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OVEMBER 2, I939 IP ©GOtf The Dornier Do 215 as fitted with Daimler-Benz DB 601 engines. THE DORNIER BOMBERS Development and Characteristics of the Do 17 and Do 215 J.R By H. F. KING NYONE who, like the writer, has browsed round the tarised Junkers Ju 52/3:01, was a standard type until two Dornier "museum" at Friedrichshafen will agree or three years ago, after which it was relegated to training Ai that this old German company has a distinguished duties. historical background of metal-aircraft construc­ The Do 23 was a high-wing monoplane with a fixed under­ tion. For the past five years or so it has been building carriage and two B.M.W. VI upright vee-twelve engines. bombers and flying boats for the German Air Force; this The plan form of the wing was remarkable, as the leading article will review the former. edge had a marked curve while the trailing edge was Production and flying activities centre round Manzell, straight. At a flying weight of 19,3001b. the top speed Allmansweiller and Lowenthal on the outskirts of Fried- was about 160 m.p.h., which permitted manual operation nchshafen, though Dornier bombers have also been con­ of the gun mountings in the nose, on top of the fuselage structed in series by other German manufacturers, notably and below the fuselage, the upper mountings being unpro­ Henschel. tected. Dormer's first tangible contribution to German rearma By 1936 there were whispers of a very fast and efficient ment was the Do 23 bomber which, together with the mili- bomber then being introduced. For a considerable time p @m NOVEMBER 2, IQ39 The spar booms are thick duralumin extrusions of unsymmetrical section with a projecting flange, the gauge of the metal being thinned at will throughout the length of each spar. Thus, there is a certain affinity between the wing of the Do 17 and that of the twelve-engined Do X flying boat. The girder-type spar bracing utilises lightened duralumin members of broad channel section, details oi this aircraft were completely secret, but when their ends being flanged inward and anchored on sub­ the first pictures appeared it was seen that, in side eleva­ stantial plates. The main ribs are built up of duralumin tion, the fuselage was extremely graceful. This charac­ channel sections, while intermediate ribs have tubular teristic, which caused the machine to be dubbed the bracing. Fuel tanks are slung between the spars on the "flying pencil," was accentuated by the long nose then inboard sections of the wing. fitted, though this feature as we shall see, was subsequently Fabric covering extends between the spars on the modified very considerably. lower surface, the remaining covering being smpoth, The various models of the Do 17 differ only in the design flush-riveted metal. of the nose, the installation of the military equipment The trailing edge is of special formation to provide a and the power plant, so that the following structural slot effect for the flaps, which extend between the description will apply in the main to all varieties. ailerons and the fuselage and have set-back hinges. The slimness of the fuselage is apparent only in side Flap operation is mechanical. The ailerons are likewise elevation; when seen in plan it appears quite normal, and, slotted and are of high aspect ratio. They incorporate in fact, in the centre portion unusually broad, due to the trimming tabs. sloping sides. The cantile'ver wing intersects the fuselage In section the fuselage starts in such a manner that the machine is best described as a off more or less oval, but quickly "shoulder wing" type, or what the Germans call a changes to a flat-bottomed struc­ schulterdecker. It is of two-spar design, the covering ture which is about twice as being part metal and part fabric. In plan form it is of wide at the top as at the characteristically low aspect ratio with a gentle taper and bottom, returning once more rounded tips. to elliptical and circular MOVESL^ft 2, 1939 0&@BR section as it nears the tail. wireless and D/F f-quipment. The top gun position corre­ Built-up frames and inter­ sponds roughly with the leading edge of the wing, and is mediate stiffeners are used adequatelv^^J ^At. The mounting itself is not power- in the fuselage construc­ operated tion, being notched to Nose 1 ^and several photographs have receive the channel-section appeared no front gun at all. The stringers, the lips of which Yugoslav ve fixed guns in the front are flattened where required cowling, but :andard German installa- at the intersection with a tion