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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
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NASA NTRS1975

Space Shuttle Orbiter Approach and Landing Test Program

The approach and landing tests of the orbiter vehicle, planned for early 1977, will be the first actual flight activity in the NASA Space Shuttle Program. The tests are to include air-launched unpowered glide, approach, and landing tests. A review is presented of the basic Shuttle program and a description of the orbiter design is given, taking into account the flight control systems. Details of the actual test program will be partly based on the results to be obtained with an orbiter aeroflight simulator.

Fullerton, C. G.↗
NASA NTRS1977

The effect of variations in controls and displays on helicopter instrument approach capability

A flight investigation was conducted with a variable stability helicopter to determine the effects of variations in controls and displays on helicopter instrument approach capabilities. The baseline instrument approach task was a decelerating approach to a hover along a 6 deg glide slope. Pilot evaluations were obtained for both the constant speed part of the task and the deceleration and hover part of the task. The attitude stability augmentation system (SAS) was strongly preferred over the rate SAS because the aircraft had a divergent pitch response. From a display variation standpoint, it was not possible to decelerate to a hover in a consistent manner, regardless of the control system employed, with situation information only. In particular, the deceleration and hover part of the task was unacceptable without flight director command information.

Niessen, F. R.↗
NASA NTRS1976

Factors influencing tolerance to wind shears in landing approach

Flight simulator studies were conducted to examine the piloting problems resulting from encounters with unusual atmospheric disturbances late in landing approach. Simulated encounters with disturbances, including examples derived from accident data, provided the opportunity to study aircraft and pilot performance. It was observed that substantial delays in pilot response to shear-induced departures from glide slope often seriously amplified the consequences of the encounter. In preliminary assessments, an integrated flight instrument display featuring flight path as the primary controlled element appeared to provide the means to minimize such delays by improving tolerance to disturbances in landing approaches.

Bray, R. S.↗
NASA NTRS1976

Delayed flap approach procedures for noise abatement and fuel conservation

The NASA/Ames Research Center is currently investigating the delayed flap approach during which pilot actions are determined and prescribed by an onboard digital computer. The onboard digital computer determines the proper timing for the deployment of the landing gear and flaps based on the existing winds and airplane gross weight. Advisory commands are displayed to the pilot. The approach is flown along the conventional ILS glide slope but is initiated at a higher airspeed and in a clean aircraft configuration that allows for low thrust and results in reduced noise and fuel consumption. Topics discussed include operational procedures, pilot acceptability of these procedures, and fuel/noise benefits resulting from flight tests and simulation.

Edwards, F. G.↗
NASA NTRS1977

Flight investigation of a vertical-velocity command system for VTOL aircraft

A flight investigation was undertaken to assess the potential benefits afforded by a vertical-velocity command system (VVCS) for VTOL (vertical take-off and landing) aircraft. This augmentation system was conceived primarily as a means of lowering pilot workload during decelerating approaches to a hover and/or landing under category III instrument meteorological conditions. The scope of the investigation included a determination of acceptable system parameters, a visual flight evaluation, and an instrument flight evaluation which employed a 10 deg, decelerating, simulated instrument approach task. The results indicated that the VVCS, which decouples the pitch and vertical degrees of freedom, provides more accurate glide-path tracking and a lower pilot workload than does the unaugmented system.

Kelly, J. R.↗
NASA NTRS1976

Flight with lift modulation inside a planetary atmosphere

A set of dimensionless variables (modified Chapman's variables) is introduced in a derivation of general equations for lifting flight and bank modulation within a planetary atmosphere. The atmosphere is assumed spherical and at rest, and a generalized lift-drag polar is also introduced. Corresponding equations for flight over a flat planet model are attained via a straightforward transformation. Two planar flight cases: flight at constant absolute speed over a spherical planet, and flight at constant descent rate over a flat planet, are analyzed, and the required lift control law (with negative or positive lift) is exhibited in each case. Glide at very high descent rate and plane flows of trajectories are analyzed.

