completeaerogeek

And sorry-no 'Coanda effect.' If the Coanda Effect exists at all (and there is debate abut this) as a separate phenomenon from viscosity effects, it only occurs in accelerated flows such as Upper Surface lowing not in static air.

Thomo you are half there and half not. http://www.cam.ac.uk/research/news/how-wings-really-work. There are no vacuums (partial or otherwise) in normal space. also www.219sqn.aafc..org.au and click Wings don't suck! for more. or you could read my article in Australian Flying this month. (JAN/FEB 15) A wing doesn't 'suck at all' In fact suction is a very misunderstood and somewhat mythical concept. When a piston moves down in a cylinder atmospheric pressure pushes the air into the increasing space . The 'suction' idea is why so many pilots have problems understanding why a MAP gauge goes up and pressure increases when they open the throttle. isn't it 'sucking harder' shouldn't the pressure go down as 'suction increases? A wing (the simplest kind is a flat plate) moves trough the air and as it does so at an effective AOA, the lower surface pushes the 'lower air' air forwards and downwards. Lift Component 1. The Pressure bubble (bow wave_ caused by this disturbance pushes the remaining air up and over the wing where it is held against the upper surface by normal atmospheric pressure. Imagine the wing under water. The physics is identical. Now try to use your explanation. if it doesn't work it is wrong. Simple. The air that us pushed up and over the wing follows the upper surface because it has nearly 15lb/sq in making it do so. As it changes direction a force results (as it must Newton's 2nd and 3rd laws.) This resultant force is Lift Component #2. Lift is caused by the mechanical intervention of a wing bending the air away from its resting position. Pressure variations are a result of lift production not the cause. Flat wing- no AOA no lift. Flat wing, AOA + movement = lift. QED.

Coanda is not the reason the air flows a surface. Static pressure and viscosity are. The Coanda Effect (if is exists at all as a distinct phenomenon) is only present in accelerated flows such as upper surface blowing.

Swings do not need to be cambered they just need AOA. There is no 'suction' on a wing at all. look at www.219sqn.aafc.org.au and click on 'Wings don't suck'. everything y0u need to know is there.

________________________________ Mr M61- If you were trying to prove that people get their back up because of confirmation bias, you have not, what you have proven is that people get their back up when called stupid, or told bluntly that what they believe (because that's what they were taught) is nonsense. No one asked the question, you essentially just marched on in and told everybody that if they didn't believe you that they were stupid. A lot of emotion in your statement there M61. Firstly, I started the post to offer correct information. That I did and there is no doubt that it is correct. It is not my information. it is from unimpeachable sources.. No-one was obliged to comment. So why di you suppose I was abused or belittled on the basis of offering information? At no time did I say that if they didn't accept the information they were stupid. Why would you feel the need to make such a statement? I did not respond impolitely to anyone who behaved in the same way. The escalating response was only to those who initiated hostility. So one may well ask, why the hostility to correct information? if people are not mature enough to re-evaluate what they believe in the light of new evidence I wonder if they should be behind the controls of an aircraft. On that note, you appear to have some confirmation bias of your own, inasmuch as you believe that it's your student's fault that they don't believe you, not your own instructional technique or condescending attitude. A good instructor will find a way to help all of the students understand, not beat them into submission. Confirmation bias is subconsciously selecting only that information that fits your perception and then altering your behaviour comply with it. A good facilitator offers information to people and leaves it up to them to evaluate. If they disagree then the conversation is expanded looking for perceptual flaws that can be identified so that they can then understand the information. If it involves a conceptual debate then that is a good thing to increase understanding. You cannot force listeners to participate but interestingly all the insults that have been initiated have come from people telling me I was 'full of crap' or more specifically 'horseshit' instead of questioning the validity of the various concepts I was explaining or asking for clarification. Perhaps you should review some of the commenters here and ask them why they attacked me so rudely? No captive audiences? Yes they are, their boss decides that in order to comply with their legally required SMS Ahhh no. No I am talking about corporate audiences at conferences and workshops. People who pay to come voluntarily. You won't last long in business if you suck and I have been doing this successfully for over a decade so.. I would personally rethink your satisfaction scores, many students I have been on courses with, just tell the instructor what they want to hear, because they don't want to be pinned down and grilled by someone who is just going to tell them how stupid they are. I don't think you understand how tertiary scores are evaluated. They are anonymous and I can assure you that students have no problem eviscerating an lecturer they do not like. And again, if that is how you run a lecture, your students don't turn up. My classes were always exceptionally well attended. Perhaps students understand that they are there to learn and have open minds... Something in that for all of us I think...

Hi Bruce - any progress yet?

