C.Barnes Bristol Aircraft since 1910 (Putnam)
The Bristol M.R.1 Metal Biplane
Some of the earliest pioneers of flying, including the Wright Brothers and Louis Bleriot, had been makers and riders of bicycles before their first attempts at aviation, and the materials and methods of bicycle construction were well known to aircraft builders from the beginning. Thin-walled carbon-steel seamless tubing, brazed or soldered into machined sockets, bolted together and braced with piano-wire, must have seemed the logical aircraft structure to military engineers desiring to attain serviceability in such aircraft as they considered to be practicable. Many attempts were made to design aeroplanes along these lines, such as the official R.E.5 and R.E.7, but always the weight was excessive, and if very thin-walled tubes were chosen, they would not stand up to manhandling on the ground because they buckled too easily. When the first useful aluminium alloys were produced, having a strength-weight ratio better than mild steel, they were found to be very easily corroded and impossible to braze or solder. Vickers Ltd. were among the first in the field with their all-metal monoplanes based on the patents of Robert Esnault-Pelterie, and in 1911 Sir George White had commissioned in France a monoplane of steel-tube construction designed by Gabriel Voisin, but it was far too heavy to fly.
The Company's interest in metal construction continued, and in July 1914 they undertook the detail design and construction of four all-metal derivatives of the B.E.2c, called the B.E.10. The aerodynamic design of this two-seater biplane was by a syndicate of Farnborough designers led by H. P. Folland and included such refinements as full-span trailing edge flaps to reduce landing speed. After the outbreak of war, the urgent need for quantity production of the B.E.2c at Filton caused the B.E.10 to be abandoned early in 1915, when the few components and details already manufactured were delivered to the Royal Aircraft Factory for mechanical testing.
During the ensuing 12 months, aircraft production all over the country expanded enormously and the authorities foresaw the risk, if war continued, of a severe shortage of timber suitable for aircraft manufacture; already stocks of Grade A silver spruce were declining and Grade B was being substituted wherever safety allowed. In July 1916 Capt. Barnwell drafted the revised layout of the R.2A reconnaissance biplane to match the 190 h.p. Rolls-Royce engine, thereby creating the Bristol Fighter. The need for a reconnaissance two-seater still remained for use where enemy air support was not paramount, and, as such fronts were mainly in a tropical climate, there seemed to be a strong case for adopting metal construction.
With the shortcomings of the B.E.10 design in mind, he approached the problem logically and drew on his early training on the Fairfield shipyard. He believed that duralumin sheet could be used in a monocoque structure if properly protected by a good quality marine varnish and adopted this method for the fuselage of the M.R.1, as the metal biplane was designated. The fuselage was built up in four sections bolted together; the front section was a semi-monocoque open channel with channel-section struts at each frame bracing the top longitudinals to the centre of the bottom frame member. This carried the engine bulkhead and bearers at its forward end and the tanks and centre section struts above and below. The next section aft was similar and contained the pilot's cockpit, with a Vickers gun and ammunition box above. The third section was a self-contained parallel-sided monocoque unit carrying the observer's seat with a Scarff gun mounting above, and the tapered monococque rear fuselage boom was bolted to the back of this section; the design was so arranged that the observer's cockpit section could be left out altogether and the aircraft then became a single-seater to which wings of smaller area could be attached. This versatility would have been a valuable investment in a machine for which a long storage life was envisaged, but in fact the contract awarded on 2 November 1916 was for only two prototypes for evaluation and mechanical test.
As Barnwell and Frise were under extreme pressure to get the Bristol Fighter into quantity production, the detail design of the M.R.1 was handed over to W. T. Reid, who faithfully translated Barnwell's ideas into metal, using relatively small amounts of mild steel. The duralumin monocoque fuselage was one of the first examples of double-skin construction, the smooth outer skin being riveted to a longitudinally corrugated inner skin. The original wing structure was a direct adaptation from wood to duralumin, using duplicated plates on edge to form the spars, but this was found to be much too flexible on test and in the end wing design and construction were sub-contracted to The Steel Wing Company of Gloucester, who had developed a method of using rolled high-tensile steel strip and had already produced successful sample steel wings for the B.E.2d and Avro 504. Two other methods, using both steel and duralumin, the subject of patents by the Krieger Electric Car Syndicate and a Mr. Mayrow, respectively, were also tested.
By mid-19l7 the first M.R.1, No. 2067 (A5177), was complete except for the wings, which were making slow progress at Gloucester, and it was decided to build a set of conventional wooden wings (with upper ailerons only) so as not to delay flight tests. The latter were entirely successful and A5177 was handed over to the Air Board on 23 October 1917, its contract price of ?2,000 having been reduced to ?1,600 on account of the wooden wings. The second M.R.1, No. 2068 (A5178), was delayed until late in 1918 before receiving its metal wings, but was then successfully flown, a Wolseley Viper engine of 180 h.p. being fitted instead of the 140 h.p. French Hispano-Suiza of the first machine. After the Armistice A5178 was piloted frequently by Capt. Barnwell, and eventually it was accepted to delivery to the Royal Aircraft Establishment; it was flown to Farnborough by Capt. Barnwell personally on 19 April 1919, but on arrival he collided with a pine tree near the North Gate of the R.A.E. and crashed on the aerodrome, bringing down the top of the tree with the aeroplane. He was shaken, but otherwise unhurt; the M.R.1, however, was considerably damaged and no attempt was made to repair it. Meanwhile, A5177 (renumbered A58623) was being structurally tested and much valuable information on metal construction was gleaned from it. For its day, the M.R.1 was a considerable technical achievement, its disposable load amounting to more than 40% of its all-up weight. Moreover, it had been constructed almost entirely without using specialised tools and equipment, and the necessity of developing these for quantity production was perhaps the most valuable of the lessons learned.
