A.Brew Boulton Paul Aircraft since 1915 (Putnam)
At the end of the War there were two dozen aircraft manufacturers in the United Kingdom with their own design departments. All of them were faced with the fact that their only products were no longer wanted. The RAF had thousands of surplus aircraft on strength, and hundreds more were being built each week until contracts were cancelled. There was no prospect of military orders in the immediate future, but most companies hoped for a boom in civil flying, and set about converting whatever designs they had for their most suitable civil use, or drawing new purpose-built machines.
Although they had only built three aircraft of their own design at the end of the War, a Bobolink, a P.6, and the first Bourges, with two more Bourges nearly completed, Boulton & Paul had some advantages over many manufacturers. The P.6, though basically experimental, was really just a two-seat light aircraft, ready for promotion as a private aeroplane with very little modification, and the Bourges was an outstanding twin-engined bomber, once the Dragonflies were abandoned in favour of Napier Lions, and offered a very advanced basis for the design of an airliner.
The company suffered from one grave disadvantage, however. Although they had built over 2,000 aircraft during the War, because so few were of their own design, their name was not in the forefront of aviation circles. There was, however, one very good chance to place their name in the limelight and to promote a new airliner based on the Bourges at the same time. The Daily Mail ?10,000 prize for the first nonstop flight across the Atlantic had been held in abeyance since before the War.
Of course many of the other manufacturers joined the immediate race to win this prize, and to promote their own products. Each attempted to maintain the utmost secrecy so as to try and steal a march on their rivals. Quickest off the mark were Sopwith with their single-engine Atlantic, based largely on their wartime B.1 with many Cuckoo components for speed of construction, and Martinsyde with a much enlarged version of the F.4 Buzzard renamed The Raymor. Frederick Handley Page saw his four-engined V/1500 as the ideal aircraft for the job, and Vickers entered with their twin-engined Vimy. Shorts saw the excellent range of the Shirl torpedo bomber as a basis for a machine capable of flying the Atlantic east to west, unlike all the others who preferred to fly in the other direction with the prevailing winds. Fairey made preparations to convert their Fairey III seaplane for an attempt and the Alliance Aircraft Company built a special aircraft for the task, their P.2 Seabird, powered by a single Napier Lion. Finally Boulton & Paul began the preparation of what would be one of the most thoughtfully conceived designs to be prepared to contest the Daily Mail prize, the P.8 Atlantic.
Two prototypes were to be built, and from the outset the first was designed and built purely for the Atlantic attempt. The second Bourges prototype, F2904, having been heavily damaged in a crash at Mousehold, was obtained from the Air Ministry and dismantled. The remains of its structure formed the basis for the first prototype, the sloping upper wing centre section, and the Dragonfly engines being dispensed with entirely.
The wings of the P.8 were of increased span, to 60 ft 4 in, but were the same basic Bourges three-bay unstaggered units with the straight-through centre section on the upper wing which had 8 ft chord and the lower 6 ft 6 in. There were horn-balanced ailerons on all four wings. Standard wooden construction was used but the spar fittings were very substantial, with all the struts pin-jointed and backed by metal fish-plates at every junction.
Though John North had already decided that the future of aircraft construction lay in metal structures the use of wood was continued in the P.8 for convenience, and above all for speed of construction. That did not prevent him introducing certain improved techniques. For the securing of metal fittings to the wooden fuselage longerons, tubular rivets were introduced instead of bolts. The rivet was inserted through metal fishplates on each side and the ends flattened with rivetting tools which were developed especially for the job, resulting in just a splayed mouth on each side instead of a projecting bolt. This resulted in a joint which was much lighter and compact and they were much quicker to fit, though they took longer to replace than conventional bolts.
