The primary differentiating factor in the systems architecture of the 787 is its emphasis on electrical systems, which replace most of the pneumatic systems found on traditional commercial airplanes.

One of the advantages of the no-bleed electrical systems architecture is the greater efficiency gained in terms of reduced fuel burn — the 787 systems architecture accounts for predicted fuel savings of about 3 percent. The 787 also offers operators operational efficiencies due to the advantages of electrical systems compared to pneumatic systems in terms of weight and reduced lifecycle costs.

This article explores the 787’s no-bleed systems architecture and explains how the airplane’s efficiencies are realized.

REASONS BEHIND THE MOVE TO A MORE ELECTRIC AIRPLANE

Recent advances in technology have allowed Boeing to incorporate a new no-bleed systems architecture in the 787 that eliminates the traditional pneumatic system and bleed manifold and converts the power source of most functions formerly powered by bleed air to electric power (for example, the air-conditioning packs and wing anti-ice systems). The no-bleed systems architecture offers operators a number of benefits, including:

• Improved fuel consumption, due to a more efficient secondary power extraction, transfer, and usage.
• Reduced maintenance costs, due to elimination of the maintenance-intensive bleed system.
• Improved reliability due to the use of modern power electronics and fewer components in the engine installation.
• Expanded range and reduced fuel consumption due to lower overall weight.
• Reduced maintenance costs and improved reliability because the architecture uses fewer parts than previous systems.

The 787's no-bleed systems architecture will allow the airplane's engines to produce thrust more efficiently — all of the high-speed air produced by the engines goes to thrust. Pneumatic systems that divert high-speed air from the engines rob conventional airplanes of some thrust and increase the engine's fuel consumption.

Boeing believes that using electrical power is more efficient than engine-generated pneumatic power, and expects the new architecture to extract as much as 35 percent less power from the engines. Conventional pneumatic systems generally develop more power than is needed in most conditions, causing excess energy to be dumped overboard.

The ducting used to pass the pressurized air around the airplane employs check valves and pre-coolers, and is itself made of titanium, which adds hundreds of pounds of weight to the airplane.

The electric system is also inherently easier to monitor and control, and produces only enough power as needed. The power, which comes off the generators at variable frequencies, is conditioned in the electronics bay before being distributed to the appropriate systems.

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