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A flight test investigation has been conducted to determine the performance of wingtip vortex turbines and their effect on aircraft performance. The turbines were designed to recover part of the large energy loss (induced drag) caused by the wingtip vortex. The turbine, driven by the vortex flow, reduces the strength of the vortex, resulting in an associated induced drag reduction. A four-blade turbine was mounted on each wingtip of a single-engine, T-tail, general aviation airplane. Two sets of turbine blades were tested, one with a 15° twist (washin) and one with no twist. The power recovered by the turbine and the installed drag increment were measured. A trade-off between turbine power and induced drag reduction was found to be a function of turbine blade incidence angle. This test has demonstrated that the wingtip vortex turbine is an attractive alternate, as well as an emergency, power source.

A simple wing leading-edge modification has been developed that delays outer wing panel stall, thus maintaining roll damping to higher angles of attack and delaying the onset of autorotation. The stall angle of attack of the outer wing panel has been shown to be a function of the spanwise length of the leading-edge modification. The margin of spin resistance provided by the modification is being explored through flight tests. Preliminary results have been used to evaluate spin resistance in terms of the difference in angle of attack between outer wing panel stall and the maxiumum attainable angle of attack.

An investigation has been conducted in the Langley 30- by 60-Foot Wind Tunnel to evaluate the performance and stability and control characteristics of a full-scale general aviation airplane equipped with a natural-laminar-flow wing. The study focused on the effects of natural laminar flow and boundary layer transition, and on the effects of several wing leading-edge modifications designed to improve the stall resistance of the configuration. Force and moment data were measured over wide angle-of-attack and sideslip ranges and at Reynolds numbers from 1.4 × 106 to 2.1 × 106 based on the mean aerodynamic chord. Additional measurements were made using hot-film and sublimating-chemical techniques to determine the condition of the wing boundary layer, and wool tufts were used to study the wing stalling characteristics. The investigation showed that large regions of natural laminar flow existed on the wing which would significantly enhance the cruise performance of the configuration.

A series of low-speed static and dynamic wind tunnel tests of a commercial transport configuration over an extended angle of attack/sideslip envelope was conducted at NASA Langley Research Center. The test results are intended for use in the development of an aerodynamic simulation database for determining aircraft flight characteristics at extreme and loss-of-control conditions. This database will be used for the development of loss-of-control prevention or mitigation systems, pilot training for recovery from such conditions, and accident investigations. An overview of the wind-tunnel tests is presented and the results of the tests are evaluated with respect to traditional simulation database development techniques for modeling extreme conditions to identify regions where simulation fidelity should be addressed.

The Mars Reconnaissance Orbiter (MRO) launched on August 12, 2005 and started aerobraking at Mars in March 2006. During the spacecraft's design phase, thermal models of the solar panels and instruments were developed to determine which components would be the most limiting thermally during aerobraking. Having determined the most limiting components, (from a temperature limit standpoint), thermal limits in terms of heat rate were established. Advanced thermal modeling techniques were developed utilizing Thermal Desktop and Patran Thermal. Heat transfer coefficients were calculated using a Direct Simulation Monte Carlo technique. Analysis established that the solar panels were the most limiting components during the aerobraking phase of the mission.

The Mars Reconnaissance Orbiter (MRO) launched on August 12, 2005 and began aerobraking at Mars in March 2006. In order to save propellant, MRO used aerobraking to modify the initial orbit at Mars. The spacecraft passed through the atmosphere briefly on each orbit; during each pass the spacecraft was slowed by atmospheric drag, thus lowering the orbit apoapsis. The largest area on the spacecraft, most affected by aeroheating, was the solar arrays. A thermal analysis of the solar arrays was conducted at NASA Langley Research Center to simulate their performance throughout the entire roughly 6-month period of aerobraking. A companion paper describes the development of this thermal model. This model has been correlated against many sets of flight data. Several maneuvers were performed during the cruise to Mars, such as thruster calibrations, which involve large abrupt changes in the spacecraft orientation relative to the sun.

