CoA. Aero Reports (1953-1969)
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Item Open Access The double and single shear strengths of avdel light alloy blind rivets in DTD 546 b aluminium alloy sheet(College of Aeronautics, 1957-04) Lempriere, B. M.Tests have been performed to compare the double- and single-shear strengths of joints in DTD 546b light alloy sheets using Avdel blind rivets. The tests were an extension of work done on solid rivets, and followed conventional procedures. The double-shear proof and ultimate strengths were found to be appreciably better than the single-shear strengths over a useful range of sheet thickness/rivet diameter ratio. The effect of manufacturing tolerance was examined and found to be important, though adherence to the rivet manufacturer’s recommended procedures ensures good strength. The above conclusions lead to a consideration of the physical behaviour of the joints which is seen to differ in three ranges of thickness/diameter ratio.Item Open Access The interference of a rearward facing jet on the flow over three representative afterbody shapes in a uniform subsonic flow(College of Aeronautics, 1957-04) Craven, A. H.This report contains the results of an experimental investigation into the interference of a ,rearward facing undeflected jet on the flow over three afterbody shapes at subsonic speeds. The tests were performed at a Reynolds number of 0.3 x 10(6) based on body diameter. It was found that the form (or pressure) drag coefficient of the bluff afterbody of a right cylinder increased appreciably with increase in jet thrust coefficient. A similar but much smaller increase in form drag was found on an ellipsoidal afterbody and a 'boat-tail'. The effect of the jet was found to extend to approximately three body diameters upstream of the jet exit but that beyond one body diameter the effect was very small.Item Open Access A note on the machinability of ultra high tensile steel(College of Aeronautics, 1957-01) Purcell, J.The requirements of this investigation were to determine optimum tool geometry and cutting conditions for turning Ultra High Strength Alloy Steel (fully heat treated to 120 tons per sq.ins.). The material will be used for bolts, whose screw threads will be produced by thread rolling. Dimensional accuracy required on the blanks is 0.0002". The material in the above state presents extremely severe conditions, especially on the nose of the turning tool, and results in rapid wear and loss of dimensional accuracy. Application of cutting coolants or lubricants made no measurable improvement on tool nose wear, benefits gained from the use of coolants being confined to reduction of flank wear.Item Open Access Production, employment and productivity in the United Kingdom, 1948-55(College of Aeronautics, 1956-10) Harris, J. T.Production movements are analysed statistically according to the contribution of changes in, productivity within industries and activities, employment, and the re-distribution of employment between industries and activities, both singly and in combination. When applied in turn to the Index of Gross Domestic Product and the index of Manufacturing Production for the period 1948-55, the main contributors to increased output are seen to be improved productivity and higher employment levels. The Index of Gross Domestic Product increased by 27% during the period, the main contributors accounting for 67% and 22% of the value respectively. In the case of Manufacturing industry they accounted for 57% and 32% respectively, of the 42% increase in output. Significantly, a11 of the increase in employment went into manufacturing industries. The movements for the individual broad groups of industries and activities contributing to the indices were very varied so that a relatively small section of the economy accounted for a large proportion of the overall increase in production and productivity.Item Open Access Double shear strength of B.S.L.69 snap head rivets in L.72 and L.73 aluminium alloy sheet(College of Aeronautics, 1956-07) Howe, D.A limited series of tests has been carried out on single and double shear riveted joints using 1469 (D.T.D.327) snap head rivets and L.72 (D.T.D.610) and L.73 (D.T.D. 546) sheets. The specimens were similar to those used by the Royal Aeronautical Establishment (ref.1), the double shear specimens being essentially two single shear specimens placed back to back. In each case the 1 per cent, 2 per cent and ultimate strengths were found, the single shear values being in agreement with the equivalent R.A.E. tests (ref. 2). It was found that at high bearing stresses the permissible shear stress in the double shear joint falls below that of the single shear joint having the same nominal bearing stress, This reduction of permissible shear stress was found to increase with joint extension and to be independent of the sheet materials tested. Design curves are given.Item Open Access A note on some equipment used for boundary layer measurements in flight. Part 1, the design and construction of a large multitube manometer for use in flight. Part 2, two fixed head type combs for boundary layer investigations(College of Aeronautics, 1956-07) Burrows, F. M.Some notes are presented relating to the design and construction of a large multitube manometer and to two 'fixed head' type boundary layer combs to be used for the measurement in flight of the boundary layer characteristics of a swept back wing. Although the equipment described was designed with a particular object in view, there is no reason why the designs should not be modified as and where necessary for the construction of similar equipment.Item Open Access Four papers contributed by members of the staff and published on the occasion of the 10th anniversary of its foundation(College of Aeronautics, 1956-11) College of Aeronautics, (Cranfield)THE kinetic heating associated with supersonic flight produces temperature gradients within the aircraft structure. These in their turn are responsible for so-called 'thermal stresses' in the components. The calculation of these effects falls into two stages. The first stage consists in the application of the theory of heat transfer to obtain the history of the temperature distribution in the structure. The second stage uses this data to obtain distributions of stress within the structure, resulting from these imposed temperature gradients and proceeds to assess their influence on strength and stiffness. The present paper is concerned entirely with this second stage of the problem and derives basic formulae for the analysis of beam-like structures and