Boeing X-53 Active Aeroelastic Wing

https://en.wikipedia.org/wiki/Boeing...roelastic_Wing

The X-53 Active Aeroelastic Wing (AAW) development program is a completed
American research project that was undertaken jointly by the Air Force Research
Laboratory (AFRL), Boeing Phantom Works and NASA's Dryden Flight Research
Center, where the technology was flight tested on a modified McDonnell Douglas
F/A-18 Hornet. Active Aeroelastic Wing Technology is a technology that
integrates wing aerodynamics, controls, and structure to harness and control
wing aeroelastic twist at high speeds and dynamic pressures. By using multiple
leading and trailing edge controls like "aerodynamic tabs", subtle amounts of
aeroelastic twist can be controlled to provide large amounts of wing control
power, while minimizing maneuver air loads at high wing strain conditions or
aerodynamic drag at low wing strain conditions. This program was the first
full-scale proof of AAW technology.

Development

Gerry Miller and Jan Tulinius led the development of the initial concept during
wind tunnel testing in the mid 1980s under Air Force contract. The designation
"X-52" was skipped in sequence to avoid confusion with Boeing's B-52
Stratofortress bomber. Ed Pendleton served as the Air Force's program manager.

The pre-production version of the F/A-18 was an ideal host aircraft for proving
AAW technology, a relatively high wing aspect ratio for a fighter, with adequate
strength, but no additional stiffness was added for static aeroelastic issues.
The X-53 F/A-18 was modified to allow two leading edge control surfaces to work
in concert with its two trailing edge surfaces to control wing aeroelastic twist
and provide excellent high speed rolling performance.

AAW developed from the observation that the aeroelasticity can be offset by the
deployment of other control surfaces on the wing. In particular, almost all
modern aircraft use some form of slat along the wing's leading edge to provide
more lift during certain portions of flight. By deploying the slats at the same
time as the ailerons, the torque can be equalled out on either side of the
spars, eliminating the twisting, which improves the control authority of the
ailerons. This means that less aileron input is needed to produce a given
motion, which, in turn, will reduce aileron drag and its associated negative
control aspects. Better yet, the wing is already designed to be extremely strong
in the lift component, eliminating the torque requires lift, converting the
undesired torque into an acceptable lift component.

But if one can use the controls to eliminate the twisting and its negative
effects on control input, the next step is to deliberately introduce a twisting
component to improve the control authority. When applied correctly, the wing
will twist less and in an opposite direction to a conventional wing during
maneuvering. So this change, which can be accomplished in software, benefits
overall performance.


Role
Technology Demonstrator

National origin
United States

Manufacturer
McDonnell Douglas
Northrop Corporation
Boeing

First flight
15 November 2002

Primary user
NASA

Number built
1

Developed from
McDonnell Douglas F/A-18 Hornet

Flight testing

To test the AAW theory, NASA and the USAF agreed to fund development of a single
demonstrator, based on the F/A-18. Work started by taking an existing F/A-18
airframe modified with a preproduction wing, and added an outboard leading edge
flap drive system and an updated flight control computer. Active aeroelastic
wing control laws were developed to flex the wing, and flight instrumentation
was used to accurately measure the aeroelastic performance of the wing planform.
Flight software was then modified for flight testing, and the aircraft first
flew in modified form on November 15, 2002. The aircraft successfully proved the
viability of the concept in full scale during roll maneuver testing in
2004–2005. The test aircraft was re-designated X-53 on August 16, 2006, per memo
by USAF Deputy Chief of Staff, Strategic Plans and Programs.

Specifications

General characteristics
Crew: 1
Wingspan: 38 ft 5 in (11.71 m)
Height: 15 ft 3 in (4.65 m)
Max takeoff weight: 39,000 lb (17,690 kg)
Powerplant: 2 × General Electric F404-GE-400 low-bypass turbofan engines, 16,000
lbf (71 kN) thrust each

Performance
Maximum speed: 1,188 mph (1,912 km/h, 1,032 kn)
Service ceiling: 50,000 ft (15,000 m)

Avionics
The leading edge flap drive system was modified at McDonnell Douglas (now Boeing
Phantom works) using an outboard actuation unit developed by Moog Inc. AAW
flight control laws were programmed into a research flight control computer
modified to include independently actuated outboard leading edge control
surfaces



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