By Bjorn Fehrm
May 15, 2026, ©. Leeham News: We have finished a series on Blended WingBody (BWB) airliners, where one of the tougher challenges will be the design of the airframe structures.
In aircraft design, the aerodynamic shape of the aircraft gets a lot of attention for obvious reasons; it’s what we see, and if it’s well-made, it’s aesthetically beautiful.
For successful aircraft designs, a well-thought-out and designed structure is equally important. Aircraft designers and experts recognize a well-thought-out, well-designed structure when they see it, and it is an equally beautiful experience. In the series, we will see that the most iconic aircraft had a brilliant structural design.
Figure 1. The typical structural parts of an airliner fuselage (A320 fuselage structure). Source: Airbus.
We start the series on structures with what these must cover in terms of requirements. Then we go through how they have evolved over time, and finally we describe the changes that must occur over the next few years to meet the requirements of the next generation of airliners.
What are the requirements for an aircraft’s structure?
When we think about an aircraft’s structure, the first thought is that it must be strong enough so that pieces don’t crumble or fall off the aircraft during flight, like the wings folding as a result of a strong gust.
But there is a range of requirements that must be fulfilled:
- To hold the aircraft parts together, not only during the highest loads envisioned in flight (the so-called limit loads) but also when subject to ultimate load (1.5 times higher), and after 30,000 flights or more.
- In all modern aircraft, it also forms the plane’s aerodynamic surface. It was not always the case, as we will see in the historical part of the series.
- To protect the pilots, passengers, and payload from the forces of outside air during flight and any encountered weather (rain, hail as large as golf balls).
- To be the shell that forms a pressurized compartment for all aircraft that fly higher than 10,000ft, the highest allowed cruise altitude without either extra oxygen to the humans on board or a pressurized cabin that keeps the air pressure below 8,000ft at all times.
The above can be described as the primary functions, but there are several more that are needed for a successful aircraft structure:
- It must be designed to hold up to use, which means being resistant to water intrusion, both during flight and when parked. The structure must also be protected from corrosion caused by condensed water that forms during descents or spills from lavatories and from deterioration caused by other factors, such as sunlight.
- It must be designed to withstand fatigue-induced deterioration of its materials, a phenomenon that caused the last major airplane crash in the US, the UPS MD-11 freighter crash in Louisville, Kentucky, in November last year.
- Be easy to produce and assemble so that the designer’s intentions can be realized in production. This is a harder requirement than it seems. The airplane may be delivered and operated only when it is 100% in accordance with the approved design drawings/information.
- The producibility affects the cost of the structure. If the structure is too costly to produce, the airplane project will not be successful, as it can’t be priced to the market’s expectations. We will describe a recent highly advertised project that was stopped because of the high structural costs.
The science of airplane structures is very much tied to the science of materials. We will describe the salient features of the different materials used to produce aircraft and how advances in materials and their properties have driven the largest changes in how aircraft structures are designed and built. New materials that can be shaped more freely have also enabled the use of more advanced aerodynamic shapes.
We start the series with a historical review next week. The history of structures is also the story of aircraft development, and we will see that advances in structures are very much tied to advances in aircraft design.
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