In the study of wing stability it is useful to define the terms inflection Least) on the sweep, on the leading edge radius and the twist. Trailing-edge actually stall from the leading-edge. Leading-edge separation due to induced camber in the three-dimensional wing may causeĪ bubble of large spanwise extent, so that airfoils that ordinarily stall from the The stability limit is approximated in the figure belowįor untapered wings (tapered wings have less conservative limits).įigure 2: Longitudinal stability limits (empirical data). Longitudinal stability depends mostly on the aspect-ratio and the sweep angle Moment with the lift coefficient, that is strongly dependent on the wing sweepĪnd various technical devices (tip devices, fences, nacelles, etc.). One important aspect is the behavior of the pitching Longitudinal and lateral stability of low aspect-ratio wings have been Magnitude as to more than compensate for the lift losses that occur when the tip Separation and therefore capable of developing local lift coefficients of such large These two effects is such as to make the root sections highly resistant to flow Outward drain of the boundary layer from the root sections.
In addition, the spanwise pressure gradients are such as to cause an Sweep moves the point of maximum lift outboard, which on turns may promoteĮxperimental investigations showed that the root sections do not experience high LE Lift is mostly concentrated in the inboard sections and reaches high values. The spanwise distribution of lift is another interesting aspect of these wings. The presence of the strong tip vortices that separate closer to the leading edge,Īccording to a mechanism similar to that governing the delta wing. Increases at a faster rate than that predicted with a linear theory. Squared wings show Clmax as high as 1.3.Īt even lower aspect ratios the wing is subject to strong vortex flows and CL This angle increases progressively andĮasily reaches 30 degrees. AtĪspect-ratios 1 < AR < 2 the most evident effect is the shift of the angle ofĪttack at which maximum lift is reached. The values of the maximum lift coefficient are largely independent from theĪspect-ratios at aspect-ratios above 2 and a Reynolds number 1 million. Having reference data at aspect-ratio AR=5, one can derive the polarĬharacteristics of shorter wings with remarkable precision, at least in the Quite well using the Prandtl-Lanchester formula, originally derived for elliptic Data for different aspect-ratios can be correlated
#ASPECT RATIO OF A HALF WING SERIES#
Handley-Page (1911) found that a squared wing (AR=1) stalled atĪngles above 40 degrees, while a moderately slender wing (AR=6.25) stalled atĪ large body of data was published in the 1920s as a result of a series ofĮxperiments at Gottingen, Germany. Of attack stall of the low aspect-ratio wings has been known since the early days ofĪerodynamics. Short wings for low speeds have been studied for a long time.
1 below shows a qualitative example of how strongĪn influence the leading edge vortex can have on the lifting characteristics of aįigure 1: Lift characteristics at very low aspect-ratios Wing Performance at Low Speeds Truckenbrodt, and others) provided simple means to predict the vortex lift created byįig. Later a number of non-linear lifting line theories (Multhopp, Gersten, Theoretical analysis was performed by Betz in theġ920s. Squared wings and wings withĮven lower aspect ratios are still interesting from a theoretical point of view, but We define a low aspect-ratio wing a wing having AR < 5. The expense of some stability (see below). Low aspect ratios (about 2 ÷ 3) inįighter aircraft are necessary to maintain a high degree of manouvrability, though at (typical aspect ratios AR < 3) short wings are also part of control devices inĬompetition sailing boats and micro air vehicles. Wing-in-ground ship (AR = 1 ÷ 3) there are also short wings in racing cars Why short wings, then ? – There can onlyīe practical limitations to use such wings. The high angle of attack stall of the low aspect-ratio wings has been known since theĮarly days of aerodynamics. Wings of low aspect-ratio are known for having poor aerodynamic efficiency L/DĪt low speeds, along with stability problems, both static and dynamic.