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Aviation History
1937
1937 - 0918.PDF
b FLIGHT. APRIL 8, 1937. •:..-::.,.,:..,•...;. ^^^m . • . • • .:'•• •: \ Wmmm STRAIGHT OFF THE LINE : A Bristol Blenheim medium bomber iresh in its camouflage paint. machine of its type in the world. The Blenheim is the lastest BRISTOL BRETHREN A Famous Trio oj Twin-engined Monoplanes—the Britain First, Blenheim and 143 SO brilliant have been the performances put up by the Bristol monoplane Britain First and its companion type, the Model 143, and so close is the resemblance of these machines, particularly the former, to the Blenheim medium bomber now in production for the R.A.F., that detailed information on their structural features and flying qualities has been withheld. Lately, however, the Bristol Company has made some interesting disclosures, perforce of a somewhat general nature, relating to these outstandingly successful aircraft. It will be recalled that the prototype Britain First, or type 142, was Built to the order of Lord Rothermere and was in tended tc. demonstrate the capabilities of an up-to-date British aeroplane. The results obtained were so excellent as to lead the Air Ministry to request the development of a medium bomber on similar lines. Bearing the Bristol works number 142M (denoting the similarity to its forerunner) and the Service name Blenheim the military machine is now in large-scale production at Filton. The third machine of the trio under discussion is unnamed but bears the designation 143. This model is planned on similar lines to the 142 and Blenheim but is intended for economical commercial operation, being fitted, to this end, -with sleeve-valve Aquila engines of lower power than the Mercuries in the other two types. Production of the 143 has been postponed indefinitely owing to magnitude of the work being undertaken at Filton in the interests of national defence. A Famous Prototype Britain First, the senior member of the trio, was designed as a six-passenger monoplane, having a low cantilever wing and mounting two radial engines. The fuselage is composed in the main of bulkhead formers and torc-and-aft stringers covered with sheeting, the whole being of aluminium alloy The portion forming the pilot's cockpit is of similar construction on the underside but the upper and extreme forward sections are made up of tubes which form the base for window framing. Tapermur in pian form and thickness the main planes have front and rear spars embodying H.T. steel flanges and light alloy webs, the whole being riveted together. The light- alloy ribs have circular flanged holes and are riveted to the spars; the covering is of light alloy sheet riveted to the spars ana ribs The centre section picks up on the fuselage by channels on the spar faces bolted to the main fuselage formers and the outer wing panels are secured by bolts. A fixed tailnlane is used (resembling, like the fin, the main planes in structuie) wmle the ailerons and elevators have a steel tube as their basic member, their light-alloy ribs bearing fabric covering The post which forms the basis of the fabric- covered rudder structure is built up of light alloy and carries the ribs and hinges Each engine-mounting is built in two portions. The rear part is of iteel tubes and picks up on the faces of front and rear spars, while the forward portion, forming the base of the engine cone mounting, is of similar construction and carries the mounting ring. Tubular framing is attached and forms the base for the nacelle fairing. Though originally designed to take two Bristol Aquila sleeve-valve engines, the Bristol 142 was produced in the first instance with the more powerful Mercury Vis rated at 605 h.p. at 12,500 ft. Subsequently these units were replaced by a pair of Mercury VIIIs delivering 825 h.p. apiece at 13,000 ft. with a maximum output of 840 h.p. at 14,000 ft. Low-drag long-chord cowlings with leading-edge exhaust collector rings are specified, and the airscrews are three-bladed variable-pitch de Havillands. The undercarriage is made up of port and starboard units embodying medium-pressure wheels and twin shock-absorber struts. These units retract rearward hydraulically and are housed in suitable fairings at the rear of the engine nacelles. A castering tail wheel is fitted, this having a shock-absorber unit and being arranged to return to the "aft central" position when it leaves the ground. Standard lighting and navigational equipment is carried to gether witn a landing lamp in the nose of the fuselage, and wireless mav be fitted just behind the pilot's seat. Little information is available on the Blenheim medium bomber other than that which has already appeared in Flight. It may be pointed out, however, that in this machine (arranged as a mid-wing monoplane to facilitate bomb stow age) the tail wheel retracts with the main undercarriage. The Blenheim carries a crew of three—a pilot and navigator in the nose and a wireless operator cum rear gunner in the aft portion of the cabin. The engines are Mercury VIIIs and the principal overall dimensions as follows: length 39 ft. 9 in., span 56 ft. 4 in., height (tail down) .9 ft. 10 in., maximum depth of fuselage 5 ft. 6in., maximum width of fuselage 4 ft. 4 in., diameter of airscrews 10 ft. 6 in. The Bristol 143 is a low-wing monoplane designed for the transport of passengers, freight or mail. The normal accom modation is for a pilot and navigator and eight passengers. There is a lavatory compartment aft of the cabin and about 60 cubic feet of baggage space. Window are provided not only in the sides, but in the roof of the cabin and, although normally fixed, they may be pushed out bodily after releasing their safety locking mechanisms, affording means of exit in an emergency. The two 500 h.p. civil-rated Aquila sleeve-valve engines have long chord cowlings with leading-edge exhaust collectors and are fed from two fuel tanks located in the centre section of the wings, each having a capacity of 102 gallons. The oil tanks are in the leading edge of the centre section, each having a capacity of 10 galls., and the coolers are of the skin type The span of the 143 is 56 ft. 6 in., length 42 ft., and height 12 ft. 3 in. Its loaded weight is about 9,000 lb., its speed approximately 200 m.p.h. and its range over 1,000 miles.
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