components. The results can be applied to wings, fuselages, etc., on the one hand, and to linear reinforcing members like stringers and longerons on the other, in the same way as the usual theories of bending and torsion are applied in the isothermal case. The formulae obtained in this paper represent a generalization of the so-called engineering theory of bending and of the Wagner-Kappus torsion theory to include the effects of non-uniform temperature distribution. Kinematically, allowance is made for overall longitudinal extension, for curvature in two principal planes, for twist and for cross-sectional warping of the kind occurring in Saint Venant's torsion theory. Relationships between end load, bending moments and torques on the one hand and the kinematic parameters on the other are obtained, in a manner modelled on that of Ref. (1), by means of a 'Principle of Stationary Free Energy' established by the present writer in Ref. (2). These results, when combined with the well-known equilibrium equations for bending and torsion, constitute a complete theory of the problem under consideration. Applications to problems of stress analysis are indicated.Item Open Access Aircraft design studies: variable sweepback naval aircraft(College of Aeronautics, 1967) Howe, D.A preliminary survey of the possible applications of variable sweepback indicated that a substantial improvement in performance can be expected when the concept is applied to a naval strike aircraft. In order to assess this performance gain and to obtain experience of the engineering problems involved, the subject of the design study 'ay the students in the Department of Aircraft Design during the 1964 academic year was chosen to be a variable sweepback naval strike aircraft. The aircraft has a maximum take off weight of 60, 000 lb. and a limiting Mach number at altitude of 2. 5. Various payloads up to a maximum of 4000 lb. can be carried externally over ranges which vary up to 4000 n. miles according to the role. Alternative mechanical arrangements for the wing hinge system were investigated.Item Open Access Aeroplane design studies: bpropeller turbine and pure jet powered general purpose transport aircraft (academic years 1963 and 1965)(College of Aeronautics, 1967-05) Howe, D.The recent interest in the air bus conception of air travel is reflected in the aircraft chosen for study by the students in the Department of Aircraft Design during the 1963 and 1965 academic years. The first study was based upon the use of four propeller turbine engines to power an aircraft capable of carrying up to 40,000 lb. of payload over short stage lengths. Emphasis was placed on the need for operations with mixed passenger and freight loads and the fuselage layout incorporates two decks, the lower one of which is designed as a freighthold with nose loading doors. The second study was similar except that four wing mounted pure jet engines replaced the propeller turbines of the earlier design. The cruising speed is thus some 50 per cent higher with a Mach number limitation of 0.8. The two deck fuselage layout is retained, but with a rear loading door for the freighthold, and the wing has 28° of leading edge sweepback . An initial economic comparison of the two aircraft revealed that when the aircraft are operated over 250 n. mile stage lengths the direct operating costs of the propeller turbine powered design are some 20 per cent less than those of the pure jet version. This is mainly due to the much lower first cost of the simpler aircraft.Item Open Access Aeroplane design studies mach 2.2 and mach 3.0 supersonic airliners (academic years 1960 and 1962)(College of Aeronautics, 1965-02) Howe, D.This report is divided into three parts. The first two of these describe the A-60, Mach 2.2 airliner and the A-62, Mach 3.0 airliner design studies respectively. Apart from the different cruise speeds these two aircraft were designed to meet the same basic requirements and the third part of the report is a comparison of them. The Mach 2.2 design was based upon the use of a slender, integrated, delta layout with six turbojet engines buried in the rear fuselage. It was intended to carry up to 120 passengers over transatlantic ranges. Although the chosen engine installation enabled a compact aircraft to be designed it did introduce severe structural and installation difficulties. A canard delta arrangement was proposed for the Mach 3.0 aircraft. Drooping of the wing tips for supersonic flight was found to confer important stability advantages without introducing an unacceptable weight penalty. The steel structure was designed around the use of both corrugated reinforced and honeycomb sandwich skins, the former being preferable. An interesting feature was the choice of a sealed, cryogenic, environmental control system. This was found to be very attractive but as it proved to be somewhat heavier than anticipated it is suggested that a good compromise could be obtained by using a more conventional system for subsonic flight phases. The major conclusion from the comparison between the two study aircraft was that in many respects there is very little to choose between them. However the Mach 2.2 aircraft represents a more logical step from existing airliner designs and presents fewer materials problems. As it is comparable economically it represents a better choice for a first generation supersonic design.Item Open Access Aeroplane design studies conventional and V.T.O.L. freighter aircraft (Academic Years 1959 and 1961)(College of Aeronautics, 1963-11) Howe, D.During the second year of their course in the Department of Aircraft Design, students have the option of working as a member of a team engaged in a design study. The subjects for the studies are chosen to represent the current interests of the industry and include unusual features considered to be worthy of investigation. Examples of these design studies are the F-59 freighter and its derivative the F-61, V. T.O. L. freighter. In a conventional role these designs are intended to carry a payload of up to 77000 lb. , over 800 nautical miles range, using four turboprop engines. V. T.O. L. capability is given to the F-61 design by the addition of two wing pods, each of which houses 22 lift engines. The application of boundary layer control in the form of blown ailerons and flaps has been investigated for the F-59 design. Both aircraft have been designed in detail. The major conclusion of the studies is that the application of V. T.O. L. to large freight aircraft is feasible, but further detailed work is necessary to resolve some flutter and noise problems.