4. Elastic twist of the wing suddenly becoming
theoretically infinite
Phenomenon occurring only in wings with ailerons or
other control surfaces, where control surfaces
reverse their usual functionality
DIVERGENCE:
CONTROL REVERSAL:
STATIC AEROELASTICITY
7. First flight -8 December 2006
Role -Technology Demonstrator
National origin -United States
Manufacturer -McDonnell Douglas
Northrop Corporation
9. Integrates wing aerodynamics, controls, and
structure to harness and control wing aero
elastic twist at high speeds and dynamic
pressures.
10. An aircraft maneuvers - deploying flight
control surfaces into the airflow, which
modify the lift of the surface they are
attached to.
11. 1. Taking an existing F/A-18 airframe
2. Modified with a preproduction pre roll mod
wing
3. Added an outboard leading edge flap drive
system and an updated flight control
computer
12. 2 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)
Power plant: 2 × General Electric F404-GE-400
low-bypass turbofan engines, 16,000 lbf (71 KN)
thrust each
Performance
Maximum speed: 1,032 KN; 1,912 km/h (1,188
mph)
Service ceiling: 50,000 ft (15,000 m)
13.
14. Aero elastic twist can be controlled
Enables the use of high aspect ratio, thin,
swept wings
Provide excellent high speed rolling
performance
No additional stiffness was added for static
aero elastic issues
Overall control authority is affected
Editor's Notes
Aeroelasticity is the branch of physics and engineering that studies the interactions between the inertial, structural, and aerodynamic forces that occur when an elastic body is exposed to a fluid flow.
In 1947, Arthur Collar defined aero elasticity as “the study of the mutual interaction that takes place within the triangle of the inertial, structural, and aerodynamic forces acting on structural members exposed to an airstream.”
Now let us have a glance at the case study on Aero Elasticity.
This is the application of study of aero elasticity in Aeronautics.
That is Boeing X-53 Active Aero elastic Wing.
The X-53 Active Aeroelastic Wing (AAW) development program is a completed research project that was jointly undertaken by the Air Force Research Laboratory (AFRL), Boeing Phantom Works and NASA's Dryden Flight Research Center.
The concept uses high aspect ratio, thin, swept wings that are aero elastically deformed into shapes for optimum performance.
This makes it possible to achieve the multi-point aerodynamic performance required for future fighter, bomber, and transport aircraft.
The technology used here integrates wing aerodynamics, controls, and structure to control wing aero elastic twist at high speeds and dynamic pressures.
AAW Technology employs wing aero elastic flexibility through use of multiple leading and trailing edge control surfaces activated by a digital flight control System
For instance, the ailerons on the wings used to roll an aircraft work by increasing or decreasing the lift of the outer portion of one wing, while doing the opposite on the other wing. This imbalance in lift forces causes the aircraft to rotate around its longitudinal axis.
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 pre roll mod 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.
The leading edge flap drive system was modified at McDonnell Douglas (now Boeing Phantom works) using a new outboard actuation unit developed by Moog. AAW flight control laws were programmed into a research flight control computer modified to include an independently actuated outboard leading edge control surfaces.
By using multiple leading and trailing edge controls like “aerodynamic tabs”, subtle amounts of aeroelastic twist can be controlled.
The concept enables the use of high aspect ratio, thin, swept wings that are aeroelastically deformed into shapes for optimum performance.
It provides excellent high speed rolling
But beyond this advantages there are some limitations.
No additional stiffness was added for static aero elastic issues.
The aeroelasticity still exists and is affecting the overall control authority