Cranfield Institute of Technology - CoA. Aero (1970- 1978)
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Item Open Access High frequency vibration analysis of plate structures(1993-03) Bercin, A,NNoise and vibration are important design issues for many types of vehicles such as ships, cars, and aeroplanes. Structure borne sound, which may be of relatively high frequency, usually emanates from an engine or some other type of localised source and propagates through the vehicle. Excessive vibration levels, and thus structural damage, may occur while structural acoustic interactions may lead to unacceptable interior noise. In the analysis of energy transmission between plate structures, it is common practice to consider only bending modes (or waves) of the structure. However if the concern is with high frequency vibration analysis, then due allowance may need to be made for the presence of inplane shear and longitudinal modes. Due to the infeasibility of the industry standard technique, the Finite Element Method, at high frequencies, almost all of the studies that have investigated the importance of in-plane energy transmission have used Statistical Energy Analysis (SEA). In this study an existing dynamic stiffness method is extended to include in-plane effects, and used as a benchmark against which SEA is assessed. Additionally the Wave Intensity Analysis (WIA) technique, which is an improved form of SEA, is extended to in-plane vibrations, and used to identify some of the reasons for the poor performance of SEA in certain applications. All three methods are applied to a wide range of plate structures within the frequency range of 600 Hz to 20 kHz. While the response levels as predicted by the WIA are generally quite close to exact results, it has been found that although all of the requirements which are usually postulated for the successful application of SEA are fulfilled, SEA severely underpredicts the energy transmission in large structures because of the diffuse wave field assumption. It is also shown that the exclusion of in-plane modes may lead to sizeable errors in energy predictions unless the structure is very simple.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 - 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 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 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 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 - 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.