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Aircraft engines need preheating to be able to start without damage in cold weather. It is possible to do this efficiently by placing a small amount of heat in the proper places. An installed electric system is very convenient and easy to use. A good design will be light weight and energy efficient. Corrosion in engines that operate in cold weather can be reduced or eliminated by the right preheater design and the proper operation of the engine. Some designs of preheater systems aggravate other problems. A certain amount of caution is needed in selecting the system. The unit should be specifically matched to the aircraft and engine.

This paper describes research to analyze widespread fatigue damage in lap joints. The particular objective is to determine when large numbers of small cracks could degrade the joint strength to an unacceptable level. A deterministic model is described to compute fatigue crack growth and residual strength of riveted panels that contain multiple cracks. Fatigue crack growth tests conducted to evaluate the predictive model are summarized, and indicate good agreement between experimental and numerical results. Monte Carlo simulations are then performed to determine the influence of statistical variability on various analysis parameters.

Two specific concerns that could affect safety limits for aging aircraft are the effects of corrosion damage and widespread fatigue damage (WFD) on structural integrity. A common joint in fuselage structure is the riveted lap joint, which overlaps two fuselage skin panels. This design creates complex loading conditions that require various analysis methods for accomplishing a durability and damage tolerance (DaDT) analysis. Under an Air Force research project, Boeing evaluated the capabilities of several advanced analysis tools for assessing the effects of corrosion and WFD on the structural integrity of riveted lap joints.

An experimental study was conducted to investigate ice-adhesion on clean and coated aluminum surfaces. A test apparatus using the parallel plate linear shear technique was designed along with a data acquisition system for conducting the tests and recording the experimental data. A low pulling rate was applied to specially prepared test specimens for measuring the strength of ice adhesion for a range of test conditions. The effects of surface roughness, surface contamination, and water impurity on ice adhesion were investigated. In addition, tests were conducted to evaluate the effectiveness of a low ice-adhesion coating applied to aluminum test specimens. The results obtained showed that the bond between ice and metal was considerably lower for tap water than for distilled water. For the clean and coated aluminum surfaces the strength of ice adhesion varied with specimen roughness. However, no clear trend was established between ice adhesion strength and surface roughness.

Ice accumulation on aircraft wings during flight is a dangerous situation. To deal with this problem, current deicing systems either prevent ice accumulation by heating or break the ice layer once it is formed by dynamic motion of a leading edge device such as a boot. These systems may be deficient due to excessive energy requirements or ineffectiveness. In this project, the feasibility of using shape memory alloy (SMA) composite material for deicing purposes is investigated. SMA such as Nitinol wire has an unusual characteristic where it can be trained to generate a compressive strain upon application of an electric current through the wire. Several different versions of two inch radius semi-circular SMA composite specimen were manufactured and tested at Wichita State University. Ice was successfully shed in static icing tests while each of the subsequent versions reduced the power input requirement.

This paper presents a method of detecting aircraft icing by monitoring its effects on aircraft dynamics. This paper shows that uncontrolled icing on control surfaces directly influences control effectiveness. Using data from onboard attitude and navigation sensors via highly computationally efficient algorithms, the control effectiveness is estimated, thereby detecting icing. Using actual flight test data from NASA Lewis Research Center, this paper demonstrates the ability of this method to detect the loss of elevator effectiveness that occurs with uncontrolled horizontal stabilizer icing that could result from a failed deicing boot. The method is generally applicable to loss of control effectiveness due to icing. Icing affects the aerodynamic performance of aircraft by contaminating the aerodynamic surfaces. Without anti-icing equipment icing, if sufficiently severe, can relatively quickly lead to a situation in which controllable flight is impossible.

President Clinton announced in February 1997 a national goal to reduce the fatal accident rate for aviation by 80% within ten years. Weather continues to be identified as a causal factor in about 30% of all aviation accidents. An Aviation Weather Information Distribution and Presentation project has been established within the National Aeronautics and Space Administration’s Aviation Safety Program to develop technologies that will provide accurate, timely and intuitive information to pilots, dispatchers, and air traffic controllers to enable the detection and avoidance of atmospheric hazards. This project, described herein, addresses the weather information needs of general, corporate, regional, and transport aircraft operators.

The study of piston aircraft engines with the propeller mounted as the load has been restricted due to the equipment needed to measure the combination of instant engine torque and vibrational movements. This work details the development of an engine mount that has a torque sensitivity of less than 0.05 pound-feet for measuring horsepower, vibration forces, and torque. The hydraulic force measurement system used in the project is discussed and evaluated with the limitations encounter. A torque balance system that can be checked with primary weights for absolute accuracy was developed and described as well as the methods for determining instant vibrational forces and rotational stresses.

This paper describes the final chapter of the military specifications for aviation piston engine lubricants. The adoption and evolution of the Society of Automotive Engineers (SAE) Standards J1966 and J1899 from their initial development in 1991 to the present is reviewed. It includes the fine-tuning and revisions of the technical requirements derived from experience gained in qualification programs conducted. Also included are notes regarding the overall commercial oil qualification process and the remaining role of the U.S. Navy for military use approvals

Aerospace manufactures purchase millions of drill bits each year for the manufacture of large aircraft structures. This paper describes an ongoing research project for the development of an automated system to detect poor quality drill bits before they are put to use.

Drilling is one of the most widely applied manufacturing operations. Millions of holes are drilled today in manufacturing industries especially in aerospace industry where high quality holes are essential. Rejection and rework rate of the products because of the bad hole is quite high. In this research graphite/honeycomb composite material and aluminum sheet metal has been used. The results show that drill geometry, speed and feed rate have substantial effects on the hole quality and also there was gradual variation of the thrust and lateral forces with feed rates.

