Top technologies for 2002
Aircraft window shading alternative
Research Frontiers Inc. has licensed InspecTech Aero Service, Inc. to use its suspended particle device (SPD) light-control technology for aircraft applications. The license enables InspecTech to purchase SPD film from Research Frontier-licensed manufacturers to incorporate the technology in aircraft windows and cabin dividers. These applications have the potential for significant weight and cost savings. The technology would enable operators to remove existing window shades from aircraft and replace them with the thin SPD film that can electrically control the degree of light transmission. Aircraft occupants could instantly and precisely control shading via a knob.
SPD refers to light-absorbing microscopic particles that are suspended between two electronically coated surfaces. The film is placed between two panes of electrically conductive-coated glass or plastic. By turning the electrical voltage up or down, one can manually or automatically increase or decrease the amount of light transmitted through the glass or plastic window. When the device is in the "off" state, no voltage is applied, and the particles are randomly dispersed and absorb light, creating a dark appearance. When it is in the "on" state, the particles will align, and the view through the glass or plastic will change from dark to clear. If only a partial voltage is applied, the viewing area becomes only partially clear. This offers users complete control over the degree of shading.
According to Alex Martinez, Head of Engineering at InspecTech, the company considered several alternative window-shading technologies such as liquid-crystal windows, but they were hazy in the "on" state, especially when viewed from an angle. "They also did not offer the ability to tune the amount of light coming into the aircraft, and in fact did not reduce light, but instead just scattered it, creating an undesirable "halo" effect when direct sunlight shined through these windows," he said.
Electrochromic windows were also explored and found to have several drawbacks, according to Martinez. Although the windows were similar to SPD in appearance, they exhibited a non-uniform response over the surface of the window when tuning out light. Response time was also slow with these windows.
For more information from Research Frontiers, circle 31
ATFI geared turbofan makes first run
 Pratt & Whitney Canada has successfully completed the first test run of its geared turbofan engine demonstrator, the Advanced Technology Fan Integrator. |
Pratt & Whitney Canada (P&WC) has successfully completed its first test run of its geared turbofan engine demonstrator, the Advanced Technology Fan Integrator (ATFI), designed for the regional and corporate jet markets. According to the company, the ATFI demonstrator exceeded its maximum thrust target of 12,500 lb during the first run.
The ATFI demonstrator program was formally launched at the Farnborough Air Show in July 2000. The engine is being developed in close collaboration with Pratt & Whitney's Large Commercial Engines Division in Hartford, CT, which has been developing geared-fan system technology for more than 10 years. Also participating as partners are MTU Aero Engines from Germany, which has been selected to supply the low-pressure turbine for the engine, and FiatAvio from Italy, responsible for the fan drive gearbox assembly, intermediate case, and accessory gearbox.
The ATFI demonstration program will enable P&WC to improve on the technology before introducing it in its new PW800 engine family, which will be in the 10,000-19,000-lb thrust range. The PW800 family will complete the company's product line by bridging the gap between the PW300 series for small regional and business jets and the PW6000 family for the 100-passenger market and above.
The PW800 engines will feature a reduction gearbox that will allow the fan to run at a slower speed than the low-spool compressor and turbine, permitting all three components to operate at their most effective speeds and efficiencies. The slower fan speed contributes to very low noise levels, while the higher turbine and LP compressor speeds lead to an engine configuration with fewer stages. With fewer parts, operating costs will be reduced.
The new engine will also feature an advanced swept-fan blade design, which brings the dual advantage of better top-of-climb performance derived from increased fan flow capacity and reduced noise levels, enabling the powerplant to meet the increasingly strict rules imposed by airport and regulating bodies.
