Browsing by Author "Howe, D."
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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.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: 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 study STOL airliner (A71). Part 1- configuration description and data(Cranfield Institute of Technology, College of Aeronautics, 1972-06) Howe, D.; Ward, R. E.The interest in STOL airliners was reflected in the choice of a 100-118 passenger short range aircraft of this type as the 1971 design project. In addition to the use of the study for detailed investigation by the students of Aircraft Design it also served as the basis for an investigation of the low speed lift and control problems of STOL aircraft. This report is concerned with a description of the configuration adopted and specification of geometric and aerodynamic data. As such it is the first part of the complete reporting of the investigation, subsequent parts being concerned with the more detailed work. The aircraft was designed to operate from 2000 ft long single runways and have a cruising speed of up to 11 - 0.83 at 30,000 ft altitude. The estimated gross weight is 115,000 lb and when landing at 100,000 lb weight the approach speed is 79 knots. The high lift coefficients necessitated by this are obtained either by externally blown jet flaps or an augmenter wing arrangement.Item Open Access Aeroplane design study STOL airliner (A71). Part 2- detail design features(Cranfield Institute of Technology, College of Aeronautics, 1972-07) Howe, D.This report is concerned with a description of the detail design features of the A71 project study. This aircraft is an airliner designed for operation off single 2000 ft long runways. The overall description of the design and its aerodynamic characteristics are contained in Part I of the report (Ref.1). The detail design of the structure and systems is conventional in most respects. The need to provide a long stroke undercarriage for STOL operations incurred a large weight penalty and it is concluded that further work is necessary to establish acceptable requirements for this type of undercarriage. A separate investigation (Ref.3) has shown that the aircraft does not meet its stipulated design objectives due to an inability to cope with engine failure and gusting cross wind conditions. A study to investigate the potential of the cross-coupling of adjacent powerplants to mitigate engine failure control problems suggests that the weight penalty is not justified (Ref.-).Item Open Access Aircraft design optimisation conceptual evaluation of a three-lifting surface turbo-fan airliner(Cranfield University, 1995-02) Basto Nunes, J. M.; Howe, D.Today's high competitiveness in the airline industry urges for the development of even more efficient transport aircraft. In many cases lower operating costs are the key to survival. Although the introduction of emerging advanced technologies has shown improvements both in safety levels and performance, with the associated reductions in costs, the search for more economical aircraft must also take into consideration changes in current design practice. The study of novel configurations is a contribution to this view. In this research project, advantage was taken from multidisciplinary synergism to design and optimise conventional and three-surface configuration commercial aircraft, to satisfy the same mission and operational requirements. An integrated conceptual design synthesis approach was employed where typical aeronautical disciplines, as well their complex inter-relations, were taken intoaccount. All these considerations, together with both cruise and field performance, and static stability and control requirements, resulted in different baseline configurations of the two concepts, although sharing the same fuselage and the same technology standard, but with different Maximum Take-off Weights (MTOW), lifting surfaces, turbo-fan engine sizes, and economics. After coupling the design synthesis program to a gradient based numerical minimization routine, optimisation of these designs was performed for minimum Direct Operating Costs (DOC) and minimum MTOW, and their performance and economics were compared on an equal basis. Trade-off studies were conducted on all aircraft for 1000 through 3000 NM design mission ranges while keeping the same fuselage size, lifting surface planform shapes and same static longitudinal stability margin (inherently stable designs), as obtained for the respective datum designs (Range = 1250 NM). Thus, using the same comprehensive design tool, built on the same primary assumptions, and using the same analytical methods and principles which include many real life considerations, a systematic and conýistent study of both design concepts was conducted. The potential merits of a realistic three-surface transport design were clearly established, when comparison was made with an equivalent mission conventional twin turbo-fan airliner. Within the usual limitations of any initial conceptual design study, it appears that the concept of the three-lifting surface transport can effectively improve in terms of performance and direct operating costs, when compared to conventional aircraft designed for the same operational environment and mission profiles, and may show a promising future.Item Open Access Aircraft design studies - counter insurgency aircraft with suction boundary layer control(Cranfield Institute of Technology, College of Aeronautics, 1970-04) Howe, D.A design study of a counter insurgency aircraft with a suction boundary layer controlled wing to give high lift has been undertaken. The work was carried out by the students in the Department of Aircraft Design during the 1966 academic year and was intended to provide evidence on the feasibility of the configuration employed. The aircraft has a gross weight of 9800 lb. and is designed to carry a variety of payloads of up to 2000 lb. at a maximum speed of 380 m. p. h. The flight usable lift coefficient of five is achieved at an incidence of approximately 30 o which introduced particular layout and undercarriage problems. A twin boom configuration with a variable geometry undercarriage was adopted. It is concluded that the use of a suction boundary layer control system can confer significant performance benefits but the aircraft might well be handicapped by climatic operational