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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 289 records · Page 16
All sourcesNASA NTRSDOE OSTI
NASA NTRS1976

NASA's 91-cm. airborne telescope

The Gerard P. Kuiper Airborne Observatory (KAO), commissioned in May 1975, is the result of the multi-year NASA program of infrared observations from high-flying aircraft. The KAO is a highly modified Lockheed C-141 jet transport, equipped with a 91-cm bent-Cassegrain telescope, as an international facility for research in infrared astronomy. To minimize the effects of aircraft vibration, the telescope is mounted on four pneumatic shock absorbers, and the entire assembly is balanced on the side of a spherical compressed-air bearing, containing a 0.018 mm-thick air film under a pressure of 19 atmospheres. The use of the KAO is not limited to infrared research, its total observable wavelength band extending from the near UV (3000 A) to the millimeter region. Design and technical characteristics of the telescope are discussed, including the image stabilization and target acquisition systems, as well as observational results obtained during the first year of the KAO operation.

Cameron, R. M.↗
NASA NTRS1977

Evaluation of flight spoilers for vortex alleviation

The paper describes the facilities and test procedures used in a series of wind-tunnel and full-scale flight investigations of the effectiveness of flight spoilers currently existing on wide-bodied transport jet aircraft when used as trailing vortex hazard alleviation devices. Examples of the results of such studies include the variation of trailing wing rolling-moment coefficient with downstream distance behind a B-747 airplane model with various segments of its flight spoilers deflected 45 deg, and comparisons with models without spoilers deflected. It is concluded that the existing flight spoilers on the B-747 are effective as trailing vortex attenuators.

Croom, D. R.↗
NASA NTRS1977

The effect of a visual/motion display mismatch in a single axis compensatory tracking task

An experiment was performed to determine the effect of a performance mismatch between the visual and motion display systems on a real time piloted aircraft simulation. Pilots performed a compensatory roll tracking task with dynamics typical of medium jet transports. Between 0 and 10 rad/sec, visual and motion system responses were equivalent to either unity or a first order lag at 4.8 rad/sec. Pilot describing functions and error scores were calculated. Results show that the mismatch between visual and motion display systems has no significant effect. It is the absence of high frequency visual and/or motion cues which significantly affects pilot performance.

Shirachi, D. K.↗
NASA NTRS1977

The development and use of spoilers as vortex attenuators

Results are presented of groundbased and flight investigations performed to develop spoilers as trailing vortex alleviation devices. Based on the results obtained in these investigations, it was found that the induced rolling moment on a trailing model can be reduced by spoilers located near the midsemispan of a vortex generating wing. Substantial reductions in induced rolling moment occur when the spoiler vortex attenuator is located well forward on both unswept and swept wing models. In addition, it was found that existing flight spoilers on the jumbo-jet transport aircraft can be effective as trailing vortex attenuators.

Croom, D. R.↗
NASA NTRS1978

Analytical study of ride smoothing benefits of control system configurations optimized for pilot handling qualities

An analytical study was conducted to evaluate the relative improvements in aircraft ride qualities that resulted from utilizing several control law configurations that were optimized for pilot handling qualities only. The airplane configuration used was an executive jet transport in the approach configuration. The control law configurations included the basic system, a rate feedback system, three command augmentation systems (rate command, attitude command, and rate command/attitude hold), and a control wheel steering system. Both the longitudinal and lateral directional axes were evaluated. A representative example of each control law configuration was optimized for pilot handling qualities on a fixed base simulator. The root mean square airplane responses to turbulence were calculated, and predictions of ride quality ratings were computed by using three models available in the literature.

Powers, B. G.↗
NASA NTRS1978

Concorde noise-induced building vibrations John F. Kennedy International Airport

The outdoor and indoor noise levels resulting from aircraft flyovers and certain nonaircraft events were recorded at six home sites along with the associated vibration levels in the walls, windows, and floors of these test homes. Limited subjective tests conducted to examine the human detection and annoyance thresholds for building vibration and rattle caused by aircraft noise showed that both vibration and rattle were detected subjectively in several houses for some operations of both the Concorde and subsonic aircraft. Preliminary results indicate that the relationship between window vibration and aircraft noise is: (1) linear, with vibration levels being accurately predicted from OASPL levels measured near the window; (2) consistent from flyover to flyover for a given aircraft type under approach conditions; (3) no different for Concorde than for other conventional jet transports (in the case of window vibrations induced under approach power conditions); and (4) relatively high levels of window vibration measured during Concorde operations are due more to higher OASPL levels than to unique Concorde source characteristics.