Current viscous drag reduction research explores the limits of practical applications of natural laminar flow (NLF) for airplane drag reduction. To better understand these limits, advanced measurement techniques are required to study the characteristics of laminar to turbulent boundary-layer transition. Recent NASA research indicates that the transition mode which involves laminar separation can be detected using arrayed hot-film laminar separation sensor concepts. These surface-mounted sensors can provide information on the location of the laminar separation bubble as well as bubble length. This paper presents two different laminar separation sensor configurations developed in the NASA program and presents results of wind-tunnel and flight evaluations of the sensors as tools to detect boundary-layer transition.

The effect on general aviation (GA) pilots' abilities to fly a small airplane while using a prototype data-linked weather information system (WIS) display, located in various cockpit positions, was investigated in comparison to the effect on their flying of acquiring weather information through conventional means. Ten GA pilots performed en route flying tasks of varying difficulty while concurrently performing weather information acquisition tasks. Pilots' subjective workload ratings, weather information acquisition times and accuracy levels, and preliminary flight path parameter deviation data indicate that using a WIS display results in smaller flight path parameter deviations, lower workload, and faster and slightly more accurate information retrieval than when weather information is obtained via the radio.

The General Aviation Element of the Aviation Safety Program's Synthetic Vision Systems (SVS) Project is developing technology to eliminate low visibility induced General Aviation (GA) accidents. SVS displays present computer generated 3-dimensional imagery of the surrounding terrain on the Primary Flight Display (PFD) to greatly enhance pilot's situation awareness (SA), reducing or eliminating Controlled Flight into Terrain, as well as Low-Visibility Loss of Control accidents. SVS-conducted research is facilitating development of display concepts that provide the pilot with an unobstructed view of the outside terrain, regardless of weather conditions and time of day. A critical component of SVS displays is the appropriate presentation of terrain to the pilot. An experimental study is being conducted at NASA Langley Research Center (LaRC) to explore and quantify the relationship between the realism of the terrain presentation and resulting enhancements of pilot SA and performance.

Prior studies have been performed where basic fabric lay-ups of the current Shuttle spacesuit were tested for radiation shielding capabilities. It was found that the fabric portions of the suit give far less protection from radiation than previously estimated. This is due to the porosity and non-uniformity of the fabrics and LCVG components. These findings were incorporated into the spacesuit model developed at NASA Langley Research Center to estimate exposures for mission planning and evaluation of safety during radiation field disturbance. Overall material transmission properties were also less than optimal. In order to evaluate the radiation protection characteristics of some proposed new spacesuit materials, fifteen test target combinations of current baseline and new proposed spacesuit materials were exposed to a low-energy proton beam at Lawrence Berkeley National Laboratory. Each target combination contained all of the necessary spacesuit layers, i.e.

This paper reports the status of the NASA Langley Research Center program aimed at the development of the technology required for large-scale Magnetic Suspension and Balance Systems. The use of magnetic suspension of the model in a wind tunnel is seen to be the only viable method to eliminate aerodynamic interference problems arising with mechanical model-supports. The two small-scale magnetic suspension systems in operation at Langley are the only ones now active in the U.S. The general features and capabilities of these two systems and all of the ongoing research in the use of magnetic suspension are described.

With the resurgence of the General Aviation industry, the incentive to develop new airplanes for the low-end market has increased. Increased production of small airplanes provides the designers and manufacturers the opportunity to incorporate advanced technologies that are not readily retrofitable to existing designs. Spin resistance is one such technology whose development was concluded by NASA during the 1980’s when the production of small airplanes had slipped into near extinction. This paper reviews the development of spin resistance technology for small airplanes with emphasis on wing design. The definition of what constitutes spin resistance and the resulting amendment of the Federal Aviation Regulations Part 23 to enable certification of spin resistant airplanes are also covered.

An extensive general aviation stall/spin research program is underway at the NASA Langley Research Center. Flight tests have examined the effects of tail design, wing leading edge design, mass distribution, and minor airframe modifications on spin and recovery characteristics. Results and observations on test techniques are presented for the first airplane in the program. Configuration changes produced spins varying from easily recoverable slow, steep spins to unrecoverable, fast flat spins.

