Drag

Drag is a backward force that limits the speed of the airplane.

Aspect Ratio

Aspect ratio is the span of the wing, wingtip to wingtip, divided by its average chord.

Aircraft fly as a result of and in spite of many forces acting on the aircraft. A force is a push or pull by something on something. When standing we push down on the floor and the floor pushes up on our feet. Forces always act in pairs, on different bodies and in opposite directions. There are four major forces acting on an aircraft in flight. Lift is the upward force countering gravity. The aircraft must produce enough lift to fly. Thrust is the push or pull forward that allows the aircraft to move. Drag is a slowing force. Drag always acts in a direction opposite thrust.

Drag

Drag is associated with lift. It is caused by any aircraft surface that deflects or interferes with the smooth airflow around the airplane. If you increase airspeed, or angle of attack, you increase drag (and lift). Drag acts in opposition to the direction of flight and limits the forward speed of the airplane. Decreasing drag makes things go faster. Increasing drag makes things slow down.

Aspect Ratio

One primary factor in determining lift/drag characteristics is the relationship between the length and width of a wing. This is known as the aspect ratio. In general, the higher the aspect ratio, the higher the lifting efficiency of the wing. Different variables on the aircraft can contribute to drag. The amount of (form) drag created is related to both the size and shape of any structure which protrudes into the wind. Skin friction drag is caused by any uneven surface on the airplane. Drag also occurs when currents of air meet and interact. Total drag for an airplane is the sum of all these things.

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