In-situ high speed photographic observations through transparent ceramic cutting tools have been used to observe the dynamic contact interactions at the chip-tool interface while cutting commercially pure copper under a range of cutting speeds and rake angles. Under all conditions it is observed that the chip slides over the rake surface of the tool close to the cutting edge. Under low cutting speeds some chip material is transferred to the tool where the chip curls out of contact with the tool in the form of a fairly thick deposit. At higher cutting speeds a fine layer of chip material is transferred to the tool closer to the cutting edge and the thick deposits formed at lower speed are removed. The tendency for deposition is decreased as the rake angle is decreased. In all cases the dynamic nature of the cutting process and the slow evolution of the deposition are clearly evident.

During full body fatigue testing, an aircraft wing spar initiated a crack from a rivet hole and crack growth data was obtained unique to the test spectrum loading. Fatigue testing of the 7050-T73511 spar material was used to obtain crack growth rate data and variable amplitude fatigue crack growth tests were performed on specimens fabricated from the spar material. Calculated results were in excellent agreement with these experimental results. A layered analysis of the adhesively bonded spar showed that the stress intensity in the lower cap was approximately constant, independent of crack length. When the constant stress intensity is used in a variable amplitude fatigue crack growth analysis, there is good correlation between the predicted and observed crack growth rates.

This paper describes a methodology to simulate multistage sheet metal forming with intermediate heat treatments and its application to the three stage forming of an engine nacelle inlet lip. This capability has been validated by comparing results of finite element simulations for plastic strains at various points in the sheet with values obtained experimentally using the strain circle technique.

A new implementation of the vortex step method for predicting subsonic propeller blade aerodynamic loading is described. The analysis, taking advantage of the classical work by Rankine, Betz, and Glauert, also accounts for the effects of an axisymmetric nacelle in both the vector boundary condition and Glauert velocity diagram. Wake-induced velocities are examined, including effects of wake extent and “observer” position. A certain “equivalence” is demonstrated for the classical results of Betz, Glauert, Goldstein and Theodorsen for the optimum-wake-induced velocities. The effects of wake continuity and rollup are studied, relative to a simple helical wake. Thrust loading calculations are compared to NACA wake-pressure-derived test data. Rationale and methods for geometry “math modeling” are shown and illustrated. Finally, geometric and aerodynamic models are integrated for the preliminary design of a new propeller.

A cooperative project between the Federal Aviation Administration (FAA) Civil Aeromedical Institute (CAMI), Applied Safety Technologies Corp. (ASTC), and Robert A. Denton, Inc. was conducted to investigate modifications to the standard Hybrid III anthropomorphic test dummy (ATD) lumbar spine and its interface to the pelvis and thorax. The impetus for this project was based on the desires of aviation researchers, manufacturers, and dynamic test laboratories to utilize the Hybrid III ATD in the development and certification of aircraft seats. The goal was to develop a lumbar spine modification for the Hybrid III that would produce similar responses to those measured with a Hybrid II. The primary focus of this project was the compressive force measured at the base of the lumbar column during the vertical test condition required by FAA’s regulations.

It is common to develop extensive dynamic models for new equipment early in the design stage. While dynamic characteristics are often determined from impulse, step, and sinusoidal inputs to the models, the actual response of the equipment will be a response to inputs made by the human using control levers, knobs and switches. The work described here is the use of a robot manipulator that allows the human to provide natural motion and force inputs to the simulated dynamic system and to use the response to evaluate the performance of the system and controls. A heavy lift assist device is used as the test system here, where an operator grasps handles attached to the lifting jaws, and uses a large partially powered mechanism to provide load support. The kinematic and dynamic model of this system are derived and programmed to provide the expected system output in response to human motion and force inputs.

The success of mobile construction machinery owes a great deal to the proper use of hydraulic power. Hydraulic power systems are usually configured with a positive displacement hydraulic pump. Different work functions require a variety of hydraulic flow and pressure values to provide the desired operations. System branches, therefore, must include a variety of specialized flow and pressure regulating valves. The correct configuration of these valves can be accomplished by building and testing variations of a valve until desired conditions are achieved. However, since machinery build programs are expensive; the use of mathematical modeling of a fluid power component is often well worth the time required to establish the model. Use of the model to study the operation of a component will then lead to fewer hours of shop testing. This example discusses the design and mathematical model of a pressure control valve that provides priority to selected circuits on a mobile machine.

A Generalized Predictive Kinetic Energy Controller (GPKEC), which has been previously developed, is implemented to control the machine tool vibration in a lathe turning process. The control variable, tool feed, is computed using acceleration feedback through the GPKEC algorithm. The feed is controlled by attaching a high torque/low inertia permanent magnet DC servomotor to the main feed rod through a high performance timing belt. Experiments are carried out for a number of cases. The system identification of the overall machining process is done on-line and precedes the control action. Accelerometers have been used to sense the vibration signal in the feed direction. The experimental results show that GPKEC can effectively suppress the chatter vibration in a single point turning process, even in presence of an appreciable change in the dynamics of the process. GPKEC has also been observed to be robust against step disturbances.

Electron beam (EB) welding process is characterized by an extremely high power density that is capable of producing weld seams which are considerably deeper than width. Unlike other welding process, heat of EB welding is provided by the kinetic energy of electrons. This paper presents a computational model for the numerical prediction of microstructure and residual stress resulting from EB welding process. Energy input is modeled as a step function within the fusion zone. The predicted values from finite element simulation of the EB welding process agree well with the experimentally measured values. The present model is used to study an axial weld failure problem.