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Tapscott, Robert J

Publications and source records attributed to Tapscott, Robert J.

13 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS1958

Methods for obtaining desired helicopter stability characteristics and procedures for stability predictions

Part I of this report presents a brief review of methods available to the helicopter designer for obtaining desired stability characteristics by modifications to the airframe design. The discussion is based on modifications made during the establishment of flying-qualities criteria and includes sample results of theoretical studies of additional methods. The conclusion is reached that it is now feasible to utilize combinations of methods whereby stability-parameter values are realized which in turn provide the desired stability characteristics. Part II reviews some of the methods of predicting rotor stability derivatives. The procedures by which these rotor derivatives are employed to estimate helicopter stability characteristics have been summarized.

Gustafson, F B↗
NASA NTRS1956

Studies of the Speed Stability of a Tandem Helicopter in Forward Flight

Flight-test measurements, related analytical studies, and corresponding pilots' opinions of the speed stability of tandem-rotor helicopter are presented. An undesirable instability, evidenced by rearward stick motion with increasing forward speed at constant power, is indicated to be caused by variations with speed of the front-rotor downwash at the rear rotor. An analytical expression for predicting changes in speed stability caused by changes in rotor geometry is derived and constants for use with the analytical expression are presented in chart form. Means for improving stability with speed are studied both analytically and experimentally. The test results also give some information as to the flow conditions at the rear rotor.

Tapscott, Robert J↗
NASA NTRS1956

Charts for estimating performance of high-performance helicopters

Theoretically derived charts showing the profile-drag-thrust ratio are presented for helicopter rotors operating in forward flight and having hinged rectangular blades with a linear twist of 0 degree, 8 degrees, and 16 degrees. The charts, showing the profile-drag characteristics of the rotor for various combinations of pitch angle, ratio of thrust coefficient to solidity, and a parameter representing shaft power input, are presented for tip-speed ratios ranging from 0.05 to 0.50. Also presented in chart form are the ratio of thrust coefficient to solidity as a function of angles of attack, as a function of inflow ratio and collective pitch, and as a function of power and thrust coefficients. The charts in this report are considered more accurate than previous ones for flight conditions involving high inflow velocities and large regions of reversed velocity that may be encountered by high-performance helicopters. The charts may be used to study the effects of design changes on rotor performance and to indicate optimum performance conditions, as well as to estimate quickly rotor performance in forward flight. They are also useful in obtaining inflow-ratio and pitch-angle values for use in calculating flapping coefficients and spanwise loadings. The method of applying the charts to performance estimation is illustrated through sample calculation of a typical rotor-performance problem.

Gessow, Alfred↗
NASA NTRS1955

Note on Hovering Turns with Tandem Helicopters

The source of an appreciable pitching-moment difference between left and right hovering turns for a tandem helicopter is described. The difference in pitching moment results from the difference in rotational speed of the counter rotating rotors with respect to the air while the helicopter is turning.

HELICOPTERS↗
NASA NTRS1954

Studies of the Lateral-Directional Flying Qualities of a Tandem Helicopter in Forward Flight

An investigation of the lateral-directional flying qualities of a tandem-rotor helicopter in forward flight was undertaken to determine desirable goals for helicopter lateral-directional flying qualities and possible methods of achieving these goals in the tandem-rotor helicopter. Comparison between directional stability as measured in flight and rotor-off model tests in a wind tunnel shows qualitative agreement and, hence, indicates such wind-tunnel test, despite the absence of the rotors, to be one effective method of studying means of improving the directional stability of the tandem helicopter. Flight-test measurements of turns and oscillations, in conjunction with analytical studies, suggest possible practical methods of achieving the goals of satisfactory turn and oscillatory characteristics in the tandem helicopter.

Amer, Kenneth B↗
NASA NTRS1953

Studies of the speed stability of a tandem helicopter in forward flight.

Flight-test measurements, related analytical studies, and corresponding pilots' opinions of the speed stability of a tandem-rotor helicopter are presented.An undesirable instability, evidenced by rearward stick motion with increasing forward speed at constant power, is indicated to be caused by variations with speed of the front-rotor downwash at the rear rotor. An analytical expression for predicting changes in speed stability caused by changes in rotor geometry is derived and constants for use with the analytical expression are presented in chart form. Means for improving stability with speed are studied both analytically and experimentally. The test results also give some information as to the flow conditions at the rear rotor.

Tapscott, Robert J↗