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Brown, P. W.

Publications and source records attributed to Brown, P. W..

18 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS1989

Investigations of modifications to improve the spin resistance of a high-wing, single-engine, light airplane

A general aviation aircraft with drooped leading edge modifications for improvement of lateral stability at high angles of attack has been flight tested in combination with a ventral fin which improves directional stability. The two modifications were assessed in light of spin-resistance criteria proposed for incorporation into FAA certification regulations. The configuration combining outboard wing leading-edge droop and a ventral fin yielded a substantial increase in spin resistance, but fell short of all requirements encompassed by the proposed spin-resistance criteria.

Manuel, G. S.↗
NASA NTRS1986

Piloted simulation study of the effects of an automated trim system on flight characteristics of a light twin-engine airplane with one engine inoperative

A simulation study was conducted to investigate the piloting problems associated with failure of an engine on a generic light twin-engine airplane. A primary piloting problem for a light twin-engine airplane after an engine failure is maintaining precise control of the airplane in the presence of large steady control forces. To address this problem, a simulated automatic trim system which drives the trim tabs as an open-loop function of propeller slipstream measurements was developed. The simulated automatic trim system was found to greatly increase the controllability in asymmetric powered flight without having to resort to complex control laws or an irreversible control system. However, the trim-tab control rates needed to produce the dramatic increase in controllability may require special design consideration for automatic trim system failures. Limited measurements obtained in full-scale flight tests confirmed the fundamental validity of the proposed control law.

Stewart, E. C.↗
NASA NTRS1986

In-flight flow visualization of F-106B leading-edge vortex using the vapor-screen technique

A flight program was conducted with the objective to study the vortex flow systems existing around the F-106B aircraft. Level 1-G decelerating flight with varying angle of attack was considered along with conditions involving G levels in the range from 4.5 to 5.5 and angles of attack in the range from 16 to 19 degrees. It was demonstrated that the vapor screen technique can be applied successfully to flight vehicles under a variety of test conditions, taking into consideration the transonic maneuver performed by fighter aircraft. Details regarding the employed in-flight flow visualization technique are discussed, taking into account the seeding system, the light sheet system, the video system, the control system, and the recording of the data. Attention is also given to the flight program, the data development, and the scientific observations.

Lamar, J. E.↗
NASA NTRS1986

Development of spin resistance criteria for light general aviation airplanes

A brief history of stall/spin technology for light general aviation airplanes is presented. Criteria needed to describe desirable characteristics of a spin-resistant airplane and means to evaluate airplanes for compliance with the criteria have been developed. Initial results from limited flight tests of an experimental high-wing airplane indicated that the basic configuration would not meet the spin resistance criteria. Further tests with the airplane modified to enhance its spin resistance are planned.

Dicarlo, D. J.↗
NASA NTRS1986

Description of and results from camera systems for recording daytime lightning strikes to an airplane in flight

Photographic still and movie and video camera systems have been developed to reveal more about the characteristics of daytime lightning strikes to airplanes in flight. Equipment selection and design is particularly important with regard to time of event occurrence, time correlation between cameras, rapidity of actuation, ease of photogrammetric analysis, and selection of fields of view. The most recent such camera systems flown in an NASA F-106B research airplane are described and design considerations are discussed. Daytime depictions of lightning strikes are presented as illustrative of some of these considerations.

Brown, P. W.↗
NASA NTRS1986

Summary of NASA storm hazards lightning research, 1980-1985

Lightning swept-flash attachment patterns and the associated flight conditions were recorded from 1980-1985 during 1378 thunderstorm penetrations and 690 direct strikes with a NASA F-106B research airplane. The individual lightning attachment spots, along with crew comments and onboard photographic data have been used to identify lightning swept-flash attachment patterns and the orientations of the lightning channels with respect to the airplane. The altitudes, ambient temperatures, and the relative turbulence and precipitation levels at which the strikes occurred also are summarized and discussed, with an emphasis on the differences between high and low altitude strikes.

