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At least 595 records · Page 33
All sourcesNASA NTRSDOE OSTI
NASA NTRS1943

The Measurement of Fuel-Air Ratio by Analysis for the Oxidized Exhaust Gas

An investigation was made to determine a method of measuring fuel-air ratio that could be used for test purposes in flight and for checking conventional equipment in the laboratory. Two single-cylinder test engines equipped with typical commercial engine cylinders were used. The fuel-air ratio of the mixture delivered to the engines was determined by direct measurement of the quantity of air and of fuel supplied and also by analysis of the oxidized exhaust gas and of the normal exhaust gas. Five fuels were used: gasoline that complied with Army-Navy fuel Specification No. AN-VV-F-781 and four mixtures of this gasoline with toluene, benzene, and xylene. The method of determining the fuel-air ratio described in this report involves the measurement of the carbon-dioxide content of the oxidized exhaust gas and the use of graphs for the presented equation. This method is considered useful in aircraft, in the field, or in the laboratory for a range of fuel-air ratios from 0.047 to 0.124.

Gerrish, Harold C.↗
NASA NTRS1949

Sound-Level Measurements of a Light Airplane Modified to Reduce Noise Reaching the Ground

An Army liaison-type airplane, representative of personal airplanes in the 150 to 200 horsepower class, has been modified to reduce propeller and engine noise according to known principles of airplane-noise reduction. Noise-level measurements demonstrate that, with reference to an observer on the ground, a noisy airplane of this class can be made quiet -- perhaps more quiet than necessary. In order to avoid extreme and unnecessary modifications, acceptable noise levels must be determined.

Vogeley, A W↗
NASA NTRS1946

High-Speed Wind-Tunnel Tests of a Twin-Fuselage Pursuit Airplane

At the request of the Air Technical Service Command, U.S. Army Air Forces, a 0.22-scale model of a twin-fuselae pursuit airplane was built and tested at the Ames Aeronautical Laboratory. The tests of this model were made in order that the aerodynamic characteristics of the airplane, especially at high speed, might be predicted. The results shown in this report consist of force data for the model and critical Mach numbers of parts of the model as determined from pressure-distribution measurements. The results indicate that a diving tendency of the airplane can be expected at Mach numbers above 0.70 at lift co-efficients from 0 to 0.4. There is an indication that the Mach number at which the airpolane would first experience a diving tendency for lift coefficients from 0 to 0.2 can be increased if the critical speed of the radiator enclosures is increased, and the wing-fuselage-juncture fillets are improved.

WIND TUNNEL TESTS(AAL-HIGH-SPEED-16')(AMER )↗
NASA NTRS1942

Aerodynamic Characteristics for Internal-Balance and Frise Type Ailerons on an NACA 6 Series Low-Drag Tip Section of the Wing for the XP-63 Airplane

At the request of the Army Air Forces, Materiel Command, tests were made in the two-Dimensional low-turbulence tunnel of a mode l submitted by Bell Aircraft Corporation as the tip section of the wing of the xp-63 airplane. " The model was a NACA 66, 2x-2l6 a = 0.6 airfoil section of 50-inch chord and made of dural according to standard sheet-metal practice. The model was fitted for an internal-balance aileron with a tab and a Frise type aileron. Several alterations of the skirts and balance on the internal- balance aileron were tested to obtain the various aerodynamic characteristics of the aileron.

AILERONS - DEFLECTION↗
NASA NTRS1943

The Measurement of Fuel-air Ratio by Analysis of the Oxidized Exhaust Gas

An investigation was made to determine a method of measuring fuel-air ratio that could be used for test purposes in flight and for checking conventional equipment in the laboratory. Two single-cylinder test engines equipped with typical commercial engine cylinders were used. The fuel-air ratio of the mixture delivered to the engines was determined by direct measurement of the quantity of air and of fuel supplied and also by analysis of the oxidized exhaust gas and of the normal exhaust gas. Five fuels were used: gasoline that complied with Army-Navy Fuel Specification, No. AN-VV-F-781 and four mixtures of this gasoline with toluene, benzene, and xylene. The method of determining the fuel-air ratio described in this report involves the measurement of the carbon-dioxide content of the oxidized exhaust gas and the use of graphs or the presented equation. This method is considered useful in aircraft, in the field, or in the laboratory for a range of fuel-air ratios from 0.047 to 0.124