Mayes, W. H.↗
NASA NTRS1976

Acoustic design of the QCSEE propulsion systems

Acoustic design features and techniques employed in the Quiet Clean Short-Haul Experimental Engine (QCSEE) Program are described. The role of jet/flap noise in selecting the engine fan pressure ratio for powered lift propulsion systems is discussed. The QCSEE acoustic design features include a hybrid inlet (near-sonic throat velocity with acoustic treatment); low fan and core pressure ratios; low fan tip speeds; gear-driven fans; high and low frequency stacked core noise treatment; multiple-thickness treatment; bulk absorber treatment; and treatment on the stator vanes. The QCSEE designs represent and anticipated acoustic technology improvement of 12 to 16 PNdb relative to the noise levels of the low-noise engines used on current wide-body commercial jet transport aircraft.

Loeffler, I. J.↗
NASA NTRS1977

Radiation safety in high-altitude air traffic

Results of an experimental and theoretical study on dose equivalent rates at high altitudes are presented. The flight personnel flying 500 hours per year at SST cruise altitude in high latitudes (maximum of radiation) would be exposed to less than 14% of the maximum permissible dose rate (MPD) for radiation workers (5 rem/yr), averaged over the solar cycle. One-half or more is due to energetic secondary neutrons that are penetrant and highly biologically effective. Passengers would, in general, be exposed only to the low-level galactic cosmic rays, except for a relative few who encounter rare, intense, and energetic solar-particle events. If the airplane descends to subsonic altitudes during events such as that of Feb. 23, 1956 - the most intense and unique giant energy event of the last 35 years - passenger exposure even then remains at or below permissible levels (0.5 rem for the general population). Systems of radiation monitoring are briefly discussed which will prevent false alarms and which would be useful in disproving overexposure in potential malpractice suits against the airlines. In subsonic jet transports the exposure of the crews is lower by a factor 3 to 4; for passengers it is about the same for the same distance traveled. Solar events, except for giant energy events, will yield only a minor fraction of the MPD of the general population.

Foelsche, T.↗
NASA NTRS1979

Development of a digital guidance and control law for steep approach automatic landings using modern control techniques

The development of a digital automatic control law for a small jet transport to perform a steep final approach in automatic landings is reported along with the development of a steady-state Kalman filter used to provide smooth estimates to the control law. The control law performs the functions of localizer and glides capture, localizer and glideslope track, decrab, and place. The control law uses the microwave landing system position data, and aircraft body-mounted accelerators, attitude and attitude rate information. The results obtained from a digital simulation of the aircraft dynamics, wind conditions, and sensor noises using the control law and filter developed are described.

Halyo, N.↗
NASA NTRS1979

Simulation study to evaluate a constant-groundspeed approach method in moderate and severe wind shears

The use of a constant-groundspeed procedure for flying final approaches in moderate and severe wind shear environments was investigated. Performance was compared to results of simulated constant-airspeed approaches in identical wind profiles. The simulation model was a medium twin-jet transport equipped with an autothrottle for maintaining constant groundspeed or constant airspeed. For both moderate and severe wind shears, the constant-groundspeed approach method was shown to provide a way to more safely negotiate the shears while also providing predictable and acceptable touchdown performance. Results showed airspeeds on final approach to be considerably higher using the constant-groundspeed method, which supplied the additional stall margin needed when tail-wind shears were encountered. Throttle movements were noticeably reduced in all wind profiles when constant-groundspeed approaches were flown. Touchdown conditions were practically identical for both approach methods in moderate wind shear.

Kelley, W. W.↗
NASA NTRS1978

Effect of longitudinal stringers on sound transmission into a thin cylindrical shell

In the context of the transmission of airborne noise into an aircraft fuselage, a mathematical model is presented for the transmission of airborne noise into a stiffened cylindrical shell. The stiffeners are longitudinal stringers and are modeled as discrete structural elements. The numerical cases examined were typical of a narrow-bodied jet transport fuselage. The stringers appeared to raise the cylinder transmission loss in the mass-controlled region, although they produced dips at the stringer resonances. The ring-frequency dip in transmission loss, which is characteristic of monocoque shells, was found to still be present. There appeared to be a small increase in transmission loss as the number of stringers was increased. The effect of high damping was also investigated.

