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Aviation History
1944
1944 - 1590.PDF
122 FLIGHT •^ v--3 AUGUST 3RD, 1944 ENGINE MOUNTINGS A point of interest is that the complete mounting is interchangeable with the Rolls- Royce- mounting on the Beaufighter, though the latter is a bolted-up structure. American Mountings The Mustang was designed to a British speci fication, and this may have accounted for the mounting being as compact as it is, although y*e*construction differs appreciably from British practice. The "horizontal bearers" incor porate the "integrating" structure, and are made up from plate webs and extruded top and bottom members. This construction is suitable for mass production. Similar to German prac tice there is no cross-bearing, the bearers being independent of each other. The box-like struc ture facilitated the mounting of the two-nose 0.50m. m/g.s., and allowed the armament to be increased without weakening the wing. To remove the mounting four bolts only have to be removed.. Now the Mustang is being fitted with the Packard Merlin, it will be worth while noting whether the mounting for this is .similar to that used for the Allison or whether the design is .altered. The Airacobra * p^ •MP "'T.-- SEHS^TISk ?:- "• H^KS IP^^S**^^^ •••• .'iiM mm In the Hawker Hector the engine mounting was built up and resembled that of the modern Mustang or the welded box bearer of the Me 2to. ttjedox The Airacobra, one of the most unortf fighters of recent years, has a very unusual engine mounting, which. is rather similar in construction to that of the old Mureaux 170 Merlin mounting in the Hawker Hurricane follows the standard typical Hawker fuselage construction, with tubes and fishplates. and In the North American Mustang the engine bearers are of horizontal " Y " shape and of riveted box section. It may be compared with the Me 210 mounting on p. 120. The mounting of the Merlin engine in the De Havilland Mosquito. There is no cross-bracing between the two bearers other than that provided by the engine itself. fighter. The position of the engine is nearly ideal from the weight and manoeuvrability points of view, and although the mounting of the engine itself gave little trouble, the attachment of the airscrew reduction gear and shaft drive assembly at the front of the machine presented an immense structural problem. The Problem of Flexing Flexing of the fuselage is usually undesirable at any time, but in this case it was imperative that the structure be as stiff as possible. The fuselage was thus built up from two massive '' box '' girders, cradle shaped in profile, running from just aft of the engine to the front bulkhead. These girders, although evident^yprimarily for the engine installation, provided a fkm.-"ftxture for the bearing of the nose wheel oleo leg pivot. The airscrew is some 12ft. in front of the engine, necessitating 10ft. of special shaft ing. This, and the special centre bearing, increased the weight by 50.7 lb. To the rear of the girders are two sturdy forged angles for the engine itself, which is mounted on four " Fabreeka" pads inserted between the engine lugs and the angles. It is held down by eight bolts arranged in pairs, through brackets riveted to the webs. The two girders, although giving the Airacobra its required stiffness, also gave what is perhaps its greatest defect— non-serviceability in the field. It is hard to imagine how the girders are repaired if damaged by enemy action. The serviceability of the Airacobra on the whole is poor—there is a popular rumour that once it took a small army of mechanics, engineer officers, and AC "Plonks" nearly three days to remove a broken instrument from the instru ment panel. s It has been reported that quite a/lot of research has been carried out by Messrs. Rolls-Royce and Packard on the Allison style of extension shaft with the object of installing a Merlin 61 in the Airacobra. If this is possible, another great drawback—loss of performance with height— will be eliminated, and the Airacobra should be able to show by deeds and not advertisements that it is a "con centrated dose of very bad medicine for the Axis."
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