Engineering topics

Crane, Harold L.

Publications and source records attributed to Crane, Harold L..

6 records

NASA NTRS1965

Low-Speed Flight Characteristics of a Powered-Lift Jet Transport During the Landing Approach

A flight-test program to determine the flight characteristics of large jet transports equipped with powered-lift systems indicated the following results: Speed margins appear to be primarily related to power-on stall speeds. At these speed margins, the maneuver margins were adequate and did not appear to be a problem or limiting factor during powered-lift operation. No large detrimental effects on handling qualities were apparent but in some areas stability augmentation would be required to obtain satisfactory flight characteristics. Use of the powered-lift airplane would result in a sizable increase in the noise levels; these increases are primarily the result of higher engine power settings in the approach.

Schade, Robert O.↗

NASA NTRS1961

Effects of Control-Feel Configuration on Airplane Longitudinal Control Response

A general study of longitudinal control feel was made with a transonic fighter-type airplane equipped with a control-feel system which 4 was adjustable in flight. The control-feel system provided a feel component with individual gain control in proportion to each of five quantities: stick deflection, stick rate, airplane normal acceleration, pitching acceleration, and pitching velocity. A number of feel configurations were investigated in flight and analytically. These feel configurations had feel components in various amounts from various combinations of these five sources. The results contained herein are all for an airplane center-of-gravity position at approximately 25 percent of the mean aerodynamic chord, a Mach number of 0.85, and an altitude of 28,000 feet. Results are presented as time histories, as plots of the variation of peak force per g with input duration, and as frequency-response plots. A number of frequency-response plots are included to illustrate the effects of choice of feel sources and gains. The results illustrate the desirability of balancing a normal-acceleration feel component with a pitching-acceleration feel component. Pitching-velocity feel is shown to be useful for shaping control-system frequency response. The results suggest the desirability of designing a control-feel system to a large extent by means of frequency-response analysis in order to keep the shapes of the frequency-response curves within desirable limits.

Crane, Harold L.↗

NASA NTRS1961

Analog-Computer Investigation of Effects of Friction and Preload on the Dynamic Longitudinal Characteristics of a Pilot-Airplane Combination

With an electric analog computer, an investigation has been made of the effects of control frictions and preloads on the transient longitudinal response of a fighter airplane during abrupt small attitude corrections. The simulation included the airplane dynamics, powered control system, feel system, and a simple linearized pseudopilot. Control frictions at the stick pivot and at the servo valve as well as preloads of the stick and valve were considered individually and in combinations. It is believed that the results which are presented in the form of time histories and vector diagrams present a more detailed illustration of the effects of stray forces and compensating forces in the longitudinal control system than has previously been available. Consistent with the results of previous studies, the present results show that any of these four friction and preload forces caused some deterioration of the response. However, even a small amount of valve friction caused an oscillatory pitching response during which the phasing of the valve friction was such that it caused energy to be fed into the pitching oscillation of the air-plane. Of the other friction and preload forces which were considered, it was found that stick preload was close to 180 deg. out of phase with valve friction and thus could compensate in large measure for valve friction as long as the cycling of the stick encompassed the trim point. Either stick friction or valve preload provided a smaller stabilizing effect primarily through a reduction in the amplitude of the resultant force vector acting on the control system. Some data were obtained on the effects of friction when the damping or inertia of the control system or the pilot lag was varied.

Crane, Harold L.↗

NASA NTRS1961

A Longitudinal Control Feel System for In-Flight Research on Response Feel

An adjustable feel system connected to the longitudinal control system of a transonic fighter airplane has been developed and has been evaluated in flight. Variable control feel including response feel is provided from the following five sources: control position, control rate, normal acceleration, pitching velocity, and pitching acceleration. This system provides a very flexible tool for more detailed study of longitudinal control feel characteristics than has previously been possible. The evaluation program for the variable-feel system yielded flight time histories which illustrate effects on the stability of airplane and control-system response modes of large amounts of response feel. These results illustrate the need for balancing the amounts of feel from normal acceleration and pitching acceleration to maintain the stability of the short-period and control-system modes. At the frequency of the short-period mode, large amounts of normal-acceleration feel cause the control system to oscillate and excite the airplane short-period mode of oscillation. At the same frequency the pitching acceleration component of feel, which leads the normal-acceleration component by 180 deg, is almost equivalent to viscous damping on the stick. However, at slightly frequencies the lag of the response-feel components increases by 90 deg or more so that a large pitching-acceleration component excites an oscillation of the control system at 4 cycles per second. These results by confirming and supplementing the conclusions of previous observers indicate that the adjustable feel system is operating properly.

Faber, Stanley↗

NASA NTRS1948

Preliminary Results of an Investigation by the Wing-Flow Method of the Longitudinal Stability Characteristics of a 1/50-Scale Semispan Model of the McDonnell XP-88 Airplane

This paper presents the results of measurements of longitudinal stability of a 1/50-scale model of the XP-88 airplane by the wing-flow method. Lift, rolling-moment, hinge-moment, and pitching-moment characteristics as well as the downwash at the tail were measured over a Mach number range from approximately 0.5 to 1.05 at Reynolds numbers below 1,000,000. No measurements of drag were obtained. No abrupt changes due to Mach number were noted in any of the parameters measured. The data indicated that the wing was subject to early tip stalling; that the tail effectiveness decreased gradually with increasing Mach number up to M = 0.9, but increased again at higher Mach numbers; that the variation of downwash with angle of attack did not change appreciably with Mach number except between 0.95 and 1.0 where d(epsilon)/d(alpha), decreased from 0.46 to 0.32; that at zero lift with a stabilizer setting of -1.5 deg there was a gradually increasing nosing-up tendency with increasing Mach number; and that the control-fixed stability in maneuvers at constant speed gradually increased with increasing Mach number.

Crane, Harold L.↗

NASA NTRS1948

Longitudinal Stability Characteristics of a 1/40-Scale Model of a Proposed Configuration of the XF-91 Airplane Measured by the Wing-Flow Method

This report presents the results of an investigation in the transonic speed range of the longitudinal stability characteristics of a proposed configuration for the Republic XF-91 airplane. The tests covered a Mach number range of 0.55 to 1.05 and a Reynolds number range from 400,000 to 1,375,000. Lift, pitching-moment, and rolling-moment characteristics of the half model and the hinge moments on the all-moving tail were measured. The downwash factor delta x epsilon / delta x alpha at the tail was determined from the pitching-moment data. A calculation of the elevator deflection and stick force required for trim was also made. It was found that the variation of force and moment coefficients was linear through the test angle-of-attack range of -1 deg to 8 deg at any Mach number; that the stability increased markedly at Mach numbers above 0.85; that the effectiveness of the tail in producing pitching moments decreased about one-third with increasing Mach numbers and that the value of the downwash factor, delta x epsilon / delta x alpha, at the tail decreased from about 0.35 at a Mach number of 0.85 to about zero at a Mach number near 0.95 and became slightly negative at higher Mach numbers. The calculated values of stick force per g and elevator deflection per g, assuming no aerodynamic balance, increased rapidly above a Mach number of 0.85.

Crane, Harold L.↗