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A technique is proposed for examining complex behaviors in the “pilot - vehicle - operational conditions” system using an autonomous situational model of flight. The goal is to identify potentially critical flight situations in the system behavior early in the design process. An exhaustive set of flight scenarios can be constructed and modeled on a computer by the designer in accordance with test certification requirements or other inputs. Distinguishing features of the technique include the autonomy of experimentation (the pilot and a flight simulator are not involved) and easy planning and quick modeling of complex multi-factor flight cases. An example of mapping airworthiness requirements into formal scenarios is presented. Simulation results for various flight situations and aircraft types are also demonstrated.

This paper describes a series of ongoing experiments to capture the details of perpendicular vortex-airfoil interaction. Three test cases explored are: 1) a 21% thick symmetric airfoil at 1.1° angle of attack, 2)a thin flat plate of 2.5% thickness with rounded leading edge, sharp trailing edge and zero angle of attack and 3) A 12% thick symmetric airfoil at zero angle of attack. The tip vortex was generated by a NACA0016 wing at 5° AOA. The strength of the vortex was computed from the velocity profile measured upstream for the first two cases. Pressure measurements on the 21% airfoil were used to quantify the effect of the vortex as a function of its stand-off distance from the airfoil. Vortex trajectories over the airfoils were obtained from laser sheet videography. The vortex motion conforms to potential flow expectations except in regions of pressure gradient and during head-on interaction.

This paper outlines work performed by the Aeronautical Systems Division of the Aerospace and Transportation Laboratory at the Georgia Tech Research Institute (GTRI). The paper provides limited, but pertinent information relative to the technical viability of a tiltwing configurations as civil powered-lift aircraft. Emphasis has been placed on identifying the complexity differences with tiltrotor and helicopter configurations. Complexity differences normally impact both acquisition and/or operating and support costs, although specific cost estimates are not presented.

An evolving aircraft synthesis simulation environment which offers improvements to existing methods at multiple levels of a design process is described in this paper. As design databases become obsolete due to the introduction of new technologies and classes of vehicles and as sophisticated analysis codes are often too computationally expensive for iterative applications, the design engineer may find a lack of usable information needed for decision making. Within the environment developed in this paper, rapid sensitivity analysis is possible through a unique representation of the relationship between fundamental design variables and system objectives. The combined use of the Design of Experiments and Response Surface techniques provides the ability to form this design relationship among system variables and target values, which is termed design-oriented in nature.

The growth of international markets as well as business partnerships between U.S. and Asian-based firms has lead to an increased interest in an economically viable business jet capable of supersonic cruise and trans-Pacific range with one stop over (or non-stop trans-Atlantic range)1. Such an aircraft would reduce the travel time to these regions by as much as 50% by increasing cruise Mach number from roughly 0.85 to 2.0. In response to this interest, the 1996 AIAA / United Technologies / Pratt & Whitney Individual Undergraduate Design Competition has issued a Request for Proposal for the conceptual design of a supersonic cruise business jet. The design of this aircraft considered both performance and economic issues in the conceptual design phase. Through the use of Response Surface Methodology (RSM) and Design of Experiments (DoE) techniques, the aerodynamics of this vehicle were modeled and incorporated into an aircraft sizing code, FLOPS.

The desire of achieving faster cruise speed for rotorcraft vehicles has been around since the inception of the helicopter. Many unconventional concepts have been considered and researched such as the advanced tilt rotor with canards, the tilt-wing, the folding tiltrotor, the coaxial propfan/folding tiltrotor, the variable diameter tiltrotor, and the stopped rotor/wing concept, in order to fulfill this goal. The most notable program which addressed the technology challenges of accomplishing a high speed civil transport mission is the High Speed Rotorcraft Concept (HSRC) program. Among the long list of potential configurations to fulfill the HSRC intended mission, the stopped rotor/wing is the least investigated due to the fact that the existing rotorcraft synthesis codes cannot handle this type of vehicle. In order to develop such a tool, a designer must understand the physics behind this unique concept.

Cutter runout has been a target for monitoring and control of machining processes in view of the constraint it places on the achievable productivity. Off-line metrology based on various displacement probes such as dial indicators or proximity sensors provides information regarding the runout characteristics in a non-cutting state. However, during the actual process of machining off-line calibrations often become irrelevant since the cutting parameters and machining configuration significantly affect the behavior of runout. This paper presents a methodology of in-process identification of cutter runout in end milling based on the analysis of cutting forces. The presence of cutter runout generates cutting force components at one spindle frequency above and below the tooth passing frequency.

Previous work on the cooling jackets of the Cummins L10 engine revealed flow separation, and low coolant velocities in several critical regions of the cylinder head. The current study involved the use of detailed cooling jacket temperature measurements, and finite element heat transfer analysis to attempt the identification of regions of pure convection, nucleate boiling, and film boiling. Although difficult to detect with certainty, both the measurements and analysis pointed strongly to the presence of nucleate boiling in several regions. Little or no evidence of film boiling was seen, even under very high operating loads. It was thus concluded that the regions of seemingly inadequate coolant flow remained quite effective in controlling cylinder head temperatures. The Cummins L10 upon which this study has focused is an in-line six cylinder, four-stroke direct injection diesel engine, with a displacement of 10 liters.

The quantification of aircraft survivability in modern battlefield environments is a complex mathematical problem. In general, consideration must be given to the quantification of aircraft vulnerability to individual weapon systems, single encounter aircraft survivability, and the mathematical mapping of single encounter aircraft survivability into mission attrition. A methodology for quantifying the impacts of electronic warfare (EW) upon aircraft survivability is realized by the General Effectiveness Methodology (GEM) which is based upon a hierarchy of computer models. This paper describes this hierarchy of computer simulation tools which extensively employs probability theory to estimate the various engagement events such as aircraft detection, acquisition, missile launch, missile intercept, and probability of aircraft kill.

A procedure is developed for evaluating various candidates for thermal control in the orbiting space station. Candidates for acquisition, transport and rejection are considered. For example, thermal rejection candidates include heat pipe radiators, high capacity heat pipe radiators and liquid droplet raditors. A computer program has been developed which computes subsystem and total system weights, volumes, powers and costs for a system consisting of selected acquisition, transport and rejection candidates. The program user is also able to select mission parameters such as duration, resupply interval, thermal loads, transport distance, acquisition temperature and rejection temperature. Simulation models are included in the program which allow the user to change candidate designs. For example, for a high capacity heat pipe radiator the user may change working fluid, materials, radiator temperature, radiator geometry, surface emissivity and surface absorptivity.

The characteristics of cordierite type compositions and the relationship between thermal expansion and raw materials, processing, and gross composition are examined. Other possible support materials are reviewed briefly. These include mullite, zircon, beryl, spodumene, aluminum titanate, silicon nitride, and other low expansion compositions. Raw material cost, processing, and reactivity with the catalysis are discussed for these materials.

The present use of the carburetor to supply fuel to the Otto cycle engine has placed it in a difficult competitive position with the diesel engine, which has successfully operated with a fuel injection system. The purpose of this study was to consider the feasibility of utilizing a low pressure injection system for the Otto cycle engine. The proposed design is discussed in detail. As the author points out, this system will allow design changes in the engine that would be impossible if the carburetor were retained, and thus considerable improvement in performance and efficiency can be realized for the Otto cycle engine.