The Aurora D8, also known as the D8 Airliner, is an

airliner An airliner is a type of aircraft for transporting passengers and air cargo. Such aircraft are most often operated by airlines. Although the definition of an airliner can vary from country to country, an airliner is typically defined as an ...

concept under development as of mid 2017. The project was initiated in 2008 by

Aurora Flight Sciences Aurora Flight Sciences is an American aviation and aeronautics research subsidiary of Boeing which primarily specializes in the design and construction of special-purpose Unmanned aerial vehicles. Aurora has been established for 20+ years and th ...

, the Massachusetts Institute of Technology (MIT) and

Pratt & Whitney Pratt & Whitney is an American aerospace manufacturer with global service operations. It is a subsidiary of Raytheon Technologies. Pratt & Whitney's aircraft engines are widely used in both civil aviation (especially airlines) and military aviat ...

under

NASA The National Aeronautics and Space Administration (NASA ) is an independent agency of the US federal government responsible for the civil space program, aeronautics research, and space research. NASA was established in 1958, succeeding t ...

's sponsorship of $2.9 million (£2.19 million). Aurora is refining the fuel-efficient D8 designed for NASA by MIT, hoping to fly a half-scale demonstrator in 2022. The 180-seat, -range airliner is designed to fly at within the capabilities of the

Boeing 737 The Boeing 737 is a narrow-body aircraft produced by Boeing at its Renton Factory in Washington. Developed to supplement the Boeing 727 on short and thin routes, the twinjet retains the 707 fuselage width and six abreast seating with two un ...

Airbus A320 The Airbus A320 family is a series of Narrow-body aircraft, narrow-body airliners developed and produced by Airbus. The A320 was launched in March 1984, Maiden flight, first flew on 22 February 1987, and was introduced in April 1988 by Air F ...

and could be in test service by 2027 at the earliest and 2035 at the latest. Aurora Flight Sciences was purchased by

Boeing The Boeing Company () is an American multinational corporation that designs, manufactures, and sells airplanes, rotorcraft, rockets, satellites, telecommunications equipment, and missiles worldwide. The company also provides leasing and product ...

on November 8, 2017 for their drone developments. The subsidiary is intended to accelerate Boeing's development of autonomous technology.

Design

The side-by-side "double bubble"

fuselage The fuselage (; from the French ''fuselé'' "spindle-shaped") is an aircraft's main body section. It holds crew, passengers, or cargo. In single-engine aircraft, it will usually contain an engine as well, although in some amphibious aircraft t ...

provides additional lift along the nose section as well as faster turnaround owing to its wider fuselage. As a result, smaller wings can be used to generate lift which reduces drag. The mounting of the engines at the rear end of the D8 instead of below the wings used in conventional aircraft design allows reduction of thrust requirements by minimizing inefficiency from Boundary Layer Ingestion (BLI). This results in the ability to use smaller and lighter high

bypass ratio The bypass ratio (BPR) of a turbofan engine is the ratio between the mass flow rate of the bypass stream to the mass flow rate entering the core. A 10:1 bypass ratio, for example, means that 10 kg of air passes through the bypass duct for ev ...

engines An engine or motor is a machine designed to convert one or more forms of energy into mechanical energy. Available energy sources include potential energy (e.g. energy of the Earth's gravitational field as exploited in hydroelectric power ...

. However, the chassis features less radical than competing

blended wing body A blended wing body (BWB), also known as blended body or hybrid wing body (HWB), is a fixed-wing aircraft having no clear dividing line between the wings and the main body of the craft. The aircraft has distinct wing and body structures, which a ...

concepts without modifying existing airport infrastructure, and BLI. The original goal was to reduce fuel burn by 70% and

noise Noise is unwanted sound considered unpleasant, loud or disruptive to hearing. From a physics standpoint, there is no distinction between noise and desired sound, as both are vibrations through a medium, such as air or water. The difference arise ...

by 71 dB by flying at Mach 0.74, but a more traditional Mach 0.82 wing and fuselage growth resulted in a more-conservative 49% fuel burn reduction and 40 EPNdB noise reduction against a

Boeing 737-800 The Boeing 737 Next Generation, commonly abbreviated as 737NG, or 737 Next Gen, is a narrow-body aircraft powered by two jet engines and produced by Boeing Commercial Airplanes. Launched in 1993 as the third generation derivative of the Boein ...

