Search Results

The Navy is engaged in programs to reduce the visible smoke emitted by gas turbine engines. These programs include the use of alternate fuels, the use of smoke suppressant fuel additives, and the use of combustor design technology. The current status in each of these areas is presented, as is a review of previous investigations. Tests of alternate fuels have shown that a significant but inadequate reduction of smoke was obtained. Of the fuel additives tested, one additive has shown superior performance to the others, and is suitable for use in certain engines. In order to determine the potential smoke reduction possible through combustor design, the combustion system of several engines is being redesigned. Some of the results of the redesign programs are discussed. Also presented is a brief description of the most commonly used methods of smoke measurement.

The measurement of the smoking characteristics of jet engines and jet engine components is necessary to evaluate the relative merits of proposed methods of smoke reduction, identify sources, and estimate the visibility of the exhaust plume. Several techniques have been employed by the General Electric Co. to collect data over a wide range of environment. Techniques evaluated included optical systems, quantitative gravimetric system, and soiled tape methods. Many of the soiled tape methods of measuring smoke are compared, and a calculation procedure is described for making a direct comparison of any two soiled tape methods. The soiled tape method used by General Electric to measure jet engine smoke is described in detail. The measurement system utilizes a GE spot meter which filters the smoke through Whatman paper and produces a smoke number that is based upon the diffuse reflection from the filtrate produced by filtering 0.3 cu ft of smoke through a square inch of filter paper.

The main forms of atmospheric pollution by gas turbine exhaust are smoke and oxides of nitrogen at top speed and unburned fuel and carbon monoxide at engine idle conditions. Smoke trails constitute a visual nuisance and the other contaminants are either toxic or irritant or both. Combustor design with improvements in fuel air mixing and the use of air assisted sprayers will reduce smoke to barely visible levels on future engines. In addition, the latest annular chambers will give reduced concentrations of unburned fuel and carbon monoxide. Oxides of nitrogen will be difficult to reduce but current concentrations are less than measured on the automobile.

The fuel vapor conditions that may exist in aircraft fuel tanks and their relative flammability characteristics are very complex. These complexities result from the infinite conditions that may be produced by aircraft motion, atmospheric changes, and the multicomponent nature of turbine fuels. The objective of this investigation, which was sponsored by the FAA, was to define the effects that these many variables might have on fuel tank flammability, especially when considering turbulent flight conditions. By means of instrumental techniques which were developed primarily for this study, the equilibrium flammability characteristics were then compared to those which were conducted under simulated aircraft dynamics. It was determined that spraying fuel droplets into the tank vapor space by vibration can cause marked changes to the normal equilibrium flammability characteristics of turbine fuels.

Pollution emissions due to jet aircraft operations at the major commercial airports in the New York Metropolitan Area were estimated. The impact on air pollution of the region was assessed. Pollutants considered in this report were: carbon monoxide, nitrogen oxides, hydrocarbons, aldehydes, and particulates.

Results of experimental testing show that smoke can be significantly reduced by increasing the amount of air admitted to the primary zone. However, the location of the air entry ports, manner of air injection, and fuel spray quality are critical factors. Significant changes in combustor stability, ignition, carbon deposition, and durability characteristics are affected by the alteration of the primary zone fuel and airflow pattern. Extensive work has also been required to develop smoke measuring systems. A modified Von Brand Filtering Recorder has been selected as the standard measuring system.

This paper discusses some of the factors which give rise to the need for continuing surveillance against fatigue in the field of aircraft maintenance. The subject is presented in relation to the limitations of statistically significant data on fatigue producing forces in some areas, and the problem of scatter in fatigue behaviour of structures. Finally, the applications of various non-destructive inspection techniques are discussed.

Past airline maintenance practice has been to purchase or sometimes build special required test equipment for the various avionics units to be checked in the airline facility. This is time consuming and expensive because the tester is not universal in nature. A new trend, automatic test equipment, a more general purpose piece of test gear, is being introduced into use by airlines and manufacturers. This paper discusses some reasons why it is becoming a necessity, and highlights problem areas in its implementation and use under actual airline shop conditions during the past year.

Factors which the powerplant designer must consider in the choice of engine location are discussed, including the basic cowling and its influence on accessory disposition and pod aerodynamic performance, the engine mount, engine piping, and H.P. air ducting. A design proposal to integrate the engine and powerplant structure in order to achieve low weight and high thrust with minimum dimensions is discussed. The reliability of civil transport engines is affected by stage length. An analysis of Rolls-Royce turbojet and turbofan experience shows a distinct relationship between premature removal rate and stage length which provides a basis of comparison for engines in different operations. No such relationship has been found between shutdown rate and stage length.

