This is due to the difference in fluid behavior in the subsonic and transonic/supersonic regimes. This decrease in aspect ratio causes an increase in induced drag which is detrimental to the airplane’s performance during takeoff but may be beneficial during landing.Īircraft which approach or exceed the speed of sound sometimes incorporate variable-sweep wings. This unreferenced section requires citations to ensure verifiability.Įxtending the trailing-edge wing flaps causes a decrease in aspect ratio because extending the flaps increases the wing chord but with no change in wingspan. Airfield Size: Airfields, hangars and other ground equipment define a maximum wingspan, which cannot be exceeded, and to generate enough lift at the given wingspan, the aircraft designer has to lower the aspect-ratio and increase the total wing area.Practicality: low aspect ratios have a greater useful internal volume, since the maximum thickness is greater, which can be used to house the fuel tanks, retractable landing gear and other systems.However, this variation is very small when compared to the variation in induced drag with changing wingspan.įor example, the section drag coefficient of a NACA 23012 airfoil (at typical lift coefficients) is inversely proportional to chord length to the power 0.129:Ī 20 percent increase in chord length would decrease the section drag coefficient by 2.38 percent. Due to the effects of Reynolds number, the value of the section drag coefficient is an inverse logarithmic function of the characteristic length of the surface, which means that, even if two wings of the same area are flying at equal speeds and equal angles of attack, the section drag coefficient is slightly higher on the wing with the smaller chord. This is because, for an equal wing area, the average chord (length in the direction of wind travel over the wing) is smaller. Parasitic drag: While high aspect wings create less induced drag, they have greater parasitic drag, (drag due to shape, frontal area, and surface friction).Due to the lower roll rates, high aspect ratio wings are usually not used on fighter aircraft. A higher aspect ratio wing will also have a higher moment of inertia to overcome. Maneuverability: a high aspect-ratio wing will have a lower roll rate than one of low aspect ratio, because in a high-aspect-ratio wing, an equal amount of wing movement due to aileron deflection (at the aileron) will result in less rolling action on the fuselage due to the greater length between the aileron and the fuselage.if the deflected wing interferes with aileron movement). Also, longer wings have greater deflection for a given load, and in some applications this deflection is undesirable (e.g. Structural: A long wing has higher bending stress for a given load than a short one, which requires stronger structure to withstand.There are several reasons why not all aircraft have high aspect wings: Is the circumference-to-diameter ratio of a circle, Is the aircraft zero-lift drag coefficient, This property of aspect ratio AR is illustrated in the formula used to calculate the drag coefficient of an aircraft The interaction between undisturbed air outside the circular cylinder of air, and the downward-moving cylinder of air occurs at the wingtips and can be seen as wingtip vortices. Therefore the larger downward velocity produces a larger aft-leaning component and this leads to larger induced drag on the aircraft with the smaller wingspan and lower aspect ratio.

The aft-leaning component of this change in velocity is proportional to the induced drag. For two aircraft of the same weight but different wingspans the small cylinder of air must be pushed downward by a greater amount than the large cylinder in order to produce an equal upward force. A large wingspan is working on a large cylinder of air, and a small wingspan is working on a small cylinder of air. The diameter of that cylinder is equal to the wingspan. An airplane in flight can be imagined to affect a circular cylinder of air. Very high aspect ratio wing of the Glaser-Dirks DG-808 glider (AR=27.4)Īspect ratio and planform can be used to predict the aerodynamic performance of a wing.įor a given wing area, the aspect ratio is proportional to the square of the wingspan, and the wingspan is of particular significance in determining the performance.

Aspect ratio of a half wing