Engines

Clustering the engines together atop the wide tail of a flattened fuselage enables them to reenergize the slow-moving

boundary layer In physics and fluid mechanics, a boundary layer is the thin layer of fluid in the immediate vicinity of a bounding surface formed by the fluid flowing along the surface. The fluid's interaction with the wall induces a no-slip boundary condi ...

over the fuselage to increase efficiency, and allow a clean, low drag, high aspect ratio wing. Starting with slower flow, the reduction in

exhaust velocity Specific impulse (usually abbreviated ) is a measure of how efficiently a reaction mass engine (a rocket using propellant or a jet engine using fuel) creates thrust. For engines whose reaction mass is only the fuel they carry, specific impulse is ...

increases the

propulsive efficiency In aerospace engineering, concerning aircraft, rocket and spacecraft design, overall propulsion system efficiency \eta is the efficiency with which the energy contained in a vehicle's fuel is converted into kinetic energy of the vehicle, to accele ...

with a similar

specific thrust Specific thrust is the thrust per unit air mass flowrate of a jet engine (e.g. turbojet, turbofan, etc.) and can be calculated by the ratio of net thrust/total intake airflow. Low specific thrust engines tend to be more efficient of propellant (a ...

. By ingesting and reenergizing the boundary layer flow, BLI reduces by 40% in the D8 the wasted kinetic energy in the combined high-velocity jet exhaust and slow-speed wake behind the fuselage. Large-scale

wind-tunnel Wind tunnels are large tubes with air blowing through them which are used to replicate the interaction between air and an object flying through the air or moving along the ground. Researchers use wind tunnels to learn more about how an aircraft ...

testing with NASA showed a power-saving from BLI from 8.4% with the same

jet nozzle A propelling nozzle is a nozzle that converts the internal energy of a working gas into propulsive force; it is the nozzle, which forms a jet, that separates a gas turbine, or gas generator, from a jet engine. Propelling nozzles accelerate the av ...

area to 10.4% with the same

mass flow Mass flow, also known as mass transfer and bulk flow, is the movement of fluids down a pressure or temperature gradient,Moyes & Schulte (2008). Principles of Animal Physiology. Pearson Benjamin Cummings. San Francisco, California particularly in ...

. The BLI benefit is an order of magnitude more than the loss from ingesting distorted boundary-layer flow. A large fan size is needed to exceed a 20:1

. Developed by

United Technologies United Technologies Corporation (UTC) was an American multinational conglomerate headquartered in Farmington, Connecticut. It researched, developed, and manufactured products in numerous areas, including aircraft engines, aerospace systems ...

Research Center, a distortion-tolerant fan was scale tested at NASA and coped with flow distortion from ingesting the boundary layer close to the upper fuselage surface. As a compact core limits blade

tip clearance Tip clearance is the distance between the tip of a rotating airfoil and a stationary part. * Gas turbine: Rotor blade and casing * Propeller (ship or aircraft): Propeller and structure ** Ground tip clearanc* Wind turbine A wind turbine is a ...

s issues due to bending but cannot house the fan to low-pressure turbine driveshaft,

turned the core backwards, similar to

PT6 The Pratt & Whitney Canada PT6 is a turboprop aircraft engine produced by Pratt & Whitney Canada. Its design was started in 1958, it first ran in February 1960, first flew on 30 May 1961, entered service in 1964 and has been continuously up ...

arrangement, with hot gas discharged forward through a low-pressure power turbine connected to the fan via a short shaft and a gearbox. To avoid the risk of an

uncontained engine failure A turbine engine failure occurs when a turbine engine unexpectedly stops producing power due to a malfunction other than fuel exhaustion. It often applies for aircraft, but other turbine engines can fail, like ground-based turbines used in power ...

causing the second engine to fail, the cores are angled by 50° since they are no longer mechanically linked to the fan, with low pressure losses since only the core flow is turned. Not connected to the power section, the core can be disassembled for maintenance.

References

{{reflist

External links

Real Engineering: The Future of Airliners? - Aurora D8
Twinjets Twin-boom aircraft NASA aircraft Aurora Flight Sciences aircraft T-tail aircraft

Design

Engines

See also

References

External links