Koval, L. R.↗
NASA NTRS1979

Decoupled longitudinal controls for shear penetration in the terminal area environment

The use of decoupled longitudinal controls is simulated for the approach and landing of a twin engine jet transport in the presence of wind shear. Decoupled or independent control of pitch angle, flight-path angle and forward velocity using constant prefilter and feedback gains was compared to conventional control of a B-737 aircraft simulator. It is found that the mean flight-path angle, the mean glideslope error and the mean deviation in indicated airspeed generally improved when decoupled controls were used in the approach. An improvement in touchdown parameters was also observed, especially in strong shear, when 44% of conventionally-controlled flights impacted short of the runway. Simulator pilots reported improved approach performance and a reduced workload when decoupled controls were used.

Miller, G. K., Jr.↗
NASA NTRS1980

On sound transmission into a stiffened cylindrical shell with rings and stringers treated as discrete elements

In the context of the transmission of airborne noise into an aircraft fuselage, a mathematical model is presented for the transmission of an oblique plane sound wave into a finite cylindrical shell stiffened by stringers and ring frames. The rings and stringers are modeled as discrete structural elements. The numerical case studied was typical of a narrow-bodied jet transport fuselage. The numerical results show that the ring-frequency dip in the transmission loss curve that is present for a monocoque shell is still present in the case of a stiffened shell. The ring frequency effect is a result of the cylindrical geometry of the shell. Below the ring frequency, stiffening does not appear to have any significant effect on transmission loss, but above the ring frequency, stiffeners can enhance the transmission loss of a cylindrical shell.

Koval, L. R.↗
NASA NTRS1980

Sound transmission into a laminated composite cylindrical shell

In the context of the transmission of airborne noise into an aircraft fuselage, a mathematical model is presented for the transmission of an oblique plane sound wave into a laminated composite circular cylindrical shell. Numerical results are obtained for geometry typical of a narrow-bodied jet transport. Results indicate that from the viewpoint of noise attenuation on laminated composite shell does not appear to offer any significant advantage over an aluminum shell. However, the transmission loss of a laminated composite shell is sensitive to the orientation of the fibers and this suggests the possibility of using a laminated composite shell to tailor the noise attenuation characteristics to meet a specific need.

Koval, L. R.↗
NASA NTRS1981

An analytical study of the longitudinal response of airplanes to positive wind shear

The longitudinal response of jet transport aircraft to vertical variation of the horizontal winds is analyzed. Specific reference is given to the role of the speed (u) stability derivatives in the interaction of the airplane and its environment. The relative importance of the u stability derivatives is determined. The wind shear tolerance factor is found which can be used to determine, in a qualitative manner, the stability (tolerance) of an airplane to wind shear. A further study of the control problem shows that the criteria for good control could be reduced from two to one automatic control systems. Only a speed control system is necessary for good control in wind shear.

Sherman, W. L.↗
NASA NTRS1981

Design for supercommuters

Action to be taken to prepare to implement efficient, modern commuter aircraft for the 1990s is outlined. The increase in the contribution of jet fuel costs to aircraft direct operating costs (DOC) is noted as the motivation for the introduction of turboprop-powered commuter aircraft, which use 15-20% less fuel per seat mile at short stage lengths, to replace larger jet transports. Designs proposed by various manufacturers which will make use of existing technology for 19-, 30- and 50-seat aircraft capable of carrying a full payload of passengers and baggage for 600 n mi and optimized for minimum DOC over a 100-n mi stage length are presented, and the improvements in fuel usage, DOC and passenger comfort to be obtained with the use of advanced technology are pointed out. The goals and considered technologies of the dedicated small-transport aircraft technology program recommended by a commuter air transport subcommittee of the NASA Advisory Council Aeronautics Advisory Committee to speed the development of commuter technology are then presented, with attention given to efforts of analysis, design and testing of propulsion systems, structures, aerodynamics and systems intended to result in 16-24% savings in DOC and up to 40% savings in fuel. The commuter development plans of various manufacturers are also indicated.

Williams, L. J.↗
NASA NTRS1981

Airborne method to minimize fuel with fixed time-of-arrival constraints

A method for generating a minimum-fuel, fixed-range, fixed-time-of-arrival flight path in an on-board flight management system computer for commercial aircraft is described. It is shown that up to 6% of the fuel otherwise used can be saved by means of this capability, despite time-of-arrival delays of up to 30 min, by a medium-range, tri-jet transport aircraft.

Sorensen, J. A.↗