Ross Clarkson Posted July 22, 2009 Share Posted July 22, 2009 I bascially just wrote a big lecture and then when i posted it timed out!!! Hate it when it does that For us beginners Stephen. Basically every aircraft has a stall speed which is only relevant to airspeed and not groundspeed and does not matter whether there is a 30knt headwind, 15knt tailwind, 500knt crosswind etc etc... When the airspeed falls below the stall speed the aircraft WILL stall!! So, on that downwind leg when us beginners panic becuase we think it is going so fast we chop the throttle, the airspeed dramatically reduces and groundspeed increases. The wind is pushing the model and the prop is not pulling it! Then, if we havent already, when we turn base/finals the inevitable result is ground impact, due to stall (Because our airspeed was still low even though the model looked like it was going fast) and at low altitude there is no time to recover. Airspeed = Speed through air. Groundspeed = Speed over ground. We actually think it is going fast but it isnt, so the airspeed drops below stall speed and then STALL! Practice taking your aircraft up high and gradually slowing it down whilst pulling more and more up elevator. This will teach you the charactheristics of a stall and give you a rough idea of your models stall speed. Cheers, Ross. Quote Link to comment Share on other sites More sharing options...
Stephen Grigg Posted July 22, 2009 Author Share Posted July 22, 2009 Thankyou, for that Ross Ill do that very helpfull S Quote Link to comment Share on other sites More sharing options...
Ross Clarkson Posted July 22, 2009 Share Posted July 22, 2009 Also, real world pilots have the comfort of being able to continuously monitor an airspeed indicator so in theory they could just keep the throttle set at a setting where the airspeed is just above stall speed and fly around into wind, crosswind, downwind etc. There will be no difference in the aircrafts airspeed but all the pilot will notice is the ground going passed them faster or slower!! If they panic and reduce throttle on downwind because they think they are going to fast, airspeed will reduce and STALL. Quote Link to comment Share on other sites More sharing options...
Stephen Grigg Posted July 22, 2009 Author Share Posted July 22, 2009 My instructor is always telling me the model must fly faster than the wind ,down wind otherwise the controls wont work is this a similar sonario? Quote Link to comment Share on other sites More sharing options...
Stephen Grigg Posted July 22, 2009 Author Share Posted July 22, 2009 Its funny actually .I often flew my Boomerang flat out.,All the gear from that is in the Seagull 40 but Im flying it slower! Quote Link to comment Share on other sites More sharing options...
Ross Clarkson Posted July 22, 2009 Share Posted July 22, 2009 Im not sure about models Stephen but i dont think so. Somebody experienced will probably clear this up but, If your model can fly at 10mph and the wind happens to be 20mph downwind then the controls will still work but your groundspeed will just be 30mph. Your airspeed could still be 10mph. It is down to airspeed v groundspeed again. Forget groundspeed, think about airspeed. Quote Link to comment Share on other sites More sharing options...
Stephen Grigg Posted July 22, 2009 Author Share Posted July 22, 2009 I understand,so even though my model is going fast through the air down wind to me standing on the ground bacause of the speed of the wind the model is actually possibly travelling a lot nearer to stall speed so before turning I must give it more power,unless of course Im going fast enough.So now I need a speedo on the model and one to read the wind speed then Il be OK,except by the time Ive read them and worked the airspeed out " wheres me model gone"! Quote Link to comment Share on other sites More sharing options...
Ross Clarkson Posted July 22, 2009 Share Posted July 22, 2009 Sort of. The reason why you would stall or lose height is not directly related to the wind, it is because your airspeed is too slow, no matter what the wind is doing!!! Stalling is directly related to airspeed and does not take groundspeed or wind into consideration. Therefore, wind is indirectly related as you THINK the aircraft is going too fast downwind because of its apparent high groundspeed (caused by the wind pushing the aircraft) but because you have practically cut the throttle off, the airspeed is close to stall speed. (As the prop is practically not pulling the aircraft through the air, so it has hardly any airspeed) But you are right, in mid-high winds you are going to have to increase power quite a bit just before you turn base/finals, so you gain enough extra airspeed to retain lift through the turn. Quote Link to comment Share on other sites More sharing options...
Stephen Grigg Posted July 22, 2009 Author Share Posted July 22, 2009 Thanks Ross got it flat out every where just to be safe Quote Link to comment Share on other sites More sharing options...
Tim Mackey Posted July 22, 2009 Share Posted July 22, 2009 I do hope this is not going to digress into another heated argument about the stall this has been thrashed out in another, now infamous thread all about the stalling wing.Now I am no aerodynamic expert, but I thought that out of all the discussions over there, I had pretty much settled on the fact that a wing stall is ONLY brought on by the AOA being too much, and not actually anything to do with airspeed / groundspeed.Sure, flying too slowly will cuase the aeroplane to drill a hole in the ground, but thats because of insufficient lift being generated, not because the wing stalled.Now quick ...get me a Taxi out of here Quote Link to comment Share on other sites More sharing options...
