Aerodynamic condition related to helicopter flight
This article may be too technical for most readers to understand. Please help improve it to make it understandable to non-experts, without removing the technical details.(February 2022) (Learn how and when to remove this message)
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. Often the term settling with power is used as a synonym, e.g., in Australia, the UK, and the US,[2][3][4] but not in Canada, which uses the latter term for a different phenomenon.[5]
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 a 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.
This is also why the condition is often mistaken for "settling with insufficient power": high-powered maneuvers can both induce a vortex ring state in free air, and then at low altitude, during landing conditions, possibly break it. If sufficient power is not available to maintain the airfoil of the rotor at a stalled condition, while generating sufficient lift, the aircraft will not be able to stay aloft before the vortex ring state dissipates, and will crash.
This condition also occurs with tiltrotors, and it was responsible for an accident involving a V-22 Osprey in 2000. Vortex ring state caused the loss of a heavily modified MH-60 helicopter during Operation Neptune Spear, the 2011 raid in which Osama bin Laden was killed.[6]
^Helicopter Flying Handbook, FAA-H-8083-21A(PDF). U.S. Dept. of Transportation, FAA, Flight Standards Service. 2012. pp. 11-8–11-12, 11-17–11-20.
^"Assessment Requirements for AVIY0029 Operate rotary wing remote pilot aircraft systems" (PDF). Australian Government. Retrieved 16 April 2023. recognition and avoidance of settling with power/vortex ring state
^"Private Pilot Licence Examinations – 070 Operational Procedures Aeroplane and Helicopter" (PDF). Civil Aviation Authority. Retrieved 16 April 2023. Settling with power (vortex ring)
^"Helicopter Emergencies and Hazards" (PDF). Federal Aviation Administration (FAA). Retrieved 16 April 2023. Vortex ring state (formerly referenced as settling-with- power) describes an aerodynamic condition in which a helicopter may be in a vertical descent with between 20 and 100 percent power applied, and little or no climb performance. The previously used term settling-with-power came from the fact that the helicopter keeps settling even though full engine power is applied.
^"Helicopter Flight Training Manual (TP 9982) – Exercise 26 – Vortex Ring" Transport Canada, 20 May 2010. Accessed: 13 September 2014.
^Capaccio, Tony (5 May 2011). "Helicopter Carrying SEALs Downed by Vortex, Not Mechanical Flaw or Gunfire". Bloomberg L.P.
The vortexringstate (VRS) is a dangerous aerodynamic condition that may arise in helicopter flight, when a vortexring system engulfs the rotor, causing...
A vortexring, also called a toroidal vortex, is a torus-shaped vortex in a fluid; that is, a region where the fluid mostly spins around an imaginary axis...
The vortexring gun is an experimental non-lethal weapon for crowd control that uses high-energy vortexrings of gas to knock down people or spray them...
quadcopters are subject to normal rotorcraft aerodynamics, including the vortexringstate.[citation needed] The main mechanical components are a fuselage or...
arrest its descent. This hazard can develop into vortexringstate if not corrected early. Vortexringstate is a hazard induced by a combination of low airspeed...
In fluid dynamics, a vortex (pl.: vortices or vortexes) is a region in a fluid in which the flow revolves around an axis line, which may be straight or...
Rhein-Sieg, public transport in the Cologne/Bonn region of Germany Vortexringstate, a helicopter flight condition Skoda vRS car models an alternate abbreviation...
Paul Edwards has stated that the AW609 was not susceptible to the vortexringstate phenomena, naturally slipping out of the vortex on its own since both...
effect (aerodynamics) Transverse flow effect Dissymmetry of lift VortexringVortexringstate Croucher, Phil (2007). Professional Helicopter Pilot Studies...
altitude permits, autorotations may also be used to recover from a vortexringstate, also known as settling with power. In all cases, a successful landing...
configuration. If such a craft is flown in a way where it enters a vortexringstate, one of the rotors will always enter slightly before the other, causing...
first helicopter experienced a hazardous airflow condition known as a vortexringstate. This was aggravated by higher-than-expected air temperature and the...
pick-up from departing LNG tanker in night VFR conditions, entered a vortexringstate. After ditching, it stayed afloat for over two hours.[citation needed]...
of tail-rotor effectiveness, Retreating blade stall,Dynamic stall, Vortexringstate, Servo transparency, Must bumping, and Tailstrike. Because the main...
Investigation report determined "The helicopter probably entered a vortexringstate during the final approach". The pilot and crewman received minor injuries...
projected onto a flat surface, an optical vortex looks like a ring of light, with a dark hole in the center. The vortex is given a number, called the topological...
indicated that a combination of factors had placed the helicopter into a vortexringstate at low altitude which made impact "unavoidable". The Lerwick and Aith...
A vortex sheet is a term used in fluid mechanics for a surface across which there is a discontinuity in fluid velocity, such as in slippage of one layer...
The Arctic tropospheric polar vortex A circumpolar vortex, or simply polar vortex, is a large region of cold, rotating air; polar vortices encircle both...