For more information from Pratt & Whitney Canada, circle 32
JSF and STOVL
 The VAAC Harrier during the ship-based JSF research program. |
The Vectored thrust Aircraft Advanced flight Control (VAAC) Harrier operated by Defense Evaluation and Research Agency (DERA) has completed the second phase in the Follow-on Research Program (FRP) sponsored by the U.S./UK Joint Strike Fighter (JSF) program. The aircraft has been operating at sea with the Royal Navy carrier HMS Invincible to test aircraft-control concepts applicable to the short takeoff vertical landing (STOVL) variant of the JSF. DERA stated that the first, land-based evaluation phase in 2000 built on the results of previous trials, familiarized new pilots with the advanced control concepts of the VAAC Harrier, "and resolved known deficiencies." The major aim of the second phase has been to assess compatibility of advanced recovery modes, including novel techniques such as translational rate command applied to operations from a ship's moving deck. Two main control modes were tested with two variants of the hover positioning sub-mode, reported DERA. It was the first full evaluation of the control laws at sea. It involved UK, U.S., and Italian pilots performing 85 deck landings in various winds and sea states. One of the pilots had no previous experience in a STOVL aircraft or of shipboard operations. The shipboard operations were used to confirm the few concerns with some of the control modes that had already been raised and also allowed comparisons to be made to identify potential preferences, said DERA. VAAC Harrier Test Pilot Lt. Cmdr. Phil Hayde said the work with Invincible had demonstrated the VAAC's capability for a low workload solution that provided carefree handling and a low risk of cognitive failure. This would ease the training burden and cut costs.
The VAAC Harrier is currently at DERA's Boscombe Down site where evaluations are being performed on the STOVL automatic recovery system on the aircraft. A later phase of the FRP will research advanced control for short takeoffs and an enhancement of one of the control concepts that was investigated at sea.
The two-seat VAAC Harrier features a digital flight control system with advanced programmable fly-by-wire capabilities from the rear seat. This gives the backseat pilot full-authority digital control of the aircraft via a computer interface that allows various flying modes to be developed and installed. Also, modifications to the software and the flying experience can be achieved between flights with pilot systems and behavior comparison and feedback. The digital flight-control system also offers STOVL capability without the necessity of what DERA terms "the tricky third control lever, thus, significantly reducing pilot workload." The JSF trials build on previous DERA/NASA research into advanced control laws, but the latest work incorporates the first comprehensive shipboard evaluations.
For more information from DERA, circle 33
Flutter testing at Dryden
 The ATW was mounted on a special ventral flight test fixture and flown on board NASA Dryden's F-15B research Testbed aircraft. |
NASA's Dryden Flight Research Center in Edwards, CA, has begun demonstrations of a new software data-analysis tool, the flutterometer, which is designed to increase the efficiency of flight-flutter testing.
Flutter is the rapid and self-excited vibration of wings, tail surfaces, and other aircraft parts that can damage or destroy an aircraft component. It is caused by the airflow around the surface of a structure; the aerodynamic forces couple with structural bending and twisting to result in the vibration. Flight-flutter testing is the process of determining an aircraft's flight envelope. According to NASA, traditional approaches to flight-flutter testing do not accurately predict the onset of instability, resulting in increased costs and testing time.
The flutterometer is an online software tool that enables flight data to be analyzed immediately to determine the aircraft's stability properties. It is designed to predict the flight conditions at which the onset of flutter may occur, enabling the aircraft's operating envelope to be determined more quickly and safely than traditional approaches.
Dryden engineers demonstrated the flutterometer during the Aero-structures Test Wing (ATW) experiment, which consisted of an 18-in carbon-fiber test wing with surface-mounted piezoelectric strain actuators. The test wing, which was designed by NASA Engineer Cliff Sticht and manufactured by Fiberset, Inc. in Mojave, CA, was mounted on a special ventral flight test fixture and flown on Dryden's F-15B Research Testbed aircraft.
 Research objectives of the ATW experiment included validation of the new flutterometer and the aerodynamic load predictions on the test wing, as well as analytical strain-gauge-calibration techniques. |
The five flights consisted of increasing speeds and altitudes leading to the final test point of Mach 0.85 at an altitude of 10,000 ft. At each Mach and altitude, stability estimations of the wing were made using accelerometer measurements in response to the piezoelectric actuator excitation. The test wing was intentionally flown to the point of structural failure, resulting in about a third of the 18-in wing breaking off. This experiment enabled engineers to record the effectiveness of the flutterometer over the entire regime of flutter testing, up to and including structural failure.
The actuators were moved at different magnitudes and frequency levels to induce wing vibrations and excite the dynamics during flight. Mercedes Reaves, Engineer at NASA Langley Research Center in Hampton, VA, determined the placement of the piezoelectric actuators for maximum effectiveness. The ATW experiment represents the first time that piezoelectric actuators were used during a flight flutter test.
For more informatin from Dryden, circle 34