Former Member Posted July 22, 2009 Share Posted July 22, 2009 [This posting has been removed] Quote Link to comment Share on other sites More sharing options...
andy watson Posted July 22, 2009 Share Posted July 22, 2009 I think the difference here Timbo is that we are talking about the stall as in a sudden drop/loss in altitude. Whether that's due to broken air flow, or insufficient lift is pretty much irrelevant. All we are really bothered about is stopping the aircraft falling out of the sky! In my experience if you are dropping too much in the turns you are probably banking too sharply.Edited By andy watson on 22/07/2009 15:42:51 Quote Link to comment Share on other sites More sharing options...
Stephen Grigg Posted July 22, 2009 Author Share Posted July 22, 2009 Just gaining useful knowledge frompeople who know more than I do.which is pretty well everyone,what is AOA Quote Link to comment Share on other sites More sharing options...
Michael Hickman Posted July 22, 2009 Share Posted July 22, 2009 Stephen Angle of attack (the angle at which the air hits the wing). MikeEdited By Michael Hickman on 22/07/2009 16:02:10 Quote Link to comment Share on other sites More sharing options...
Stephen Grigg Posted July 22, 2009 Author Share Posted July 22, 2009 Thanks Michael For me Andy has my problem,LOss of height when turning.I give up elevator whicn normally corrects the problem Im just trying to gain as much knowledge so I dont incurr problems in futureWhen flying that could be terminal for my model. Quote Link to comment Share on other sites More sharing options...
Ross Clarkson Posted July 22, 2009 Share Posted July 22, 2009 Posted by Timbo - Moderator on 22/07/2009 15:00:39: I do hope this is not going to digress into another heated argument about the stall this has been thrashed out in another, now infamous thread all about the stalling wing. Now I am no aerodynamic expert, but I thought that out of all the discussions over there, I had pretty much settled on the fact that a wing stall is ONLY brought on by the AOA being too much, and not actually anything to do with airspeed / groundspeed. Sure, flying too slowly will cuase the aeroplane to drill a hole in the ground, but thats because of insufficient lift being generated, not because the wing stalled. Now quick ...get me a Taxi out of here Fair point Timbo but i was trying to keep it as simple as possible for Stephen and in relevance to him losing height on the base/final turn and hitting the ground, because i assume he wouldnt just fly it into the ground on purpose without increasing the AOA, or pulling up in laymens terms causing a STALL!!!! ha ha Quote Link to comment Share on other sites More sharing options...
Ross Clarkson Posted July 22, 2009 Share Posted July 22, 2009 Stephen, That is exactly the problem. If you pull too much elevator whilst at too low an airspeed you will STALL. Timbo: I know you dont want to go on about this but just one more thought. An F-16 is travelling at a high airspeed and suddenly pulls nose up into a straight climb. No evident stall even though AOA has increased massively. It then does the same thing but at very slow airspeed.......and stalls!! AOA is the primary reason but it needs to be combined with airspeed.Edited By Ross Clarkson on 22/07/2009 16:22:36 Quote Link to comment Share on other sites More sharing options...
Stephen Grigg Posted July 22, 2009 Author Share Posted July 22, 2009 And you did a great job RossThankyou everyone for your help Quote Link to comment Share on other sites More sharing options...
Stephen Grigg Posted July 22, 2009 Author Share Posted July 22, 2009 Spoke to the chairman of the club and he has suggested a new place to look.So itll be trekking with the steps again soon.The book"Model Flying--Find that Model comes out in January.It covers all my exploits and adventures looking for the Super Air it ll have you on tender hooks and the edge of your seats,the drama is captivating,and the end well youll have to wait and seeyes folks its all there,and Im talking film rights as we read Quote Link to comment Share on other sites More sharing options...
Ross Clarkson Posted July 23, 2009 Share Posted July 23, 2009 Cant wait! I wonder what the end will be!!!!!!!!!!!!!!!!!!!!!!!!! Quote Link to comment Share on other sites More sharing options...
Brian Lambert Posted July 23, 2009 Share Posted July 23, 2009 Stephen, did you mean "tenterhooks" http://www.worldwidewords.org/qa/qa-ont1.htmSorry, I just needed to make a post to check a change to my settings.Best of luck with the search, and the book.Brian Quote Link to comment Share on other sites More sharing options...
Stephen Grigg Posted July 23, 2009 Author Share Posted July 23, 2009 Thats the word Brian thankyou its because Im colour blind you know Quote Link to comment Share on other sites More sharing options...
Brian Lambert Posted July 23, 2009 Share Posted July 23, 2009 Sometimes I hate myself for being so picky! Any news on the super air?Brian Quote Link to comment Share on other sites More sharing options...
Stephen Grigg Posted July 23, 2009 Author Share Posted July 23, 2009 Yas Brian I made areal discovery tonight this field is very big,and when you are carrying a step ladder and scambling through 6 ft under growth or more like over growth it gets very tiring.I abandoned the steps half way round because I convinced myself I was to far round.I could see I was passed the club caravan on the other side of the field so Ive narrowed it down to half the field.I found a path through the rape to a ridge and when I set the ladder up at the highest point realised its an impossible task.We are going to put the camera back in the air next week.Its a race between locating it by air or by combine Quote Link to comment Share on other sites More sharing options...
Phil Claridge Posted July 24, 2009 Share Posted July 24, 2009 stephen its not the recommended way to weather a model you know Quote Link to comment Share on other sites More sharing options...
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