Written by Bjorn Fehrm

March 15, 2024, ©. Leeham News: We started this series a year ago. new aircraft technology It can be used to replace current single-aisle airliners.

We have covered a lot including typical development stages, from early research to preparation for the aircraft's in-service phase.

Let's create a resume that includes what we've discussed so far.

Figure 1. Boeing's truss-braced wing X-66A demonstrator based on the MD-90. Source: Boeing.

new aircraft technology

Over the course of 49 articles, we've covered a lot of ground. Let's take a quick look at what we've researched and learned about the ideas and technologies that could be used to replace the current single-aisle Airbus A320 and Boeing 737 MAX series.

  • The first question is the configuration of the airplane. Are winged tube alternatives mature enough to be considered? We need to realize that single aisle is a breadwinner for both Airbus and Boeing. Businesses have a very low risk appetite because of the potential risks of failure. To summarize, we can assume that the next generation will also keep the winged tube.
  • The next question is whether to maintain the single-aisle configuration, or as passenger numbers increase year on year and slot constraints at major airports increase, a shorter, more capacity two-aisle configuration is preferred. Is it true? It all depends on the expected passenger growth. The challenge is to accurately predict the behavior of the market core over the 50-year lifespan of a new airliner.
  • Next, we focused on aerodynamic advances made possible by new aerodynamic tools, structural materials, and control technologies. Boeing has installed folding wingtips on airliners with his 777X. We can expect folding wingtips to appear in new generation aircraft. Boeing is also considering truss-braced wings (TBW), the next step in wider wings (to reduce induced drag). The question is whether the MD-90's truss-braced wing tests (Figure 1) give Boeing the confidence to take on the next generation. We'll know by the end of the decade.
  • Achieving more advanced aerodynamic shapes with minimal aircraft mass requires wings with advanced shapes and curvatures, and materials that enable a strong and durable fuselage. The wing material will likely be a classic thermoset composite, chemically hardened and then bolted together (called a fastener in aviation terminology) to form a larger assembly. More complex fuselages benefit from labor-intensive assembly methods rather than bolted “drill and fill.” Here, heat-aged thermoplastic composites allow parts to be welded together into an assembly, similar to how automotive chassis parts are spot-welded to the final chassis.
  • The legacy airframe accounts for about one-third of the efficiency gains, and the new engine technology accounts for two-thirds. The problem with classic turbofan engines is that the simplest efficiency improvement is to reduce the average exhaust velocity (excess velocity of the gases relative to the surrounding air) of the hot gases exiting the engine, which increases propulsive efficiency. Improve. The problem is that the method of increasing the bypass ratio (BPR) to get there has been frequently used in the last generation, from a BPR of about 4 in the CFM56 generation to a BPR of 12 (a 3x increase) in the Pratt & Whitney GTF. That's what I'm doing. . It is not possible to further triple his BPR of a conventional turbofan, which would make his BPR more than 30. The engine and its nacelle are too large.
  • The only technology that can achieve a BPR of 30+ is Open Rotor technology, which can achieve twice that BPR. GE and SAFRAN are proposing a simplified open rotor for next-generation aircraft called RISE (Revolutionary Innovation for Sustainable Engines). It has a rotor in front and a non-rotating vane stage behind the single rotor that acts as a death swirler. Simplifies open rotor configurations without sacrificing efficiency.
  • Another major efficiency improvement is in the engine core, where new design principles and materials allow for more efficient air compression, combustion, and power extraction. However, this increases mechanical and thermal loads. That has led to the current engine durability crisis, with airlines struggling to ground planes. We plan to do a follow-up series on what we can do to change this situation.

We will summarize the series in the next section.

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