Any system for controlling the airworthiness of aircraft engines in service should meet the following conditions:

• (a) it should be such that the incidence of in-flight shut-downs is kept to an acceptably low level;

• (b) it should ensure that aircraft are not flown with engines delivering significantly lower power than that used in establishing the scheduled Flight Manual performance; and

• (c) it should provide maximum protection against failures of a potentially catastrophic nature, regardless of probable incident rate.

In this paper, the foregoing principles are discussed in relation to experience with turbine engines in transport aircraft. Particular emphasis is placed on the importance of monitoring, by which is meant any procedure or device that can be used to determine engine condition in flight or on the ground. Some current trends in turbine engine overhaul policies are also reviewed briefly.

Although the title of this paper, for brevity, refers to engine performance monitoring, in fact we mean performance and condition monitoring. In presenting such a paper with particular emphasis on the problems that arise for the Operator with relatively small aircraft fleets operating in the main over short stages, although the comments we have to make are based on TAA experience, a similar situation must exist for any operator with a multiplicity of aircraft types and relatively small numbers of each.

We refer to performance and condition monitoring to define the complete task, as it is essential to correlate performance parameters to condition evidence such as vibration level or lubricant deterioration status to obtain a useful perspective.

Polar aviation is a branch of flying to which the domestic British (that is excluding the Canadians) have contributed modestly. Indeed, we do not have the Arctic on our doorstep like the Americans, Canadians, Russians, Finns, Swedes and Norwegians but, in exploration, we have a tradition second to none in Antarctica, a tradition fostered and developed in bygone years so dauntlessly by men of the Royal Navy. In fact it was Captain Robert Falcon Scott who was the first man ever to become airborne in Antarctica, early in January 1902, when he went aloft near Cape Adare in an observation balloon. Admittedly he let go all the ballast at once and shot up to 800 feet so rapidly that only the mooring rope prevented him from making a free-balloon voyage over the ice-bound wastes, and he did not enjoy the experience very much. But it was a pioneering flight. A few months later, the German Drygalski made a similar flight for the purpose of ice observation; but balloons never caught on in the Antarctic and there was no more flying there until Sir Hubert Wilkins’ expedition made the first aeroplane flight, from Deception Island, off Graham Land, with a Lockheed Vega wheeled aeroplane on 16th November 1928.

It would not, perhaps, be an exaggeration to say that aeronautics and space technology represent the most dynamic, progressive and exciting field of modern knowledge, where many bold dreams of yesterday are rapidly becoming the spectacular realities of today and tomorrow. Never before, and in no other field, has man learned so much and so profoundly in such a short space of time as he has here during the past ten years or so. This explosion of aerospace knowledge has brought forward and established new dimensions and criteria of national defence, international relations, military strategy, socio-political thought, economics, commerce, etc, and affects everyone’s life in one way or another.

Work on the finite element analysis of flat plates in bending has been directed towards elements which satisfy kinematic conditions between the adjacent elements in conjunction with the theorem of minimum potential energy, eg Argyris, Bazeley et al, Clough and Veubeke.

The purpose of this Note is to provide the main details of a triangular element which satisfies equilibrium conditions between the adjacent elements and which is used in conjunction with the complementary energy principle. The bending moments vary linearly within the element and use is made in the derivation of the analogy (see eg Southwell, Fox, Fung and Morley that exists between problems of plane stress and plate bending. In particular, many of the present details are taken directly from the plane stress analysis of Veubeke who, along with Argyris, considers a displacement triangular element with linearly varying strain.

The problem of a static two-dimensional hovercraft over a solid surface has been studied by many authors and the solutions show reasonable agreement with experiment; the main source of error appears to be the neglect of viscous effects in the simple theories. It was recently pointed out by Hogben that no comparable simple inviscid solution exists for hovercraft over water. The main difficulty with the over-water solution is that there is no obvious reason why water should not occupy part of the cushion and some extra condition would be needed to determine this depth of water h2.

A family of alternative expressions is presented suitable for the representation of the lateral deflection of rectangular plate elements in bending. Such expressions are extensions of a simple polynomial representation assumed in earlier work. The new expressions are such that not all displacement continuity conditions are met completely but, nonetheless, a criterion ensuring convergence of numerical results to true stiffness levels is satisfied. Deflection and natural frequency estimates based on one expression of the proposed family demonstrate rapid convergence and high numerical accuracy.

The pressure reading of a pitot tube in a supersonic flow corresponds to the position of the nose shock wave. Results of measurements of the shock stand-off distance are presented for three different streamwise Mach number gradients and for a uniform flow. These results are compared with existing theoretical values.

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).