limitations. The variable geometry undercarriage is complex and an alternative layout using a tilt wing might be preferable.Item Open Access Aircraft design studies - E67 tilt-wing executive aircraft(Cranfield Institute of Technology, College of Aeronautics, 1973-08) Howe, D.The E67 design was for a vertical take off and landing aircraft for executive use. Vertical flight capability was achieved by using the tilt wing concept. In the initial version of the design power was provided by two Rolls Royce H1400 Gnome turbo shaft engines driving two 16 ft. diameter propellers. Cross shaft interconnection between the propellers was included in the layout. Subsequently the need for four engines to cater for an engine failure condition in vertical flight became apparent. The pressurised cabin was designed to accommodate up to 18 passengers in a high density feeder role. Conventional design techniques were used throughout. A market survey showed that the design had significant advantages relative either to a helicopter or a twin jet executive type (Reference 3).Item Open Access Aircraft design studies - vertical take off and landing airliner(Cranfield Institute of Technology, College of Aeronautics, 1972-05) Howe, D.During the 1970 academic year the students in Aircraft Design worked on the design of a vertical take off and landing airliner. The aircraft is intended to be capable of carrying up to 118 passengers over stage lengths of 500 n.miles. The maximum cruise speed is Mach 0.83 at an altitude of approximately 20,000 ft and the predicted take off weight is 125,000 lbs. Vertical take off is achieved by using 12 fan lift engines, each of 1.500 lb thrust, which are based on the Rolls Royce RB 202 design. The lift engines are housed in two large nacelles which are mounted on the high, sweptback wing. The installed thrust/weight ratio of 1.4 makes allowance for hot and high operation, control requirements, and lift engine failure. An unusual feature of the design is the location of the two propulsion engines on either of the vertical fins. Some indication was gained of the penalties associated with this type of aircraft, but the weighing of these against the realisable advantages was outside the scope of the work.Item Open Access Aircraft design studies: S68 multi-role strike aircraft(Cranfield Institute of Technology, College of Aeronautics, 1975-08) Howe, D.The 868 aircraft design study was for a multi-role strike aircraft with a variable sweepback wing. The study was undertaken as the result of experience gained in a previous investigation of a naval strike aircraft, the 864 (Ref.1). The more recent design was for a land based aircraft intended to be capable of fulfilling strike, interception and search roles. The design take off weight was 50,000 lbs and the normal maximum speed condition was Mach 2 at altitude although a short dash to M 2.5 was catered for. An internal bay was provided for the carriage of various combinations of stores. Side by side seating was adopted for the two crew members and some difficulty was experienced with the structural layout of the fuselage and the design of the main undercarriage because of this.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 Analysis of two-cell swept box with ribs parallel to the line of flight under loading by constant couples(College of Aeronautics, Cranfield, 1953-03) Howe, D.The method of oblique co-ordinates is used to analyse the problem associated with the strength and deformation of a uniform, rectangular, two- cell swept box beam having ribs parallel to the line of flight. The case of loading by constant couples is considered, but no account of root effects is taken. Continues…Item Open Access An approximate solution to the swept wing root constraint problem(College of Aeronautics, Cranfield, 1956-02) Howe, D.This report presents an approximate solution to the problem associated with the root constraint in a swept wing.Item Open Access Composite faced sandwich construction for primary spacecraft structures(Cranfield University, 1989-09) Slade, R.; Howe, D.This study investigated the application of fibre reinforced composite materials to spacecraft sandwich structures. In particular, aspects of the manufacture, analysis and design optimisation of components fabricated using the co-cure process were studied. The manufacturing process was developed to ultimately enable a full size thrust tube structure to be built using a single step cure, the design of which was verified by a modal survey test. Techniques for the analysis of stiffness, strength., vibration frequencies and local instability were established and found to correlate well with tests on co-cured sandwich specimens. The current wrinkling theory for composite faced sandwich was extended to the more general case to allow facesheet constitutive matrix coupling and multiaxial loding to be accomodated. The analytical methods were incorporated within simple optimisation schemes, amenable to employment at the preliminary design stage, to allow alternative feasible designs for panel and thrust tube structures to be generated. These illustrated the benefits of the use of composite materials and the co-cure manufacturing technique for spacecraft sandwich components.Item Open Access Design considerations of future short haul transport aircraft(Cranfield University, 1976-05) Howe, D.The rapid escalation of air transport in the past two decades has resulted in difficulties associated with airport congestion and ground trip delays. These have been particularly acute for short haul operations. Suggestions have been made that they might be alleviated by the use of smaller airfields located nearer to population centres than existing large airports which operate aircraft specifically designed for the purpose. This paper reports a systematic investigation of the requirements, design parameters and performance characteristics of short haul transport aircraft. Designs intended for operation- in the VTOL, STOL, RTOL or CTOL modes have been considered and compared in an attempt to predict the more promising prospects for the future. A number of specific design studies were used as the basis for the comparison of the weight, economic and noise characteristics of the aircraft concepts which fall into the categories investigated.Item Open Access Design of aerobatic aircraft wing(Cranfield University, 1969-05-19) Potter, J. G.; Howe, D.The