Vinh, N. X.↗
NASA NTRS1977

Control logic to track the outputs of a command generator or randomly forced target

A procedure is presented for synthesizing time-invariant control logic to cause the outputs of a linear plant to track the outputs of an unforced (or randomly forced) linear dynamic system. The control logic uses feed-forward of the reference system state variables and feedback of the plant state variables. The feed-forward gains are obtained from the solution of a linear algebraic matrix equation of the Liapunov type. The feedback gains are the usual regulator gains, determined to stabilize (or augment the stability of) the plant, possibly including integral control. The method is applied here to the design of control logic for a second-order servomechanism to follow a linearly increasing (ramp) signal, an unstable third-order system with two controls to track two separate ramp signals, and a sixth-order system with two controls to track a constant signal and an exponentially decreasing signal (aircraft landing-flare or glide-slope-capture with constant velocity).

Trankle, T. L.↗
NASA NTRS1977

Flight-test evaluation of two electronic display formats for approach to landing under instrument conditions

The results of a flight evaluation of two electronic display formats for the approach to landing under instrument conditions are presented. The evaluation was conducted for a base-line electronic display format and for the same format with runway symbology and track information added. The evaluation was conducted during 3 deg, manual straight-in approaches with and without initial localizer offsets. Flight path tracking performance data and pilot subjective comments were examined with regard to the pilot's ability to capture and maintain localizer and glide slope by using both display formats.

Morello, S. A.↗
NASA NTRS1977

Problems pilots face involving wind shear

Educating pilots and the aviation industry about wind shears presents a major problem associated with this meteorological phenomenon. The pilot's second most pressing problem is the need for a language to discuss wind shear encounters with other pilots so that the reaction of the aircraft to the wind shear encounter can be accurately described. Another problem is the flight director which gives a centered pitch command for a given angular displacement from the glide slope. It was suggested that they should instead be called flight path command and should not center unless the aircraft is actually correcting to the flight path.

Melvin, W. W.↗
NASA NTRS1978

Simulator evaluation of a flight-path-angle control system for a transport airplane with direct lift control

A piloted simulator was used to evaluate the flight path angle control capabilities of a system that employs spoiler direct lift control. The system was designated the velocity vector control system and was compared with a baseline flight path angle control system which used elevator for control. The simulated airplane was a medium jet transport. Research pilots flew a manual instrument landing system glide slope tracking task and a variable flight path angle task in the landing configuration to obtain comparative performance data.

Kelley, W. W.↗
NASA NTRS1978

Pilot evaluation of sailplane handling qualities

The evaluation sailplanes were found generally deficient in the area of cockpit layout. The pilots indicated general dissatisfaction with high pitch sensitivity especially when coupled with inertially induced stick forces. While all sailplanes were judged satisfactory for centering thermals and in the ease of speed control in circling flight, pilot opinions diverged on the maneuvering response, pull-out characteristics from a dive, and on phugoid damping. Lateral-directional control problems were noted mainly during takeoff and landing for most sailplanes with the landing wheel ahead of center of gravity. Pilot opinion of in-flight lateral-directional stability and control was generally satisfactory. Five of the evaluation sailplanes exhibited a very narrow airspeed band in which perceptible stall warning buffet occurred. However, this characteristic was considered not objectionable when stall recovery was easy. The pilots objected to the characteristics of a wide airspeed band of stall warning followed by a stall with yawing and rolling tendency and substantial loss of altitude during the stall. Glide path control for the evaluation sailplanes was found to be generally objectionable.

Bennett, A. G., Jr.↗
NASA NTRS1977

Helicopter response in gusty winds about a building

In an earlier work Krynytzky (1971) investigated the performance of a helicopter landing in the steady-state mean flow-field behind a tall building in a wind tunnel. The present paper extends his method to the case of an unsteady flow field. A model is first developed for the gusty wind over a block two-dimensional geometry building. A set of simplified dynamic equations governing the motion of a helicopter is then derived. Finally the performance of the helicopter in an unsteady wind field about the building is computed for the helicopter landing or taking off on a 6 deg glide slope over the building.

