Hello everyone!

I am currently doing my instructor rating, as we pass threw a whole lot of stuff we sometimes find some mind bleeding theory that we have to present in its simplest way.I have here a problem where no one could find a coherent answer to it until now!

Here is the problem:

When you are in a turn in a single engine plane (cessnas...) The procedure is saying to put your stick and rudders back to a neutral point when the turn is set to its desire attitude(consider that you will have to make small adjustment). The flight manual is mentioning that your plane stops rolling when you put back your ailerons to there neutral position.


They state that the wing inside the turn has a bigger angle of attack then the outer wing . The outer wing has more speed so she compensates for the inner wing and they create the same amount of lift.

That all sound plausible to me but can somebody explain to me why is the inner wing with a greater angle of attack!!! I guess if somebody could explain this it would be easier to explain and visualize.

Thanks

Please note that the procedures is not complete, I have mention what is necessary for the understanding of this problem.

Bronco Billy

Please feel free to ask for more explanation, English is after all my second language.

Consider that Angle of Attack relates to RELATIVE wind. Then get the gears turning in your mind......

Have you read "stick and rudder"? It's valuable in this regard.



(I'm not an instructor but I stayed at a holiday inn express...........)

The relative wind is oppose to the path of the plane so the relative would present itself with about the same angle on both wings... Anyway i also mention that its not that hard to understand that the solution is not that complicated but to visualize it is much more!

the wing inside the turn has a bigger angle of attack then the outer wing

Which manual are you reading this in? I believe this statement is incorrect for a level turn. In a level turn the wings meet the relative airflow at the same angle and have the same angle of attack. The angle of attack on the wings are only different when in climbing and descending turns.

The outer wing has more speed so she compensates for the inner wing and they create the same amount of lift.

The outside wing is creating more lift due to the increased speed but the rest of this statement is incorrect. In any coordinated turn you will always have an over-banking tendency but especially a level or climbing turn compared to a descending turn. In most training aircraft it is hardly noticeable in normal turns done at normal speeds. At lower speeds however you may actually need to maintain aileron inputs toward the outside of the turn. This is most pronounced in slow, high angle of bank turns in aircraft with long wing spans but can still be seen in Cessnas when doing steep turns at slower speeds or especially in slow flight. Next time you are flying slow flight do a 60 degree level steep turn an notice how the control column is positioned.

Thanks for your reply,

I must say that it was my mistake, my description was incorrect. So here is my new problem:

Why is the angle of attack different when you turn in a descent or climb, I cant visualize all of this, the flight manual gives the example of a spiral stair set... I cant really get it, so if someone could add a little bit of clarity.


Thanks

Bronco

I have often wondered this myself, everyone I ask just says that it involves many complicated vectors that they can't draw

I found this explanation on a yahoo answers website that possibly makes sense:
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"Because both wings traveled the same vertical distance but the outer wing traveled a greater horizontal distance" So relative to the air, the inner wing is in a steeper climb.

"Shouldn't its AoA be lower?" The AoA required should be lower but since both wings are at a fixed angle the AoA is higher on the outer wing. The wings are angled up but the rate of climb of the outer wing is lower than the inner wing.

Another way to look at it. Imagine a blade of a prop on a plane traveling straight up, the tip travels a greater horizontal distance and the same vertical distance, so if the blade didn't have a twist, like the wings of a plane from tip to tip, the AoA would be higher at the tip. That's why they twist the the blade to give it the same AoA as the inner portion.
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So in other words, the outer wing in a climb has a higer AoA than needed, so it will stall first...? It sort of begins to make sense to me.

Interesting enough I've even posed this question to a Transport Canada examiner, and all he could do is regurgitate what was written in the Flight Training Manual. Then, I asked him to draw it, and he got all flustered and turned the colour of some screw-top red wine.
Students have asked me to explain the theory of one wing operating at a greater or lesser angle of attack during climbing/descending turns, and truthfully - all I could do is give them the same old bullshit written in the Flight Training manual.

Bottom Line: We NEED VISUALS. In this case, you truly can't understand the angles of attack unless it can be visualized.

So, if any of you have a good grafic/visual relating to the concept of angles of attack during climbing/descending turns - PLEASE post it, or PM me, OR even better yet, tell those douchebags at Transport that if they expect pilots to know it, then they should also be able to explain it - both verbally AND VISUALLY.

Well If I can remember correctly, and please correct me as this is many years ago, but back in my little cessan training days i remember practicing departure stalls, now i dont quite remember the steps but i can remember banking a little to the left, the right wing would drop upon stall, doesnt that indicate the outer wing has a higher AOA.

Is this even what this thread is about???? Im tired

When an aircraft is completing a level turn the planes of rotation is purely horizontal. However when the aircraft is climbing or descending there is also a rotation on the vertical, either up (climbing) or down (descending). The combination of these two rotations causes the difference in how the airflow meets the wings and causes a difference in the angle of attack between the wings. Wings that are dihedral will increase the effect of the angle difference between the wings as they are already at different angle to each other. As far as a picture or diagram goes, you already have a perfect one in your Flight Training Manual. Go to exercise 13, spins. The diagram which illustrates autorotation also shows the angle of attack difference between the wings. In this case it would be a descending turn. In case you don't have a flight training manual, here is a diagram I found through Google. http://overtheairwaves.com/Vol3-111.jpg

Some people who are less visual learners find help in a table to illustrate the difference between the angle of attack for the wings. The link for the table is at the bottom. In the table the aircraft is flying at 100 knots and is climb or descending at 500 feet per minute and is completing a standard rate turn. As you can see the difference in speed versus angle of climb or descent for each wing is what causes a difference in angle of attack.

So to briefly summarize; the left and right wing have a different angle of attack when completing a climbing or descending turn. This is because the wings are traveling in slightly different directions and have a different relative wind. This causes the outer wing to have a higher angle of attack in a climbing turn and the inner wing to have a higher angle of attack in a descending turn.

vrrotate - this is a good start.
I appreciate the post.

Thanks for all that information,

You have all put some interesting statements and ways of presenting it in there but the only person that tried to explain why is the angle of attack different between both wings is vvrotate in his last post.

Lots of people explained how you can VISUALIZE the differential speed between the wings.This part is great to me.

Great Graphics and all, but what I really want to know is WHY is there a differential AoA between the wings...

vrrotate wrote:So to briefly summarize; the left and right wing have a different angle of attack when completing a climbing or descending turn. This is because the wings are traveling in slightly different directions and have a different relative wind. This causes the outer wing to have a higher angle of attack in a climbing turn and the inner wing to have a higher angle of attack in a descending turn.

Again, I can get what is stated in books but I would love to have the reason why they state this and how they got to these conclusion. A conclusion without proof of experimentation isn't worth a cent.

Thanks

Bronco

i made a post this morning in a similar thread

viewtopic.php?f=3&t=50654