FUELS-TOLUENE↗
NASA NTRS1941

Wind-tunnel Tests of Four Curtiss Propellers Embodying Different Blade Sections

Tests of four 10-foot propellers were made in the propeller-research tunnel for the Army Air Corps to check flight and static thrust test results made on several propellers embodying Clark Y and modified NACA 16-series sections. These propellers were identical as to diameter and activity factor and very closely identical in thickness ratio and pitch distribution. The blades embodied sections with both single- and double-cambered Clark Y, modified NACA 16-series, and a combination of Clark Y and modified NACA-16 airfoils. Tests covered a range of blade angles from 20 deg. to 70 deg., and were all made at tip speeds below 280 feet per second. Although these tests were not conclusive in themselves, owing to the conditions under which they were made, the results seem to check the flight and static tests as closely as would be expected.

AIRFOILS - CLARK Y - CHARACTERISTICS PROPELLER↗
NASA NTRS1994

Low-Noise Spiral Bevel Gears

Modified spiral bevel gears that generate relatively little noise and vibration designed and fabricated for use in U.S. Army OH-58D helicopter. Noise reduced by 12 to 19 dB. Similar low-noise, low-vibration spiral bevel gears used in other helicopters, with consequent benefits in comfort and health of pilots and passengers, enhancement of pilots' performance and safety through reduction of audible distraction, and reduction in cost and weight of helicopters through reduction in amount of sound-proofing material. Low-noise, low-vibration spiral bevel gears also used in drive axles of cars and trucks for smoother, quieter rides.

Lewicki, David G.↗
NASA NTRS1993

Measures for simulator evaluation of a helicopter obstacle avoidance system

The U.S. Army Aeroflightdynamics Directorate (AFDD) has developed a high-fidelity, full-mission simulation facility for the demonstration and evaluation of advanced helicopter mission equipment. The Crew Station Research and Development Facility (CSRDF) provides the capability to conduct one- or two-crew full-mission simulations in a state-of-the-art helicopter simulator. The CSRDF provides a realistic, full field-of-regard visual environment with simulation of state-of-the-art weapons, sensors, and flight control systems. We are using the CSRDF to evaluate the ability of an obstacle avoidance system (OASYS) to support low altitude flight in cluttered terrain using night vision goggles (NVG). The OASYS uses a laser radar to locate obstacles to safe flight in the aircraft's flight path. A major concern is the detection of wires, which can be difficult to see with NVG, but other obstacles--such as trees, poles or the ground--are also a concern. The OASYS symbology is presented to the pilot on a head-up display mounted on the NVG (NVG-HUD). The NVG-HUD presents head-stabilized symbology to the pilot while allowing him to view the image intensified, out-the-window scene through the HUD. Since interference with viewing through the display is a major concern, OASYS symbology must be designed to present usable obstacle clearance information with a minimum of clutter.

Demaio, Joe↗
NASA NTRS1993

ADS-33C related handling qualities research performed using the NRC Bell 205 airborne simulator

Over 10 years ago a project was initiated by the U.S. Army AVSCOM to update the military helicopter flying qualities specification MIL-8501-A. While not yet complete, the project reached a major milestone in 1989 with the publication of an Airworthiness Design Standard, ADS-33C. The 8501 update project initially set out to identify critical gaps in the requisite data base and then proceeded to fill them using a variety of directed research studies. The magnitude of the task required that it become an international effort: appropriate research studies were conducted in Germany, the UK and Canada as well as in the USA. Canadian participation was supported by the Department of National Defense (DND) through the Chief of Research and Development. Both ground based and in-flight simulation were used to study the defined areas and the Canadian Bell 205-A1 variable stability helicopter was used extensively as one of the primary research tools available for this effort. This paper reviews the involvement of the Flight Research Laboratory of the National Research Council of Canada in the update project, it describes the various experiments conducted on the Airborne Simulator, it notes significant results obtained and describes ongoing research associated with the project.

J Murray Morgan↗
NASA NTRS1993

Some lessons learned in three years with ADS-33C

Three years of using the U.S. Army's rotorcraft handling qualities specification, Aeronautical Design Standard - 33, has shown it to be surprisingly robust. It appears to provide an excellent basis for design and for assessment, however, as the subtleties become more well understood, several areas needing refinement became apparent. Three responses to these needs have been documented in this paper: (1) The yaw-axis attitude quickness for hover target acquisition and tracking can be relaxed slightly. (2) Understanding and application of criteria for degraded visual environments needed elaboration. This and some guidelines for testing to obtain visual cue ratings have been documented. (3) The flight test maneuvers were an innovation that turned out to be very valuable. Their extensive use has made it necessary to tighten definitions and testing guidance. This was accomplished for a good visual environment and is underway for degraded visual environments.

