The Airbus A350 Was Built Around Composite Materials

Credit: Airbus

As one of the newest widebody aircraft on the market, the Airbus A350 continues the trend set by the Boeing 787 in terms of construction. Earlier Airbus widebodies like the Airbus A330 and Airbus A340, relied heavily on aluminum alloy structures. Rather than continuing with the aluminum design that dominated for decades, the A350 was instead built from approximately 53% composite materials. This includes large portions of the A350’s fuselage, wing structures, empennage, center wing box, and tail cone. In total, the A350 features roughly 70% advanced materials by weight, making it one of the most composite-intensive commercial aircraft ever produced.

The decision to use a majority of carbon fiber materials in the A350’s construction boils down to the advantages it offers over traditional metallic construction. Composite materials offer an exceptional strength-to-weight ratio, enabling engineers to reduce aircraft weight while maintaining the airframe’s critical structural rigidity. The lower weight of the A350 directly translates to improved fuel efficiency, range, and payload capacity, with the aircraft offering up to 25% lower fuel burn and up to 1,500 NM (2,780 km) more range than the A330.

In addition to fuel savings, composite fiber-reinforced plastic structures are highly resistant to corrosion and fatigue cracking, two major long-term problems that have historically impacted aluminum airframes. It also reduces the number of parts needed by fabricating large sections at once, lowering the number of individual nuts and bolts required. However, despite the numerous advantages composite construction offers, carbon fiber composites also pose challenges, with the difficulty of visually detecting structural damage among the most significant.

The Invisible Damage Problem: Barely Visible Impact Damage

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Barely Visible Impact Damage, otherwise known as BVID, is one of the largest issues with composite aircraft structures. This type of damage happens when a strong impact with the ground, most commonly during a landing, can cause significant internal structural damage without leaving evidence on the surface of the aircraft. Where aluminum tends to deform visibly when overloaded, creating dents or cracks that clearly indicate damaged areas, carbon fiber composites do not fail the same way. Composite materials behave differently because they can flex and rebound while sustaining hidden damage beneath the outer skin layer.

The danger posed by BVID is especially significant on larger composite aircraft like the A350 and Boeing 787 because these aircraft depend on the integrity of layered carbon fiber laminates bonded together during manufacturing. When strong forces are applied to the airplane, like during heavy hailstorms or drought landings, the forces travel through the entire airframe simultaneously. Even though the outer fuselage appears intact, the internal layers could become separated and resin cracked, causing severe structural damage that is invisible from the outside.

This hidden-damage characteristic of the A350 and similar composite-focused aircraft changes how airlines and engineers must respond to hard landings. Aluminum aircraft will more often than not provide visual clues of damage. It deforms permanently and visibly, showing maintenance workers exactly what is broken and needs to be fixed. Since composite airframes absorb energy internally, producing few visible warning signs, maintenance personnel cannot rely on simple visual inspections to determine whether an aircraft is safe for flight.

Why The A350 Requires An Ultrasonic Inspection After Hard Landings

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Due to the possibility of barely visible impact damage, Airbus requires extensive inspection procedures after hard landings or other impact events. The primary inspection method used for the A350 is ultrasonic testing. This technology works by sending high-frequency sound waves through the composite structure and analyzing how those waves reflect from internal layers. Variations in the reflected signals can reflect hidden defects, crushed core material, or separation between bonded components.

The problem is that ultrasonic inspections are both labor-intensive and time-consuming, especially after major hard landing incidents, when engineers may not initially know which areas absorbed the highest stress loads. Maintenance teams may need to scan extensive sections of the lower fuselage, wing attachment points, and other critical areas before determining if the aircraft is safe to return to service. Portable ultrasonic inspection units are available to airlines that can provide automatic diagnoses quickly. When damage is observed, these inspections can keep an A350 grounded for days, costing airlines revenue and capacity.

The A350, however, does have systems in place to avoid or mitigate hard landings, most notably through its landing gear system. The A350 is designed to handle a vertical descent rate of up to 600 feet (183 meters) per minute at the A350’s maximum landing weight without requiring structural inspections. This is made possible through the air-oleo shock absorber strut that compresses to distribute the aircraft’s landing force. Additionally, the A350’s carbon fiber wings are designed to flex on landing, dispersing the forces from landing across the entire airframe.

