While each of the iconic plane makers produced these two planes to capitalize on composite technology and advanced digital avionics, the minor differences in their target customers and niche missions created some design peculiarities that distinguish the two in unique ways. For starters, the A350-900 has a tall nose profile that keeps the cabin floor level, unlike the A340’s forward-tilted nose.
Each of these jets uses a significant amount of carbon fiber-reinforced plastic (CFRP) in the construction of the airframe. The A350 has a slight advantage, with the new material being 53% of its weight, but the Boeing plane is not far behind. Airbus also came to market years later, and while it has not matched the record-setting orders that have made the Dreamliner the best-selling widebody in history, the company has learned from further technological advances to refine its Xtra Wide Body jets.
787 SLG: What is Semi-Levered Gear?
Boeing faced unique engineering challenges when designing the 787-10 because it is a double-stretched version of the previous models, with an overall length of 224 feet. For that reason, the 787-10 features a distinct semi-levered landing gear system, in contrast to the A350-900, which employs a traditional center-pivoting main landing gear bogie. This difference arises from the unique dynamics of the two planes during takeoff rotation. The mechanism effectively ‘stretches’ the gear, allowing the main strut to lift the fuselage higher off the ground.
If Boeing had adopted a typical center-pivot landing gear for the elongated fuselage, the tail would risk striking the runway at a shallow takeoff angle, thus limiting the rotation speed during takeoff. The cabin extension makes the tail structure protrude well behind the main landing gear compared to the shorter 787-8 and 787-9 models. The SLG uses a hydraulic actuator during takeoff to restrict the tilt of the main wheel bogie, thereby pushing up the main strut and lifting the fuselage higher.
Airbus designed the A350-900 as a clean-sheet project, unlike the 787-10. Thus, engineers set the landing gear struts to an exact height from the outset to avoid the complexities of a secondary mechanical locking system, thereby facilitating smoother and safer takeoffs. The Airbus A350-900 does not require a semi-levered system due to its shorter overall fuselage length of approximately 219 feet, which allows for a steeper rotation angle before tail strikes become a risk.
Size Matters: Shock Struts & Ole-Air
The A350-900 is equipped with a nitrogen-oil shock absorber strut in its main landing gear, supporting a maximum landing weight of over 300 tons. The A350-900 is a substantial advance over the preceding A330, with a high-pressure strut capable of supporting higher landing weights. This oleo-pneumatic system effectively dissipates the heavy impact of the long-haul Airbus while also stabilizing the big widebody against crosswinds, though it adds to the overall gear weight.
While using the same ‘oleo-air’ systems, the Boeing 787-10 is designed differently as it has a slightly lower maximum landing weight in comparison to the A350. By declining to create a special, heavy strut for the expanded 787-10, Boeing leveraged its weight advantage. Rather, they repurposed a small, compact oleo-pneumatic cylinder that was initially shared by the smaller 787-8 and 787-9 models.
While each of these aircraft is a modern, high-tech jet primarily made of carbon fiber, the 787-10 is a late entry in the Dreamliner family. Whereas the A350-900 was designed by Airbus as the first in its series to be a dedicated long-range, high-capacity platform. To withstand the severe vertical stresses of a maximum landing weight of 205 metric tons, a huge, heavy-duty, wide-bore nitrogen-oil shock strut was designed. This custom high-pressure cylinder protects the airframe during harsh landings and offers optimal cushioning for a comfortable passenger experience.
Taxi & Runway Steering Systems
Airbus fully embraced the digital future with the A350-900, implementing pure FBW nose-wheel steering. When a pilot moves the cockpit controls, electronic sensors interpret the input and translate it into digital commands for the hydraulic steering actuators. Boeing chose a Liebherr Remote Electronic Unit that follows a similar engineering approach. Electronic signals from the cockpit tiller and rudder pedals are processed by the REU, which commands the hydraulic steering actuators digitally.
The Airbus A350-900 incorporates an advanced digital fly-by-wire nose-wheel steering system that provides the sidesticks with feedback for precise ground maneuvering. This system uses electronic sensors to convert pilot inputs into hydraulic signals, allowing the nose gear to rotate up to 72 degrees for tight turns. It also features automatic steering adjustments to counteract crosswinds, integrating nose-wheel steering with main rudder controls during takeoffs and landings.
The 787-10 also uses steering-by-wire for the yoke and rudder pedals. However, it reportedly provides more tactile feedback for pilots to feel the resistance of the nose tires. Although it features more electronic safety backups, the assembly still prioritizes maintenance and dependability, like legacy planes, giving it more refined ground handling characteristics and a smaller turning radius than its predecessor, the 767.
The A350-900’s entirely digital system replaces the A340’s outdated mechanical cable-and-pulley structure, turning physical exertion into smoother operations via sensors that sync nose-wheel angles with the rudder. The 787-10, on the other hand, strikes a more hybrid balance, retaining its analog feeling tiller while incorporating electrical backups to reduce oversteering and tire scrubbing, both of which are absent from the 767’s mechanical design.
Source: Simple Flying
