clayfenderstrat Posted September 27, 2009 Report Share Posted September 27, 2009 Hello Vertical Reference, Let me introduce myself. I am a fixed wing pilot, but was referred here from JetCareers.com. I am doing a speech for my COM class explaining how an autorotation works. Could someone help me out and give me simple explanation, a detailed scientific explanation, and how I should explain it to a group of non-aviators? I am pretty sure I know how it works, but I would like somebody who flies a helicopter to let me know. I plan on using a video to show how it works, but I need to actually explain the workings. Thanks in advance for all the help. Quote Link to comment Share on other sites More sharing options...
kodoz Posted September 27, 2009 Report Share Posted September 27, 2009 This isn't perfect, but it covers the aerodynamics okay. Simply, the upward airflow through the rotor system keeps the blades spinning and produces some lift. Not so simply, the rotational relative wind varies along the length of the blade. Near the hub (the inboard portion), the rRW is slow and essentially the blade is stalled (high drag, low lift). At the tip, the rRW is high, resulting in high lift (but also high drag). The total reaction is inclined aft, so this region produces lift but acts to slow the rotation of the rotor. Somewhere in between is the "driving region", where the rRW strikes at an angle that produces lift with little drag, and at an angle that inclines the total reaction forward. This region produces lift, but, more importantly, keeps the rotor spinning. How should you explain it to non-aviators? "Magic". Or get one of those spinny helicopter toys [link]. Quote Link to comment Share on other sites More sharing options...
Tom22 Posted September 27, 2009 Report Share Posted September 27, 2009 Here is a fun activity on autorotations for your class. http://www.grc.nasa.gov/WWW/k-12/TRC/Aeron...Maple_Seed.html Quote Link to comment Share on other sites More sharing options...
Tom22 Posted September 27, 2009 Report Share Posted September 27, 2009 Here is another one. Quote Link to comment Share on other sites More sharing options...
COhelipilot Posted September 28, 2009 Report Share Posted September 28, 2009 If you really want a simple reply just refer to the fact that lift acts perpendicular to Relative wind... This puts the force of lift ahead of the axis of rotation during autorotation or rapid descents. Although the actual aerodynamic description deals with blade twist, rate of descent flow, relative velocity, drag, and resultant force the basic idea is just the opposite of induced drag. ID is just the rearward pull of the force we call lift due to the angle of the RW and autorotation is the forward pull of this same force due to the change in the angle of the relative wind. Hope this helps. Quote Link to comment Share on other sites More sharing options...
rotorrodent Posted September 29, 2009 Report Share Posted September 29, 2009 Hello Vertical Reference, Let me introduce myself. I am a fixed wing pilot, but was referred here from JetCareers.com. I am doing a speech for my COM class explaining how an autorotation works. Could someone help me out and give me simple explanation, a detailed scientific explanation, and how I should explain it to a group of non-aviators? I am pretty sure I know how it works, but I would like somebody who flies a helicopter to let me know. I plan on using a video to show how it works, but I need to actually explain the workings. Thanks in advance for all the help. Let's keep it simple if not over simple! Autorotations are just like a bicycle. When you pedal the bike (engine driving the rotor system), everything flys just fine. When you stop pedaling the bike, (engine quit), the rotor system keeps turning as does the bike wheels (coasting). When you are recovering from the autorotation (assuming practice) , you start pedaling again, bringing the engine rpm back up to drive the rotor system. Remember the sycamore seed? When you throw it up into the air, it autorotates to the ground! Now that is a simplistic view of autorotations. Cheers Rotorrodent Quote Link to comment Share on other sites More sharing options...
Goldy Posted September 30, 2009 Report Share Posted September 30, 2009 Remember the sycamore seed? When you throw it up into the air, it autorotates to the ground! And all this time I've been throwing fans off the rooftop to simulate an auto...now you guys give me the sycamore seed trick! Goldy Quote Link to comment Share on other sites More sharing options...
500E Posted September 30, 2009 Report Share Posted September 30, 2009 New you had a Lot of fans Goldy, but there is a limit to how much abuse a Fan will stand Quote Link to comment Share on other sites More sharing options...
beckwith Posted October 3, 2009 Report Share Posted October 3, 2009 Three diagrams from section 4-3 of the rotorcraft flying handbook which can be downloaded for free somewhere or other. Quote Link to comment Share on other sites More sharing options...
rotorrodent Posted October 4, 2009 Report Share Posted October 4, 2009 Three diagrams from section 4-3 of the rotorcraft flying handbook which can be downloaded for free somewhere or other. Nice photos but what good are they to non aviation, non technical folks! He just wanted a simple way to tell the class that don't know a tail rotor from a pencil sharpener! Cheers Rotorrodent Quote Link to comment Share on other sites More sharing options...
rotorrodent Posted October 4, 2009 Report Share Posted October 4, 2009 And all this time I've been throwing fans off the rooftop to simulate an auto...now you guys give me the sycamore seed trick! Goldy Goldy, I'm experienced in this! When I was a small lad, I would jump from the house roof with an umbrella hoping to prove that flying works. What I didn't know at the time was basic aerodynamics in that air loading is something you can't ignore. Well... a folded up brelly and broken ankle proves you can't fly unless the rotor is turning!!!! ...anyway, back to nature and the seed! Cheers Rotorrodent Quote Link to comment Share on other sites More sharing options...
beckwith Posted October 4, 2009 Report Share Posted October 4, 2009 (edited) Nice photos but what good are they to non aviation, non technical folks! He just wanted a simple way to tell the class that don't know a tail rotor from a pencil sharpener! Cheers Rotorrodent He is an aviation person. I'm fairly sure the still discus airfoils in fixed wing training. and depending on the length of his presentation I'm confident he can easily clear up any tail rotor vs pencil sharpener confusion. If necessary I could provide images to help with that as well... Edited October 4, 2009 by beckwith Quote Link to comment Share on other sites More sharing options...
Chewie Posted October 6, 2009 Report Share Posted October 6, 2009 (edited) He is an aviation person. I'm fairly sure the still discus airfoils in fixed wing training. and depending on the length of his presentation I'm confident he can easily clear up any tail rotor vs pencil sharpener confusion. If necessary I could provide images to help with that as well... Bravo sir... Also, I would be interested in seeing what you could come up with in the TR vs sharpener non verbal imagery area now that you brought it up lol! Non-aviator/non-technical people being taught how an auto works? Prepare for a lot of glazed over looks imo lol... Edited October 6, 2009 by Chewie Quote Link to comment Share on other sites More sharing options...
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