Ahh a retrospective qualification. How is providing information a negative experience? Making a correct statement and then having people abuse you for it is part of public discourse. I don't mind it as long as the overall information and discussion of benefit.If your ego isn't in the way you can learn many new concepts. I have no problem being wrong. it is how we all learn. But if you care going to criticise me then you need to support it with facts and objective assessment. Otherwisse it is just your ego talking. So my question to you is this: Is your statement and that of M61 an objective one? Read my first post with all of the valid information and then see the hostile response it got from some. No-one was coerced into responding or commenting. Their egos led them to lash out and insult me despite the fact that what I was saying was 100% correct. This has been happening from time immemorial when anyone dismantled cultural myths. it is called shooting the messenger and it comes from insecurity and lack of intellectual courage. If one person on this site now better understand basic aerodynamics then I have succeeded in my intent.

Ahhh no...

Would you please specify why giving information that some clearly do not understand was arrogant?

Ahhh M61. I see you have twigged. Thanks for your comments. The first part of my purpose was to explain clearly that what may people think is correct is in fact nonsense and hopefully be of help. The second part was to see what sort of response I got. The vociferous arguments based on fallacies are exactly what we in the industry need to fix. An authority figure (instructor or captain) using the cockpit or classroom power gradient consciously or unconsciously can teach new pilots or F/Os all kinds of bad habits or suppress their correct views and the junior pilot will often accept this just to 'get along'. This is the 'Authority from Eminence' logical fallacy I mentioned earlier. (I am currently writing a book on this) One of the posters said just this thing "it's just a hoop you have to jump through to get to the next stage". That is dangerous unprofessional thinking. (As for being one of my students, I had the highest Student Satisfaction scores ever recorded in the department. Students still call me for advice and mentoring because they know I genuinely care about them knowing the right information and how to use it in the real world, not just the lecture room. As for inconsistent- can you point it out please? The only thing I would ask is that you view the comments in context and start by reading my first post on Page 1. It was concise, referenced and provided resources. If you are jumping in the middle no doubt it would look fragmented but you have to look at the whole subject in context. Providing information with references that are unimpeachable and then watching people make emotional and inflammatory comments without having read them is quite interesting. It is the kind of mentality that says 'I have always operated this way and I haven't had any problems in 30 years and you are not going to convince me otherwise' and then next thing you read about them in an ATSB report. See Mr Turboplanner' comments. He is comprehensively wrong but will not see it. This is called 'Confirmation Bias' where someone only accepts information that fits with their pre-existing view. This has been a significant causal factor is quite a number of airline accidents. The unwillingness to revise opinions or practices on the basis of new information is extremely dangerous and one of the contributing factors for the number of GA/RA accidents. And no. Most of my facilitation has been in the corporate world-Airline and business and a corporate speaker here and overseas in Aviation where if you are crap, they don't ask you back. No captive audiences there. I hope that has made some sense to you. Cheers.

___________________- No that would be a buoyancy problem. Wow you guys really need to read what I am saying and think before you post...Could you please explain why if the relative air speed outside the aircraft was higher than inside (which of course it is) that by his explanation of Bernoulli the air would not go out? Air goes from high to low pressure. Daffyd, in what way is air different to water? (apart from density) I am always happy to learn new things. And I am sorry but you are incorrect. Again...The principle I was describing was a hydrodynamics one not a hydrostatic one.. Might be time for some reading. If an aircraft is a solid form immersed in air it behaves exactly the same as a solid object immersed in water. That’s why aerodynamics is also called fluid dynamics. Air is considered incompressible below M1.0. Also it is perfectly reasonable that an open cockpit aircraft is subject to fumes for the same reason. There is a pressure wave built up at the front of the aircraft. Combine this with slipstream (if the aircraft is accelerating, and you have a higher dynamic pressure forward of the cockpit. If the dynamic air pressure is higher than that in the cockpit- Fumes. Not difficult really. In your last point you missed the dynamic pressure rise where the air is impinging on the vertical and horizontal stabilisers at the root. This is a higher pressure point as at the leading edge of a wing so if the air is ingressing there of course it will be higher than in the cabin and push fumes in.

