Pages From Understanding Aircraft Structures - Cutler
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Chapter 5 The Form of Structures 5.1 Structure relative to aircraft design In the last chapter we looked at the loads which the aircraft has to carry; in this chapter we consider how the structure is arranged to support the loads (or, more exactly, how the structure links the loads to the reactions). Perhaps the most significant thing about a piece of aircraft structure is that it is a compromise. Some years ago an amusing cartoon was printed showing how different people in the aircraft business thought of an aero- plane.To the commercial operator it was a flying box for carrying people or freight; to the avionics engineer it was just a means of getting his radar aerials and navigation aids airborne; to the aerodynamicist it was a slim, shining and beautiful creation with no unsightly access panels or skin joints or rivet heads, not even room for passengers; to the structural engi- neer it was a few simple robust members reminiscent of a railway bridge or a tower crane. Like all good cartoons this was not totally ridiculous. An aeroplane is all of these things but not one thing alone, so compromises have to be made.The structures engineer is constantly compromising with his own requirements; for example, discarding methods or materials which would ideally satisfy one set of conditions but which would be unsuitable for another set, or correcting an apparently satisfactory design which proves to be impossible to manufacture. However, he mainly needs to adjust his ideas to satisfy both the aerodynamicist, who (broadly speak- ing) specifies the external shape of the aircraft, and the payload, that is the passengers, freight or armament, which, together with the fuel, deter- mine the internal dimensions. 5.2 Historic form of structure In the early days of flying the aircraft structure or airframe had almost only one requirement: it was the minimum which the designer (who was probably also the test pilot) thought adequate to keep the wings intact and support the control surfaces and the pilot (see Fig. 2.1). Later, the basic structure was covered with fairing which improved the streamline shape without contributing to the strength (see Fig. 2.3).Wings, of course,
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Transcript of Pages From Understanding Aircraft Structures - Cutler
Chapter 5
The Form of Structures
5.1 Structure relative to aircraft design
In the last chapter we looked at the loads which the aircraft has to carry;in this chapter we consider how the structure is arranged to support theloads (or, more exactly, how the structure links the loads to the reactions).
Perhaps the most significant thing about a piece of aircraft structure isthat it is a compromise. Some years ago an amusing cartoon was printedshowing how different people in the aircraft business thought of an aero-plane. To the commercial operator it was a flying box for carrying peopleor freight; to the avionics engineer it was just a means of getting his radaraerials and navigation aids airborne; to the aerodynamicist it was a slim,shining and beautiful creation with no unsightly access panels or skinjoints or rivet heads, not even room for passengers; to the structural engi-neer it was a few simple robust members reminiscent of a railway bridgeor a tower crane. Like all good cartoons this was not totally ridiculous. Anaeroplane is all of these things but not one thing alone, so compromiseshave to be made.The structures engineer is constantly compromising withhis own requirements; for example, discarding methods or materials whichwould ideally satisfy one set of conditions but which would be unsuitablefor another set, or correcting an apparently satisfactory design whichproves to be impossible to manufacture. However, he mainly needs toadjust his ideas to satisfy both the aerodynamicist, who (broadly speak-ing) specifies the external shape of the aircraft, and the payload, that isthe passengers, freight or armament, which, together with the fuel, deter-mine the internal dimensions.
5.2 Historic form of structure
In the early days of flying the aircraft structure or airframe had almostonly one requirement: it was the minimum which the designer (who wasprobably also the test pilot) thought adequate to keep the wings intactand support the control surfaces and the pilot (see Fig. 2.1). Later, thebasic structure was covered with fairing which improved the streamlineshape without contributing to the strength (see Fig. 2.3). Wings, of course,
