While airplanes and gliders share many design, aerodynamic, and piloting factors, the lack of an engine fundamentally changes the way a glider flies.

Streamlined Fuselage

Since there’s no engine taking up space, a glider is sized around the cargo it carries; the fuselage is designed to be as small and light as possible. Most gliders have seats for two people in the small cockpit, with pilots sitting in a reclined position, vs. powered airplanes, where pilots typically sit upright. Why the difference? By sitting reclined, the cockpit and canopy can be more streamlined, creating less drag in flight.

The surface of a glider’s fuselage is designed to be as smooth as possible, allowing the plane to fly through the air with little parasitic drag. The earliest of gliders were constructed from wood covered with canvas; later versions were made from riveted structural aluminum skins. Unfortunately, the seams and rivets typical of aluminum significantly reduced performance due to parasitic drag, so gliders continued to adapt. Today, many advanced gliders are constructed from seamless materials like fiber glass and carbon fiber.

High Aspect Ratio Wings

Gliders have high aspect ratio wings, which means they are longer and narrower than wings on normal, powered airplanes. Aspect ratio is calculated by dividing the square of the span of the wing by the area of the wing. As you can see in the diagram above, the Schleicher ASH 31 glider has an aspect of 33.5, while the Piper Cherokee has an aspect ratio of 5.6.

High aspect ratio wings produced less induced drag, which is what makes them so efficient on gliders. So why don’t all aircraft have high aspect ratio wings? There are several different factors.

First, high aspect ratio wings bend more than shorter wings, which means they need to be designed with stronger design specs. Since gliders are light, the bending isn’t as much of a problem. But with heavier aircraft, like airliners, a high-aspect ratio wing would be impractical. Next, high aspect ratio wings are more susceptible to wing warping when ailerons are used. Since gliders fly a relatively slow speeds, wing warping isn’t as pronounced, but it would be a real problem in a fast aircraft.

Maneuverability is another major factor. High aspect ratio wings decrease maneuverability, because they have a higher moment of inertia. Think of it like a tightrope walker: they carry a long rod to balance themselves, preventing them from quickly falling left or right. It’s great if you want to stay in one place, but not so great if you want to quickly move (or roll) left or right.

Finally, airport size limits the aspect ratio an aircraft can have. Take the Boeing 777 for example. The 777 has an aspect ratio of approximately 9. If it had an aspect ratio of 30+, it wouldn’t be able to park near any other aircraft on the ramp, and its wings would be so long that they would hang over the taxiways during takeoff and landing. Obviously, that wouldn’t be practical.

Control Surfaces

Like most airplanes, gliders use ailerons, a rudder, and an elevator to fly. Flaps are fitted on gliders to control descent rates by producing drag and increasing lift. Many modern gliders also use airbrakes or spoilers which, when used, drastically disrupt airflow over the wing, increasing drag and reducing lift.

Another significant difference between powered airplanes and gliders is that gliders normally have only one landing gear, situated directly below the pilot. Having only one gear save a lot of weight, but what happens to the wings on takeoff and landing when you’ve only got one gear? The wingtips are protected by skids or small wheels, and when the glider lands, it comes to rest on the main gear and one of the wingtips.