Boeing X-48

Role : Experimental unmanned aerial vehicle
Manufacturer : Boeing
First flight : July 20, 2007
Status : In testing
Primary user : Nasa
Produced : 2

The Boeing X-48 is an experimental unmanned aerial vehicle (UAV) for investigation into the characteristics of blended wing body (BWB) aircraft, a type of flying wing.

Boeing designed the X-48 and two examples were built by Cranfield Aerospace in the UK.

Boeing has been using the X-48 in flight testing for Nasa since 2.007.

Design and development

Background

Boeing had studied a blended wing body design,when? but found that passengers did not like the theater-like configuration of the mock-up, and the design was dropped for passenger airliners, but reserved for military aircraft such as tankers.

McDonnell Douglas developed the X-48 concept in the late 1.990s,and Boeing presented it during an annual Joint AIAA/ASME/SAE/ASEA Propulsion Conference in 2.004.

The McDonnell Douglas engineers were confident that their design had several advantages, but their concept, code named "Project Redwood" found little favor at Boeing after their 1.997 merger.

The most difficult problem they solved was that of ensuring passengers a safe and fast escape in case of an accident, since emergency door locations were completely different from those in a conventional aircraft.

The blended wing body (BWB) concept offers advantages in structural, aerodynamic and operating efficiencies over today's more conventional fuselage-and-wing designs.

These features translate into greater range, fuel economy, reliability and life cycle savings, as well as lower manufacturing costs.

They also allow for a wide variety of potential military and commercial applications.

Boeing Phantom Works developed the blended wing body (BWB) aircraft concept in cooperation with the Nasa Langley Research Center.

In an initial effort to study the flight characteristics of the BWB design, a remote-controlled propeller-driven blended wing body model with a 17 ft (5.2 m) wingspan was successfully flown in 1.997.

The next step was to fly the 35 ft (10.7 m) wide X-48A in 2004, but that program was later canceled.

Boeing's research at Phantom Works then focused on a new model, designated X-48B, two examples were built by United Kingdom-based Cranfield Aerospace.

Norman Princen, Boeing's chief engineer for the project, stated in 2.006 : "earlier wind-tunnel testing and the upcoming flight testing are focused on learning more about the BWB's low-speed flight-control characteristics, especially during takeoffs and landings.

Knowing how accurately our models predict these characteristics is an important step in the further development of this concept."

The X-48B has a 21-foot (6.4 m) wingspan, weighs 392-pound (178 kg), and is built from composite materials.

It is powered by three small turbojet engines and is expected to fly at up to 120 kn (220 km/h) and reach an altitude of 10,000 feet (3,000 m).

The X-48B is an 8.5% scaled version of a conceptual 240-foot wide design.

Though passenger versions of the X-48B have been proposed, the design has a higher probability of first being used for a military transport.

The X-48C featuring two engines and inboard vertical stabilizers

Wind tunnel testing on a 12 ft wide blended wing body model was completed in September 2.005.

During April and May 2.006, Nasa performed wind tunnel tests on X-48B Ship 1 at a facility shared by Langley and Old Dominion University.

After the wind tunnel testing, the vehicle was shipped to Nasa's Dryden Flight Research Center at Edwards Air Force Base to serve as a backup to X-48B Ship 2 for flight testing.

X-48B Ship 2 then conducted ground tests and taxi testing in preparation for flight.

The second X-48B was modified into the X-48C starting in 2.010 for further flight tests.

The X-48C has its vertical stabilizers moved inboard on either side of the engines, and its fuselage extended aft, both in an attempt to reduce the aircraft's noise profile; it was to be powered by two JetCat turbines, each producing 80 pounds-force (0.36 kN) of thrust.

The X-48C was instead modified to use two Advanced Micro Turbo (AMT) turbojet engines in 2.012.

Operational history

The X-48B first flew on July 20, 2.007, reaching an altitude of 7,500 ft (2,286 m); the flight lasting 31 minutes.

The remotely-piloted aircraft was successfully stalled for the first time on September 4, 2.008, with fixed leading edge slats, a forward center of gravity, and 23-degree angle of attack (2° beyond the maximum coefficient of lift).

Stall testing was repeated on September 11 with a Nasa pilot at the console.

On March 19, 2.010, Nasa and Boeing successfully completed the initial flight testing phase of the X-48B.

Fay Collier, manager of the Era Project in Nasa's Aeronautics Research Mission Directorate commented on the completion of the first phase of testing saying, "this project is a huge success.

Bottom line : the team has proven the ability to fly tailless aircraft to the edge of the low-speed envelope safely."

Following the installation of a new flight computer in 2.010, the X-48B was to continue a new phase of flights tests to investigate controllability aspects.

The second phase of flight tests with the X-48B began in September 2.010.

The X-48C first flew on August 7, 2.012.

Engine yaw control is among the aspects to be studied.

Variants

X-48A

The initial planned 35 ft (10.7 m) wide version. It was canceled before manufacture.

X-48B

Two 8.5% scale aircraft that have been used for flight testing.

X-48C

A modified, two-engine version of the X-48B intended to test a low-noise design.

Specifications (X-48B)

A three percent scale model of the X-48C in Nasa Langley's 12-Ft Low-Speed Tunnel

General characteristics :

Crew : None
Wingspan : 20 ft 5 in (6.22 m)
Wing area : 100.5 sq ft (9.34 m2)
Aspect ratio : 4.1
Gross weight : 500 lb (227 kg)
Powerplant : 3 × JetCat P200 turbojet, 52 lbf (0.23 kN) thrust each

Performance

Maximum speed : 136 mph; 219 km/h (118 kn)
Endurance : 40 minutes
Service ceiling : 10,000 ft (3,048 m)