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Review of Information on Induced Flow of a Lifting Rotor

Description: "A brief review of the available information relating to included flow of a lifting rotor is presented. The available material is summarized in a table as to flight conditions, type of information, source, and the reference papers in which the data can be found. Some representative aspects of some of the reference material are discussed" (p. 1).
Date: August 1954
Creator: Gessow, Alfred
Partner: UNT Libraries Government Documents Department
open access

Equations and Procedures for Numerically Calculating the Aerodynamic Characteristics of Lifting Rotors

Description: "Equations and procedures are presented for numerically determining the aerodynamic characteristics of lifting rotors. The equations are general and can account for stall and compressibility effects, as well as variations in hub and blade configurations, that are normally omitted from conventional analytical rotor treatments. The application of the method to solution by automatic computing machines is discussed" (p. 1).
Date: October 1956
Creator: Gessow, Alfred
Partner: UNT Libraries Government Documents Department
open access

Standard Symbols for Helicopters

Description: "A list of standard symbols for rotating-wing aircraft is presented. The list of symbols is subdivided for ready reference under appropriate headings, the symbols being restricted to those most generally used in studies of helicopter aerodynamics" (p. 1).
Date: June 1948
Creator: Gessow, Alfred
Partner: UNT Libraries Government Documents Department
open access

Effect of Rotor-Blade Twist and Plan-Form Taper on Helicopter Hovering Performance

Description: Note presenting a theoretical analysis of the hovering performance of rotors with various combinations of twist and plan-form taper in order to estimate the effects of blade twist and taper on rotor efficiency in hovering. The calculations were made with the aid of a strip-analysis procedure similar to that used in propeller analysis, the comparisons being made for rotors of equal solidity.
Date: February 1948
Creator: Gessow, Alfred
Partner: UNT Libraries Government Documents Department
open access

Flight Investigation of Effects of Rotor-Blade Twist on Helicopter Performance in the High-Speed and Vertical-Autorotative-Descent Conditions

Description: Note presenting flight-performance measurements made on an untwisted, plywood-covered rotor in the high-speed and vertical-autorotative-descent conditions. The results were compared with measurements on a similar rotor with 8 degrees of linear washout and with theoretical calculations in order to determine the effects of rotor-blade twist on helicopter performance.
Date: August 1948
Creator: Gessow, Alfred
Partner: UNT Libraries Government Documents Department
open access

Charts for estimating tail-rotor contribution to helicopter directional stability and control in low-speed flight

Description: "Theoretically derived charts and equations are presented by which tail-rotor design studies of directional trim and control response at low forward speed can be conveniently made. The charts can also be used to obtain the main-rotor stability derivatives of thrust with respect to collective pitch and angle of attack at low forward speeds. The use of the charts and equations for tail-rotor design studies is illustrated. Comparisons between theoretical and experimental results are presented. The… more
Date: October 27, 1953
Creator: Amer, Kenneth B. & Gessow, Alfred
Partner: UNT Libraries Government Documents Department
open access

Charts for Estimating Performance of High-Performance Helicopters

Description: "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 present… more
Date: November 23, 1955
Creator: Gessow, Alfred & Tapscott, Robert J.
Partner: UNT Libraries Government Documents Department
open access

A Method for Studying the Transient Blade-Flapping Behavior of Lifting Rotors at Extreme Operating Conditions

Description: Note presenting a method for studying the transient behavior of the flapping motion, as well as for calculating the steady-state flapping amplitudes, of free-to-cone and seesaw rotors operating at extreme flight conditions. The method is general and can be applied to blades of any airfoil section, mass distribution, twist, plan-form taper, root cutout, and flapping-hinge geometry.
Date: January 1955
Creator: Gessow, Alfred & Crim, Almer D.
Partner: UNT Libraries Government Documents Department
open access

Charts for Estimating Performance of High-Performance Helicopters

Description: Note presenting theoretically derived charts showing the profile-drag-thrust ratio for a helicopter rotor operating in forward flight and with hinged rectangular blades with a linear twist of -8 degrees. The charts, which show 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.
Date: January 1955
Creator: Gessow, Alfred & Tapscott, Robert J.
Partner: UNT Libraries Government Documents Department
open access

An introduction to the physical aspects of helicopter stability

Description: "In order to provide engineers interested in rotating-wing aircraft but with no specialized training in stability theory some understanding of the factors that influence the flying qualities of the helicopter, an explanation is made of both the static stability and the stick-fixed oscillation in hovering and forward flight in terms of fundamental physical qualities. Three significant stability factors - static stability with angle of attack, static stability with speed, and damping due to a pit… more
Date: November 1949
Creator: Gessow, Alfred & Amer, Kenneth B.
Partner: UNT Libraries Government Documents Department
open access

A Theoretical Estimate of the Effects of Compressibility on the Performance of a Helicopter Rotor in Various Flight Conditions

