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Investigation of a Stall Deterrent System Utilizing an Acoustic Stall Sensor

Mississippi State University-A. G. Bennett, J. K. Owens
NASA Langley Research Center-R. L. Harris
Published 1977-02-01 by SAE International in United States
A simple rugged acoustic stall sensor which has an output proportional to angle of attack near wing stall has been evaluated on a Cessna 319 aircraft. A sensor position has been found on the wing where the sensor output is only slightly affected by engine power level, yaw angle, flap position and wing roughness. The NASA LRC General Aviation Simulator has been used to evaluate the acoustic sensor output as a control signal for active stall deterrent systems. It has been found that a simple control algorithm is sufficient for stall deterrence.
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High Fuel Economy in an Aircraft Piston Engine When Operating Ultralean

AVCO - Lycoming Division-L. A. Duke
Jet Propulsion Laboratory-J. E. Chirivella, W. A. Menard
Published 1977-02-01 by SAE International in United States
This paper presents the results of Phase II of the Hydrogen Enrichment for Aircraft Piston Engines Program. The overall program, and specifically the Phase I results, have been discussed by Menard et. al.4 previously. In Phase II, a Lycoming TIO-541-E engine was equipped with a gasoline operated hydrogen generator and installed on the dynamometer stand of the experimental facility at AVCO-Lycoming Division. A matrix of lean-out curves at sea level for different spark advances, hydrogen enrichment rates and power levels were obtained. An analysis of these data shows that while the lean-out to very low equivalence ratios with hydrogen enrichment does not present any difficulty, it seems that for certain types of engines one may achieve even better results with gasoline only, if the engine is properly timed. It has been found also that in this ultralean region, power recovery can be achieved by boosting the manifold pressure without exceeding the engine red line temperatures even at relatively high powers. Test cell altitude checks confirm the possibility of utilizing certain ultralean techniques at useful altitudes,…
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The Controlwing Aircraft

Spratt Co. Inc.-George G. Spratt
Published 1977-02-01 by SAE International in United States
A new concept in aircraft control and stability has been developed having greater control effectiveness than the Aileron, rudder, elevator system. It is structurally simple having no movable vanes subject to flutter. There are no stall or spin characteristics. This system has natural gust-alleviation properties and as there are but two primary controls no coordination is needed in piloting.
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Automotive Engines-A Viable Alternative for Aircraft

Geschwender Aeromotive Inc.-John T. Camden
Published 1977-02-01 by SAE International in United States
The current status of automotive liquid-cooled aircraft engine conversions is described with respect to the air-cooled powerplants they replace. A brief historical background is included along with information on some of the most recent applications of automotive engines in aircraft. The gains in efficiency, improvement in performance, and reduction of noise level, vibration, and cost are plus factors to be considered when comparing automotive engine conversions to conventional air-cooled aircraft engines.
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An Inexpensive Electronic Method for Measuring Takeoff and Landing Distances

FAA Central Region Flight Test-F. D. Schick
Published 1977-02-01 by SAE International in United States
The Gates Learjet airplanes are certificated under the F.A.R. 25 Transport Category airplane rules, the same as most other business jets, and all the Jumbos and Wide-Bodied jets. Take-off and landing field lengths must be measured in the certification process and had been measured at Learjet since its beginning with a portable phototheodolite owned by the FAA. The search for a modern replacement for that device progressed through the expensive photographic devices in use currently by the large airplane manufacturers to a relatively inexpensive system; completely electronic, acceptably accurate, and simple to use. The system consists of a Del Norte Technology, Inc., Trisponder for measuring horizontal distance and a Sperry AA-220 Radio Altimeter for measuring height. The outputs of those devices are recorded on a magnetic tape data acquisition system. The data are computer reduced and plotted much faster than any photographic reduction. The only system component which was not in the Gates Learjet inventory at the time was the Trisponder, so the theodolite replacement system was operational for a cost of about $19,000, which…
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The Influence of Design Parameters on Light Propeller Aircraft Noise

Cessna Aircraft Co.-Ronald K. Rathgeber, Douglas E. Sipes
Published 1977-02-01 by SAE International in United States
Through research and test work, the aircraft industry has gained a better knowledge of the design parameters which influence the noise produced by light propeller driven aircraft. The parameters found to have a major affect on the noise include: propeller tip speed, propeller blade tip thickness, and engine exhaust system characteristics. To date, many special design considerations such as geared or shrouded propellers have not proven effective in reducing noise levels. When developing an aircraft for reduced noise, its cost, performance, and utility must be considered.
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Weather Radar for Light Centerline Thrust Aircraft

Cessna Aircraft Co.-Jim Grandfield, Bruce Barrett
Published 1977-02-01 by SAE International in United States
An airborne weather radar installation has been developed for light centerline thrust aircraft. A pod was developed and tested to attach to the underside of the wing and provide a location for a light weight antenna-receiver-transmitter unit. The offering of this installation to operators of these aircraft provides additional capability in the detection and avoidance of significant weather systems.
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Application of Numerical Optimization to the Design of Supercritical Airfoils without Drag-Creep

Ames Research Center, NASA-Raymond M. Hicks, Garret N. Vanderplaats
Published 1977-02-01 by SAE International in United States
Recent applications of numerical optimization to the design of advanced airfoils for transonic aircraft have shown that low-drag sections can be developed for a given design Mach number without an accompanying drag increase at lower Mach numbers. This is achieved by imposing a constraint on the drag coefficient at an off-design Mach number while the drag at the design Mach number is the objective function. Such a procedure doubles the computation time over that for single design-point problems, but the final result is worth the increased cost of computation. The ability to treat such multiple design-point problems by numerical optimization has been enhanced by the development of improved airfoil shape functions. Such functions permit a considerable increase in the range of profiles attainable during the optimization process.
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The Influence of Curriculum on Aerospace Design Decisions

University of Kansas-Howard W. Smith
Published 1977-02-01 by SAE International in United States
Structural design decisions, materials selections, and the choice of analysis methods used in practice are derived from the engineer's education and experience. Details of two new aerospace structural technical elective courses; Composite Materials, and Crashworthiness, are presented to illustrate how new ideas may be introduced into the crowded aero engineering curriculum. Details of some courses in aero structures and materials are presented in the appendix. Close coordination between engineering educators and engineers in practice will result in improved course content, and better design decisions in the future.
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Interior Noise Analysis and Control for Light Aircraft

Columbia University-Rimas Vaicaitis
NASA Langley Research Center-John S. Mixson, C. Kearney Barton
Published 1977-02-01 by SAE International in United States
This paper describes experimental and analytical studies of the interior noise of twin-engine, propeller-driven, light aircraft. Experimental results indicate that interior noise levels due to propeller noise can be reduced by reduction of engine rpm at constant airspeed (about 3 dB), by synchronization of the twin engines/propellers (up to 12 dB), and by increasing the distances from propeller tip to fuselage. The analytical model described uses modal methods and incorporates the flat-sided geometrical and skin-stringer structural features of light aircraft. Initial results show good agreement with measured noise transmitted into a rectangular box through a flat panel.
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