N 8 8-1663 0 Comprehensive Rotorcraff Analysis Methods
The paper describes the development and application of comprehensive rotorcraft analysis methods in the field of rotorcraft technology. These large scale analyses and the resulting computer programs are intended to treat the complex a_'.romechanicM phenomena that describe the behavior of rotorcraft. They may be used to predict rotor aerodynamics, acoustics, performance, stability and control, handling qualities, loads and vibrations, structures, dynamics, and aeroelutic stability characteristics for a variety of applications including research, preliminary and detail design, and evaluation and treatment of field problems. The principal comprehensive methods developed or under development in recent year1 and generally available to the rotorcraft community because of US Army Aviation Research and Technology Activity (ARTA) sponsorship of all or part of the software systems are the Rotorcraft Flight Simulation (C81), Dynamic System Coupler (DYSCO), Coupled Rotor/Airframe Vibration Analysis Program (SIMVIB), Comprehensive Analytical Model of Rotorcraft Aerodynamics and Dynamics (CAMRAD), General Rotorcraft Aeromechanical Stability Program {GRASP}, and Second Generation Comprehensive Helicopter Analysis System (2GCHAS). 312 https://ntrs.nasa.gov/search.jsp?R=19880007247 2018-04-23T06:50:56+00:00Z
Substructure program for analysis of helicopter vibrations
A substructure vibration analysis which was developed as a design tool for predicting helicopter vibrations is described. The substructure assembly method and the composition of the transformation matrix are analyzed. The procedure for obtaining solutions to the equations of motion is illustrated for the steady-state forced response solution mode, and rotor hub load excitation and impedance are analyzed. Calculation of the mass, damping, and stiffness matrices, as well as the forcing function vectors of physical components resident in the base program code, are discussed in detail. Refinement of the model is achieved by exercising modules which interface with the external program to represent rotor induced variable inflow and fuselage induced variable inflow at the rotor. The calculation of various flow fields is discussed, and base program applications are detailed.
Livestock Aspects of Feed Grain Policy
It is a signal event that our topic should be included on this program. In recent years, the livestock and poultry economy has scarcely been considered in the making of price and income policy for feed grains. It has been disregarded by pragmatic policy makers. It has been almost equally bypassed by theoretical economists, who usually kibitz freely. Policy for support and target prices for corn, grain sorghums, and other feed grains has been made with an eye almost exclusively fixed on the producers of those crops. The target price has been set relatively high in order to protect crop farmers' income. The latest (and current) loan rate policy has been to hold the rate low. Although a low rate facilitates moving grain into livestock and poultry consumption when crops are abundant, it does nothing to provide buffer stocks for years when crops are short. In addition, a couple of years ago it became administrative policy to dispose of the stocks inherited from an earlier period, even subsidizing their sale abroad. But the foremost example of one-sidedness is the attitude toward release prices. In all the rhetoric heard recently about the peril of holding corn or sorghums in reserve, the scold has been that release prices would not be set high enough. What group can the spokesmen have had in mind? Feed producers, of course! Not feed consumers, that is, livestock and poultry men. It has been a one-sided consideration of a two-sided issue. If all groups are to have equal voice in policy making, how can livestock and poultry interests be so ostracized? The one-sidedness has more impact now that so much livestock and poultry production has become detached from feed supply on individual farms. The livestock-poultry economy is therefore more sensitive to the availability and price of feed. It is in fact a contradiction that historically, livestock and poultry got more attention when they were still closely connected with feed production on the farm. In the early years of farm programs, the "ever-normal granary" was consciously designed to level out the supply and price of feed for livestock and poultry. Now that livestock and poultry have become more commercial and more vulnerable to a volatile feed situation, feed price stabilization has been progressively removed from the councils of farm policy. And the ultimate contradiction is that the alleged price-depressing perils of a feed reserve have been proclaimed in disregard of the fact that the main defense of feed grain producers' incomes is the target price-direct payment mechanism, not support prices. If grains on reserve should cause market prices to be reduced below target level, producers would get bigger direct payments, that is, producers with a base on their farm are protected in that way. Admittedly, production outside such a base would not be eligible for payment.