Key, David L.↗
NASA NTRS1993

Investigation of the effects of bandwidth and time delay on helicopter roll-axis handling qualities

Several years of cooperative research conducted under the U.S./German Memorandum of Understanding (MOU) in helicopter flight control has recently resulted in a successful handling qualities study. The focus of this cooperative research has been the effects on handling qualities due to time delays in combination with a high bandwidth vehicle. The jointly performed study included the use of U.S. ground-based simulation and German in-flight simulation facilities. The NASA-Ames Vertical Motion Simulator (VMS) was used to develop a high bandwidth slalom tracking task which took into consideration the constraints of the facilities. The VMS was also used to define a range of the test parameters and to perform initial handling qualities evaluations. The flight tests were conducted using DLR's variable-stability BO 105 S3 Advanced Technology Testing Helicopter System (ATTHeS). Configurations included a rate command and an attitude command response system with added time delays up to 160 milliseconds over the baseline and bandwidth values between 1.5 and 4.5 rad/sec. Sixty-six evaluations were performed in about 25 hours of flight time during ten days of testing. The results indicate a need to more tightly constrain the allowable roll axis phase delay for the Level 1 and Level 2 requirements in the U.S. Army's specification for helicopter handling qualities, ADS-33C.

Pausder, Heinz-Juergen↗
NASA NTRS1993

A piloted simulation investigation of the normal load factor and longitudinal thrust required for air-to-air acquisition and tracking

A piloted simulation study was performed by the U.S. Army Aeroflighydynamics Directorate to develop insight into the maneuverability requirements for aggressive helicopter maneuvering tasks such as air-to-air combat. Both a conventional helicopter and a helicopter with auxiliary thrust were examined. The aircraft parameters of interest were the normal and longitudinal load factor envelopes. Of particular interest were the mission performance and handling qualities tradeoffs with the parameters of interest. Two air-to-air acquisition and tracking tasks and a return-to-cover task were performed to assess mission performance. Results indicate that without auxiliary thrust, the ownship normal load factor capability needs to match that of the adversary in order to provide satisfactory handling qualities. Auxiliary thrust provides significant handling qualities advantages and can be substituted to some extent for normal load factor capability. Auxiliary thrust levels as low as 0.2 thrust/weight can provide significant handling qualities advantages.

Whalley, Matthew S.↗
NASA NTRS1993

Preliminary design features of the RASCAL: A NASA /Army rotorcraft in-flight simulator

Salient design features of a new NASA/Army research rotorcraft - the Rotorcraft-Aircrew Systems Concepts Airborne Laboratory (RASCAL) - are described. Using a UH-60A Black Hawk helicopter as a baseline vehicle, the RASCAL will be a flying laboratory capable of supporting the research requirements of major NASA and Army guidance, control, and display research programs. The paper describes the research facility requirements of these programs together with other critical constraints on the design of the research system, including safety-of-flight. Research program schedules demand a phased development approach, wherein specific research capability milestones are met and flight research projects are flown throughout the complete development cycle of the RASCAL. This development approach is summarized, and selected features of the research system are described. The research system includes a full-authority, programmable, fault-tolerant/fail-safe, fly-by-wire flight control system and a real-time obstacle detection and avoidance system which will generate low-altitude guidance commands to the pilot on a wide field-of-view, color helmet-mounted display.

Aiken, Edwin W.↗
NASA NTRS1993

Diffractive optics in adverse environments

An investigation at the Army Research Laboratory is in progress to characterize DOE performance in mil-spec environments. One of the most significant environmental influences is temperature. An analysis of a diffractive lens is presented in which optical performance is described as a function of temperature. In particular, we review the thermal dependence of focal length and diffraction efficiency. It is shown that the change in these parameters is independent of lens shape and relates only to material properties. Thermalized hybrid refractive/diffractive designs are discussed.