Although the major visual change in the P.8 from its predecessor was the fact that the fuselage filled the 6 ft 6 in gap between the wings, the fuselage actually retained the basic Bourges structure. The upper part was merely a fairing of bridges and runners, this, too, was to speed completion, to prepare the aircraft for the Atlantic attempt before its rivals. The fuselage had four longerons braced and cross-strutted with tie-rods. The upper longerons being dead straight when the aircraft was in the flying position, and therefore very useful for bracing purposes. The gunner's position in the nose was replaced by a rounded construction covered with plywood and fabric.
The pilot's cockpit was situated just in front of the wings, as in the Bourges, but it was given a fully-enclosed canopy, a very advanced feature for the day. It was faired into the fuselage upper surface, so that rear view was restricted, but the view forward, sideways and down was excellent, better than any airliner extant, and not equalled until the D.H. Dragon appeared. For conservative pilots who liked to feel the wind around their ears, an upper skylight was provided, which could be opened. In the first prototype, for the Atlantic attempt, provision was made for a relief pilot and a radio operator who was provided with two sets, one for communications and one for direction finding. In the event of ditching in the Atlantic, a small balloon and hydrogen bottle were provided, to carry the radio aerial aloft for emergency signals. The radio operator and navigator were accommodated in a cabin just behind the cockpit, illuminated by large rectangular windows on each side.
Behind the crew compartment the whole of the cabin space was taken up with six fuel tanks. They were fitted with jettison valves, so that the entire fuel load could be dumped in 1 1/4 minutes, and were so situated that once empty, they would keep the aircraft afloat the right way up. The fuel capacity was sufficient for a flight of 3,850 miles, and the performance of the aircraft was such (its cruising speed of 116 mph was much higher than any potential competitor), that it could maintain height on only one engine after only two hours' fuel had been consumed. More importantly, of course, this meant that the aircraft could maintain height at only half throttle, thus putting little strain on the engines.
The engines were 450 hp Napier Lions, with aluminium cowlings, carried on the lower wings inside the inner interplane struts. The frontal radiators fitted to each engine on the Bourges P.7b were dispensed with, and replaced by one retractable fuselage mounted radiator. This was connected to a header tank above each engine with two cut-off valves each side so that the system could be closed off should a leak develop on either side. The oil tanks, each of 6 gal capacity were fitted behind each engine, alongside self-starting magnetos. The engines drove four-blade propellers of 9 ft 6 in diameter, and were braced by steel tubing to the fuselage longerons, forming a strong triangulation with the bracing wires.
The fin and horn-balanced rudder were circular in profile, but the tailplane was square-cut like the wings, and the elevators had no horn balance. Because the rudder was insufficient to maintain heading on asymmetric power two small fins were fitted, projecting above and below the tailplane. These could be locked at an angle in the airstream in the event of one engine failing.
The P.8 was so stable it could virtually be flown hands off when fully trimmed, and it was possible, by moving a single lever, to lock the elevators and ailerons and transfer rudder control to the wheel. This was unusual in that such a device would normally have operated the ailerons only, since on most aircraft steering on rudder only produces the effect of tightening into a dive. On the P.8 a slight touch of rudder was enough to return it to the required heading with no loss of height. This device was also useful for steering the aircraft on the ground using hands only instead of feet, as long as the pilot remembered to unlock the controls before taking off!
To the left of the pilot was the wheel for lowering and raising the radiator, to his right were two wheels, one to set the angle of the auxiliary fins on the tailplane, to overcome asymmetric thrust, and the other for controlling the angle of tailplane incidence.
The undercarriage was probably the most advanced feature of the aircraft. The units were V-shaped, with the legs attached at the inner interplane struts, giving a very wide track, and the split-axles hinged at the bottom fuselage longerons. One very large Palmer aircraft wheel and tyre was fitted on each side. The technological advance was in the springing, which was not the normal simple rubber bungee, but also contained an oleo-pneumatic leg to take landing shocks. This combination springing was even more advanced in concept that the pure oleo-pneumatic undercarriages which were soon to appear. The early oleo-pneumatic systems could take landing shocks very well, but were less able to absorb the frequent vertical jolts caused by taxi-ing over rough grass aerodromes.
