Elastomeric and Fluidlastic® absorbers are proposed to be embedded in blade cavity to reduce troublesome second harmonic flap-wise blade loads of rigid rotors. A simple model of a blade with a flap-wise dynamic absorber is derived to investigate centrifugal force effects on the absorber's rotating frequency. The system's dynamic equations of motion indicate that centrifugal force has no effect on absorber's frequency under rotation. Aeroelastic simulation of the coupled rotor and absorber system based on an elastic beam model in generalised force formulation is used to explore load reduction extent and dynamic absorber behaviour. At a forward speed of 200 km/h, the elastomeric absorber reduces the second harmonic flap-wise root-bending moment by 88.8% for unacceptably large stroke; the Fluidlastic® absorber reduces the moment by 78.5% with a stroke 4.26% of blade chord length. Results indicate that placing an embedded Fluidlastic® absorber in the blade's flap-wise direction has potential for reducing load in different flight states with relatively small strokes. Increasing tuning port area ratio or Fluidlastic® absorber mass can distinctly decrease strokes without increasing loads. However, deviation from normal rotor speed significantly lowers Fluidlastic® absorber performance.

An experimental investigation was carried out to study the flow development of a jet issuing from a 2:1 rectangular nozzle with mixing tabs using two-component hotwire anemometry. A pair of tabs of trapezoidal configuration (with 2% total blockage area) is placed on the minor-axis side of the rectangular nozzle and tested for two tab inclination angles of 135° and 45°, with respect to the flow direction. Tests were conducted for a nominal jet exit velocity of 20m/sec corresponding to a Reynolds number based on nozzle equivalent diameter of 5·013 × 104. Relative to the plain jet, the jet with tabs show significant reduction in jet-core length (by 67%) followed by a faster decay in jet centreline velocity (U/Ue). This is also accompanied by a significant upstream shift in peak centreline turbulence intensity (u’/Ue). The presence of tabs is observed to inhibit the jet growth along the minor-axis plane thereby introducing large distortion in the jet cross-sectional development that ultimately leads to jet-core bifurcation along its major-axis. While a mushroom-like flow structure develops behind the tab with 135° inclination, the flow structure behind a 45° inclined tab rather takes the shape of the tab itself. The former flow development is seen to enhance the jet growth more along the minor-axis while the latter improves the jet growth more along the major-axis plane. From application point of view, since both tab inclinations result in more or less similar jet characteristics, a 135° inclined tab would be preferable over a 45° inclined tab from the view of improved jet mixing.

This paper presents an integrated design and costing method for large stiffened panels for the purpose of investigating the influence and interaction of lay-up technology and production rate on manufacturing cost. A series of wing cover panels (≈586kg, 19·9m2) have been sized with realistic requirements considering manual and automated lay-up routes. The integrated method has enabled the quantification of component unit cost sensitivity to changes in annual production rate and employed equipment maximum deposition rate. Moreover the results demonstrate the interconnected relationship between lay-up process and panel design, and unit cost. The optimum unit cost solution when using automated lay-up is a combination of the minimum deposition rate and minimum number of lay-up machines to meet the required production rate. However, the location of the optimum unit cost, at the boundaries between the number of lay-up machines required, can make unit cost very sensitive to small changes in component design, production rate, and equipment maximum deposition rate.

I t is perhaps unfortunate, from the point of view of aviators, that the extinct flying reptiles known as “pterodactyls” or “pterosauria” no longer exist. There can be no doubt, that in the case of the more highly evolved members of the group the organisation was more specialised for flight than that of any other animal of which we have knowledge. Other flying animals can walk, run, or swim, besides fly. But in the case of the higher pterodactyls their structure is such that it is difficult to understand how they can have had any other means of progression than flying. With a body little larger than that of a cat they had a span of wing asserted in some cases to have reached 21 feet or more.

The equations showing how to correct for the effect of non-uniformity of the Atmosphere when computing the angle-of-climb (or descent) are well known and can be found in Refs. 1 and 2.

From Ref. 1, a climb at constant Mach number M implies a factor F on the Aircraft Weight to give the true angle-of-climbs (in our units for R) given by the expression

There is at present no thoroughly satisfactory method of measuring accurately the true air speed of an aircraft, particularly at high speeds.

Ground radar can accurately follow a high-speed aircraft but, without the development described here, can only measure the speed of the aircraft relative to the ground. The method developed by the authors makes immediate allowance for wind speed and is capable of giving the true air speed of an aircraft to within one per cent. There is no apparent reason why the method should not be applicable even at very high speeds and there is no limit in aircraft altitude at which the measurement may be made.

The rate of progress in most technical fields, and propulsion is no exception, has increased so rapidly during the past 50 years that it is becoming difficult to predict the trend of development for more than a few years ahead. On the other hand, there are fundamental limits to progress in certain directions and it is within these limits that this paper is written. One must, of course, devote some thought to the validity of the limit. Not so long ago it was thought that the speed of sound would be a limiting speed for aircraft, for instance. One cannot go far wrong with the basic laws of physics and the intention, at least, of this paper is not to transgress such laws.