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Repairing composite aircraft like the Airbus A350 is a lot more complicated than repairing older aluminum airframes. The reason behind this comes down to the fact that the A350 is built using large integrated structural sections rather than the smaller aluminum panels used on older aircraft. According to industry discussions surrounding modern composite airframes, including analysis from Simple Flying, these large one-piece structures improve efficiency and reduce weight, but they also complicate repairs because damaged areas cannot always be removed and replaced individually.

In many cases, repairs must be carried out directly on the aircraft using highly controlled bonding and curing procedures. Where aluminum aircraft can be repaired in almost any standard hangar, no matter the weather, composite materials are very sensitive to their surroundings. This means technicians have to control the temperature and humidity in the repair area to ensure proper bonding between layers. Technicians may also have to sand away damaged laminate layers resulting from the hard landings, then rebuild composite piles one section at a time, carefully curing the prepared area to restore the aircraft’s structural integrity.

Another major challenge is that composite materials are directional, meaning their strength depends heavily on the orientation of the fibers within the structure. Aluminum behaves relatively uniformly regardless of direction, making repairs more difficult. For carbon fiber, however, even small mistakes during the repair process can dramatically weaken the repaired structure. Given this, airlines must provide technicians with special training and repair procedures for the A350. All together, even minor repairs on an A350’s fuselage can take over 15 hours of constant maintenance, representing a significant time and labor investment for airlines in the event of fuselage damage.

The Multi-Level Repair System Developed For The A350

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Because composite repairs are so complex, Airbus created a three-level repair system for the A350 based on the severity of the damage. The first category covers non-structural or cosmetic repairs, including scratches, paint damage, and surface defects that do not affect the aircraft’s structural strength. In some cases, temporary fixes can even be performed using high-speed repair tape before the aircraft is repaired in a maintenance shop.

The second category involves standard structural repairs, where the damage affects load-bearing composite sections but remains within the predefined repair limits set by Airbus. Depending on the location and severity of the damage, technicians could use temporary aluminum bolted repairs or permanent bonded and bolted composite repairs. These procedures usually require technicians who are specially trained because composite drilling and bonding processes are more complicated than aluminum repairs.

The final category covers major structural repairs caused by incidents like severe hard landings, ground equipment strikes, bird strikes, or landing gear incidents. For these situations, Airbus developed Pre-Defined Repair Solution (PDRS) kits that include repair instructions, replacement parts, tools, and support equipment to speed up the repair process. In the most extreme scenarios, Airbus engineering teams may directly assist airlines with repairs, underscoring how difficult it is to repair a heavily damaged composite airframe.

The Qatar Airways Dispute: A Warning For Composite Repair Challenges

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The limits of carbon fiber reinforced plastic (CFRP) repairability became highly visible in the 2021 Qatar Airways grounding dispute. The Doha-based carrier raised concerns about deterioration affecting portions of its A350 fleet, including paint cracking and exposure of the lightning protection mesh embedded within the composite fuselage structure. This resulted in regulators ordering 13 of the airline’s A350s to be removed from service over concerns about accelerating deterioration of the CFRP fuselage skin beneath the paint layer.

This disagreement highlighted how differently composite fuselage problems are compared to traditional aluminum or metallic airframes. On aluminum aircraft, surface degradation and corrosion are generally well understood, backed by decades of operational experience. Composite fuselages, however, are still relatively new, and feature entirely different inspection and repair processes. The Qatar Airways dispute highlighted how even surface-level composite damage can pose significant challenges for assessment and repair.

Ultimately, the Airbus A350 highlights both the advantages and hidden complications of modern composite aircraft construction. Its carbon fiber fuselage allows airlines to operate longer routes with lower fuel burn than older aluminum widebodies, but those same materials can become a major liability after severe hard landings. Complex ultrasonic inspections and specialized repair procedures can quickly turn these events into major engineering and financial challenges. Importantly, the A350 is not alone in facing these issues, as the Boeing 787 Dreamliner shares many of the same repair and maintenance complications due to its heavy use of composite materials. As airlines continue shifting toward next-generation carbon fiber aircraft, the industry is discovering that while composites deliver major efficiency in the air, they are far more difficult to repair on the ground than traditional aluminum airframes.