Adverse Yaw

咩係adverse yaw 呢 ?

Adverse yaw 係飛機rolling 嘅時候aircraft nose 同roll 嘅方向相反，例如當飛機roll去右邊，nose 就會yaw 去左邊，就好似下面幅圖咁~

形成adverse yaw 嘅原因係rolling時左右兩邊機翼嘅lift & drag 唔一樣 (詳細可以睇下面個表)，呢個左右不平均會產生我地唔想要嘅yaw tendency，如果唔counteract 就會有slip 情況出現，姐係一個uncoordinated turn ~

有咩方法可以counteract adverse yaw呢?

1. Rudder

Rudder 可以比返相應嘅opposite force 抵消adverse yaw~

- Rolling to the left, left rudder

- Rolling to the right, right rudder

不過比得太多rudder會變左skidding Turn; 太少rudder 就係slipping turn，所以最好都係睇返turn coordinator，然後”kick the ball” 就可以做到好嘅coordinated turn喇~

2. Differential Ailerons

Differential Ailerons 即係Up going aileron 移動嘅幅度比down going aileron 嘅幅度大，咁樣up going aileron 嘅drag 就會增加; down going aileron 嘅drag 會減少，從而減低左右兩邊嘅lift drag difference~

3. Frise Ailerons

Frise ailerons 嘅leading edge 係唔對稱嘅，當aileron up 嘅時候，有一部份嘅aileron 會係機翼下面突出黎，呢個部份會增加form drag; 而aileron down 嘅時候同正常aileron 冇分別嘅。所以 Fries ailerons 同樣地可以減少左右兩邊嘅lift drag difference~

4. Aileron – Rudder Coupling

當aileron 郁嘅時候 rudder 會自動一齊郁去counteract 個adverse yaw ~

5. Spoilers

用spoilers 去roll 架飛機係唔會有adverse yaw 嘅，因為spoilers 只會destroy lift (produce drag only) 所以roll 嘅方向同spoilers 升起嘅方向係一樣嘅，而最後產生出黎嘅yaw moment 同roll moment 係同一邊~