From the correspondence columns of the JOURNAL it is obvious that there is a great deal of interest in the present-day standard of maintenance design and that the general consensus of opinion is that it is not up to a high enough standard.

In order to stimulate still further the interest in design for maintenance the following series of questions are asked. These questions are the thoughts that run through the mind of a maintenance engineer when he is introduced to a new item of equipment. The perfect maintenance design is extremely rare, i.e. when all the questions can be answered in a satisfactory manner.

It is easy to produce what seems to be an efficient design on paper but the conditions of a well-lit and well-heated drawing office are different from an unheated hangar early in the morning of a winter day.

The importance of maintenance being considered right through all the design stages is even more vital these days, when the number of aircraft being manufactured is less than during the war years and the economic side is just as important as the performance figures. In fact, the words “economy” and “maintenance” are bound together. It is not possible to issue modifications in order to correct faulty maintenance design and still keep a high percentage of aircraft flying.

Aerodynamics is naturally associated with the external air flow past aircraft, but with the advent of the gas turbine it has also become of the greatest importance for the internal flow through such engines. The efficiency and bulk of the compressor and turbine components in gas turbines are largely an aerodynamic matter, and their design is determined by a knowledge of the lift coefficients, drag coefficients, Mach numbers, and so on that can be used. The same fundamental laws, if they were fully known, would apply to both internal and external flows, but there are at present considerable differences in practice between the data obtained, and the detail methods used, for the two categories of flow. This lecture attempts to cover in a general way the internal aerodynamic flow through gas turbines.

The 23rd Main Lecture to be given before a Branch of the Society was held under the auspices of the Merthyr Tydfil Branch on 10th November 1955. The Lecture, entitled “A Review of Some Combustion Problems Associated with the Aero Gas Turbine,” was given by Dr. J. S. Clarke, O.B.E., M.I.Mech.E., F.R.Ae.S. Mr. C. S. Gardner, Past President of the Merthyr Tydfil Branch, opened the proceedings by welcoming the guests. He was deputising for Mr. W. R. Morgan, the Branch President, who had unfortunately had to go into a nursing home for treatment for an old war injury. He apologised also for the absence of Mr. McGibbon who arrived back from America only that day and was unable to be present. He then introduced Mr. N. E. Rowe, President of the Royal Aeronautical Society, whom they were very honoured indeed to have with them. When they thought of the journeyings that his presence involved he thought they should be all the more grateful that he could come and support them in their Branch. He would ask Mr. Rowe to take the Chair.

In a previous note the authors gave a method of solution for the problem of a finite rectangular plate under constant skew and inclined loadings, two of the edges being rigidly held and the other two simply-supported. In this note the same problem is considered for a plate in the shape of a parallelogram.

From a general consideration of the available data on the flutter of wings with localised masses certain deductions are made as to the possible types of flutter that can occur. On the basis of these deductions it is shown that there is an optimum choice of modes for use in flutter calculations for wings with localised masses. These modes are obtained with artificial constraints imposed on the wing at the localised mass section fixing the wing at this section in translation and/or pitch. It is deduced that for certain mass locations types of flutter are obtained that are insensitive to increase of localised mass, beyond a certain value, with flutter speeds considerably greater than that of the fixed root bare wing. It is also deduced that for the majority of aircraft configurations the maximum flutter speeds for these types of flutter will be realised when the localised mass is in the region of two-thirds semi-span from the root. A limited theoretical investigation is made for a rectangular unswept uniform wing with symmetric and antisymmetric body freedoms, to illustrate and confirm the conclusions derived from general considerations. At the same time the investigation shows that an ill placed localised mass can reduce the wing flutter speed to a very low value.