The crew chosen for the Atlantic flight was, Maj K S Savory as first pilot, Capt A L Howarth as second pilot and radio operator, and Capt J H Woolner as navigator. Boulton & Paul's managing director, Maj Guy ffiske went to Newfoundland and chose a suitable take-off field, and the weather conditions over the North Atlantic were studied in great detail for several months.
The race for the prize was developing publicly. After test flights in February 1919 the Sopwith was shipped, and on 19 March the Daily Mail was officially notified of its entry for the prize. The entries of the Short Shamrock as the modified Shirl had been named in honour of its proposed take-off point at the Curragh, the Martinsyde Raymor, and the Fairey III seaplane were to follow in quick succession.
The Sopwith Atlantic arrived in Newfoundland on 29 March, and shortly afterwards the Martinsyde had a 24 hr ground test, followed by its Rolls-Royce Falcon engine being stripped down and examined. At Vickers the modifications to the 13th Vimy off their production lines were nearing completion and both the pilot, John Alcock and the navigator, Arthur Whitten Brown had been chosen.
Preparations by Boulton & Paul were severely delayed when the still unregistered P.8 crashed. In the haste to get the P.8 ready for the Atlantic flight, Frank Courtney ran up each of the engines separately before the first flight in April 1919, thereby failing to discover that there was a fault in the fuel system which did not give an adequate supply to both at once. One of the Lions cut out just after take off, the aircraft yawed into wind and a wingtip struck the ground, virtually writing it off. The entire nose section broke free, with Courtney within it, and he was unhurt.
The second P.8 was being built, and preparations were put in place to use this on the Atlantic flight. On 11 April the Sopwith Atlantic had been test flown in Newfoundland, but was soon grounded because of rain and thick mist. The Martinsyde had just arrived in Newfoundland and four days later the Handley Page V/1500 was shipped.
On 18 April the Vickers Vimy was test flown at Brooklands, and on the same day the Short Shamrock, which was basically a Shirl with the wing extended to three bays and a huge droppable cylindrical fuel tank bringing the total fuel load to 435 gal, took off from Eastchurch for Ireland. Piloted by Maj J C P Wood with Capt C C Wyllie as navigator, it was refuelled at Holyhead, and then took off for the Curragh, which was considered the only place in Ireland with a long enough take-off run for the fully-laden machine. Twelve miles out across the Irish Sea the engine stopped and Wood had to ditch. The Shamrock remained afloat, though upside down, and was towed into Holyhead harbour, and Wood announced his intention of remaining in the contest.
Although not in competition for the Daily Mail prize, the Americans were mounting an official government attempt to be the first across the Atlantic, albeit in stages via the Azores. Three Curtis NC flying-boats would fly in formation via Newfoundland and the Azores to Lisbon, along a route which would be marked by a line of 68 destroyers stationed at intervals of 50 miles, with five battleships stationed at distances of 500 miles. Every fourth destroyer would act as a meteorological station. Just in case the flying-boats failed to make it, despite this massive support, a four-man airship was moved to Newfoundland to make the attempt. On 8 May the three NCs took off from Rockaway, New York, on the first leg to Newfoundland, though it took five days for them all to get there.
The threat of the Americans being first spurred the small private British teams into action. Both the Sopwith and Martinsyde crews made hasty preparations, but the Americans took off first. On 16 May the three NCs lifted off from Trepassey Bay and headed for the Azores, but only one was to arrive, NC-4 at 9.25 am on 17 May.
Though news of the Americans' arrival in the Azores reached Newfoundland, there was still a chance that the British could be first across. On 18 May the Sopwith Atlantic took off from Newfoundland, piloted by Harry Hawker, with Lieut Cdr MacKenzie-Grieve as navigator. It was eight days before anything more was heard from them. They had ditched in the ocean, and were luckily picked up by a ship, though they were over 100 miles off course after flying 800 miles on dead reckoning. Their failure justified safety measures built into the Boulton & Paul P.8, the single-engined performance, and the direction-finding radio in particular.
