Flight, December 1934

DESIGNED FOR MASS PRODUCTION
The Martin-Baker "MB1" a New and Well-equipped Cabin Monoplane Designed Throughout to Allow Easy Production and Assembly

   WHAT may be called the “Meccano” system of construction has long been held up by practical engineers as the ideal one for an aeroplane which it is intended should be built in large quantities. Unfortunately, design features which satisfy the production engineer are all too often opposed to the ideals of the aeroplane designer. Notwithstanding this, the majority of aeroplanes to-day are naturally, for economical reasons if for no others, built so that they can be so produced more or less to a pattern, that is, they are jig-built to ensure interchangeability of the main structures. This, however, is as far as the majority of modern aeroplanes go, for their structures are either welded ones or follow some form of builtup construction making the whole into a unit, which, more often than not, has to be returned to the manufacturer in the event of damage. There are, of course many manufacturers who design so that small pieces can be replaced or changed by unskilled labour.
   Carrying this idea to its (almost) logical conclusion, Mr. James Martin, of the Martin-Baker Aircraft Company, has produced a low-wing two-seater in-line cabin aeroplane to cater for the luxury two-seater market, and at the same time to demonstrate the feasibility of his ideas on mass production. Generally speaking, the "MB1," as it is called, is built up of a large number of small pieces of steel tube bolted together, any of which may be replaced with a minimum of trouble and very little skilled supervision.
   The fuselage has longerons of T.5 steel tubing. In the after portion, the strut bracing between the longerons is bolted to the latter by an interesting patented form of joint which is also used for the wing spars. This joint consists of a short liner pushed inside the spar so that a hole through the spar wall coincides with a tapped hole in the liner, the nut for which is brazed to its inner surface. A stud is then screwed through the longeron into the liner and a saddle washer dropped over the stud to bear on the outer surface of the longeron, leaving the outer screwed end of the stud sufficiently long for the flattened end of a strut or struts to be dropped over it and bolted on. The nuts are usually of the castle type locked with a wire through the slots. The centre and front portions of the fuselage do not use this form of joint, but the sections of the longerons finish with fork-ends which, like the struts, are bolted to machined fittings.
   The wing spar is particularly interesting, as Mr. Martin has used three booms, all of thin-gauge but comparatively large-diameter tube. Two booms form the after surface of the spar and are more or less vertically mounted above each other. The third boom forms what may be termed the leading edge of the spar, being in front of the other two and on a level with the lower one. The wing is arranged to fold about the joints of the after pair of booms.
   These booms taper towards each other as the wing tip is reached, and are braced by a system of smaller tubes with flattened ends bolted to them in the same way as the struts and longerons in the fuselage are bolted to each other. The wide base of this pyramidal spar and the large diameter of the three booms certainly appears to make it very strong in torsion.
   The wing ribs are aerofoil sections of very small-diameter T.5 tube, mostly braced in Warren girder fashion with small tubes brazed into position with a bronze preparation. This form of brazing is used in a large number of places in the machine, not only for the wing ribs but also for the tail units, fairings, and so on. After a series of tests Mr. Martin is convinced that, from the strength point of view, the results are even better than those of welding, and, as the temperatures used are so low, the brazing causes no distortion.
   The "M.B.1" bristles with neat features of the sort which private owners so often wish were included in their machines. For example, the hinge pins on the rear face of the spar are so arranged that there is no tendency for the wing to fall backwards as soon as the front pin is released. Folding is, therefore, a one-man job. The front pin is on a screw, and can be withdrawn or inserted by the rotation of a small handle on the leading edge, and the wing can, after two flaps have been raised at the back, be pushed back without fear that it will bump into the fuselage, because there is a stop to prevent it doing so.
   Another useful feature is the storage of the fuel in long triangular welded-aluminium tanks placed in the centre of each wing spar, in such a position that, if necessary, they can be withdrawn with a minimum of trouble when the wings are folded. In the cockpits there is again evidence of forethought. The cocks for turning on the fuel supply, isolating the pumps, and for other functions, are all loaded with a spring ball so that there is a definite "click" when they are fully opened or shut, and there can be no doubt about their position. The seats are comfortable and the cockpit is totally enclosed with an oval transparent hood which can be slid back to allow entrance. The windscreen is a sharp “vee” with vertical front panes, which should not collect fine rain or snow and should obviate any reflection from internal or external lighting.
   In the mounting of the Napier “Javelin” engine and its cowling is still more evidence of the practical nature of Mr. Martin's design. The doping pump has connections both to the carburetter and to the induction pipe, the inlet manifold is carefully lagged and warmed, the fuel and oil filters are conveniently placed, and the sides of the cowling can be supported from their hinges in a horizontal position so that they form shields if, as sometimes unfortunately happens, the owner has to attend to the engine when it is running. An electric starter is fitted, and the machine will be very fully equipped throughout.
   From an aerodynamical point of view, the "M.B.1" is a fairly straightforward design. As yet no figures are available, but a comfortable cruising speed of 140 m.p.h. and a stalling speed of 50 m.p.h. are hoped for when the machine is fully loaded with two persons and luggage, in which condition the all-up weight will be somewhere in the neighbourhood of 2,350 lb.
   It will be seen that the main interest of the machine lies in its detail design, and for that reason we are departing from our usual procedure of delaying this form of aircraft description until we can give full performance figures and photographs of the finished product.
   The "M.B.1" is being manufactured at the makers' works at Higher Denham, Bucks.