Have you ever looked at an X-15 and wondered to yourself “how does that thing stay in flight?” The tiny wings on it surely can be for no more than stability and decoration, right? Well, no. They’re just as important for creating lift on the aircraft as the oversized wings of a butterfly are.
An airplane wing’s size, shape, and angle on the body all affect it’s takeoff and landing performance, stall speed, and maneuvering ability.
So, what is wing loading? Wing loading is the total operational weight of an aircraft divided by the area of its wing. The higher the wing loading, the smaller the size of the wing in proportion to its mass. All things being equal, an airplane with smaller wings will have a lower stall speed (generally meaning it is a faster airplane at cruising speed) than one with larger wings. It will also be more stable in steady flight than an airplane with lower wing loading.
The amount of design and testing that goes into each aircraft is mind-boggling. An airline jet can easily take up to ten years to design, and another two to build. This is partly due to the complete precision of balance that must be found between an aircraft’s weight, wing size, the mounting angle of a wing, and it’s power loading.
In this article, we’re going to discuss examples of modern airplanes with the highest and lowest wing loading. We’re also going to look at the capabilities and stall speeds of some common airliners as well as what it takes to recover an airplane from a stall.
Table of Contents
What airplanes have the highest wing loading?
While there are many experimental aircraft with exceptionally high wing loading (the X-15 mentioned above has an unbelievable ratio of 829 kg/m2), some of the highest numbers in the world are on common passenger airlines. Below are some comparisons to give you an idea:
Wing loading examples
| Aircraft | MTOW | Wing area | kg/m2 |
| General Dynamics F-16 | 19,200 kg (42,300 lb) | 27.87 m2 (300.0 sq ft) | 688.9 |
| Boeing 747 | 333,000 kg (734,000 lb) | 511 m2 (5,500 sq ft) | 652 |
| Airbus A380 | 575,000 kg (1,268,000 lb) | 845 m2 (9,100 sq ft) | 680 |
The Airbus A380 above weighs well over a million pounds and is capable of carrying almost 900 passengers. While its wings are still considerably massive, it’s weight-to-wing-size ratio still makes it one of the highest wing load designs in the world.
In comparison, a small Cessna-172’s max gross weight is somewhere in the range of 2500 lbs, with a total wing load of approximately 14.7 lbs/sq. (21.87/M/sq).
What airplanes have the lowest wing loading?
Depending on what you classify as an airplane, the answer will be a little different. For instance, paragliders and hang gliders often have wing loadings as low as a couple of kilos per square meter (around 0,5-1 lb/sqft).
As has been mentioned earlier, gliders also tend to have a low wing loading, in order to be able to ride the thermal currents without onboard propulsion.
Ultralight and microlight airplanes also have very low wing loading, which is expected given that they often have a wing area that’s the size of a normal smaller plane, despite being much lighter.
For example, in the UK, a microlight should not have a wing loading that exceeds 25 kg per square meter.
Effects of High and Low Wing Loading on Airplane Performance
The wing loading of an airplane will affect the flight characteristics in several ways. Let’s look at three different aspects!
Stability
Airplanes with higher wing loading will be less affected by turbulence and wind gusts, since a smaller wing means that there is a smaller area for the wind to act on. This means that the ride generally will be smoother.
The amount that an airplane is affected by turbulence often is referred to as gust response.
Landing and takeoff speeds
Quite logically, an airplane with lower wing loading will have lower landing and take-off speeds, since the wings will produce more lift relative to the weight of the airplane.
As an example, a fully loaded Boeing 747 will have a takeoff speed of around 160 knots, while an ultralight plane could take off at 35 knots.
Tighter turns
The lower the wing loading, the more agile the airplane will become when it comes to performing tight turns. For example, gliders that use thermals to gain altitude need to be able to circle the rising air current. Due to their low wing loading, they’re able to achieve this. The same applies to birds, which need to perform tight turns when catching insects.
Wing Loading vs. Power Loading
We have already discussed what wing loading is. In general, the higher the wing loading, the faster an airplane needs to be, and vice versa. With this increased speed comes increased stability, but also has two major downfalls:
- Increased stall speed
- Increased landing and takeoff distance
To fulfill this need for speed and thrust, an airplane is designed with another ratio known as power loading. Power loading is the airplane’s weight to engine power output. Engine output is generally measured in horsepower for propeller planes and in pounds of thrust for jet engines.
A plane is designed around the needs it must meet. This means a fighter jet has an extremely high power loading in order to complete the maneuvers required in combat. A glider, on the other hand, has no power loading and relies entirely on its wing loading and design to generate lift.
Can All Planes Stall?
Considering that the wing loading varies a lot between airplanes, you might wonder if all airplanes can stall, regardless of their wing loading.
According to the Airplane Flying Handbook put out by the FAA a stall “...is an aerodynamic condition which occurs when smooth airflow over the airplane’s wings is disrupted... ”
Specifically, a stall occurs when the AOA—the angle between the chord line of the wing and the relative wind—exceeds the wing’s critical AOA. It is possible to exceed the critical AOA at any airspeed, at any attitude, and at any power setting.”
This tells us that yes, any wing is capable of an aerodynamic stall.
However, this is extremely rare in airlines due to the pilot’s training and experience. In addition, new aerodynamic rules are used at high speeds (over 224 KTS), because at these speeds air takes on the properties of a fluid.
Even in the event of a stall, the correction techniques for most aircraft make it possible to recover in a matter of seconds.
What exactly happens in a stall?
The FAA has some great material on the physics behind what causes a stall and how to recover which is linked here. However, in this article, we’ll cover the basics of what a normal stall looks like and the most common recovery techniques.
As we mentioned, a stall occurs when a wing exceeds the angle it was designed to fly at in relation to the relative wind. This means a stall could theoretically happen at any angle, speed, or power setting. Stall speed is determined by the airplane manufacturer based upon the wind and airplane design.
Most commonly, a stall is caused by a pilot pulling up on the nose of the aircraft, without adding any power. This causes the speed to decrease, the wings to generate less lift, and eventually, once the critical angle of attack is exceeded, the wings will stop generating lift altogether and the plane will begin falling out of the sky.
How do pilots recover from a stall?
So how is this corrected? Assuming the aircraft is properly weighted (something every good pilot ensures well before take-off), the pilot simply needs to decrease the angle of attack, usually, this means by pushing the nose back down.
With smaller airplanes, power is generally given simultaneously to gather airspeed and once again generate lift with the wings. It is a process that has an almost infinite amount of aspects to be considered, but generally takes a total of about 10 seconds to occur.
In the event, a pilot is unable to recover the airplane from a stall, the plane will devolve into a ‘spin’, a much more serious situation, but one that is also recoverable.
Again, these can technically happen to any aircraft, however, it is incredibly rare in passenger airlines for a stall to happen without extenuation circumstances.
Concluding Words
The wing loading simply is a measurement that tells us the weight of the plane relative to the wing area. A higher wing loading means that the stall, takeoff, and landing speeds will become higher, while a lower wing loading allows the plane to operate at lower speeds.
Some airplanes that have a low wing loading including ultralight airplanes and gliders. On the other side of the spectrum, we have some of the denser military jets, as well as jumbo jets such as Boeing 747 and Airbus 380.
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