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Turns

  • sydpilot
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sydpilot created the topic: Turns

Hi Bob,

I'm having trouble with the concept of turning and AOA.

In a climbing turn, the outer wing has a larger AOA and is travelling faster .
In a descending turn, the inner wing has a larger AOA and outer wing is travelling faster.
This is where my understanding ends.

How does the continuous roll-out or roll-in casue the outer or inner wing AOA to increase?
I wasn't sure how to interpret figure 9.16 either.

Thanks.
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bobtait replied the topic: Turns

I must admit that it is not an easy concept to grasp when you are reading text on a page. If you grab a model aircraft and hold it by the fuselage, then make it do a climbing turn without moving your wrist, you will find that the angle of bank at the end of the turn is much greater than it was at the beginning. The only way to keep the bank the same during a climbing turn is to continuously roll the aircraft out of the turn. That means that the outside wing is continuously moving downwards and, since the relative airflow is always opposite the direction of motion, the relative airflow is moving up towards the wing. That's why the angle of attack is increasing.

If you do a climbing turn in an actual aircraft, you will notice that to keep the angle of bank constant, you need to apply aileron opposite to the direction of turn. Take note of that next time you go flying. That opposite aileron is causing the aircraft to continuously roll out of the turn. Figure 9.16 is an attempt to illustrate the same effect using vectors. Some people don't find that quite as convincing. Both wings gain the same height, but the outside wing travels a greater distance. That causes the relative airflow to approach the wing at a greater angle - that is from further beneath the wing.


Bob
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