SCIENTIFIC AND TECHNICAL AEROSPACE REPORTS

A Biweekly Publication of the National Aeronautics and Space Administration
VOLUME 43, ISSUE 20 - OCTOBER 07, 2005

08 AIRCRAFT STABILITY AND CONTROL
Includes flight dynamics, aircraft handling qualities, piloting, flight controls, and autopilots.

For related information see also 05 Aircraft Design, Testing and Performance and 06 Avionics and Aircraft Instrumentation.

20050215401 Systems Technology, Inc., Hawthorne, CA, USA

On-Line Loss of Control Detection Using Wavelets

Brenner, Martin J., Technical Monitor; Thompson, Peter M.; Klyde, David H.; Bachelder, Edward N.; Rosenthal, Theodore J.; July 2005; 474 pp.; In English Contract(s)/Grant(s): NAS4-01004 Report No.(s): NASA/CR-2005-212873; STI-TR-1341-1; STI-TR-1341-2; STI-TR-1341-3; No Copyright;Avail.: CASI: A20, Hardcopy

Wavelet transforms are used for on-line detection of aircraft loss of control.Wavelet transforms are compared with Fourier transform methods and shown to more rapidly detect changes in the vehicle dynamics. This faster response is due to a time window that decreases in length as the frequency increases. New wavelets are defined that further decrease the detection time by skewing the shape of the envelope. The wavelets are used for power spectrum and transfer function estimation. Smoothing is used to tradeoff the variance of the estimate with detection time. Wavelets are also used as front-end to the eigensystem reconstruction algorithm. Stability metrics are estimated from the frequency response and models, and it is these metrics that are used for loss of control detection. A Matlab toolbox was developed for post-processing simulation and flight data using the wavelet analysis methods.Asubset of these methods was implemented in real time and named the Loss of Control Analysis Tool Set or LOCATS.Amanual control experiment was conducted using a hardware-in-the-loop simulator for a large transport aircraft, in which the real time performance of LOCATS was demonstrated. The next step is to use these wavelet analysis tools for flight test support. Author

On-Line Systems; Wavelet Analysis; Detection; Aircraft Control; Algorithms

20050215587 Federal Aviation Administration, Oklahoma City, OK, USA

Investigation of In-Flight Medical Incapacitations and Impairments

DeJohn, Charles; Pathological Aspects and Associated Biodynamics in Aircraft Accident Investigation; August 2005, pp. 4-1; In English; See also 20050215585; Original contains color illustrations; Copyright; Avail.: CASI: A03, Hardcopy; Available from CASI on CD-ROM only as part of the entire parent document

This flight experiment program is separated into several tasks:

Approach/landing Visual meteorological conditions. 2 flight crew, 7 flight attendants, 240 passengers.

No accident. No injuries or fatalities.

Captain did not ask for landing gear.

Approach flown at higher than normal airspeed.

Reverse thrust used longer than normal.

Captain applied full power on taxiway.

FO reduced power to idle.

Capitan again applied full throttle.

Capitan incoherent.

FO shut down engines and called for assistance. Derived from text

Flight Crews; Injuries; Landing Gear; Thrust Reversal

20050215692 QSS Group, Inc., USA, Army Research Lab., Cleveland, OH, USA

Enhanced Bank of Kalman Filters Developed and Demonstrated for In-Flight Aircraft Engine Sensor Fault Diagnostics

Kobayashi, Takahisa; Simon, Donald L.; Research and Technology 2004; June 2005; 3 pp.; In English; No Copyright; Avail.: CASI: A01, Hardcopy