____________________- Well Complete, your statement that " the plane is moving and the air is not".. is at best irrelevant and at worst means you have an incorrect understanding of the physics of motion Bruce, I am afraid you have a shovel and you keep digging yourself a bigger hole. I have used this example in a conceptual (not mathematical) context every time I have mentioned it. Conceptually it is important as people ascribe all kinds of properties to the air that it does not have. Still air does not have momentum or kinetic energy. It has inertia and potential energy. Is that irrelevant? Your statements are a perfect reason why this perspective is important. You seem to be unable to visualise flow. To understand the concept of lift or flow it is important to visualise it in the way that it occurs not the way you think it does. Now to your statement: Of course initially it "goes in" momentarily due to both wanting to seek a lower pressure area and simple inertia, but the moment it finds pressure balance and then continues to come in raising pressure, it then tries to go back out again. I have done tufting tests on race cars to prove to the owners that their cooling system problem's are due to airflow actually going forward against the direction of travel much to their disbelief's Now on to some other glaring conceptual errors: First I think you mean momentum not inertia. Inertia is resistance to change or motion. (Newton’s 1st Law) Secondly, what you are describing is ram effect. Ram effect occurs when the volumetric capacity of an intake is reached and the pressure in the intake equals or exceeds static. Our Nene Vampires had this problem with the elephant ear intakes. The usual solution to this is spill doors. (I don't think it is me with the problem with the physics of motion...) Also your racing car analogy is not valid here because you have not mentioned a key aspect-heat. You can reduce the size of the intake while enlarging the exit and actually increase the velocity of the air because as the air is heated by the engine it expands. This principle was applied to the Spitfire and Mustang in their radiators by having a variable exit. It actually gave a thrust boost. This is called the Meredith effect after the RAE engineer who discovered it Now on to your challenge. I would think carefully if I were you. I am happy to take your money and donate it. Let me use an analogy:You see I have a nice Porsche and when I crack the window driving down the freeway it gives me a nice breeze for as long as the window is open... It doesn't fill up and magically reverse flow. Again what you are describing is ram effect not parallel flow. The pressure at the point where the windscreen rises from the bonnet is higher than static. It creates a bow wave (pressure wave) that forces air up and over and round the side of the pillar. At that point the air comes in if I choose. Your plane is no different. Aircraft are solid objects immersed in a viscous gaseous fluid. They behave in exactly the same way. Aircraft are subject to the laws of displacement just like a submarine. Now if your door apertures are parallel to the airflow and the air comes in it entirely defeats your Bernoulli explanation because if the streamline flow along the fuselage (which is obviously at a higher relative speed to the air inside the cabin) causes a pressure reduction the air would go out not in. Physics is simple you can't have it both ways. Simply put, if outside pressure is higher than inside, air comes in. F=Ma is not negotiable. As for your fume problem: Your tailplane probably has a localised flow impinging somewhere that creates a pressure wave higher than static and it is this that is causing a pressure rise, pushing the fumes back into your cabin. Pressure rises like this occur where the vertical or horizontal stabs join the aircraft. Now to your insult: I don't think there is evidence of me strutting or treating people as inferior. If giving correct information is strutting then the problem doesn't lie with me. In fact your statement about me not knowing about the physics of motion when you are clearly incorrect in your assertions rather points to you doesn’t it? Bruce, air is a fluid. Water and air act in the same way. Air is considered incompressible below M1.0. That is why the study of aerodynamics comes under fluid dynamics. Air and water behave in exactly the a same way unless you have come across a law of physics I have not heard of.

Mr Turbo, my purpose is to inform and help people be better aviators not to have arguments. The information I have give is correct and in accordance with NASA and other aviation institutions. You may take it or leave it. Entirely up to you.

Hi Daffyd, I have looked up and read several references on this. Biot-Savart is associated with Prandtl's lifting line theory and to do with circulation theory and unbound vortices. A couple of problems I can see: The Kutta condition ceases with vortex breakaway at relatively low speeds. Winglets and swept tips significantly reduce the strength of wing tip vortices and unbound vortices have no influence on the wing. Downwash velocity of wingtip vortices is does not appear to be relevant. In any case this is far too complex for a pilot. Again this can be left to aerodynamicists to argue over. The basic Newtonian explanation is clear and correct in terms of lift due to turning flow which was my original point. I hope that clears up my question.

Hi Bruce, My apologies about the Uni bit I have sticky key problems. That was meant for Turbo and his nasty little insults. I agree with you about the National Assessment idea but the variation in lecturers is a problem world wide. I lived and worked in the US for 9 years a lot of that for a major carrier and I was often astounded at the lack of knowledge of college graduates I dealt with. Still the level of education here is far better than many places. OECD shows us 13th in the world where the US/UK are around 35th.