The Sopwith aircraft actually passed over the heads of the Martinsyde crew as they were making frantic attempts to get the Raymor ready. Attempting to take off 20 min after the Sopwith had disappeared the undercarriage of the overloaded Raymor collapsed, and the aircraft was heavily damaged.
On 27 May the NC-4, commanded by Lieut Commander Read left the Azores and reached Lisbon the same day, the first aircraft to fly the Atlantic. The honour of making the first nonstop flight, and with it the ?10,000 prize still remained to be captured however.
Meanwhile the Handley Page V/1500 and Alcock and Brown's Vickers Vimy had arrived in Newfoundland. The Handley Page was found to be damaged, and repairs were put in hand. It was to have a four-man crew, Maj H G Brackley, pilot, Admiral Mark Kerr, second pilot, Tryggve Gran, navigator and third pilot and F Wyatt, wireless operator. After the repairs had been completed, a trial flight could not be made until 10 June because of bad weather conditions. Trial flights revealed that the engines had an alarming tendency to overheat, and new radiators were sent for from England, but were not to arrive before the 18th.
Repairs were also instituted to the Martinsyde Raymor, but before a second attempt could be made and before the second Boulton & Paul P.8 could be finished John Alcock and Arthur Whitten Brown made the first nonstop transatlantic flight in their Vickers Vimy, taking off on 14 June.
The Boulton & Paul project was abandoned, but the Martinsyde crew did make a second attempt, only for the undercarriage to collapse again on take off. The Handley Page was sent instead on a publicity flight to Long Island, where many demonstrations took place.
The second P.8 was completed and was flown for some time as both the prototype airliner and as a flying aerodynamic test-bed, registered G-EAPE. It was never converted to airliner configuration but the company did build a fuselage mock-up of the proposed layout, and artist's impressions of the finished product were prepared by Geoffrey Watson.
Although the layout of the passenger/cargo accommodation and fuel tankage was kept fluid to suit any airline requirements, the basic version offered was with 100 gal of fuel and seven passengers. The main tank was sited within the fuselage, just beneath the upper wing, so the engines could be gravity fed. Forward of that was a cabin for three passengers, and behind it another cabin for four passengers. Passengers entered through separate doors to each cabin. To improve the head-room on entry, a portion of the roof over each compartment could be slid aside. The forward door was rather high off the ground being just behind the cockpit, and necessitated climbing aloft high set of steps to gain entry. Even the door sill of the rear cabin was about 6 ft off the ground. Both cabins were heated, and great play was made in the brochure that passengers would not have to be wrapped up in warm clothing, an inconvenience on many of the makeshift airliners being put into service at the time. Both cabins had large picture windows on each side.
A mail box, capable of carrying up to 500 lb of mail could be loaded by special loading gear patented by Boulton & Paul, and directly related to the bomb cell hoist developed for the Bourges. The full disposable load of the aircraft, not including fuel was 1,870 lb. The top speed was a remarkable 149 mph at sea level, and 143 mph at 10,000 ft, and even its cruising speed of 116 mph was faster than the top speed of all contemporary airliners being offered for sale. The P.8 was in fact claimed to be the fastest twin-engined aircraft in the world.
With a wing loading not much above that of the Bourges, at 10 1/4 lb/sq ft, the P.8 also retained much of its forebear's agility. To placate the conservative nature of most pilots of the day, the airliner version was also offered with either the enclosed canopy, or an open cockpit with a simple windscreen.
There is little doubt that the P.8 was the most advanced and competent design to be prepared for the Atlantic flight, but fate decreed that lasting fame was not to come Boulton & Paul's way. The company's attempts to market the P.8 as an airliner, were also without success. The power which gave it such an outstanding performance and made it safe to fly on one engine, meant it could not compete economically with some of its competitors, and with the desperate economics of some of the early airline operations, this counted more than safety and passenger comfort.