is a single starboard frame. The frames are most side of v the cc substantial, of course, in on can be clamped in a fixed poi pilot uses the vicinity of the wing. the ring and bead sights At the forward end the a free gun by the occupant of the s> erated as covering is applied in very " freedom " obtained must be very li: pugh the large formed panels. be made for a downward-firing gun to •• sion can On the extremities of the floor of the fuselage. ^k on the tailplane are the twin fins Bombs are carried horizontally in the b J and aerodynamically lage behind the plane of the front spar balanced rudders, the tail- opening the traps being in the fore part plane having holes to re­ where it is accessible to the pilot and bom ceive the mass - balance ternal racks may be attached to the sides of weights of the elevators. A typical bomb loading would be about 1,5001b. Each half of the under­ carriage retracts hydraulic- Nose Design ally with a rearward motion The first Do 17, as already stated, had a long, pointed into an engine nacelle, leav­ nose without transparent panelling. Next came two modi­ ing a section of the wheel fied designs, one hemispherical (this was adopted as, exposed, though "clam­ standard for aircraft of the Luftwaffe) and one longer and shell" doors fair off the more angular with transparent panelling in the lower bottom of the nacelle. The section. The latter was used on the first Do 17 prototype tail wheel retracts during to be fitted with Daimler-Benz engines and on the Yugoslav the final stage of the dis­ machines. appearance of the main Do 17s of the first series delivered to the Luftwaffe were gear. fitted with two unsupercharged B.M.W. VI prestone-cooled For normal bombing engines, giving a maximum output of 750 h.p. apiece. duties a crew of • three is These units did not lend themselves well to a good nacelle carried, being grouped in entry, the thrust line being well below the cylinder banks. the forward part of the fuse­ With the Daimler-Benz DB 600 inverted-vees as specified lage. The pilot's seat is off­ for later machines smoother lines were obtainable. In both set to port and should cases the radiator is mounted below the crankcase. The permit changing pilots in standard airscrew is a three- flight. Internal equipment bladed variable-pitch V.D.M. which one noted in a Ger­ With the unsupercharged man Air Force machine at B.M.W. engines performance Allmansweiller includes an was quite low, the top speed automatic pilot, two-way near the ground being only Above is a Flight copyright study of the " business end" of a Daimler-Benz-powered Do 215. Below is the Do 17. This drawing is based on one executed by Max Millar at the Dornier works. November 2, 3Q A Do 215 as powered »;«. radials which may be B M W 132 Dc's or Bramo Fafnirs and undercarriage of thi machine are similar to those of the earlier model I Hit the accommodation of the has been revised. crew Like the Do i7, the new machine can be fitted out as a short-range heavy bomber- a long-range machine with a smaller bomb load; for lone- distance reconnaissance; for ground attack work and even as a fighter, though it is not used in the latter guise in the German Air Force. It may be distinguished from the Do 17 by the '' swollen '' nose sec­ tion which accommodates the crew. The extreme nose portion is composed of "facets" of transparent material which not only light the bomb aimer's position but improve about 235 m.p.h. The introduction of the B.M.W. 132DC the pilot's view in a forward and downward direction. In and Bramo Fafnir radials gave a much improved perform­ this respect the machine bears a marked resemblance to ance as, of course, did the fitting of the Daimler-Benz the "short-nosed" version of our own Bristol Blenheim DB 600s. Unlike the Blenheim, however, the Do 215 has its pilot's Although the Dornier concern has been fairly liberal in windscreen and cockpit enclosure external to the main lines releasing structural particulars, performance and weight of the fuselage. Actually, this cockpit enclosure is data are very scanty and, for that matter, on the optimistic extended aft to a point just above the leading edge of the side. The following figures might apply to the machine as wing and terminates there as the upper gun position. On fitted with two Daimler-Benz DB 601 engines. Standard the underside the nose portion extends aft to a point just service aircraft would not be so efficient: Disposable load, forward of the leading edge and there embodies with the 6,6oolb.

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