In-flight sensor fault detection and isolation (FDI) is critical to maintaining reliable engine operation during flight. The aircraft engine control system, which computes control commands on the basis of sensor measurements, operates the propulsion systems at the demanded conditions. Any undetected sensor faults, therefore, may cause the control system to drive the engine into an undesirable operating condition. It is critical to detect and isolate failed sensors as soon as possible so that such scenarios can be avoided. A challenging issue in developing reliable sensor FDI systems is to make them robust to changes in engine operating characteristics due to degradation with usage and other faults that can occur during flight.Asensor FDI system that cannot appropriately account for such scenarios may result in false alarms, missed detections, or misclassifications when such faults do occur. To address this issue, an enhanced bank of Kalman filters was developed, and its performance and robustness were demonstrated in a simulation environment. The bank of filters is composed of m + 1 Kalman filters, where m is the number of sensors being used by the control system and, thus, in need of monitoring. Each Kalman filter is designed on the basis of a unique fault hypothesis so that it will be able to maintain its performance if a particular fault scenario, hypothesized by that particular filter, takes place. Derived from text

Engine Control; Fault Detection; Kalman Filters; Propulsion System Performance

20050215693 NASA Glenn Research Center, Cleveland, OH, USA

Innovative Adaptive Control Method Demonstrated for Active Suppression of Instabilities in Engine Combustors

Kopasakis, George; Research and Technology 2004; June 2005; 4 pp.; In English; No Copyright; Avail.: CASI: A01, Hardcopy

This year, an improved adaptive-feedback control method was demonstrated that suppresses thermoacoustic instabilities in a liquid-fueled combustor of a type used in aircraft engines. Extensive research has been done to develop lean-burning (low fuel-to-air ratio) combustors that can reduce emissions throughout the mission cycle to reduce the environmental impact of aerospace propulsion systems. However, these lean-burning combustors are susceptible to thermoacoustic instabilities (high-frequency pressure waves), which can fatigue combustor components and even downstream turbine blades. This can significantly decrease the safe operating life of the combustor and turbine. Thus, suppressing the thermoacoustic combustor instabilities is an enabling technology for meeting the low-emission goals of the NASA Ultra-Efficient Engine Technology (UEET) Project. Derived from text

Adaptive Control; Combustion Chambers; Feedback Control; Fuel-Air Ratio; Propulsion System Performance

20050216527 Air Force Inst. of Tech., Wright-Patterson AFB, OH USA

Head Tracking for 3D Audio Using a GPS-Aided MEMS IMU

Joffrion, Jacque M.; Mar. 1, 2005; 130 pp.; In English; Original contains color illustrations Report No.(s): AD-A437051; AFIT/GE/ENG/05-09; No Copyright; Avail.: Defense Technical Information Center (DTIC)

Audio systems have been developed which use stereo headphones to project sound in three dimensions. When using these 3D audio systems, audio cues sound like they are originating from a particular direction. There is a desire to apply 3D audio to general aviation applications, such as projecting control tower transmissions in the direction of the tower or providing an audio orientation cue for VFR pilots who find themselves in emergency zero-visibility conditions. 3D audio systems, however, require real-time knowledge of the pilot's head orientation in order to be effective. This research describes the development and testing of a low-cost head tracking system for 3D audio rendering applied in general aviation. The system uses a low-cost MEMS IMU combined with a low-cost, single frequency GPS receiver. Real-time data from both of these systems was sent to a laptop computer where a real-time Kalman filter was implemented in MATLAB to solve for position velocity, and attitude. The attitude information was then sent to a 3D audio system for sound direction rendering. The system was flight tested on board a Raytheon C-12C aircraft. The accuracy of the system was measured by comparing its output to truth data from a high-accuracy post-processed navigation-grade INS/DGPS solution. Results showed that roll and pitch error were accurate to within 1-2 degrees, but that heading error was dependent upon the flight trajectory. During straight-and-level flight, the heading error would drift up to 10-15 degrees because of heading unobservability. However, even with heading error, the ability of a pilot to determine the correct direction of a 3D audio cue was significantly improved when using the developed head tracking system over using the navigation-grade INS/GPS system fixed to the aircraft. DTIC

Flight Tests; Global Positioning System; Microelectromechanical Systems; Pilots; Radio Receivers

Source: NASA.