§ 52. Mr. R. Bell
asked the Minister of Supply what progress has been made in research by his Department into the silencing of aircraft engines.
§ 55. Mr. Beswick
asked the Minister of Supply if he will give an estimate of the cost during the current year of his research into the problem of reduction of noise of aircraft; and what progress has so far been made.
§ The Minister of Supply (Mr. Duncan Sandys)
The main research effort into the problem of reducing aircraft noise is being undertaken by the Ministry of Supply. However, important work in this field is also being done by the Ministry of Transport and Civil Aviation, by the universities and by aircraft firms acting on their own initiative.
In order, therefore, to give a complete picture, I propose, with permission, to circulate in the OFFICIAL REPORT a detailed statement covering the progress of research on this subject as a whole.
§ Mr. Bell
In view of the widespread personal hardship and loss of value on private houses which is caused in all parts of the country nowadays through aircraft noise, will my right hon. Friend make full use of the powers which he has taken under the Statutory Instrument of 4th June, in order to ensure that no possible precaution is neglected?
§ Mr. Sandys
I think that the powers to which my hon. Friend refers are powers taken by the Minister of Transport and Civil Aviation, and perhaps he would raise that point on another occasion. I well recognise that aircraft noise is becoming an increasingly serious and urgent social problem to which a solution has to be found—and found quickly—and I warmly welcome the stimulus which has been given by public interest and public criticism.
§ Mr. Beswick
While agreeing about the magnitude of this social problem, may I ask whether the Minister is quite satisfied that the scale of research matches the problem? Can he say what is the total sum of money being spent upon it, because. although there is a good 897 deal of work, many of us are not certain that the scale of research is sufficiently wide?
§ Mr. Sandys
The figures are contained in a statement which I am circulating. I agree with the hon. Member, and I should like to see more spent, and more effort go into this, but, in fact, the expenditure has been more than doubled in the last year, compared with the previous year, and I have no doubt that it will go on increasing.
§ Following is the statement:
§ The problem of reducing aircraft noise is being tackled from a number of different angles. The main effort has been concentrated on jet engines.
§ A leading firm of engine-makers have been given a substantial contract by the Ministry of Supply to carry out an extensive programme of studies and experiments. This includes a detailed analysis of the noise of a jet engine operated with various alternative types of nozzle on an open air test bed. The nozzles which are being tested include toothed, corrugated, convergent-divergent and fishtail types. Promising results have been obtained from toothed and corrugated nozzles and further studies are being made to decide the optimum shapes for these types.
§ Since it is known that the by-pass engine causes less noise than the conventional jet engine, a special study of the by-pass engine in relation to the noise problem is being carried out, with the object of determining the relationship between noise, jet velocity and temperature. The effect on noise of injecting water into the jet stream is also being investigated.
§ Two other engine companies are working under Ministry of Supply contract on the development of silencers for piston engines used in helicopters. Some of the types of silencers which are being tested are showing encouraging results, Work is now proceeding on the task of lightening the weight of these silencers and of reducing their adverse effect upon engine power.
§ The Ministry of Transport and Civil Aviation is experimenting with the construction of a brick baffle wall at London Airport. This wall is shaped to accommodate the forward part of a large civil aircraft, with the object of reducing noise in certain directions when engines are being run on the ground. However, results are not yet entirely satisfactory and the investigation is being continued.
§ After obtaining competitive tenders from appropriate firms, the Ministry of Supply has 898 placed a contract for the design of two types of mobile ground mufflers. One of these is to be suitable for single-engined aircraft and the other for multi-engined aircraft. The first muffler of the single-engine type is expected to be ready for experimental testing in the course of the next few months.
§ One firm of aircraft manufacturers has been experimenting with portable screens which are placed round the aircraft while the engine is being run up. Some reduction of noise has been obtained and further screens are on order. In addition, four other aircraft manufacturers are employing a firm of consulting engineers to advise them on the use of specially designed pens for muffling the sound of aircraft whose engines have to undergo running tests on the ground. Another firm, on its own initiative, are building a pair of mobile ground mufflers to its own design.
§ In addition, a series of tests are being carried out by the College of Aeronautics under contract from the Ministry of Supply. These tests include:
- (a) The measurement of thrust and noise levels of engines with nozzles fitted with noise reduction devices of various designs.
- (b) Measurement of the sound field from small jets at supersonic speeds, combined with Schlieren investigations.
- (c) Measurement of the turbulence structure in the mixing region at the jet exit, both at low and high speeds.
§ Southampton University, with some financial support from the Ministry of Supply, is carrying out valuable laboratory work with the object of obtaining a fuller understanding of the nature of jet flow. Their programme of research includes:
- (a) Development of a shock tube for recording the interaction between an eddy and a shock wave.
- (b) Development of an optical eddy-counting technique, including a focusing device.
- (c) Measurement, by means of the hot wire technique, of turbulence, velocity and temperature distribution along the jet.
- (d) Examination of noise from jets of non-circular shape.
- (e) Study of noise emitted from special jet extensions, with annular corrugated orifices, designed to reduce low frequency noise.
§ Manchester and Edinburgh Universities are also undertaking important fundamental research on the origin and nature of jet noise.
§ Expenditure by the Ministry of Supply on this problem during the current financial year is estimated at about £100,000, as compared with £40,000 last year. In addition, the Ministry of Transport and Civil Aviation expects to spend about £20,000 on the study of this problem in the present year. Figures of expenditure by firms and Universities on their own account are not available,