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Boeing X-53 Active Aerolastic Wing

  Today in 2006, was the first flight of the Boeing X-53 Active Aeroelastic Wing. While I’m aware of the Active Aeroelastic Wing (AAW) program and aware of the role the F/A-18 plays as NASA, including it’s roles as an airborne laboratory and as a chase aircraft, I had no idea that the AAW program…

 

NASA F/A-18 as the X-53 AAW.
NASA F/A-18 as the X-53 AAW.

Today in 2006, was the first flight of the Boeing X-53 Active Aeroelastic Wing. While I’m aware of the Active Aeroelastic Wing (AAW) program and aware of the role the F/A-18 plays as NASA, including it’s roles as an airborne laboratory and as a chase aircraft, I had no idea that the AAW program had formally received an “X” designation:

 12/11/2006 – WRIGHT-PATTERSON AIR FORCE BASE, Ohio  — Air Force Research Laboratory researchers recently received word that the Active Aeroelastic Wing (AAW) flight demonstrator has been assigned the Mission Design Series number X-53. The designation makes it the first successful X plane initiated within the Air Vehicles Directorate since the X-24 lifting body concept, which was later employed on the Space Shuttle.

The AAW program is control technology that uses wing flex (in the AAW program case of 5 degrees) in conjunction with conventional flying surfaces (ailerons, flaps and leading edge slats) to give increased control moments. This would mean less drag when these surfaces are moved at high speed, decreased structural weight. In a way the AAW comes full circle in aviation. The Wright Flyer used wing warping in much the same manner.

The Wright Flyer used aerolastic "wing warping" as control services in flight.
The Wright Flyer used aerolastic “wing warping” as control services in flight.

As mentioned, the X-53 is a pre-production F/A-18 Hornet and the structural modifications to the aircraft are:

The wings from NASA’s now-retired F/A-18 #840, formerly used in the High-Alpha Research Vehicle (HARV) project, were modified for the AAW flight research project and installed on the AAW test aircraft. Several of the existing wing skin panels along the wing box section of the wing just ahead of the trailing-edge flaps and ailerons were replaced with thinner, more flexible skin panels and structure, similar to the prototype F/A-18 wings.
Original F-18 wing panels were comparatively light and flexible. During early F-18 flight tests, however, the wings were observed to be too flexible at high speeds for the ailerons to provide the specified roll rates. This was because the high aerodynamic forces against a deflected aileron would cause the wing to deflect in the opposite direction.
In addition, the F/A-18’s leading-edge flap was divided into separate inboard and outboard segments, and additional actuators were added to operate the outboard leading-edge flaps separately from the inboard leading-edge surfaces. By using the outboard leading-edge flap and the aileron to twist the wing, the aerodynamic force on the twisted wing provided the roll forces desired. With AAW control technology, a flexible wing will now have a positive control benefit rather than a negative one.
In addition to the wing modifications, a new research flight control computer was developed for the AAW test aircraft, and extensive research instrumentation, including more than 350 strain gauges, was installed on each wing.

NASA’s 853, the X-53 AAW is one of the oldest F/A-18 Hornets still flying. This model in particular is one of the early production aircraft. Here’s photo walkaround of the X-53:

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Technicians tend to No. 853 inside one of the sprawling hangars at NASA Dryden. The plane, shown here getting routine maintenance, carries evidence of past research projects. Some of the instruments and devices are left in place because they may be used again.
Technicians tend to No. 853 inside one of the sprawling hangars at NASA Dryden. The plane, shown here getting routine maintenance, carries evidence of past research projects. Some of the instruments and devices are left in place because they may be used again.

 

No. 853’s nose is home to an array of navigation and guidance gear, along with research equipment like the Airborne Research Test System. ARTS is a computer that allows engineers to quickly and easily test new software and equipment without installing a dedicated computer for each project. That gray box at the bottom of the nose is an ARTS.
No. 853’s nose is home to an array of navigation and guidance gear, along with research equipment like the Airborne Research Test System. ARTS is a computer that allows engineers to quickly and easily test new software and equipment without installing a dedicated computer for each project. That gray box at the bottom of the nose is an ARTS.
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These tubes protruding from the wing spars of No. 853 once were connected to the static pressure sensors on the wing. The sensors measure air pressure over the top of the wing to help determine the airflow during various maneuvers. The lift generated by the wing is dependent on the flow of air around the wing. Engineers can better understand the effects of various tests such as the wing warping if they have a precise way to measure the air pressure over the wing
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No. 853’s left wing details the longest history of the plane’s role as a test mule. It bears little resemblance, aside from its shape, to the sleek, smooth wing the plane had when it left the factory. The wing is dotted with sensors, equipment and remnants of the epoxy-like material engineers use to hold everything in place.
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To accurately measure and monitor the wings during the project, sensors along the wing measured air pressure as well as strain on the wing structure.
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The blue box houses the transmitter and receiver that work in conjunction with the reflectors to measure wing strain. All of those sensors and other equipment require miles of wire, and No. 853 is packed with them.
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Small reflectors are placed along the wing. Light emitted from a transmitter along the spine of the airplane is bounced off the reflector back to the box, allowing engineers to precisely measure wing strain in three dimensions.
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NASA researchers found wing warping could produce adequate roll rates at transonic and supersonic speeds. The software control laws that manage warping to control roll offer several advantages over traditional roll control, including reduced drag and improved maneuverability. And perhaps counter intuitively, a lighter structure can be used because aerodynamic forces on the wing can be more closely controlled, reducing strain
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Aside from NASA’s test equipment, the X-53’s cockpit doesn’t differ that much from the production Hornet.

You can learn a bit more about the X-53’s Wikipedia page here and from NASA itself at the X-53 fact sheet.

It’s an interesting program with future technoloigcal applications to both civil and military airplanes.

NASA 853 in flight.
NASA 853 in flight.
NASA 853 with the gear down turns over Armstrong Flight Research Center.
NASA 853 with the gear down turns over Armstrong Flight Research Center.

“To seperate the real from the imagined through flight” – Hugh Dryden

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  1. NaCly Dog

    I see maintenance and troubleshooting issues in this technological future.

    Like

  2. Casey Tompkins

    Funny, I was thinking the same thing.

    Like

  3. timactual

    Every time I hear “metal” and “flex” I think “metal fatigue”

    Like

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