Description: The effects of compressibility arising from high-tip-speed operation on the flapping, thrust, and power of a helicopter rotor in forward speed are investigated for a particular set of airfoil characteristics. Tip-speed ratios ranging from 0.2 to 0.5 were covered at several tip-speed values.
Date: October 1956
Creator: Gessow, Alfred & Crim, Almer D.
Partner: UNT Libraries Government Documents Department
open access

Analysis of Flight-Performance Measurements on a Twisted, Plywood-Covered Helicopter Rotor in Various Flight Conditions

Description: From Introduction: "In references 1, 2, and 3, flight measurements of the performance of a conventional, single-rotor helicopter equipped with its production fabric-covered main rotor blades are presented."
Date: June 1948
Creator: Gustafson, F. B. & Gessow, Alfred
Partner: UNT Libraries Government Documents Department
open access

An Extension of Lifting Rotor Theory to Cover Operation at Large Angles of Attack and High Inflow Conditions

Description: Note presenting analytical expressions derived for the flapping, thrust, torque, and profile-drag power of a hinged rotor that are applicable to high-speed helicopters and to certain types of convertible aircraft.
Date: April 1952
Creator: Gessow, Alfred & Crim, Almer D.
Partner: UNT Libraries Government Documents Department
open access

Effect of blade stalling on the efficiency of a helicopter rotor as measured in flight

Description: Report presenting performance data on a helicopter rotor in flight over a range of combinations of thrust coefficient and tip-speed ratios, which included combinations intended to result in blade stalling. The study indicated that calculated angle of attack of the retreating tip should be a useful parameter for adequately defining the conditions at which stalling losses set in for a range of combinations of thrust coefficient and tip-speed ratio.
Date: April 1947
Creator: Gustafson, F. B. & Gessow, Alfred
Partner: UNT Libraries Government Documents Department
open access

Charts for Estimating Rotor-Blade Flapping Motion of High-Performance Helicopters

Description: Note presenting theoretically derived charts showing steady-state and first- and second-harmonic flapping coefficients for helicopter rotors with hinged rectangular blades with a linear twist of 0, -8, and -16 degrees. The charts, showing the rotor flapping coefficients for combinations of inflow ratio and blade pitch angle, are presented for tip-speed ratios ranging from 0.05 to 0.50.
Date: March 1956
Creator: Tapscott, Robert J. & Gessow, Alfred
Partner: UNT Libraries Government Documents Department
open access

Supplementary Charts for Estimating Performance of High-Performance Helicopters

Description: "Charts published in NACA TN 3323 for estimating the performance of high-performance helicopters were applicable to rotors having hinged rectangular blades with a linear twist of -8 degrees. Supplementary charts are presented herein covering twists of 0 degrees and -16 degrees" (p. 1).
Date: July 1955
Creator: Tapscott, Robert J. & Gessow, Alfred
Partner: UNT Libraries Government Documents Department
open access

Flight Tests of the Sikorsky HNS-1 (Army YR-4B) Helicopter 2: Hovering and Vertical-Flight Performance With the Original and an Alternate Set of Main-Rotor Blades, Including a Comparison With Hovering Performance Theory

Description: Report discussing testing of an HNS-1 (Army YR-4B) helicopter to determine the hovering data in the ground-effect region and at altitude with an original set of rotor blades and an alternate set with different aerodynamic design and surface condition.
Date: April 1945
Creator: Gustafson, F. B. & Gessow, Alfred
Partner: UNT Libraries Government Documents Department
open access

Effect of Rotor-Tip Speed on Helicopter Hovering Performance and Maximum Forward Speed

Description: Report presenting a study of several sample helicopters in order to evaluate the effect of rotor-tip speed on hovering performance and limiting forward speed. The main purpose of the study was to determine whether hovering performance could be increased by the use of lower tip speeds without undue sacrifice in maximum forward speed. Results regarding typical helicopters, low-solidity helicopters, and high-speed helicopters are provided.
Date: March 1946
Creator: Gustafson, F. B. & Gessow, Alfred
Partner: UNT Libraries Government Documents Department
open access

An introduction to the physical aspects of helicopter stability

Description: In order to provide engineers interested in rotating-wing aircraft, but with no specialized training in stability theory, some understanding of the factors that influence the flying qualities of the helicopter, an explanation is made of both the static stability and the stick-fixed oscillation in hovering and forward flight in terms of fundamental physical quantities. Three significant stability factors -- static stability with angle of attack, static stability with speed, and damping due to a … more
Date: September 19, 1949
Creator: Gessow, Alfred & Amer, Kenneth B.
Partner: UNT Libraries Government Documents Department
open access

Flight Tests of a Helicopter in Autorotation, Including a Comparison With Theory

Description: Note presenting the results of glide performance tests conducted on a test helicopter with its original production blades in the autorotation condition. The data was reduced to coefficient form, and performance at standard sea-level conditions were calculated.
Date: April 1947
Creator: Gessow, Alfred & Myers, Garry C., Jr.
Partner: UNT Libraries Government Documents Department
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