_________________________________ Please read my statement again and let let me know specifically where it is incorrect. I am happy to learn. Bernoulli does apply along two different places of a streamline. That particular streamline, not somewhere else in the flow field. Bernoulli is explaining F=Ma. So what I would like to know is: To what force is the static air in the hidden part of your tail section subject? By conventional Bernoulli explanations the higher relative speed of the flow past the empennage would mean a lower pressure. Would not the static air inside the aircraft push the fumes out not in? When you crack the window of your car does the air go out or in? It goes in because it has been displaced by the solid form of the car just like a boat displaces water. If the 'faster air' outside, moving past your window was at a lower pressure as you suggest, the air would go out not in would it not? Let me know about that passing grade. In mathematics, as I have said earlier the perspective does not matter but conceptually it does vert much. Relative velocity as a concept is skewed by imagining the air moving as it implies that the air has kinetic energy at rest which it does not. Pilots only need a conceptual understanding of lift and Newton does that without any complications. Can you supply a wind tunnel photo of a Jab and we will see here the streamlines go. Again, imaging the aircraft immersed in water and see what you think the cause is.

You mean all the times I proved you wrong? And I assume you do not have a tertiary education. Your insult to Universities is not supported by any facts. Just your own ignorant hubris. Your understanding of how things work is so poor that you say that 'sometimes a Sprint car wing acts like a flat plate and sometimes like an aerofoil.' A flat plate inclined to airflow IS and aerofoil.

Hi Daffyd, no intent to argue here just to make sure I understand you. Lots of people refer to' downwash' as a reason for lift but one the air has transited the wing it has no further effect. I am very aware of the positioning of the tailplane as a a design factor hence my reference to Deep Stall. I will look into the issues you have mentioned. I am always keen to learn something new. Thanks for your feedback.

Largely true. (just not so much in the small details of aerodynamics) Lift is conceptually simple. Anyone who has stuck their hand out of a car window has experienced it. It can be explained simply to a six year old who has never heard of Bernoulli but apparently not to some amateur pilots who have...

Oh no, I will not give up trying to educate people. Aviation is an applied science not a storytelling venture. Mr Turbo has been materially incorrect I every statement he has made... It just shows how stubborn people can be when their false beliefs are challenged. The key to aviation safety is learning. Always learning. The days of 'I am the Captain don't argue" are long gone because they left the countryside strewn with bodies and burning aircraft. Many years ago, on my aircrew course I was taught that challenge and response checklists must be given correctly. If one word of the response was correct it was repeated so that the understanding was clear. We cannot have aviation sitting 'thumb in bum - mind in neutral' and just accepting what they are told. it just leads to tragedy.

No but I have some wood for a weight comparison. Who asked the question no-one was asking? Isn't understanding how your aircraft works a good thing?

Newton's laws are never NOT relevant. They govern motion in every thing we do. Remember it is not a competition. Bernoulli is derived from Newton's 2nd Law.

Hi Daffyd, What it a downwash field? I thought the whole downwash thing was dead and buried? If the resultant flow vector of the air at the trailing edge is downward (there is no 'washing, the air is exiting the trailing edge at a lower 'relative speed' than the wing due to form drag and induced drag) there is no way for the disturbed air to impinge on the stabiliser except at very high AOA. (The is the reason for deep stall in T tailed aircraft) Also most non canard aircraft that I am aware of have the 'inverted aerofoil' tail as a requirement of dynamic stability but the primary reason for it is that the CofG is forward of the C/L and the stab provides a balancing force to maintain longitudinal stability. It is trimmed to allow for drag minimisation as CofG and C/L changes due to fuel use, airspeed changes, flap changes and other changes in flight.

A horizontal stabiliser is an aerofoil that uses a design that turns flow upwards. It does not 'suck' anything. It creates a resultant force on the aircraft by bending the airflow upwards instead of downwards. The amount of force can be varied by moving the stab through a range that either increases or decreases the angular momentum change of the air, no different from pitching an aircraft up and down.. Simples...

G'day Bruce, "Why? Because the flow velocity is higher at the doors and therefore the pressure is less." See this is where not understating the specifics of Benoulli can lead you astray. Please remember that the plane is moving, the air is not. What you are talking about is relative flow speed and that is not really an explanation using Bernoulli. Bernoulli is simply expanding on Newton's 2nd law. F=Ma. Bernoulli applies in a single streamline not at two different unrelated locations. What you are describing is a displacement disturbance. A lot of these misinterpretations would disappear if we imagine the aircraft submerged in water which behaves the same as air. Imagine your aircraft immersed in water like in a shipping test tank and being moved along. Where would the water come in and why? Areas exposed to direct flow will 'scoop' the water in and the water will continue moving until it finds an exit where the dynamic pressure is less. As for your comments about Master's Degrees, I would respectfully suggest you either have never been to university or went to a very dodgy one. On my MSc course I had military and civilian test pilots, a professor from Cranfield University and former chief pilots from major airlines as my course supervisors. It was by no means easy. Your statement is unfair, inaccurate and silly. Australia ranks very highly in the world in University education and in my years lecturing I was very tough on the knowledge level of would be pilots. Please restrain yourself to statements supported by facts not opinions.