Vortex Ring State

The vortex ring state (VRS) is a dangerous aerodynamic condition that may arise in helicopter flight, when a vortex ring system engulfs the rotor, causing severe loss of lift. The vortex ring state is sometimes referred to as settling with power. The Federal Aviation Administration (FAA) sees these terms as synonymous, whereas Transport Canada sees them as two different phenomena.2(https://en.wikipedia.org/wiki/Vortex_ring_state#cite_note-2) (View Highlight)

Relevant

Since the helicopter that had made the emergency landing was damaged and unable to fly the team out, it was destroyed to safeguard its classified equipment, including an apparent stealth capability.81(https://en.wikipedia.org/wiki/Killing_of_Osama_bin_Laden#cite_note-dangerroomstealth-81) The pilot smashed the instrument panel, radio, and the other classified fixtures and the SEALs demolished the helicopter with explosives. (View Highlight)

Both the corpse and bin Laden were 1.93 m (6 ft 4 in); SEALs on the scene did not have a tape measure to measure the corpse, so a SEAL of known height lay down next to the body and the height was so approximated by comparison.88(https://en.wikipedia.org/wiki/Killing_of_Osama_bin_Laden#cite_note-ST6return-88) Obama quipped: "You just blew up a $65 million helicopter and you don't have enough money to buy a tape measure? (View Highlight)

Lebron Didn't Warn Them About the Vortex Ring State Smh

"You know when I first got to Miami in 2011, I just had a strange feeling that Osama Bin Laden was hiding in Abbottabad Pakistan. I told Coach Spo and D Wade about it and they set up a meeting with Obama and we got it done #JustAKidFromAkron"

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When Turbulence is a Good Thing

A vortex ring state sets in when the airflow around a helicopter's main rotor assumes a rotationally symmetrical form over the tips of the blades, supported by a laminar flow over the blade tips, and a countering upflow of air outside and away from the rotor. In this condition, the rotor falls into a new topological state of the surrounding flow field, induced by its own downwash, and suddenly loses lift. Since vortex rings are surprisingly stable fluid dynamical phenomena (a form of topological soliton), the best way to recover from them is to laterally steer clear of them, in order to re-establish lift, and to break them up using maximum engine power, in order to establish turbulence. (View Highlight)