Fisher, B. D.↗
NASA NTRS1986

Joint thunderstorm operations using the NASA F-106B and FAATC/AFWAL Convair 580 airplanes

During the 1985 thunderstorm season, three joint thunderstorm research flights were conducted within 100 n.mi. of NASA Langley by the NASA Storm Hazards F-106B and the FAA/USAF CV-580 research airplanes with ground-based weather radar measurements by NASA Wallops. This paper discusses the thunderstorm penetration capabilities of each airplane and the techniques used to safely place the two airplanes into the same thunderstorm cell for collection of correlated EM data. It is concluded that joint thunderstorm research operations of two aircraft with significantly dissimilar thunderstorm penetration capabilities are counterproductive to both airplanes.

Fisher, B. D.↗
NASA NTRS1985

Simulation study of an automatic trim system for reducing the control forces on a light twin after an engine failure

An automatic trim system for reducing the control forces after an engine failure on a light twin has been investigated on the Langley General Aviation Simulator. The system schedules open-loop trim tab deflections as a function of differential propeller slipstream dynamic pressure and freestream dynamic pressure. The system is described and the airplane-system static and dynamic characteristics are documented. Three NASA research pilots evaluated the effectiveness of the system for takeoff and landing maneuvers. A variety of off-nominal system characteristics were studied. The system was judged to be generally beneficial, providing a 2 to 3 point improvement in pilot rating for the tasks used in the evaluations.

Stewart, E. C.↗
NASA NTRS1985

NASA storm hazards research in lightning strikes to aircraft

The lightning strike condition data gathered in the 1980-1984 period are presented, together with the lightning attachment point analysis for the NASA F-106B research aircraft are presented. The analysis of the experienced 637 direct lightning strikes shows that the highest strike rates (2.1 strikes/min and 13 strikes/penetration) occurred at altitudes between 38,000 and 40,000 ft. The regions of highest risk for an aircraft to experience a direct lightning strike were the areas of thunderstorms where the ambient temperature was colder than -40 C and where the relative turbulence and precipitation intensities were characterized as negligible to light. The presence and location of lightning, therefore, did not necessarily indicate the presence and location of hazardous precipitation and turbulence. The total onboard data show that the lightning attachment patterns on this aircraft fall into four general categories, although the 1984 data suggest that the entire surface of the F-106B may be susceptible to lightning attachment.

Fisher, B. D.↗
NASA NTRS1985

Research in lightning swept-stroke attachment patterns and flight conditions with the NASA F-106B airplane

Data on 637 direct lightning strikes and 117 close flashes observed by the NASA instrumented F-106B aircraft as part of the Storm Hazards Program at NASA Langley during 1980-1984 are compiled and analyzed, updating the report of Fisher and Plumer (1983). The airborne and ground-based measurement and recording apparatus and the flight and data-reduction procedures are described, and the results are discussed in terms of lightning-strike-conducive flight conditions and lightning attachment patterns. A peak strike rate of 2.1/min is found at altitude 38,000-40,000 ft and temperature below -40 C, with very few strikes below 20,000 ft. Four categories of swept-flash attachment pattern are identified, but it is pointed out that all exterior surfaces of the F-106B are potential attachment sites.

Fisher, B. D.↗
NASA NTRS1983

A simulation study of the low-speed characteristics of a light twin with an engine-out

Potential safety advantages provided by the two engines on a light twin aircraft are not realized in practice as evidenced by recent engine-failure accident statistics. These statistics showed twice the fatality rate from engine failure for twins as for single-engine aircraft. The statistics showed also that one-half of the fatal engine-out accidents involved a stall. An improvement of the low-speed engine-out characteristics is, therefore, needed. An investigation of the engine-out characteristics of light twin-engine aircraft is currently being conducted as part of the comprehensive stall/spin program for general aviation aircraft. The present study is concerned with the first phase of this program. The primary objective of this study is to advance the understanding of the basic flight dynamics and piloting problems for an engine-out condition. An all-digital computer system was used in the conducted simulation study.

Stewart, E. C.↗
NASA NTRS1982

Spin tests of a single-engine, high-wing light airplane

The airplane has a relatively steep spin mode (low angle of attack) with a high load factor and high velocity. The airplane recovers almost immediately after any deviation from the prospin control positions, except for one maneuver with reduced flexibility in the elevator control system.

