Submerged intakes are widely used on aircraft as a means of supplying internal flow systems with ambient air. It is the purpose of this note to show by analysis of existing experimental data that the boundary layer at the location of the submerged intake can have an appreciable effect on its performance.

Information here relates to the NACA type of divergent submerged intake with a ramp angle, a, of 7° and an aspect ratio, w/d, of 4 because this particular combination of planform and geometry is now almost universally used.

The bird hazard to aircraft at Auckland International Airport, Mangere, NZ (Lat 37° 00’ 30” S, Long 174° 47’ 30” E) is examined. Geographical features affecting the hazard are explained and the history of the hazard recounted, and the groups and component species of birds, their daily movement patterns and seasonal abundances discussed. The greatest potential danger is from the waders, but gulls are the greatest actual danger possibly because gulls live irregular, opportunistic lives in comparison with the strict, tide-governed existence of the waders. An analysis of the bird incident figures for a year tends to confirm this view, in spite of the comparative rarity of incidents.

Measures taken or projected against the birds are reviewed. Special reference is made to unorthodox methods—the provision of alternative high water roosting sites, experiments with a radio-controlled model simulating the hawk shape, and the use of gull corpses as scaring agents. While worthwhile reductions have been made to the hazard, continued work and constant vigilance is necessary.

The force on a plane wire screen at right angles to the axis of a fully-developed, turbulent and effectively two-dimensional and incompressible jet has been determined. This study was suggested by the use of perforated surfaces in the operation of aircraft. Perforated landing and takeoff pads are used to reduce adverse ground effect, and the re-ingestion of burnt gases, on VTOL aircraft with centrally-located, downward-pointing jets. Perforated baffles are occasionally used to attenuate jet speeds during ground testing of conventional jet aircraft. The study is also relevant to a process in the making of paper. The pulp and water mixture is deposited on a moving screen (Fourdrinier wire), and the jet approaches the screen at an oblique angle.

In recent years a number of authors have analysed the bending of clamped skew plates under uniform pressure. Many of these solutions are very approximate. Favre and Dorman adopted the Ritz method and their expressions for displacement are restrictive. Based on the generalised method postulated by Lardy, Mirsky has presented a solution which involves considerable algebraic and arithmetic work. Komatsu's paper contains a solution using conformal mapping. Quinlan has given a powerful method to solve skew plate problems involving different boundary conditions and various types of loadings, but no numerical work has been done.

Simple exact solutions have been tound for the modes of buckling or vibration of an equilateral triangular plate with supported edges. They may be classified as 1 (a)—modes symmetrical about all three medians, 1 (b)—modes symmetrical about one median, 2—modes anti-symmetrical about one median. Mode 2 obviously also covers the modes for a 60° right-angled triangle forming one half of the equilateral triangle. The frequency for each mode of type 2 duplicates that for a corresponding mode of type 1(b).

Using television as an instrumental aid, light helicopters can be hovered with considerable accuracy above a known ground point at altitudes of the order of a thousand metres above ground level. The image from a vertically-aimed ground-based television camera is transmitted to the helicopter and displayed on a receiver placed in front of the pilot, who uses the image of the helicopter for guidance to the hover point. With this system, the hover point has been maintained within ±1.2 m (4 feet) for periods of up to 2.5 minutes at 1200 m (4000 feet) above ground level.

Fairly elegant semi-empirical theories are available for predicting the turbulent diffusion of axisymmetric and plane jets. However, there are relatively few investigations on the non-axisymmetric jets, herein denoted as three-dimensional jets. The extensive investigations conducted at the Polytechnic Institute of Brooklyn on three-dimensional jets have shown that the flow field is characterised by three distinct regions; the potential core, the characteristic decay (CD) region and the axisymmetric decay (AD) region. In the CD region the velocity profiles in the direction of the minor axis are similar but the maximum velocity decay curves are different for different shapes. In the AD region the flow characteristics are similar to that of an axisymmetric jet. Yevdjevich has recently conducted another investigation on rectangular jets.

A need exists for empirical criteria by which the behaviour of hypersonic boundary layers flowing in adverse pressure gradients can be predicted, thereby placing the design of high Mach number intake/diffuser systems on a rational basis.

The main results of the inviscid flow performance analysis of a two-dimensional “isentropic ramp” intake diffusing to supersonic Mach numbers over the free stream Mach number range 6 to 10 are presented. Limitations on the degree of diffusion, and hence geometry, have been deduced in terms of the combustion length requirements of an idealised hydrogen/air combustion process with com-bustor inlet conditions given by the intake. The analysis can be considered as a first order approximation defining the ranges of continuous pressure gradients and oblique shock wave strengths relevant to the experimental investigation of boundary layer flow in the mixed adverse pressure gradients associated with hypersonic intakes.

In the vibration of isotropic rectangular plates, the phenomenon of the simultaneous excitation of two separate modes having equal frequencies is well known. Wallerobserved complex nodal patterns on isotropic rectangular plates, and she stated that such combinations were possible because of the internal damping of the plates, which reduced the sharpness of resonance.

Warburton considered the existence of modes m/n±n/m for a clamped plate and showed that when a plate is square, for the mode 4/2 + 2/4, the nodal lines do not lie parallel to the edges of the plate. Furthermore, it was proved that for a square clamped plate, the modes m/n±n/m have discrete frequencies.

Notations and nomenclature for aircraft dynamics and associated aerodynamic data have evolved over many years. Common usage broadly followed the ideas laid down by Bryan, Glauert, Bryant and Gates, and extensions eventually resulted in a conglomeration of symbols which generally impeded the efforts of students, teachers, and other workers and there was little scope for making further additions in a sensible way.

Much work has been done at the Royal Aircraft Establishment to rationalise the position, and the resulting scheme is presented in RAE Technical Report TR 66200. In this scheme changes are kept to the minimum possible, existing concepts are retained, and considerable care is taken to provide a flexible system which allows an author a great deal of freedom as regards simplifying the notation in particular investigations—by omitting suffixes, for example. The RAE is confident that the new notation and nomenclature will overcome the inadequacies of existing systems.

The equations of motion of many mechanical systems reduce to ordinary differential equations with time dependent parameters. A single degree of freedom system, with the damping and restoring forces varying with time according to the law … m (t+k)nhas been studied using the WKBJ approximation. The general solution of the differential equation can be used to arrive at the response of such time dependent systems, subjected to excitations which are specified to be of either deterministic or stochastic nature.