Engineering topics

Lebacqz, J. V.

Publications and source records attributed to Lebacqz, J. V..

27 records · Page 2

NASA NTRS1981

A flight investigation of static stability, control augmentation, and flight director influences on helicopter IFR handling qualities

A flight experiment was conducted using the NASA-Army V/STOLAND UH-1H variable-stability helicopter to investigate the influence of several longitudinal-static-stability, control-augmentation, and flight-director parameters on helicopter flying qualities during terminal area operations in instrument conditions. This experiment, which was part of a joint NASA/FAA program pertaining to helicopter IFR airworthiness, was designed to corroborate and extend previous ground simulation results obtained in this program. Variations examined included stable and neutral longitudinal control position gradients, rate-damping and attitude-command augmentation, and raw data versus flight-director displays. Pilot rating results agreed excellently with the ground simulation data, indicating an adequate instrument capability with rate-damping augmentation and neutral statics and the need for pitch-roll attitude augmentation to achieve a satisfactory system.

Lebacqz, J. V.↗

NASA NTRS1980

Implicit model following and parameter identification of unstable aircraft

A transformation in the s-plane is described which has utility in implicit model-following optimal control design application and in estimation or parameter identification problems. The objective of the transformation is, for the control problem, to achieve an unstable closed-loop system, and, for the estimation problem, to alleviate algorithm convergence problems that may arise in identifying unstable systems. For the control problem, the transformation is a shift along the real (sigma) axis of the plant and model poles and zeros. This transformation is shown to be equivalent to a modified performance index but offers the advantage of compatibility with existing optimal control solution algorithms. For the estimation problem, the data are multiplied by an exponential function and the assumed measurement and process noise covariances are appropriately modified. Examples of both control and estimation applications are presented.

Lebacqz, J. V.↗

NASA NTRS1980

A piloted simulator investigation of static stability and stability/control augmentation effects on helicopter handling qualities for instrument approach

A ground simulator experiment was conducted on the Flight Simulator for Advanced Aircraft at Ames Research Center to investigate the influence of several static stability and stability/control augmentation design parameters on helicopter flying qualities during terminal area operations in instrument conditions. Effects of light turbulence were included. Two levels of static stability in each rotational axis (pitch, roll, yaw) were examined for a hingeless rotor configuration. The variations in pitch and roll were: (1) stable and (2) neutral static stability; in yaw there were two stable levels. Four types of stability/control augmentation were also examined for the lower level of static stability in each axis. This latter investigation covered three helicopter rotor types: hingeless, articulated, and teetering. Four pilots performed a total of 105 evaluations of these parameters for a representative VOR instrument approach task. Pilot rating results indicate the acceptability of neutral static stability longitudinally and laterally and the need for pitch-roll attitude augmentation to achieve a satisfactory system.

Lebacqz, J. V.↗

NASA NTRS1979

Survey of helicopter control/display investigations for instrument decelerating approach

Control-display requirements for helicopters conducting decelerating approaches in the terminal area under instrument meteorological conditions were surveyed. The programs are organized on the basis of the control augmentation concepts that were considered, and the results are summarized and compared. Nine control-display combinations are hypothesized as possible candidates for future ground and in-flight investigation. Specific guidelines for the guidance relationship, control characteristics, and display presentation concepts are given.

Lebacqz, J. V.↗

NASA NTRS1979

A review of helicopter control-display requirements for decelarating instrument approach

This paper reviews research and operational test programs that have dealt with control and display requirements for helicopters performing decelerating approaches in the terminal area under instrument flight conditions. A survey of literature concentrating on flight programs resulted in approximately 50 applicable references which were summarized and classified according to the type of stability/control augmentation that was emphasized. On this basis, display information requirements for each control system type were hypothesized consistent with documented results of these programs. Nine control-display combinations that appear to warrant further ground simulation and flight testing are defined and discussed.

Lebacqz, J. V.↗

NASA NTRS1977

Capabilities of the Navy variable stability X-22A for V/STOL flying qualities R and D

The X-22A V/STOL Flight Research Facility which provides in-flight simulation capability applicable to hover, low speed, and transition flight investigation of fixed wing V/STOL flying is described. The variable stability system, the guidance and display equipment, the data acquisition and processing system, and the ground simulator are included. Research programs involving the STOL flying qualities for landing approach, the control system, display, and guidance requirements for VTOL aircraft instrument approach and landing, and the expansion of the adverse weather operation capabilities of the Navy's VTOL aircraft are briefly summarized.

Aiken, E. W.↗

NASA NTRS1975

Results of a flight investigation of control-display interactions for VTOL decelerating descending instrument approaches using the X-22A aircraft

Control, display, and guidance requirements for VTOL instrument transitions were studied to provide meaningful data related to the interaction of aircraft control system and pilot display characteristics on pilot rating and performance during a steep decelerating descending transition from a representative forward velocity to the hover under simulated instrument conditions. Thirty seven evaluations were performed of combinations of five generic display presentations, ranging from position information only to four axis control directors, and five levels of control augmentation systems, ranging from rate augmentation only to decoupled velocity responses and automatic configuration changes. Primary results include the demonstration of an inverse relationship between control complexity and display sophistication and the definition of acceptable and satisfactory control display combinations.

Lebacqz, J. V.↗

NASA NTRS1974

Application of a Kalman filter identification technique to flight data from the X-22A variable stability V/STOL aircraft

A digital identification technique based on Kalman filter theory was developed for the estimation of V/STOL aircraft stability and control parameters from flight data. The application of this technique to flight data from flying qualities experiments using the variable stability X-22A V/STOL aircraft is discussed. The estimation algorithm is briefly reviewed, experimental and data acquisition procedures used in the X-22A flight programs are outlined, and specific problem areas such as the determination of noise statistics and selection of pilot inputs to enhance identifiability are discussed. Results are presented for a wide range of simulated dynamic configurations.

Lebacqz, J. V.↗

NASA NTRS1972

An experimental investigation of STOL longitudinal flying qualities in the landing approach using the variable stability X-22A aircraft.

The first in-flight flying qualities experiment using the variable stability X-22A aircraft investigated longitudinal flying qualities requirements for STOL aircraft in terminal area operations. Emphasis was placed on defining minimum requirements for the short-term response in VFR and IFR landing approaches at representative steep STOL approach conditions of 65 and 80 knots. Evaluation flights were conducted in negligible and moderate turbulence for a wide range of short-term frequencies and dampings. The results were compared with the short-term requirements of MIL-F-83300. The specified Level 1 and 2 VFR boundaries were found to be approximately valid in moderate turbulence for both VFR and IFR flight conditions. In negligible turbulence, the specified VFR Level 2 boundary was also approximately valid but the Level 1 boundary was found to be too stringent. Pilot rating gradients with damping were more apparent than with frequency for the range investigated.

Schuler, J. M.↗