Frost, W.↗
NASA NTRS1977

Recent flight test results using an electronic display format on the NASA B-737

This paper presents results of a flight evaluation of two electronic display formats for the approach-to-landing under instrument conditions. The evaluation was conducted for a baseline electronic display format and for the same format with runway symbology and track information added; its evaluation was conducted during 3-deg manual straight-in approaches with and without initial localizer offsets. Flight-path tracking performance data and pilot subjective comments were examined with regard to pilot's ability to capture and maintain the localizer and glide slope using both display fomats. The results of the flight tests agree with earlier simulation results and show that the addition of a perspective runway symbol with an extended centerline and relative track information to a baseline electronic display format improved both lateral and vertical flight-path tracking. Pilot comments indicated that the mental workload required to assess the approach situation was reduced as a result of integrating the perspective runway with extended centerline along with relative track information into the vertical situation display. The limited flight-test results also show that the flight-path performance with the integrated situation display format meets Category II Flight-Director performance criteria.

Morello, S. A.↗
NASA NTRS1978

Effect of wind turbulence and shear on landing performance of jet transports

Computer simulations of a Boeing 727 class aircraft landing in turbulence were developed by programming the longitudinal aircraft equations of motion into a digital computer with various input values of vertical and horizontal wind speeds. Turbulent wind data was fed to the computer in one-second intervals. The computer computed in one-second intervals the aircraft speed, altitude, horizontal distance traveled, rate-of-descent, pitch attitude, glide path angle (from edge of runway) and elevator angle. All computer runs were made in the 'stick-fixed' mode. The RMS values of altitude and velocity perturbations (from equilibrium) were found to be large when horizontal wind gusts had sinusoidal components at or near the phugoid (long period) frequency. Maximum RMS altitude deviations occurred when the vertical wind had sinusoidal components which were 1/10 to 1/5 of the phugoid frequency. When real wind data (obtained from NCAR Queen Air) were used as input winds good correlations were found to exist between RMS velocity perturbations and both horizontal and vertical wind shears.

Blick, E. F.↗
NASA NTRS1978

Terminal-area flight experience with the NASA Terminal Configured Vehicle

Increases in the volume of air traffic around major terminals, as well as the advent of MLS and other sophisticated ATC techniques, have prompted the development of aircraft specifically optimized for flight in terminal areas. A modified Boeing 737, developed by NASA, is presented as an illustration of a Terminal Configured Vehicle (TCV). Among the TCV systems discussed are the electronic attitude direction indicator (EADI) and the electronic horizontal situation indicator (EHSI), both of which are advanced display systems capable of positioning the runway center line from a variety of glide slope paths, and with reference to time, i.e., the on-board computer can predict where the aircraft will be at a given number of seconds from the time of the analysis. Thus, 4-D navigation (time path) can be selected as a control mode, together with vertical and horizontal path modes.

Morello, S. A.↗
NASA NTRS1977

Topography, structure, and mare ridges in southern Mare Imbrium and northern Oceanus Procellarum

The gross topography in southern Mare Imbrium and northern Oceanus Procellarum correlates with the buried structure and deposits of the Imbrium Basin and its rim, and many of the mare slopes may be depositional and reflect the pre-existing major features of the basin. Post-depositional, local distortion of the mare surface, however, is present and in many places associated with mare ridges. Many mare ridges are concentric to the Imbrium Basin suggesting that they are influenced by basin structures. Morphologic diversity of mare ridges suggests that not all have the same origin, and volcanic activity took place along some of them. Most mare ridges are associated with faults. The faults could be reverse and associated with a shrinking of the moon, however, some ridges parallel slopes and could be interpreted as decollement thrust faults along gliding horizons or as vertical faults caused by differential gravitational settling along lines that separate areas that are thinly flooded on topographic highs from areas that are thickly flooded in adjacent lows.

Lucchitta, B. K.↗
NASA NTRS1978

Simulator evaluation of three situation and guidance displays for V/STOL aircraft zero-zero landing approaches

A simulator study was undertaken to compare and evaluate the design features of the electronic displays for possible use in V/STOL aircraft: a combined transition display (Display A), a perspective display (Display B), and a hover display (Display C). Display B presents height information via integrated elements; Displays A and C present information similarly except that Display C presents vertical and lateral guidance via conventional cross pointers. High pilot work load was attained by evaluating the displays only as situational guidance displays in a simulated vehicle without stability augmentation. Glide slopes of 6 and 15 deg were used, and steady-state and no-wind conditions were randomly presented. Six pilots participated, and fifty-five objective performance measures were taken along with pilot opinions

Murphy, M. R.↗