Lift drag ratio

Japanese: 揚抗比 - ようこうひ（英語表記）lift drag ratio

The ratio of lift to drag acting on an aircraft in flight. The higher the lift-to-drag ratio, the less thrust is needed to move forward, and the longer the glide distance. The optimal lift-to-drag ratio is one of the indicators of the sophistication of an aircraft's aerodynamic design. For high-performance gliders, it is about 30, and for passenger jets, it is 15 to 18. The supersonic passenger aircraft Concorde has a very slim shape, but the wave-making drag caused by shock waves generated around the aircraft during supersonic flight is added, resulting in a low figure of about 7.5.

(Tsuruo Torigai, former Managing Director of the Japan Aircraft Development Corporation, Engineer (Aircraft Division) / 2007)

Source : "Chiezo" published by Asahi Shimbun Publications Co., Ltd. About Chiezo

Japanese:

飛行中の航空機に働いている揚力と空気抵抗の比。揚抗比が高ければ、前進に必要な推力は小さくて済み、滑空距離も伸びる。最良揚抗比は航空機の空力設計の洗練度を示す指標の1つ。高性能滑空機では約30、ジェット旅客機では15〜18。超音速旅客機コンコルドは非常にスリムな形態だが、超音速飛行中は機体の周囲に発生する衝撃波による造波抵抗が加わるため約7.5と低い数字になっている。

(鳥養鶴雄元日本航空機開発協会常務理事　技術士（航空機部門）／ 2007年)

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