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FOUNDATION THE Francis Mond Professorship of Aeronautical Engineering was established at Cambridge University in 1919 and was certainly the first chair in aeronautical engineering in this country. The initial holder of this Chair was B. M. Jones (now Sir B. Mclvill Jones), who had worked at the R.A.E. and other establishments during the First World War. Professor Melvill Jones, on arriving at Cambridge, found that in fact the University was not able to finance his research or supply him with laboratory space and had to rely upon the Air Ministry for funds and apparatus. This resulted in the main research activity of the department being directed towards flight experiments using R.A.F. aircraft flying from Duxford. Due to their interest in aeronautics, however, the Engineering Laboratory at Cambridge did supply Professor Melvill Jones with space, and in 1921 an optional paper was set in Aeronautics in the Mechanical Sciences Tripos.

Alternative English terms are printed within brackets; subsidiary English terms are in italics; while American words, where they differ, are in normal type.

The purpose of this paper is to identify freezing in pitot tubes at real-time, by means of the estimated heat transfer coefficient (HTC) at the tip of the probe. The prompt identification of such freezing is paramount to activate and control mechanisms for ice removal, which in turn are essential for the safety of the aircraft and its passengers.

The proposed problem is solved by means of an inverse analysis, performed within the Bayesian approach of inverse problems, with temperature measurements assumed available along the pitot probe over time. A heat conduction model is used for describing the average temperature of the pitot tube, which is then rewritten in the form of a state estimation problem. The model is linear and time invariant, so that the inverse problem can be solved using the steady-state Kalman filter (SSKF), a computationally efficient algorithm.

The results show that the SSKF is fully capable of recovering the HTC information from the temperature measurements. Any variation of the HTC – either smooth or discontinuous – is promptly detected with high accuracy. Computational effort is significantly lower than the physical time, so that the proposed methodology is fully capable of estimating the HTC at real-time.

The methodology herein solves the proposed problem not only by estimating the HTC accurately but also doing so with a very small computational effort, so that real-time estimation and freezing control become possible. To the best of the authors’ knowledge, no likewise publications have been found so far.

This bulletin is devoted to accounts of four faceted schemes of classification which were devised for particular purposes by the CRG and its members and have been in use for long enough to make possible some judgement of their practical usefulness.

This paper describes a free‐piston driven expansion tube and its instrumentation. The facility is used to generate rarefied flows at speeds of approximately 10 km/s. Although the flow in the tube itself is in the continuum regime, rarefied flow conditions are achieved by allowing the test gas to further expand as a free jet into the facility's test section. The test flow is surveyed to provide bar‐gauge pressure measurements. Numerical simulation is then used to describe more fully the test flow properties. The flows produced are suitable for the aerodynamic testing of small models at superorbital speeds and should provide data that are suitable for the calibration of Direct Simulation Monte‐Carlo codes.

THE authorities of the Institute of the Aeronautical Sciences have decided, so I am instructed, that the Wright Brothers' Lecture should deal with subjects upon which the lecturer is engaged at the time, rather than with a general survey of some wide branch of aeronautical knowledge. This decision has the advantage that the lecturer is actively interested in the subject about which he talks, but it leaves to chance the question whether he is in a position to end his lecture with simple and clear cut conclusions. I mention this because the problem upon which we are working at Cambridge, and about which I shall speak, is not yet solved and my lecture must, perforce, be confined to a discussion of aims and methods and of results so far obtained; it does not contain that simple statement of conclusions which is the ultimate aim of all good research. After this explanation you will not, I hope, be disappointed when the lecture ends on a note of interrogation.

RECENT tendencies in the design and operating conditions of aircraft have laid increasing emphasis on the short‐comings of the generally accepted pitot‐static method of measuring flight speed. The routine use of air navigation over long distances has spread widely during the past ten years, and, as a result of the greater distances involved, the percentage error in measured flight speed which can be tolerated has become smaller. This un‐satisfactory position was not until quite recently relieved by any very clear appreciation of the errors involved in fitting a pitot‐static head in any given position on an aircraft.

The report covers an extension of the surface tube technique devised by T. E. Stanton to measure the intensity of skin friction. A simple surface tube is described and a method of varying the surface tube calibration curves to cover other fluids and temperatures is developed. An empirical equation is obtained permitting values of the intensity of skin friction to be determined from surface tube static tapping readings and the width of the opening of the surface tube.