The Pratt & Whitney Aircraft 43,500 lb thrust turbofan engine will power the Boeing 747 large commercial transport airplane. The JT9D engine is a two-spool, high bypass ratio engine with outstanding performance, high thrust to weight, and low noise levels. This advanced technology gas turbine engine represents a major step in improved maintainability through the use of simplified structural design and unit component construction which will substantially reduce assembly and disassembly time and, in turn, facilitate on-the-wing maintenance. Provisions for borescope or radioisotope inspection, along with improved monitoring of engine parameters, will facilitate installed engine condition monitoring.

New approaches to problems such as noise, temperature control of accessories and equipment in the nacelle, as well as improved safety features, are necessary in a modern high by-pass engine installation. The means of supporting the engine, cowling design, and maintainability features combine to improve the state of the art that a more economic airplane will result.

The Rolls-Royce family of large high by-pass ratio engines has resulted from a long study aimed at providing the optimum compromise between first cost, operating cost, weight, and noise level for the new generation of subsonic civil transport airplanes. This paper considers the design approach applied to some aspects of reliability, failure detection, and rectification in these engines and also the mechanical implications of some noise-suppression features.

Development of structural beryllium technology at McDonnell comprising both hardware and study programs is discussed, including wing-box structures, F-4 and SST rudders, F-4 brakes, and crack propagation and damage tolerant design evaluations. Impediments to a more extensive use of beryllium are discussed and areas requiring further study and development defined.

The C-5A propulsion system installation is described and discussed. Induction system, exhaust system, and thrust reverser configurations define the general nacelle concepts. Installation features of the various subsystems, including the air bleed, engine starting, and fire protection systems are discussed. Installation requirements which are influenced by the high bypass ratio, short duct, turbofan engine configuration are noted and discussed. Where significant, comparison is made with requirements for an assumed long duct configuration. Special emphasis is placed on cooling and venting. Accessibility and maintenance features are also highlighted in the discussions.

A new product, “diffusion bonded structures,” is now available for utilization by aircraft designers for application to air transport aircraft. This new product is fabricated by an old proved joining process called solid-state diffusion bonding. This joining process has been used over the centuries and is currently being successfully utilized in the manufacture of aircraft landing gears. This same process can now be applied to the manufacture of titanium structures to new sizes and structural shapes. The aircraft designer can now arrange the material he requires in the location he desires and have his design manufactured with current technology. These structures, when tested, fail without any regard to the location of the joint, and in some applications fail at loads higher than those achievable with current material forms due to improved material properties.

An extension of the Cleveland Transit System rapid transit line is under way. This paper details studies that have been made on potential airport-to-city riding and on the feasibility of transporting cargo. It further outlines the passenger-carrying possibilities and suggests the usefulness of the rapid transit in tying together other modes of transportation. A detailed description of the extension of the system to the airport is included, covering stations along way, passenger comfort, potential usage, and future expansion.

Economic forecasts predict a vast expansion in the use of air transportation for cargo movement. Planning must begin now for airports, terminals, scheduling, air traffic control, etc., to meet this expansion. Also needed are new generation all-cargo aircraft, automated loading systems, intermodal delivery coordination, containerization. These elements are discussed in detail, in relation to meeting the needs of all users of air transportation (passengers, cargo, general aviation). All factors are part of the decision to develop aircraft and systems to carry cargo.

This paper presents an answer to the ground barrier problem. Studies have defined problems in the following areas: maximum terminal capacity, internal roadway systems, automobile parking, freeways and access roads, airfreight, and noise. To find solutions to the above problems, a satellite system of airports has been developed which will smooth out the interfaces with all other forms of transportation for people and commodities, and will disperse the volumes entering the system. In our satellite airport system studies, the Metroport, with short elevated runways capable of handling the new vertical and short take-off aircraft, has evolved. An elevated rail, and in some cases a subway system, travelling clear of ground congestion will be a vital link in the transportation network. The Los Angeles satellite airport concept is one of the best answers to bringing air transportation to all sections of the metropolitan areas.

The newly developed Coordinating Research Council oxidation test technique for aircraft gas turbine engine lubricants has been evaluated by a “round-robin” test program. With few exceptions, the participants rated the test oils in the same order by each of the stability criteria. Reproducibilities of the test criteria (percent viscosity increases, neutralization number increases and corrosivities to metals) are considered satisfactory. Information based on test and statistical data suggested revisions in the test procedure that would reduce test variables and further improve reproducibilities.