Jeff Ferland Jan 3 '18 at 2:51

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