SPECIFICATION AND DATA
Manufacturers: The British & Colonial Aeroplane Co. Ltd., Brislington, Bristol
Power Plants: One 140 hp Hispano-Suiza
One 180 hp Wolseley Viper
Span: 42 ft 2 in
Length: 27 ft
Height: 10 ft 3 in
Wing Area: 458 sq ft
Empty Weight: 1,700 lb
All-up Weight: 2,810 lb
Max. Speed: 110 mph
Endurance: 5 hours
Sequence Nos.: 2067,2068
H.King Armament of British Aircraft (Putnam)
M.R.I. Though a notable structural advance, the metal-built M.R.I of 1916 carried the same armament as the Bristol Fighter and this was similarly disposed. The fuselage was built in sections, the second embodying the cockpit. Vickers gun and ammunition box and the third the observer's seat with the Scarff ring-mounting above it.
Jane's All The World Aircraft 1919
The Bristol all-metal biplane is more or less an all-metal Bristol " Fighter " with sundry modifications and was designed primarily for use in countries where extremes of heat and cold might have a detrimental effect on woodwork.
Metal has entirely replaced wood in the construction, the fuselage being constructed of aluminium and steel and can be easily dismantled for transport and storage purposes. The wings, which are unstaggered are of all-steel construction. The fuselage is slung between the planes, as in the Bristol " Fighter," but the lower centre section is completely cut away, leaving the two main spar tubes, to which are attached, the two lower centre section struts.
Type of machine Two-seater Biplane.
Name or type No. of machine All Metal M.R.I.
Purpose for which intended Fighting and Reconnaissance.
Span 42 ft. 2 in.
Gap 5 ft. 11 In.
Overall length 27 ft.
Maximum height 10 ft. 3 In.
Chord 6 ft.
Total surface of wings 458 sq. ft.
Area of ailerons 39 sq. ft.
Total area of tail 27.8 sq. ft.
Span of tail 16 ft. 3 in.
Area of elevators 30 sq. ft.
Area of rudder 8.25 sq. ft.
Area of fin 7.8 sq. ft.
Engine type and h.p. 170 h.p. Wolseley "Viper"
Airscrew, diam., pitch and revs. 8 ft. 10 in. diam., 6 ft. 7 in. pitch, 1,700 r.p.m.
Weight of machine empty 1,700 lbs.
Load per sq. ft. 6.13 lbs.
Weight per h.p. 16.5 lbs.
Petrol tank capacity In gallons 50 gallons.
Oil tank capacity In gallons 5 gallons.
Speed low down 110m.p.h.
Speed at 5,000 feet 106 m.p.h.
Speed at 10,000 feet 98 m.p.h.
Landing speed 47 m.p.h.
Flight, January 23, 1919.
The Bristol "All-Metal" Biplane
From the earliest days of aviation the question of wood versus metal construction has been the subject of discussion, and both methods have had their supporters. Up till the present, however, the wood construction has been predominating, at any rate in this country. Particular interest therefore attaches to the few examples of the metal construction method that have been built. Among these is the Bristol type MR.1, shown in the accompanying illustrations. At the present moment we cannot, unfortunately, publish constructional details of this machine, this must be reserved until another time, but several interesting facts emerge from an inspection of the tables of particulars. Thus it will be seen that although the All-Metal machine is of somewhat larger dimensions than the Bristol Fighter, the loaded weight of the two machines is practically the same. Against this must be put the fact that the MR.1 has a 170 h.p. Hispano engine, while the F2B has a 260 h.p. Rolls-Royce. The All-Metal carries, however, slightly more fuel than does the B.F. The loading per sq. ft. is somewhat smaller for the larger machine, but the load per horse-power is considerably greater, thus accounting for the fact that the MR.1 has not so good a performance as the F2B. It might be added that the weight, empty, of the B.F., is 1,750 lbs., and that of the MR.1 1,700 lbs. It may, therefore, safely be concluded from these particulars that there is no reason to suppose that an all-metal aeroplane cannot be built as light, or nearly so, as one constructed in the ordinary way of wood. There can be little doubt that for use in tropical climates, such as will be encountered by the post-War commercial aeroplane, the metal construction will be better able to withstand the changes in temperature than will one built largely of wood, and while we should not care to assert that the days of wood construction for aeroplanes are over, we do think that metal construction will be more general in the future than it has been in the past.