FlightGlobal.com
Home
Premium
Archive
Video
Images
Forum
Atlas
Blogs
Jobs
Shop
RSS
Email Newsletters
You are in:
Home
Aviation History
1940
1940 - 0215.PDF
JANUARY 25, 1940. This experimental Great Lakes dive-bomber was of special interest because it carried its bomb internally and,although a biplane, had a retractable undercarriage. incorporated in certain machines which would otherwise attain too high a speed for the pilot to take accurate aim. Special reversible-pitch air- screws have also been tried with the same end in view. Under high-speed diving conditions the airscrew—if it is of the fixed-pitch type—will "windmill" the crank- shaft round far beyond the approved r.p.m. and will result in a relative increase in the dynamic loadings and stresses of various vital components of, perhaps, more than 70 per cent. Fortunately, airscrew design has made exceptional pro- gress during the past few years. Not long ago a Curtiss machine attained a speed of 575 m.p.h. in a 9,000ft. dive, but, being fitted with one of the new electrical automatic constant-speed airscrews, the engine at no time exceeded 2,550 r.p.m., its rated figure for normal level flight. As countries have their own pet ideas on the design of dive-bombers, let us examine selected types according to nationality. Although America can in no sense be considered to have "invented" dive-bombing, this country has done more to develop specialised equipment than any other, and will accordingly take pride of place in this survey. It was ten or eleven years ago that the Martin 125 and original Curtiss Helldiver marked the rise of interest in the technique of dive-bombing with comparative heavy loads. The Martin was the larger machine and was capable of carrying a 1,000-lb. bomb in a terminal velocity dive and of recovering without dropping the bomb. The t.v. speed was about 260 m.p.h., and the makers were very proud of the fact that, even with the bomb in position, the 125 was capable of all normal aerobatics, including loops, rolls and inverted flying. Modern Helldiver To-day the Curtiss Company still has a Helldiver, though this bears not the slightest resemblance to its forerunner. Actually the name is applied to an export version of the SBC series (Marks 1-4) as used in large numbers by the U.S. Navy's aircraft carriers. The machine is an excep- tionally clean biplane, with heavily staggered wings and single interplane struts. The undercarriage retracts into the sides of the fuselage behind the Cyclone engine. A single large bomb is carried externally beneath the fuselage and smaller projectiles can be slung beneath the wings. The fuselage bomb is provided with displacement gear, precise details of which have not been released. It may well be that this resembles the gear patented by Messrs. Schuyler and Miles (United States Navy) and D. A. Chadwick, This comprises a shaft secured to the fuselage with two dis- placing members, each capable of revolving separately upon the shaft and having a limited lateral motion in respect to the aircraft. A spring-backed swivelled fork member is mounted at the end of each displacing member, the forks being adapted to engage lugs fitted on the bomb. Elastic cords are fixed to each displacing member, the other end of the cords being secured either to the bomb rack or to the structure oi the aircraft. On the lower tvings of this unusual Curtiss biplane are '' double-split'' flaps which open like the leaves of a book to retard the speed in a bombing dive. A constant-speed airscrew keeps engine r.p.ni. within desired limits. The Douglas concern, apart from its TBD-i torpedo- bomber monoplane which is used for dive-bombing, has two types (actually Northrop designs) in service with the U.S. Navy. In appearance these resemble the Northrop attack machines and Bristol's flying test bed for the Hercules, but are specially stressed for dive-bombing and have split trailing edge flaps which, incidentally, are per- forated as on other modern Northrop designs. One of the most interesting American designs is the 79 Dive-Bombing Brewster XSBA-i mid-wing monoplane. One version of this has been released for export and another is being built at the Naval Aircraft Factory, Philadelphia. The bomb is stowed internally and the speed-reducing flaps are of unusual design as shown in our photograph on page c. Vought dive-bombers include biplanes and the SBU series of monoplanes, the latter being capable of handling a 500- or a 1,000-lb. bomb. As long ago as 1935 Hawkers produced their P.V.4 Pegasus-engined dive-bomber, which looked like a large Pegasus-Hart and which was the first British bomber to be evolved specifically for diving attacks with a 1,000-lb. bomb load. Notwithstanding its great strength the struc- ture weight was only 27J per cent, of the gross weight. The best current example of a specialised British dive- bomber is the Blackburn Skua, which has special diving- brake flaps with a combined area of 18.5 sq. ft. These are metal-covered and are normally stowed flush with the lower surface of the wing, being inset from the trailing edge. They limit the diving speed to about 220 knots. Like the Swordfish and Shark TSRs, the new Fairey Albacore deck-landing biplane is capable of delivering diving attacks with a heavy bomb-load. The pilot, being situated in front of the wings, has an excellent view over the nose. Dive-bombing is practised by squadrons of the R.A.F. equipped with the Fairey Battle Merlin-engined monoplane: This machine carries its bombs on hydraulic jacks which are normally retracted into the wing, though for dive- bombing they are lowered beneath the wing surface. The normal bomb-load is stated by the Fairey Company to be 1,000 lb. External stowage can be provided for the following U.S. pattern bombs: Ten 120-lb.; three 285-lb.; two 625-lb., or one i,ioo-lb. Diving brakes are not fitted, but the machine has frequently demonstrated in public its ability to make diving attacks. Qertnan Practice Apart from the small single-seater Henschel Hs 123, Germany uses large numbers of Junkers Ju 87 single- engined two-seater dive-bombers. The Ju 87 has a cranked wing which carries diving brakes in the form of slats mounted just aft of the leading edge on each side. These are adjusted edge-on to the air stream for dive-bombing operations. Without them the T.V. speed is 430 m.p.h. It is possible to cam- a single 550-lb. or 1,100-lb. bomb beneath the fuselage, and there are external wing racks for four bombs of no lb. each. Diving brakes somewhat similar to those on the Ju 87 are fitted to the Fokker Gi. It is believed, incidentally, that Germany's new high- speed twin-engined bomber, the Junkers Ju 88, is stressed for delivering diving attacks at a comparatively shallow angle. This form of attack obviously lacks certain advan- tages given by the vertical or nearly vertical dive. Apart from some old Gourdou-Leseurre single-seater parasol monoplane dive-bombers, the French Navy has a number of Loire-Nieuport 40 cranked-wing monoplanes with Hispano 690 h.p. engines. These are single-seaters: A number of Vought monoplanes has also been acquired. One of the most modern dive-bombers in the world is Italy's Savoia Marchetti S.M.85 twin-engined high-wing monoplane. The trailing edge flaps on this mach" ae hinge through 90 deg. to act as diving brakes.
Sign up to
Flight Digital Magazine
Flight Print Magazine
Airline Business Magazine
E-newsletters
RSS
Events
