completeaerogeek

k don't think you do understand AOA... Would you like me to demonstrate a stall for you with the nose 3 degrees lower than the horizon, in the attitude that you suggested is zero degrees AOA? Love to! You can only do that if your airspeed decays below the point that your aerofoil can no longer turn enough airflow to support the weight of the aircraft... (or you introduce a load factor) Physics again... Annoying isn't it? You still don't seem to comprehend what is happening and you continue to misquote me. Perhaps you should go back and read what I said as opposed to what you think I said?. You have to lower the nose 3 degrees below level PLUS the equivalent angle related to the upper surface camber which is effective AOA as it turns the airflow downwards creating lift in a conventional aerofoil. Get it now? Then you reach Zero Lift Pitching Angle. Drop your nose below the angle of incidence in a symmetrical aerofoil aircraft like an Extra and you will be making no lift... That's surprising, most of the experienced ATPLs I know are very knowledgeable on the subject, but it takes all kinds I guess. ATPLs get taught by instructors many of whom don't understand aerodynamics correctly. I had an airline pilot on my BSc course that didn't realise he was sitting on top of a supercritical wing. Flat on top cambered on the bottom... Kinda freaked him out when I explained how it worked... Yup, as long as your teachings suggest AoA is related to Attitude without further explanation or qualification, I'm afraid it does. My goodness you are stubborn are you? At a fixed airspeed raise the nose- AOA increases... End of story. Controlling the aircraft around its pitch axis at a fixed airspeed changes the AOA. Even the initial pitch up into a climb changes the AOA until you have established a steady/balanced climb like a cruise climb. I also note you didn't answer my question about take-off? OOPS. Kinda the essential concept don't you think otherwise you are driving a car not flying a plane...

My goodness you are stubborn are you? At a fixed airspeed raise the nose- AOA increases... End of story. Controlling the aircraft around its pitch axis at a fixed airspeed changes the AOA. Even the initial pitch up into a climb changes the AOA until you have established a steady/balanced climb like a cruise climb. I also not eyou didn't answer my question about take-off? OOPS. Kinda the essential concept don't you thing otherwise you are driving a car not flying a plane...

Ouch-Nonsense again? You have introduced another factor. Changing airspeed. (Physics does not allow for a steady state with such changing parameters. F=Ma) Do you understand the definition of AOA? AOA by definiton is Angle of Attack that is the relative angle of the chord line to the relative airflow. Now sit back and think for a second: If raising the nose doesn't cause AOA changes- do you want to explain why we rotate at Take off? Or how we typically demonstrate a stall? If you do what you say, you absolutely will change your AOA and it won't stabilise until your increased power/thrust reaches a steady state i.e. a stable climb. Also I have provided very specific information and references in my first post. I suspect you are suffering from confirmation bias. Read/watch my first post and you will be fully informed. And again, I did not state that flying instructors don't know their stuff. My point is that those people teaching pseudo Bernoulli principles like 'the wing is a venturi, and equal transit time don't know their stuff. However, just being a pilot or a flying instructor does not give you any 'special knowledge'. What most pilots have is a fairly basic level of operator level knowledge. ( I know I have been teaching CPL/ATPL aerodynamics for years) A racing driver can very competent at handling their car but that does not mean they understand the physics involved. For that-you have to educate yourself... I have had discussions with Boeing and Airbus pilots, some with many thousands of hours who attended my lectures still believing equal transit time... Amazing... Should have seen the look on their faces when I showed them the Cambridge video... Now does that still deserve your nonspecific/nonsense tag???

Yeah- not so much. Younger readers may assume the' rigger' is some kind of political operative. The correct terms are Incidence, AOA and Camber. Yes the air is viscous that is why the mathematics of Bernoulli don't accurately describe lift. He describes inviscid flow. If you watch the video in my first post (page 1) you will see the streamlines pulling each other in the direction of motion of the wing. And yes the contributor that used the term 'deflect' should perhaps describe it more correctly as 'bend'. As NASA states- Lift is caused by turning a fluid. (no magic required) The wing bends the air over both surfaces downwards. The lower surface in particular also pushes the air forwards (in the direction of wing movement) and downward. This makes a mockery of the point in the CASA Day VFR CPL syllabus that says 'explain why the upper surface creates most of the lift) If that was true an A380 wouldn't get off the ground with its big supercritical wing.

I'm blushing now. I am just a nerd. I have been in the industry 33 years. Started off in the RAAF (cadets before that) Aircraft Maintenance Engineer and then went on to train as Flight Engineer on P-3s. Later worked at QF on B747/767 RB-211 and JT-9/CF6 80C2. Got out of MX and went to the US and worked for one of the big carriers as an Operations Supervisor/Manager in Airport Ops, Corporate training for a while and then Airport GM in Chicago. Came back and consulted to Virgin for 3 years when they started up. Lots of AV consulting here and in the Middle East. Got an MSc tech in Aviation from UNSW in 2008, taught BSc Aviation ATPL/CPL Systems and Aerodynamics at UNI for 3 years . 6 years as Squadron CO in the Air Force Cadets. Written a few books on leadership and human hahaviour. Latest one out next year is on how Human Factors investigations of airline accidents can be applied to the corporate workplace. Oh and if my students used Wiki without reading and using the references at the bottom--FAIL! Google/WIKI is full of opinions and less that the ideal number of facts...