Behrmann, Gregory P.↗
NASA NTRS1993

Utilization of Shuttle small payload accommodations in the DOD Space Test Program

Over the past 27 years, the U.S. Air Force, as executive agent for the Department of Defense (DOD) Space Test Program, has flown approximately 325 space experiments for the Army, Navy, Air Force, and other DOD agencies. These experiments have made significant contributions to the improvement of military technology and operations. Flight of Space Test Program experiments has been carried out utilizing free flyer spacecraft, the Space Shuttle crew cabin, and the Space Shuttle cargo bay. This paper will concentrate on those experiments which have been flown by the NASA Space Shuttle small payload flight systems, e.g., GAS, uprated GAS (CAP), and Hitchhiker flight systems. Discussions of Space Test Program experiments flown by Space Shuttle small payloads flight systems will include the experiment objectives, the accommodations and services provided by the flight systems, experiment results, and lessons learned from the planning and conduct of the flight. Particular emphasis will be placed on those experiments which required and were provided with a new and unique capability by the small payloads flight systems. These capabilities include the first use of the GAS opening lid, the first use of the GAS payload ejection capability, and the first use of the Hitchhiker cross bay carrier.

Hagler, Thomas↗
NASA NTRS1993

Computational Methods for Crashworthiness

Presentations and discussions from the joint UVA/NASA Workshop on Computational Methods for Crashworthiness held at Langley Research Center on 2-3 Sep. 1992 are included. The presentations addressed activities in the area of impact dynamics. Workshop attendees represented NASA, the Army and Air Force, the Lawrence Livermore and Sandia National Laboratories, the aircraft and automotive industries, and academia. The workshop objectives were to assess the state-of-technology in the numerical simulation of crash and to provide guidelines for future research.

Noor, Ahmed K.↗
NASA NTRS1994

An overview of a model rotor icing test in the NASA Lewis Icing Research Tunnel

During two entries in late 1989, a heavily instrumented sub-scale model of a helicopter main rotor was tested in the NASA LeRC Icing Research Tunnel (IRT). The results of this series of tunnel tests were published previously. After studying the results from the 1989 test and comparing them to predictions, it became clear that certain test conditions still needed investigation. Therefore, a re-entry of the Sikorsky Aircraft Powered Force Model (PFM) in the IRT was instituted in order to expand upon the current rotor craft sub-scale model experimental database. The major areas of interest included expansion of the test matrix to include a larger number of points in the FAA AC 29-2 icing envelope, inclusion of a number of high power rotor performance points, close examination of warm temperature operations, operation of the model in constant lift mode, and testing for conditions for icing test points in the full scale helicopter database. The expanded database will allow further and more detailed examination and comparison with analytical models. Participants in the test were NASA LeRC, the U.S. Army Vehicle Propulsion Directorate based at LeRC, and Sikorsky Aircraft. The model rotor was exposed to a range of icing conditions (temperature, liquid water content, median droplet diameter) and was operated over ranges of shaft angle, rotor tip speed, advance ratio, and rotor lift. The data taken included blade strain gage and balance data, as well as still photography, video, ice profile tracings, and ice molds. A discussion of the details of the test is given herein. Also, a brief examination of a subset of the data taken is also given.

Britton, Randall K.↗
NASA NTRS1993

Preliminary analysis of amplitude and phase fluctuations in the JAPE multiple tone data to distances of 500 meters

The JAPE short range data provide a good opportunity for studying phase and amplitude fluctuations of acoustic signals in the atmosphere over distances of several hundred meters. Several factors contribute to the usefulness of these data: extensive meteorological measurements were made, controlled sources were used, the data were recorded with a high dynamic range digital system that preserved phase information and a significant number of measurement points were obtained allowing both longitudinal and transverse studies. Further, Michigan Tech, in cooperation with the U.S. Army TARDEC, has developed phase tracking algorithms for studying vehicle acoustic signals. These techniques provide an excellent tool for analyzing the amplitude and phase fluctuations of the JAPE data. The results of studies such as those reported here have application at several levels: the mechanisms of signal amplitude and phase fluctuations in propagating acoustic signals are not well understood nor are the mathematical models highly developed, acoustic arrays depend strongly on signal coherence and signal amplitude stability in order to perform to their design specifications and active noise control implementation in regions considerably removed from the primary and secondary sources depends upon signal amplitude and phase stability. Work reported here is preliminary in nature but it does indicate the utility of the phase tracking and amplitude detection algorithms. The results obtained indicate that the phase fluctuations of the JAPE continuous multiple tone data (simultaneous transmission of 80, 200 and 500 Hz) are in general agreement with existing theories but the amplitude fluctuations are seen to be less well behaved and show less consistency.

Rogers, James↗