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THE electric current is often compared, especially in “ popular ” works, to the flow of water in a pipe. This conception holds good in certain respects, but is definitely misleading in many ways. The ground engineer who wishes to obtain the “ X ” licence for electrical equipment need not, it is true, make such a close study of the fundamentals of electricity and magnetism as the electrical engineer or science degree student would have to do. Nevertheless, in order to understand the operation and maintenance of electrical apparatus, however simple, some theoretical knowledge is necessary. In electrical work, the beginner is confronted with one special difficulty—the absence of moving parts—and this difficulty seems to be most formidable to men who have been accustomed in their daily work to think in terms of crank‐shafts, gear‐wheels, cams, valves, push‐rods and all the other apparatus of mechanical engineering. To put the situation into a phrase, the beginner wants to “ see the wheels go round,” and is naturally somewhat baffled when he discovers that there are no wheels to go round. Some imagination is, therefore, necessary in studying electrical phenomena, and the student, particularly the engine fitter, must school himself to avoid the futile applica‐tion of well‐absorbed mechanical principles to apparatus in which they have no application.

A PASSENGER or freight‐carrying aeroplane without wireless will come to be regarded in much the same light as a ship without steering gear, and that time is probably not far distant. Wireless is to‐day accepted as being equally essential in air and marine navigation.

IN the previous section chemical methods of producing or storing electrical energy were considered. There is also the possibility of deriving the required electrical energy from some machine which converts mechanical energy into the electrical form. The ground engineer must appreciate that in no case can we get something for nothing, and that the output from the dynamo, plus the losses, does actually come from the engine of the aeroplane. Where the dynamo is wind‐driven, this is still true, the observable connexion being the reduction in the speed of the aeroplane when the dynamo is fitted. In fact, the speed of the aeroplane will vary with the electrical load on the dynamo, other conditions remaining constant, but this variation is too small or too obscured by other factors to be noticeable. In this section, the principles and general properties of the D.C. dynamo will be described.

IN the previous section it was explained how the terminal P.D. of a shunt dynamo can be adjusted manually by means of a field regulator. Although such a device may find a place where large dynamos are concerned, conditions involving a fluctuating load necessitate some form of automatic voltage control. Where a floating battery is used with the dynamo it is further desirable that the dynamo output should be suited to the state of charge of the battery, and again that it should change with every variation of load. While it would be quite possible to make all these adjustments by manual controls, such a scheme is obviously ruled out on motor vehicles and aeroplanes. The basic aim of the automatic voltage controller must, therefore, be to keep the battery fully charged, but the actual achievement of this aim turns out to involve much greater complexity than would be anticipated.

THE ground engineer must be familiar with the ordinary sources of electrical energy used on aeroplanes. For the long‐distance distribution of power on a commercial scale, alternating current is fast becoming universal, but in an aeroplane, of course, no such scheme is possible, and the comparatively small amount of electrical energy which is required has either to be taken up in the form of a storage battery, or else generated on the spot by a wind‐driven or engine‐driven D.C. dynamo. On most commercial aeroplanes of any size, a combination of both battery and dynamo will be found, the battery acting as a reservoir of electrical energy which is kept replenished by the dynamo.

THIS issue of AIRCRAFT ENGINEERING might without excess of exaggeration almost be described as a special number for inspectors and ground engineers—for, indeed, that elusive individual, to whom we have on occasion referred before, the “practical man.”

The aeronautical engineer is all the time struggling to improve aircraft performance. His problem is essentially the attainment of maximum economy—to get the maximum duty out of the material at his disposal. In the field of aerodynamics his progress depends upon the progress of his knowledge of the behaviour of air in a variety of circumstances. In the field of structures it depends upon the exactness of his knowledge of the distribution of stress and strain. In the field of oscillations, where the influences of aerodynamics, structures and inertia combine, he needs the support of the theory of vibration.

ONE of the most troublesome problems associated with the development of rotary‐wing systems in which flapping hinges are utilized to compensate for the aero‐dynamic dissymmetry of forward flight has been the rotational oscillation of the blades. To accommodate the horizontal plane dissymmetry (Fig. 4, Ref. 42) due to flapping, vertical “drag hinges” are usually provided, but an alternating bending moment is produced at the blade root due partly to the displacement of the blade about its drag hinge being out of phase with the displacing moment and partly to the necessity for some form of restraint to prevent instability of the oscillating motion of the blade about this hinge.

Over the next 25 years, STEM (science, technology, engineering, and mathematics) occupations will increase at rates higher than those in any other professional field. The inevitable rise in career opportunities, and the multiplicative impact across technology in a wide range of fields, will continue to create gaps that can and should be filled by professionals with diverse skill sets. It is essential to increase equitable access to future available jobs for historically underserved populations, such as women with autism, as they possess skills and perspectives that offer different approaches to job tasks in STEM fields. Considering the intersectional barriers that women face in the workforce, we have written this chapter to bring much needed attention to the interventions that employers can and should enact to support the women of Generation A. We offer the FACES framework (Facilitation, Awareness, Connection, Exposure, Support) as a guidepost for companies and organizations that endeavor to support women with autism in professional preparation and on-the-job development. We corroborate our framework recommendations with labor market data that offers insight into future projections regarding STEM fields and the associated opportunities and careers.

1. Zinc Zinc was closely linked with copper as a sacrificial partner and because of this relationship an increased use was found for the metal in the 19th century. Around 1838 particular interest was being shown by scientists in the protective power of zinc when in contact with other metals and articles indicate that a scientific appreciation of the principles involved was evident.