aircraft under consideration in the following text is a swing wing, 50,000 lb. (maximum weight), land based strike aircraft. The various roles of the aircraft are strike operations at a Mach number of 2.0 and height 36,000 feet or Mach number of 0.9 at low level, interceptor operations at a Mach number of 2.0 with a, dash at a Mach number of 2.0 and search and patrol operations at a Mach number of 0.76 and a height of 36,000 feet (with wings unswept). Design of the aircraft was split into several sections each one being investigated by a different student. The section analysed in this report being the forward-centre fuselage. This lies between the rear sloping pressurised bulkhead of the cockpit to the aft bulkhead of number two fuel tank. Time did not allow for the design of all the structural parts but detailed studies were conducted on two different frames (one light fabricated and one heavy machined), the nose undercarriage bay, two sections of fuselage cross-section, and the variable geometry bullet including aerodynamic loading in the intake. A sample fatigue calculations were done on a fuel tank and nose undercarriage together with a complete weight breakdown for the forward-centre fuselage (several approximations being made 'for undersigned structure). From the loading calculations the critical cases defined that the structure in this section of the fuselage was designed on the manoeuvres and landing cases. Use of Concorde material (aluminium alloy) RR. 58 was used wherever possible because of temperature effects in the high speed configuration. However, for some of the view heavily loaded members steel had to be used (with the appropriate temperature reduction factor applied to the allowable stresses) to keep the volume of material to a minimum.Item Open Access Design Project 1974/75 A 74 Aircraft Elevator Design.(Cranfield University, 1975-05) Mani Abraham, P.; Howe, D.; Tetlow, R.; Ward, R. E.Part 1 of this thesis contains the symmetric loading calculations and evolution of the design of elevator for the A 74 Reduced Take off and landing aircraft. Part 2 contains the analysis of final design of elevators. The aircraft is designed to the specifications of DES 7400 and satisfies the British Civil Airworthiness Requirement. A 74 project aircraft has longitudinal control from the tail plane and elevator combination. Tail plane is used for trimming and elevators for pitch controls. All control surfaces are hydraulic power operated. The tailplane uses an inverted supercritical section. The elevator is a four piece arrangement with duplicated hydraulic actuator system. It is of round nose type and the elevator hinge line is at 0.6 C. perpendicular to the aircraft centre line. As elevators are fully power operated mass balancing is not provided. Section 5 in part 1 gives the schemes considered in the design of elevator leading to the final choice of each major part. Section 6 gives the description of final design. Elevator is made of conventional built up construction using Aluminium alloy L 72 sheets and L 65 forgings. Part 2 gives the detailed stress analysis of the final design in accordance with normal aircraft design practise.Item Open Access A design study for a compound helicopter featured with a convertible prop/rotor(Cranfield University, 1989-10-30) Mostafa, A.; Howe, D.A compound helicopter is a hybrid vehicle, fundamentally a helicopter. It uses an auxiliary lift and propulsion device(s) in order to eliminate the lifting rotor high speed limitation of retreating blade stall effects, thus allowing flight characteristics comparable in many respects to those of fixed-wing aircraft. The primary objective of this thesis was to perform a design study investigating the validity of the concept of compounding, then selecting and designing a shaft-driven single compound helicopter intended for use as a ground support and anti-tank VTOL aircraft. The selection included a complete parametric and sizing analysis which were based on three defined maj or mission requirements: a maximum forward speed of 250 knots; payload of 1500 lb and cruising endurance of 3 hours at 225 knots. Of the many configurations studied, a single-rotor compound helicopter featured with convertible tail prop/rotor was found to be the most suitable for the intended application. Stability/control characteristics and performance capability of the designed aircraft were found to meet or exceed military specifications and flying quality requirements. structure, dynamics and cost analysis were considered to be beyond the scope of the design study.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 The employment of jet V-STOL aircraft at sea(1981-01) Kinch, M. J.; Howe, D.The means by which the Royal Navy will continue to operate fixed-wing aircraft at sea is by employing VTOL or· given an aid to-take-off, STOVL aircraft. The aid being ' brought into service is -the Skijump, which permits a large increase in payload over unassisted VTOL. The effectiveness of skijump increases with its exit angle up to about 40°, but other considerations of size and ungainliness set a practical lim~tation nearer to 20°. The endspeeds required for ballistic launch off a skijump could be achieved or-enhanced by the use of assistance by catapult or rocket motor. Both of these would call for the initiation of programmes of full research and development, while the skijump, capable of conferring. equivalent performance if it is long enough, already exists. The· smallest number of aircraft in an airgroup able to keep up a useable flying task is three. A vessel big enough to mount three aircraft together with the gear necessary to support and arm them would be big enough to mount a skijump as well. Its size is dictated too by the sea conditions in which it is expected to keep operational. The vessel in question should be a displacement ship, either conventional (e.g. large frigate) or unconventional (e.g. Small Waterplane Area Twin Hull). There is no role here for either hovercraft or hydrofoil. Commitment to the skijump.in the ship means commitment to vectored-thrust as a means of propulsion in the next aircraft~ When specified it must be compatible with existing skijump decks, and it should be single-engined. Its targets for Reliability and Maintainability mµst be wholly related to the Availability called for, and must be given equal prominence with performance.