WildBillKelsoe Posted October 13, 2011 Posted October 13, 2011 (edited) Hello, When I'm close to ending a mission, I sometimes get a shaking vibration and the helo is pulled down aground. Care to explain, and how to counteract this?? According to PeterP: All answers to almost every question about this topic could be found in this document: Model for Vortex Ring State Influence on Rotorcraft Flight Dynamics Wayne Johnson Army/NASA Rotorcraft Division NASA Ames Research Center Moffett Field, California Wayne.Johnson@NASA.gov ...or call the answer simply "42".... If the document is to complicated and "42" too simplified for you.. read this: Vortex Ring State (VRS) in short: If you enter a Vortex Ring State you have to move the rotor-disk out of this zone . To do this: 1. Don't rise the collective ( counter intuitive - but the right thing to do - If you raise it it will make the vortex even bigger that is surrounding you...) 2. Gain horizontal speed by tilting nose down (also counter intuitive but the right thing to do -yup! that's how the physics work in our universe - you cant fool "God" - If you try ...you will fool yourself.. ) 3. When above 60Kmh horizontal speed -stabilise level-flight and raise collective You will often enter a Vortex Ring State when you are in Hover above ground and descending quicker (about 6-8m/s in BS) than your own down-wash of your rotor - means: You are "falling" into your own down-wash and your top of the rotors are sucking the same air again and again... - so there is a vortex-ring around you. - that will provide no lift at all - if you will stay in this ring- you will only produce the biggest smoke-ring you have ever seen - and this will probably also be the last thing you have seen in your life... . so once again: collective down - nose down -keep calm - and "god" (for atheists: the physics - and for a Italian Rome-katholic sure good and physics are the same ) will help you to survive! Tip: Fire up DCS-BlackShark and gain some altitude and train this recovery manoeuvre - and watch your altimeter when you drop down! This image has been resized. Click this bar to view the full image. The original image is sized 1077x1064. Edited October 15, 2011 by WildBillKelsoe 1 AWAITING ED NEW DAMAGE MODEL IMPLEMENTATION FOR WW2 BIRDS Fat T is above, thin T is below. Long T is faster, Short T is slower. Open triangle is AWACS, closed triangle is your own sensors. Double dash is friendly, Single dash is enemy. Circle is friendly. Strobe is jammer. Strobe to dash is under 35 km. HDD is 7 times range key. Radar to 160 km, IRST to 10 km. Stay low, but never slow.
PeterP Posted October 13, 2011 Posted October 13, 2011 http://forums.eagle.ru/showthread.php?t=80114 BTW its also covered by the manual...
MTFDarkEagle Posted October 13, 2011 Posted October 13, 2011 (edited) Vortex Ring State Edited October 13, 2011 by MTFDarkEagle I need coffee... 1 Lukas - "TIN TIN" - 9th Shrek Air Strike Squadron TIN TIN's Cockpit thread
PeterP Posted October 13, 2011 Posted October 13, 2011 (edited) All answers to almost every question about this topic could be found in this document: Model for Vortex Ring State Influence on Rotorcraft Flight Dynamics Wayne Johnson Army/NASA Rotorcraft Division NASA Ames Research Center Moffett Field, California Wayne.Johnson@NASA.gov ...or call the answer simply "42".... :D If the document is to complicated and "42" too simplified for you.. read this: Vortex Ring State (VRS) in short: If you enter a Vortex Ring State you have to move the rotor-disk out of this zone . To do this: 1. Don't rise the collective ( counter intuitive - but the right thing to do - If you raise it it will make the vortex even bigger that is surrounding you...) 2. Gain horizontal speed by tilting nose down (also counter intuitive but the right thing to do -yup! that's how the physics work in our universe - you cant fool "God" - If you try ...you will fool yourself.. :D) 3. When above 60Kmh horizontal speed -stabilise level-flight and raise collective You will often enter a Vortex Ring State when you are in Hover above ground and descending quicker (about 6-8m/s in BS) than your own down-wash of your rotor - means: You are "falling" into your own down-wash and your top of the rotors are sucking the same air again and again... - so there is a vortex-ring around you. - that will provide no lift at all - if you will stay in this ring- you will only produce the biggest smoke-ring you have ever seen - and this will probably also be the last thing you have seen in your life... ;). so once again: collective down - nose down -keep calm - and "god" (for atheists: the physics - and for a Italian Rome-katholic sure good and physics are the same :D) will help you to survive! Tip: Fire up DCS-BlackShark and gain some altitude and train this recovery manoeuvre - and watch your altimeter when you drop down! Edited October 14, 2011 by PeterP some goofy ideas here and there... 1
WildBillKelsoe Posted October 13, 2011 Author Posted October 13, 2011 All answers to almost every question about this topic could be found in this document: Model for Vortex Ring State Influence on Rotorcraft Flight Dynamics Wayne Johnson Army/NASA Rotorcraft Division NASA Ames Research Center Moffett Field, California Wayne.Johnson@NASA.gov ...or call the answer simply "42".... :D If the document is to complicated and "42" too simplified for you.. read this: Vortex Ring State (VRS) in short: If you enter a Vortex Ring State you have to move the rotor-disk out of this zone . To do this: 1. Don't rise the collective ( counter intuitive - but the right thing to do - If you raise it it will make the vortex even bigger that is surrounding you...) 2. Gain horizontal speed by tilting nose down (also counter intuitive but the right thing to do) 3. When above 60Kmh horizontal speed -stabilise level-flight and raise collective You will often enter a Vortex Ring State when you are in Hover above ground and descending quicker (about 6-8m/s in BS) than your own down-wash of your rotor - means: You are "falling" into your own down-wash and your top of the rotors are sucking the same air again and again... - so there is a vortex-ring around you. - that will provide no lift at all. Tip: Gain some altitude and train this recovery manoeuvre - and watch your altimeter when you drop down! You're a beast mate!!! Very illustative, thank you for the clarification and instructions. This beats the manual's diagrams :book: AWAITING ED NEW DAMAGE MODEL IMPLEMENTATION FOR WW2 BIRDS Fat T is above, thin T is below. Long T is faster, Short T is slower. Open triangle is AWACS, closed triangle is your own sensors. Double dash is friendly, Single dash is enemy. Circle is friendly. Strobe is jammer. Strobe to dash is under 35 km. HDD is 7 times range key. Radar to 160 km, IRST to 10 km. Stay low, but never slow.
Daniel M Posted October 13, 2011 Posted October 13, 2011 It's been awhile since i've flown, but i think if you are below 60, keep your rate of decent above -3 and you won't have to worry about vrs (as much)
WildBillKelsoe Posted October 15, 2011 Author Posted October 15, 2011 to PeterP Done. I wish there was a smoke mod that would show the air dynamics of a VRS.. I understand now, and will do as recommended. Gain altitude, enter VRS and practice recovery while looking at the altimeter AWAITING ED NEW DAMAGE MODEL IMPLEMENTATION FOR WW2 BIRDS Fat T is above, thin T is below. Long T is faster, Short T is slower. Open triangle is AWACS, closed triangle is your own sensors. Double dash is friendly, Single dash is enemy. Circle is friendly. Strobe is jammer. Strobe to dash is under 35 km. HDD is 7 times range key. Radar to 160 km, IRST to 10 km. Stay low, but never slow.
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