Stewart, E. C.↗
NASA NTRS1981

Natural laminar flow data from full-scale flight and wind-tunnel experiments

Experimental results obtained at NASA Langley during studies of natural laminar flow (NLF) over commercially produced aircraft surfaces are reported. The general aviation aircraft examined were light aircraft, yet displayed NLF extents close to the maximum available and equivalent to high performance business aircraft flying envelopes. Sublimating chemicals and acoustic detection techniques were employed to measure the boundary layer transition. Theoretical predictions of boundary layer stability were found to match well with the experimental data, with consideration given to both swept wings and the amplitudes of allowable waves on the airfoil surfaces. The presence of the NLF on the airfoil surfaces confirmed the benefits available from use of composite materials for airfoil surfaces.

Holmes, B. J.↗
NASA NTRS1980

Flight evaluation of the effect of winglets on performance and handling qualities of a single-engine general aviation airplane

A flight evaluation was conducted to determine the effects of winglets on the performance and handling qualities of a light, single-engine general aviation airplane. The performance measurements were made with a pace airplane to provide calibrated airspeeds; uncalibrated panel instruments in the test airplane were used to provide additional quantitative performance data. These tests were conducted with winglets on and off during the same day to measure relative performance effects. Handling qualities were evaluated by means of pilot comments. Winglets increased cruise speed 8 knots (5.6 percent) at 3962 m (13,000 ft) density altitude and 51 percent maximum continuous power setting. Maximum speed at 3962 m was virtually unchanged. Rate of climb increased approximately 6 percent, or 0.25 m/sec (50 ft/min), at 1524 m (5000 ft). Stall speed was virtually unchanged. Handling qualities were favorably affected.

Holmes, B. J.↗
NASA NTRS1980

Simulator results of an F-14A airplane utilizing an aileron-rudder interconnect during carrier approaches and landings

A piloted simulator study was conducted to evaluate an aileron rudder interconnect (ARI) control system for the F-14A airplane in the landing configuration. Effects on pilot performance and handling characteristics were investigated. Two ARI configurations were tested and compared to the standard F-14 fleet control system. A nonlinear aerodynamic model of the F-14 was used in conjunction with a six degree of freedom motion base simulator. The evaluation task, which utilized three subject pilots, consistent of a night carrier approach and landing. Both ARI configurations produced improved pilot performance and pilot ratings when compared to the standard control system. Sideslip due to adverse yaw as considerably reduced by the ARI systems and heading control was more stable and precise. Lateral deviation from centerline was reduced during the approach and lateral touchdown dispersion on the carrier deck was reduced with the ARI control systems.

Kelly, W. W.↗
NASA NTRS1980

Exploratory piloted simulator study of the effects of winglets on handling qualities of a representative agricultural airplane

The effects on handling qualities of adding winglets to a representative agricultural aircraft configuration during swath-run maneuvering were evaluated. Aerodynamic data used in the simulation were based on low-speed wind tunnel tests of a full scale airplane and a subscale model. The Cooper-Harper handling qualities rating scale, supplementary pilot comments, and pilot vehicle performance data were used to describe the handling qualities of the airplane with the different wing-tip configurations. Results showed that the lateral-directional handling qualities of the airplane were greatly affected by the application of winglets and winglet cant angle. The airplane with winglets canted out 20 deg exhibited severely degraded lateral directional handling qualities in comparison to the basic airplane. When the winglets were canted inward 10 deg, the flying qualities of the configuration were markedly improved over those of the winglet-canted-out configuration or the basic configuration without winglets, indicating that proper tailoring of the winglet design may afford a potential benefit in the area of handling qualities.

Ogburn, M. E.↗
NASA NTRS1979

Simulator study of stall/post-stall characteristics of a fighter airplane with relaxed longitudinal static stability

A real-time piloted simulation was conducted to evaluate the high-angle-of-attack characteristics of a fighter configuration based on wind-tunnel testing of the F-16, with particular emphasis on the effects of various levels of relaxed longitudinal static stability. The aerodynamic data used in the simulation was conducted on the Langley differential maneuvering simulator, and the evaluation involved representative low-speed combat maneuvering. Results of the investigation show that the airplane with the basic control system was resistant to the classical yaw departure; however, it was susceptible to pitch departures induced by inertia coupling during rapid, large-amplitude rolls at low airspeed. The airplane also exhibited a deep-stall trim which could be flown into and from which it was difficult to recover. Control-system modifications were developed which greatly decreased the airplane susceptibility to the inertia-coupling departure and which provided a reliable means for recovering from the deep stall.

Nguyen, L. T.↗