What if a glider had short, stubby wings?

A glider is a plane with no engine. It has very long, thin wings.

What if the wings were short and fat instead?

A glider is an aircraft with no engine. After it is towed or launched into the sky, it glides through the air, slowly coming down unless rising air lifts it. To stay up as long as possible, it needs wings that make lift with as little waste as possible.

Look at a glider and its wings seem very long and very thin. So what if a glider had short, stubby wings with the same area? In this lab you can reshape the wings in a model and see.

Aspect ratio (AR) is a wing's span squared divided by its area; for a rectangular wing it is simply span divided by chord. Glider wings have high aspect ratios, and the FAA's Glider Flying Handbook says this generates significant lift at low angles of attack with minimal induced drag.

This lab keeps a glider's wing area, mass, speed and tilt fixed and changes only the aspect ratio, from 15 to 4. It asks what happens to lift in a simple model, and then what the model leaves out.

Gliders have long wings, like a big bird.

The long wings help them float through the sky for a long time.

Wings make lift by turning the air flowing past them downward, so the air pushes the wing up. In Olly's model, a 300-kilogram glider has 12 square meters of wing with an aspect ratio of 15: its wings stretch about 13.4 meters from tip to tip and are only about 0.9 meters front to back.

Flying at 30 meters per second with its wing tilted 5 degrees, the glider makes about 3.2 kilonewtons of lift. Its weight is about 2.94 kilonewtons, so the lift is 109 percent of its weight: enough to stay up.

The model computes lift as L = ½ρv²S·C_L, with the lift coefficient from thin-airfoil theory corrected for a finite wing: C_L = 2πα / (1 + 2/AR). For the glider here (mass 300 kg, S = 12 m², AR = 15, v = 30 m/s, α = 5°, sea-level air), C_L is about 0.48 and lift about 3.2 kN against a weight of 2.94 kN: 109 percent.

An aspect ratio of 15 with 12 m² of area means a span of about 13.4 m and a chord of about 0.9 m. Real gliders vary: the FAA handbook's examples range from an aspect ratio of 11.85 to one of 39.

Now Olly makes the wings short and wide. They have the same amount of wing.

The glider makes less lift. It can't stay up at the same speed!

Now change the aspect ratio to 4 and keep everything else the same, including the wing area. The wings now stretch only about 6.9 meters from tip to tip and are about 1.7 meters front to back.

In the model, lift drops to about 2.42 kilonewtons, only 82 percent of the glider's weight. Same area, same speed, same tilt, but not enough lift. To stay up, the stubby glider would have to fly at about 33 meters per second, or tilt its wing more: at 7 degrees it makes 115 percent of its weight.

At AR = 4 with S unchanged, the model's span falls to about 6.9 m and the chord rises to about 1.7 m. C_L at 5° drops to about 0.37, lift to 2.42 kN: 82 percent of weight. The speed needed at this tilt rises from about 29 to 33 m/s, and the slowest possible flight (at the model's 15° stall) from about 17 to 19 m/s.

The lift-curve slope is the reason: 2π/(1 + 2/AR) is about 88 percent of the ideal 2π per radian at AR = 15, but only about 67 percent at AR = 4. A stubby wing needs a bigger tilt or more speed for the same lift.

Air spills around the tips of a wing and swirls.

Short wings have the tips close together, so more of the wing is spoiled by the swirls.

Air pressure under a wing is higher than above it. Near the wingtips, air can sneak around from below to above, making swirling whirlpools of air called wingtip vortices. NASA explains that these swirls reduce the wing's effective tilt into the air, and they also cause extra drag, called induced drag.

A long, thin wing keeps most of its length far from the tips. A short, stubby wing has much more of its wing close to a tip. That is why, for the same wing area, long, thin wings make lift more efficiently.

NASA Glenn explains that at the tips of a finite wing, air flows from the high-pressure underside to the low-pressure top, forming counter-rotating tip vortices. Their induced flow lowers the effective angle of attack and tilts the aerodynamic force backward, producing induced drag: C_Di = C_L² / (π·AR·e). For the same wing area, a higher aspect ratio gives lower induced drag.

The model captures only the first effect, the lower lift slope. It has no drag at all, no engine or thrust, no flaps, and it uses the elliptic-wing correction for every planform. Its stall angle is fixed at 15°.

Real gliders and some big seabirds have long, thin wings.

The wandering albatross has the biggest wingspan of any living bird that scientists know of. It glides over the ocean and hardly flaps.

For a glider, drag decides how far it can glide. The FAA's Glider Flying Handbook compares two example gliders: one with an aspect ratio of about 12 has a glide ratio of 22 to 1, and one with an aspect ratio of 39 has a glide ratio of 60 to 1. A glide ratio of 60 to 1 means it travels 60 feet forward for every foot it drops.

Nature has long wings too. The wandering albatross has a wingspan of up to 11 feet, the largest known of any living bird, and it soars over the Southern Ocean while hardly flapping its wings.

The FAA's 2024 Glider Flying Handbook illustrates the trend with two examples: a 51 ft span glider with aspect ratio 11.85:1 and glide ratio 22:1, and an 86.9 ft span glider with aspect ratio 39:1 and glide ratio 60:1. The two also differ in weight and wing area, so the comparison shows a trend, not aspect ratio alone. Winglets, it notes, also reduce induced drag.

Woods Hole Oceanographic Institution describes wandering albatrosses, with wingspans up to 11 ft, as highly adapted to long-distance soaring: they hardly flap, relying on dynamic soaring in the wind shear over the waves plus updrafts and turbulence.