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Aviation History
1936
1936 - 3538.PDF
DECEMBER 31, 1936. FLIGHT. 689 The Outlooks All-in-one ? / S it possible to combine in one aircraft all the most desirable features of the aeroplane, the Autogiro and the helicopter? Mr. Peter Cameron, of Glasgow, believes it is, and on pp. 705-706 of this issue is described his design for a type of aircraft which he calls the Rotor Plane. Briefly explained, the Cameron machine is a combined fixed-wing and rotating-wing aircraft, the rotor blades of which can be expanded for take-off and contracted for high speed when the desired altitude has been reached. With the blades retracted and set at a small angle of incidence, the machine obtains most of its lift from the fixed wing, and as a re tractable undercarriage can be used, the drag should be relatively low, so that high speeds should be attainable. Mr. Cameron has also evolved means for preventing the whole aircraft from rotating about its vertical axis when the rotor blades are being driven by the engine and the machine lifts as a helicopter. That a number of technical difficulties and problems may be encountered in the evolution of the details of the mechanism will be granted, but the inventor has already prepared remedies for all the likely ones, such as the possi bility of '' binding '' during the expanding or contracting of the blades, due to flexing of the rotor spars. If the rotor plane is proved practicable it should have a great many advantages, and the high top speed expected plus the ability to hover as a helicopter invest it with obvious possibilities as a military aircraft. This Freedom r HE fact that it is now open to receive applications for the posts of chief aircraft surveyor and chief air craft engine surveyor has called attention to the almost forgotten Air Registration Board provided for in the Air Navigation Act passed last Session. This is the first practical and active signs of what the Government spokesmen are fond of calling '' implementing '' the recom mendations of the Gorell Committee, itself almost for gotten by now, but appointed to examine the possibility of removing from the " deadening hand of Air Ministry influence " the design, construction and inspection of civil aircraft up to a certain size. It is gathered that the Air Registration Board, about to be formed, is to set up the machinery necessary for taking over the work hitherto done by the Air'Ministry of check ing stress calculations, inspecting materials, overseeing maintenance, and so forth. The Board is to consist of groups, each group dealing with certain aspects. **. Guaranteed F LIGHT has examined the list of names of the repre sentatives of constructors, operators and insurers serving on the different groups, and as these names are, almost without exception, household words in British aviation, one may accept that side of the A.R.B. as having been laid on a sound foundation. Insurance seems to be the key to the whole matter, and as one of the groups includes four representatives of insur ance companies it is to be assumed that these have expressed willingness to co-operate and to shoulder the by no means light burden. We have always held the view that the- aircraft manu facturer's regard for his own reputation is sufficient safe guard against inferior workmanship. The fact that an insurance company will have to take the risk of covering A any aeroplane before it can fly will probably lead to a list of " approved " firms, as is the case now, onlv the insur ance companies instead of the Air Ministry will do the approving. Any firm whose products do not meet with the approval of an insurance company will be in no posi tion to market its machines. * The main stumbling block of the scheme is likely to be not of a technical but of a financial character. Although the A.R.B.'s organisation will not need to be quite as ambitious as that of the Air Ministry, it will have to be fairly extensive; this is also confirmed by the fact that the salary of the chief aircraft surveyor is to rise to a maximum of ^2,000 per annum. Obviously he will have to have under him a staff of competent men, and the cost is likely to be not inconsiderable. Who is to pay? Presumably the manufacturer and the user will, between them, have to foot the bill. The manufacturer saves money by not being obliged to have Air Ministry inspection and super vision, and can thus afford to pay something towards the new scheme. The user, on the other hand, is already having to pay fairly heavily and is entitled to expect a reduction rather than an increase in cost, the more so as excessive cost was one of the criticisms levelled against the existing system. The Boundary Layer PROFESSOR MELVILL JONES has a wonderful gift £ of being able to explain in simple language the most complicated and abstruse problems. Never has this ability been better demonstrated than at his lecture on profile drag to the Royal Aeronautical Society shortly before Christmas. The lecture was quite different from the written paper, and thus both the '' highbrows '' and the "lowbrows" were able to benefit. Unfortunately, the paper is not one which lends itself to summarising, being already something of a summary, and for that reason it has not been considered expedient to deal with it in Flight this week. Perhaps, however, a brief reference to the main points and conclusions may serve to indicate what Professor Melvill Jones is "driving at." Profile drag, of wings of different thickness ratios, for example, is what it is required to know for practical design purposes, but its variations are difficult to understand unless the position on the wing profile where the flow in the boundary layer changes from laminar to turbulent is known, and the reasons which cause early or late changes. The '' exploring'' pitot tube is the modern means cf detecting drag by indicating changes in pressure. The pressure in a pitot tube has a constant value at all points in the flow except, in boundary layers and in the wakes which they create. When the pressures have been read or recorded, the profile drag can be deduced by a fairly simple calculation. Professor Melvill Jones did not hold out hopes of any likelihood of great drag-savings by coaxing the boundary layer to remain laminar. Were this possible, the saving would be startling, but he thought it improbable that the laminar layer could be' made to extend over more than one-third of the whole wing surface. This would repre sent a drag reduction of about 20 per cent, compared with a wing over which the layer was entirely turbulent Surface roughness presents two problems: the effects of roughness on the point of transition and its effects on the skin friction applied by the turbulent boundary layer. Thus the lecture did not provide an answer to the problem of every designer about when it does and does not pay to go to the trouble and expense of flush rivets.
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