The problem of fracture characterisation of geometrically complex structures is considered. Numerical and experimental strategies are used to evaluate stress intensity factors and elastic fields for cracked thin shell and plate structures. Theoretical analyses, using different order theories, are also performed in order to evaluate stress and energy distributions in the neighbourhood of the crack tip. A geometrically complex strut component is analysed by using a ‘p-convergent’ finite element code based on hierarchic elements and on the high degree of approximating functions. Actual fracture modes, for different crack locations, have been singled out and the elastic fields are compared to those referring to cracked plate and shell structures. An experimental investigation, using the optical method of caustics, has been also performed and stress intensity factors for several crack configurations have been calculated. The numerical investigations have shown the ability of the p-version finite element method to provide accurate computation of local stress values and to quote the convergence of the numerical calculations. The caustics method has confirmed its accuracy for evaluating stress intensity factors, even for complex structures.

The two parts of this paper summarise the turbomachinery research undertaken at Pyestock during the 50 years since the National Gas Turbine Establishment was formed in 1946. The theoretical and experimental activities are described, and their influence on UK military and civil aero engines is assessed. The way in which NGTE supported non-aeronautical gas turbines is also explained. Part one provides a general introduction and then covers compressors.

You can pick up almost any history of aviation—from the early times to the present—and read of the exploits and adventures of pilots and their planes. Sir Charles Kingsford-Smith and his Fokker, Charles Lindbergh and his Ryan, Amelia Earhart and her Lockheed. We who have technical interests in aviation know that Kingsford- Smith and Lindbergh depended on their Whirlwinds, and Miss Earhart on a Wasp, but the popular stories often fail to make that point.

In more modern times, the engines are equally vital but sometimes get overlooked. Once, when a new jet aircraft was being announced at a press briefing, an airline officer breathlessly described the aircraft, showed artists’ concepts of the cabin and flight deck, and talked at length of the systems and subsystems. After an hour-long description, he called on his audience of reporters, and then he got his come-uppance from an engine man’s point of view. A reporter at the back of the room was recognised, and asked: ‘And what is this aircraft going to be? A glider?’ The by now red-faced official had neglected to mention the powerplants.

We are now, I believe, at a time of crisis in aeronautics and in Great Britain the sense of crisis is made more acute on account of the issue by the Government of the White Paper on Defence for 1957. This paper announces vitally important changes of Government policy which are intimately concerned with aeronautics. For example, the policy is to make the English Electric P.l Supersonic Fighter the last of the manned fighter aircraft in Britain and to concentrate effort in defensive aircraft upon the unmanned guided weapon.

An investigation was carried out to study the parameters affecting single-jet ground-effect hover lift loss and to identify the cause(s) behind the large discrepancies in lift loss between the experiments of Wyatt of RAE Bedford and Corsiglia et alof Nasa Ames. The cause of the discrepancies was traced to a single geometrical parameter: baffle plate edge geometry, which significantly affected the flow separation underneath the plate. In contrast, the out-of-ground lift loss is insensitive to the edge geometry, but can be significantly affected by room size restriction. The investigations have highlighted the importance of accurately representing the edge geometry in ground effect testing of Vstol aircraft, and the importance of the test environment when conducting out-of-ground hover experiments.

The spinning nose dive has confronted the aeroplane designer with two main problems. The first is to evolve an unspinnable aeroplane, and the second to provide controls of sufficient power to ensure an immediate recovery from any spin into which an aeroplane can be forced. At the present time there seems little prospect of achieving a general solution of the first class of problem, although interesting particular solutions have been evolved from time to time. It seems now to be generally accepted that the unspinnable aeroplane would be desirable for every purpose, but it is evident that it must be achieved without sacrifice of performance or manoeuvrability. Moreover, it must be remembered that an imperfect solution of the first class of problem, such as can sometimes be achieved by limiting the power of the control surfaces, may be worse than useless; for the pilot may be deprived of the power to regain normal flight quickly if his aeroplane falls into a spin in unusual circumstances. It is, in fact, very unfortunate that many devices which point the way to the evolution of the unspinnable aeroplane also add to the difficulty of recovery from a spin. It is not my purpose to consider the methods which have been devised to prevent the incipient spin, which occurs when a conventional aeroplane is stalled, but to confine my attention to the problems of ensuring recovery from established spins. For the views expressed I must, of course, accept personal responsibility.

Minitufts are increasingly used for flow visualisation on static wind tunnel models because they can be applied in larger numbers for increased detail and with less interference compared with conventional tufts. This Memorandum describes an extension of their use to continuously rotating models where the heavier conventional tufts are inadequate.

Tests on two combat aircraft models in the 4 m x 2.7 m Low Speed Wind Tunnel are described. Measured variations of rolling moment are explained with the aid of the minituft photographs.

The primary purpose of this note is to draw attention to the powerful influence of Coriolis forces and flapping pin offset on helicopter stability. It is shown that, for a conventional rotor of small offset, the damping in pitch and the flight stability are greatly reduced by the absence of drag hinges, an effect which may explain the use of stabilising bars on the successful helicopters which use this configuration. A “see-saw” rotor without some form of synthetic damping would be very unpleasant to fly by present-day standards.