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Sternfield, Leonard

Publications and source records attributed to Sternfield, Leonard.

At least 19 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS1958

A simplified method for approximating the transient motion in angles of attack and sideslip during a constant rolling maneuver

The transient motion in angles of attack and sideslip during a constant rolling maneuver has been analyzed. Simplified expressions are presented for the determination of the pertinent modes of motion as well as the modal coefficient corresponding to each mode. Calculations made with and without the derivatives for side force due to sideslip and lift-curve slope indicate that although these derivatives increase the total damping of the system they do not markedly affect the transient motion.

Sternfield, Leonard↗
NASA NTRS1955

Simulator studies of the attack phase of an automatically controlled interceptor

The attack phase of the automatically controlled interceptor is studied in two parts. Part I is a limited simulation conducted to specify the lateral and longitudinal control systems for an automatic interceptor. The results are presented as Nyquist plots and time histories of the airplane variables. Part II uses the control systems developed in Part I, together with a dynamically perfect guidance system, to study the effect of the nonlinear terms in the complete equations of motion and nonlinear aerodynamics on the airplane response. The results are presented as time histories of the airplane and control surface motions.

CONTROL, LONGITUDINAL↗
NASA NTRS1951

A theoretical analysis of the effect of time lag in an automatic stabilization system on the lateral oscillatory stability of an airplane

A method is presented for determining the effect of time lag in an automatic stabilization system on the lateral oscillatory stability of an airplane. The method is based on an analytical-graphical procedure. The critical time lag of the airplane-autopilot system is readily determined from the frequency-response analysis. The method is applied to a typical present-day airplane equipped with an automatic pilot sensitive to yawing acceleration and geared to the rudder so that rudder control is applied in proportion to the yawing acceleration. The results calculated for this airplane-autopilot system by this method are compared with the airplane motions calculated by a step-by-step procedure.

Sternfield, Leonard↗
NASA NTRS1951

Some effects of nonlinear variation in the directional-stability and damping-in-yawing derivatives on the lateral stability of an airplane

A theoretical investigation has been made to determine the effect of nonlinear stability derivatives on the lateral stability of an airplane. Motions were calculated on the assumption that the directional-stability and the damping-in-yawing derivatives are functions of the angle of sideslip. The application of the Laplace transform to the calculation of an airplane motion when certain types of nonlinear derivatives are present is described in detail. The types of nonlinearities assumed correspond to the condition in which the values of the directional-stability and damping-in-yawing derivatives are zero for small angle of sideslip.

Sternfield, Leonard↗
NASA NTRS1950

Effect of an Autopilot Sensitive to Yawing Velocity on the Lateral Stability of the Douglas D-558-II Airplane

A theoretical investigation has been made to determine the effect on the lateral stability of the Douglas D-58-II airplane of an autopilot sensitive to yawing velocity. The effects of inclination of the gyro spin axis to the flight path and of tire lag in the autopilot were also determined. The flight conditions investigated included landing at sea level, approach condition at 12,000 feet, and cruising at 50,000 feet at Mach numbers of 0.80 and 1.2. The results of the investigation indicated that the lateral stability characteristics of the D-558-II airplane for the flight condition discussed should satisfy the Air Force - Navy period-damping criterion when the proposed autopilot is installed. Airplane motions in sideslip subsequent to a disturbance in sideslip are presented for several representative flight conditions in which a time lag in the autopilot of 0.10 second was assumed.

Gates, Ordway B., Jr.↗
NASA NTRS1949

A simplified method for the determination and analysis of the neutral-lateral-oscillatory-stability boundary

A necessary condition for neutral oscillatory stability is that Routh's discriminant r, formed from the coefficients of the stability equation, is equal to zero. Computations obtained from rsub1=0 and d=0 show very good agreement with the results calculated by the expression for r=0. The nature of the modes of motion as a function of the directional-stability derivative and the effective-dihedral derivative is discussed in detail.

Sternfield, Leonard↗