The development of a Green’s function approach to ion transport greatly facilitates the modeling of laboratory radiation environments and allows for the direct testing of transport approximations of material transmission properties. Using this approach radiation investigators at the NASA Langley Research Center have established that simple solutions can be found for HZE ions by ignoring nuclear energy downshifts and dispersion. Such solutions were found to be supported by experimental evidence with HZE ion beams when multiple scattering was added. Lacking from the prior solutions were range and energy straggling and energy downshift and dispersion associated with nuclear events. In a more recent publication it was shown how these effects can be incorporated into the multiple fragmentation perturbation series. Analytical approximations for the first two perturbation terms were presented and the third term was evaluated numerically.

As part of NASA’s Aviation Safety and Security Program, a simulation study of a twin-jet transport aircraft crew training simulation was conducted to address fidelity for upset or loss-of-control flight conditions. Piloted simulation studies were conducted to compare the baseline crew training simulation model with an enhanced aerodynamic model that was developed for high-angle-of-attack conditions. These studies were conducted in a flaps-up configuration and covered the approach-to-stall, stall and post-stall flight regimes. Qualitative pilot comments and preliminary comparison with flight test data indicate that the enhanced model is a significant improvement over the baseline. Some of the significant unrepresentative characteristics that are predicted by the baseline crew training simulation for flight in the post-stall regime have been identified.

The various sources of loads of importance in the design of launch vehicles are discussed generally. The natural vibration modes, which are an essential ingredient in all loads problems, are described for the Saturn vehicle as obtained from a structural replica model. The effects of fuel loading on the structural modes are considered and the results obtained on the model are compared with full-scale results. Launch-vehicle buffeting is discussed and the buffeting characteristics of a manned lunar vehicle configuration are described. Some evaluations of buffeting scaling laws obtained with this configuration are presented. Estimates of the acoustic environment on the spacecraft associated with engine noise at lift-off and with aerodynamic noise due to buffeting are shown. The steady and vibratory loads due to ground winds as determined from wind-tunnel tests of a Saturn model are presented.

NASA antiskid braking system research programs are reviewed. These programs include experimental studies of four antiskid systems on the Langley Landing Loads Track, flight tests with a DC-9 airplane, and computer simulation studies. Results from these research efforts include identification of factors contributing to degraded antiskid performance under adverse weather conditions, tire tread temperature measurements during antiskid braking on dry runway surfaces, and an assessment of the accuracy of various brake pressure-torque computer models. This information should lead to the development of better antiskid systems in the future.

This paper will examine modern avionics and related developments coming from the electronics revolution and show how they can be applied to in-service aircraft to produce significant performance improvements. While it is recognized the discussion could be very wide ranging, this paper will focus primarily on some of the developments in which NASA-Langley Research Center has been involved, including advanced flight management concepts, flat panel displays, and innovative fuel gauge designs. This paper will also look at emerging airspace system concepts, such as navigation using satellites and communications via data links, and provide a preliminary assessment of the impact of these concepts on in-service aircraft from the perspective of retrofitting avionics.

High Ice Water Content (HIWC) has been identified as a primary causal factor in numerous engine events over the past two decades. Previous attempts to develop a remote detection process utilizing modern commercial radars have failed to produce reliable results. This paper discusses the reasons for previous failures and describes a new technique that has shown very encouraging accuracy and range performance without the need for any modifications to industry’s current radar design(s). The performance of this new process was evaluated during the joint NASA/FAA HIWC RADAR II Flight Campaign in August of 2018. Results from that evaluation are discussed, along with the potential for commercial application, and development of minimum operational performance standards for future radar products.

An experimental investigation was conducted to study the effectiveness of Synthetic Vision Systems (SVS) flight displays as a means of eliminating Low Visibility Loss of Control (LVLOC) and Controlled Flight Into Terrain (CFIT) accidents by low time general aviation (GA) pilots. A series of basic maneuvers were performed by 18 subject pilots during transition from Visual Meteorological Conditions (VMC) to Instrument Meteorological Conditions (IMC), with continued flight into IMC, employing a fixed-based flight simulator. A total of three display concepts were employed for this evaluation. One display concept, referred to as the Attitude Indicator (AI) replicated instrumentation common in today's General Aviation (GA) aircraft. The second display concept, referred to as the Electronic Attitude Indicator (EAI), featured an enlarged attitude indicator that was more representative of a “glass display” that also included advanced flight symbology, such as a velocity vector.