How Does The Boeing 787's No

Apr 29, 2024

The bleed-less architecture extracts as much as 35% less power from the engines.

The Boeing 787 Dreamliner has a significant advantage over previous Boeing jets thanks to its no-bleed architecture. In traditional aircraft systems, bleed air from the primary air stream is taken for pressurization of sumps, valves, and other internal systems. Similarly, bleed air from the bypass stream is used to actuate and cool external components.

Numerous pneumatic and hydraulic components and systems use bleed air for function. From high-pressure bleed valves to pneumatic actuators of the variable stator system, all use bleed air. A bleed-less architecture, as on the Boeing 787, reduces or completely eliminates the use of bleed air for pneumatic and hydraulic systems. Instead, electric systems are used for power.

The traditional bleed system consumes a lot of useful energy generated by the engines. The energy extracted from the engine is used to power the majority of secondary pneumatic and hydraulic systems. For example, the wing anti-ice system, including valves, actuators, and pre-coolers, uses bleed air from the engine. Moreover, the leftover energy from the bleed air is discarded through the engine exhaust. As a result, the optimal efficiency of the engine is reduced.

The replacement of hydraulic and pneumatic systems with electrical systems means reduced bleed air from the engines. The engine provides power to the critical systems in electrical form through shaft-driven generators. The fuel used to condition the air (pressurization) results in maximizing the thrust, thereby achieving optimal engine efficiency.

With minimum or no robbing of air through the bleed system, less fuel is required to produce the optimal thrust. The resultant fuel consumption is lower when most secondary systems are electrically powered. Moreover, with the removal of the bleed system, including manifolds, valves, and fittings, the overall weight of the engine is reduced by hundreds of pounds. That, in and of itself, further enhances the engine's fuel efficiency. According to Mike Sinnett, Director of Boeing 787 systems,

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%. 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.

According to Boeing, the 787’s bleed-less architecture extracts as much as 35% lower engine power than the conventional systems. Moreover, the system also saves the waste of excess energy from the bleed air that is dumped overboard. The electro-thermal wing anti-ice system comprises multiple heating layers within the leading edges.

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The layers are energized through electrical impulses to protect the wing from accumulating ice. Boeing states that the power usage of the wing anti-ice system on the 787 is half that of the pneumatic system. Other benefits include drag and noise reduction through fewer manifolds and exhaust holes within the system.

What are your thoughts on the bleed-less architecture installed on the Boeing 787 and its impact on the aircraft’s fuel efficiency? Tell us in the comments section.

Writer - Omar is an aviation enthusiast who holds a Ph.D. in Aerospace Engineering. With numerous years of technical and research experience under his belt, Omar aims to focus on research-based aviation practices. Apart from work, Omar has a passion for traveling, visiting aviation sites, and plane spotting. Based in Vancouver, Canada