The flow along the corner formed by two semi-infinite intersecting flat plates is considered in which the corner line is parallel to the streamlines of a uniform incident flow and a uniform suction is applied at the plate surfaces.

A knowledge-based computer system has been developed to automatically scan and interpret graphical displays of vibration data taken from strain gauges mounted on the blades of gas turbines performing acceleration tests. The various characteristic lines which appear on these displays are recognised and classified and the lines representing modes of vibration are examined to determine which mode is being excited and the severity of the excitation. All lines are compared, by a “blackboard” technique, against those predicted by the system working from the engine specification, laboratory tests and finite element analyses. Any unexpected features are reported for manual inspection.

Several series of tests have now been made on the system. In the first test on 130 diagrams, every one of over 3000 features visible to the human eye was detected and then classified.

We must thank Dr. Grzedzielski for the clarification of his argument and notation contained in his second note. Unfortunately, this note only shows more clearly the fundamental misconceptions and errors in his arguments. Our own argument as to the generality and validity of the initial strain concept remains unaffected.

In our previous note, we were concerned to explain the initial strain concept, which Dr. Grzedzielski had criticised as “ an oversimplification not generally admissible “ both in the calculation of thermal stresses and as a device to simulate the effects of structural cut-outs and modifications. Here, we prove independently by a direct consideration of the compatibility conditions in the final structure, that the modified stress distribution given by our analysis is the correct one—regardless of the extent of the coupling in the flexibility matrix.

Due to their high strength to weight ratio, sandwich panels have become increasingly popular in various areas of structural design. This is particularly true with the aerospace industry where high strength low density materials play an important role in the fabrication of major structural components. Along with the continual quest for strong lightweight structures, recent optimisation methods in structural design have led to a re-examination of the validity of the traditional conservative designs based on the usual linear assumptions of structural analysis and tend to adopt more realistic approaches incorporating geometric nonlinearity of the structure by using more exact finite-displacement, strain-displacement equations.

Your contributors on Specific Impulse in the May journal say, “ The mass definition, on the other hand, gives a value of specific impulse which varies according to the units used.“

It must be realised that the value of a quantity cannot depend on the units chosen. To quote therefore the example on page 371 in gravitational units, namely: —

Prior to 1914 there was no night flying proper, as we know it to-day, and therefore, so far as I am aware, there was no night lighting. I must except, of course, the night flying exhibitions which were given at Hendon in this country and at a few places abroad.

In a previous issue of this Journal (Vol. 40, pp.663-680, 1936) Mr. N. J. Hoff has investigated the buckling of an elastically encastred strut. The ingenious method used by Mr. Hoff consists in considering portions of various lengths of a rigidly encastred strut which is in a state of neutral equilibrium under the action of its critical compressive load. This load is also the critical load of an elastically encastred strut whose length is equal to the length of the considered portion, if only the rigidities of encastrement are chosen in accordance with the ratios of the slopes of the neutral axis at the ends of this portion to the bending moments there. The total length of the elastically encastred strut does not enter immediately into the formulae derived by this method, there enter only two lengths x1 and xr whose sum is equal to the total length. These quantities are the distances between the ends of the considered portion of the rigidly encastred strut and the middle of its span.

In recent years, there have been rapid advances in the development of theoretical methods in aerodynamics, particularly for transonic flow calculations. Many papers have been written on this topic. It is however appropriate that there should now be a paper that concentrates not so much on the methods themselves but on the use of the methods for computer-aided design. One could say that the most striking development in the UK in the past two-three years has been that the methods are no longer merely within the preserve of the research establishments; they are being actively used by the aircraft industry in the design of actual aircraft projects. Any air of scepticism about their value has been dispelled. The designers are now appreciating through their own experience that with the aid of a powerful computer and indeed in some cases, a computer of only modest capacity, they can specify a shape for the first wind tunnel model of a new project with much more confidence that the test results will show that the shape is near what is required to achieve their design objectives. It is already being claimed that in this way, the time-scale of the design cycle is being shortened considerably. Also, the computer and the theoretical methods are being used increasingly in the interpretation of the test data. The forecasting of the full-scale characteristics on the basis of the model test data is developing into more of a science and less of an art based on past experience.

Following a brief description of the basic radio aids and the terminology used, the paper discusses in some detail the differences between the original British and American approaches to all-weather landing; the different types of equipment resulting from these two approaches are broadly described. The mixing of ideas which occurred at the IATA Conference at Lucerne in 1963 and the more recent tendency towards a blending of British and American ideas are then discussed, and some predictions are made as to the form of the ultimate all-weather landing system. Certain Australian contributions to display research and the simulation of low visibility in flight are mentioned in context.

The paper concerns a phenomenon which occurs in rows of closely spaced blades, as in an axial flow compressor, when the flow around the blades approaches the stalling condition. Patches of stalled flow can propagate along the blade row, thus causing cyclic variations in the lift on individual blades. Under certain conditions this cyclic loading can lead to large blade stresses, and ultimately to blade failure.

For some years the author has been interested in subsonic ram-jets as a means of helicopter rotor tip propulsion and has done a considerable amount of experimental work with this end in view. Most of the effort has been concentrated on producing engines to operate at the lower end of the speed range as it was thought that, however simple a ram-jet may be, this advantage is lost when other means of propulsion are needed for starting purposes.

A distributed UAV (unmanned aerial vehicle) flocking control method based on vision geometry is proposed, in which only monocular RGB (red, green, blue) images are used to estimate the relative positions and velocities between drones. It does not rely on special visual markers and external infrastructure, nor does it require inter-UAV communication or prior knowledge of UAV size. This method combines the advantages of deep learning and classical geometry. It adopts a deep optical flow network to estimate dense matching points between two consecutive images, uses segmentation technology to classify these matching points into background and specific UAV, and then maps the classified matching points to Euclidean space based on the depth map information. In 3D matching points, also known as 3D feature point pairs, each of their classifications is used to estimate the rotation matrix, translation vector, velocity of the corresponding UAV, as well as the relative position between drones, based on RANSAC and least squares method. On this basis, a flocking control model is constructed. Experimental results in the Microsoft Airsim simulation environment show that in all evaluation metrics, our method achieves almost the same performance as the UAV flocking algorithm based on ground truth cluster state.

A range of quasi-steady and unsteady aerodynamic models are used to predict the aerodynamic forces experienced by a flapping wing and a detailed comparison amongst these predictions in provided. The complexity of the models ranges from the analytical potential flow model to the computational Unsteady Vortex Lattice Method (UVLM), which allows one to describe the motion of the wake and account for its influence on the fluid loads. The novelty of this effort lies in a modification of the predicted forces as a generalisation of the leading edge suction analogy. This modification is introduced to account for the delayed stall mechanism due to leading edge flow separation. The model predictions are compared with two sets of independent experimental data and with computational fluid dynamics (CFD) simulation data available in the literature. It is found that both, the modified analytical model and the UVLM model can be used to describe the time history of the lift force, in some cases with better results than a high-fidelity CFD model. The models presented here constitute a useful basis for the aerodynamic design of bioinspired flapping-wings micro-air vehicles.