Be nice now. Being narky can prove embarrassing when you find that you are wrong. What is your point about a full range of AOA? As long as you have elevator authority why wouldn't it? Most aircraft have 3 Degrees of Incidence. This is an effective AOA but fixed. If you lower the nose by 3 Degrees you will negate this. Then lower it further by the amount of upper surface camber (also effective AOA) you reach Zero Lift Pitching Angle... = No Lift. Simples...

Well SC wings were a real change maker. Curved on the bottom and flat on top. Messes with some people's heads!

Generally correct but not quite a simple as that. The upper surface of SC wings is not appreciably cambered. The angular change of the airflow is what creates lift. By the stuff off the back do you mean downwash? If you do be careful not to get caught in another myth. The wing pulls/pushes the air in its direction of movement so in effect. the air passing behind the wing from the upper surface is going 'slower' than when it encountered the wing.

That's kind of correct. Push your hand through water inclined to the direction of movement and you will see this occur. The behaviour in air is exactly the same as in water.

Bernoulli is derived from Newton's 2nd Law and is used for describing behaviour in a single contiguous parcel of air not around a wing. Itt has flaws in the formula as air is assumed to be inviscid. Rather than reinterpreting something, Just use Newton's Laws. No silly explanation required.

It is ridiculous. Aviation and aerodynamics are an applied science. If you want to believe unsupportable assertions, get into religion.

Have you read the first post-it's all there. It occurs with a flat plate wing. read it then come back if you are unclear.

We could just delete Bernoulli and make it much easier!

Ha Ha! But man are they good at energy management! Not to helicopter pilots!

True. That is another reason why supercritical wings are cambered underneath. The can create lift at low pitch angles at high speed.

You mean the concept? The order of power and attitude can mean the difference between life and death. Apply power first in a low airspeed situation in an airliner with underslung engines and you will violently pitch up far beyond you elevator authority to correct. STALL-STALL-STALL-DEAD

I don't know, glider pilots look pretty cool...

The problem with that philosophy is that it is dangerous and goes against basic Aviation Human factors philosophy which says to question things that look wrong. This philosophy when employed works extremely well. When ignored is deadly. I could list many, many accidents caused by the junior pilot not challenging the captain or the pilots ingnoring a query from a flight attendant about 'strange noises'.. That CASA should still be teaching nonsense should not really be of any surprise to us... It also leads to accepting other dangerous concepts taught in basic flying like Power + Attitude = Control. This only works if you are flying a centreline thrust aircraft not on any aircraft with podded engines. . Just ask the guys on AF447. Oh you can't because they believed it. This should have long ago been changed to ATTITUDE + POWER = CONTROL. With decaying airspeed or high AOA LOWER THE NOSE FIRST. Applying thrust to correct low airspeed/high AOA in most airliners with underslung engines is a death sentence. You can ask the crew of Asiana 214 at least they survived. We must continue to educate our young aviators as to the actual physical laws under which they operate. Anything else is at the least embarrassing and at worst deadly...

Not really. it is pretty simple. See my first post above or look at the NASA reference which explains it all.

You are correct. Not just aerobatic aircraft either. Military aircraft since the 1940 have been using symmetrical aerofoils. The Canberra is a good example of this. In reality a flat plate is a very good wing with an exceptional L:D ratio. It just stalls earlier. All teaching should start with a flat plate wing (such as a paper plane) I do and it is very effective in debunking silly ideas.

As to the stall part - stall happens when the upper surface air can no longer 'turn the corner' because the angle of change is too acute and it tumbles into a rotating vortex.. The lower surface does not stall until close to 90 degrees. Single surface wings (hang gliders) use the same principle as sailboats. BOTH surfaces bend the air to a new direction. This bending creates a reaction force that is lift. (Newton's 2nd and 3rd Laws at work) Stick your hand out of a car window and you can feel the effect. It is just less noticeable on the back of your hand but is still there. Wach the Cambridge University video I linked and it will all make sense. http://www.cam.ac.uk/research/news/how-wings-really-work

The reason a big or high camber aerofoil gets lots of lift at low speed is that the upper surface camber being so pronounced is equal to the angle through which it bends the air downwards. If you imagine a highly cambered wing's upper surface in isolation, you have a hang glider wing. Even in level flight it is producing a big angular change which means lots of lift. But that is also why it is speed limited. Lots of lift means lots of induced drag. A thin wing with less or no camber needs more airspeed to created the same amount of downwards moving air to support the aircraft's weight. The F-104 had essentially a flat plate wing-hence the high takeoff and landing speed.

You are essentially correct. However an aircraft with a conventional cambered upper surface will be creating lift at zero AOA. Angle of incidence is usually 3 degrees which equates to three degrees of AOA. Also the upper surface in a conventional cambered wing still bends the upper surface air downwards even if you are at zero AOA. You have to lower the nose to about 3 degrees to reach zero lift pitching angle. A helicopter usually has a symmetrical aerofoil so is producing no lift at zero AOA.

You are right. It blows. Both surfaces change the direction of the air from in line with the horizontal or rotational plane to a rearward vector. (just alike a desk fan!)

Been on an airline lately? Then you have sat on top of one. How about the biggest - the A380. (see attached) How's them apples? All modern airliners do. The entire Airbus family and all Boeings from the 767 on. Otherwise they would have to lower their cruising speed as MCrit would be too low. Standing shockwaves (which are visible by the way) would be too large and fuel consumption too high.