A total of 900 hp and only seven passengers compared unfavourably with the D.H.18, which first flew in March 1920. This lifted a pilot and eight passengers on just one Napier Lion. The fact that it had only a single engine, a top speed of only 121 mph and an abysmal view for the pilot, sited as he was behind the passenger cabin, nearer the tail than the nose, were of less importance than the economics. Even Handley Page's conversions of their 0/400 bomber, though twin-engined, were totally unable to maintain height on the power of only one, and only their very low landing speed prevented the many emergency landings becoming crashes.
If only that first P.8 had not crashed, and the Atlantic prize had been won, the kudos which would have resulted might have caused potential airline passengers to clamour to fly on the aircraft which was safe enough to fly the Atlantic.
Two 450 hp Napier Lion.
Span 60 ft 4in; length 40 ft; height 12 ft 4 in; wing area 770 sq ft.
Empty weight 5,170 lb; loaded weight 7,880 lb.
Maximum speed 149 mph at sea level, 143 mph at 10,000 ft, 138 mph at 15,000 ft; climb to 10,000 ft 8 min, to 15,000 ft 15 min; service ceiling 25,000 ft.
A.Jackson British Civil Aircraft since 1919 vol.1 (Putnam)
BOULTON AND PAUL P.8
Fast twin-engined passenger and mailplane powered by two 450-h.p. Napier Lion engines, built at Norwich 1919. One civil aircraft only: G-EAPE, c/n P.8-2, first flown 10.5 .20, used only for experimental flying. Span, 61 ft. Length, 40 ft. Tare wt., 4,000 lb. A.U.W., 7,000 lb. Max. speed 149 m.p.h.
Flight, April 17, 1919.
THE TRANSATLANTIC FLIGHT
As the days go by, the interest in the race for t he Daily Mail L10,000 prize for the first man to cross the Atlantic by air increases. Mr. Harry Hawker, the pilot of the Sopwith-Rolls-Royce "Atlantic," and his navigator and assistant pilot Commander Mackenzie Grieve, having tested their machine and had it officially sealed, are ready for the start, watching anxiously the weather and wind, and awaiting with impatience the weather reports sent twice a day from the meteorological branch of the Air Ministry in London. To add to the impatience of t he Sopwith crew, Mr. F . P. Raynham and his navigator, Capt. Morgan, have arrived at Newfoundland with their Rolls-Royce engined Martinsyde, the "Raymor," and are getting their mount ready with all speed. Every day of bad weather increases their chances of getting ready before the Sopwith machine has had an opportunity to make a start, and if the unsettled weather conditions continue there is every probability that both machines may start more or less simultaneously. Then there is the Short machine, also with Rolls-Royce engine, which, as time is pressing, it is intended to start from this side. This machine also is now ready. It is therefore not an unlikely event that this machine may meet one or more of those making the eastward journey, although, as t he routes will probably differ in location as well as in direction, they are hardly likely to get within hail of each other. The Handley-Page giant machine with four Rolls-Royce engines, is stated to be ready for shipment, and the plans call for a start from St. John's about the middle of May. Mr. Handley-Page has stated that the attempt will be made under the best conditions without any regard to being first across. It has not, up to the time of writing, been definitely stated who will be the pilot and navigator of the H.P.
The Fairey seaplane, Rolls-Royce engine, which will be piloted by Mr. Sydney Pickles, is also nearing completion, but a certain amount of secrecy as to the plans of this entrant is being maintained. The same applies to the Whitehead contingent, from whom not a word concerning their plans has been vouchsafed.
A New Entrant.
While some of the early entrants are ready and waiting for the weather to improve, others are working night and day in order to get their machines ready. Thus it has been announced that Messrs. Boulton and Paul, Ltd., of Norwich have entered a twin-engined machine fitted with two 450 h.p Napier engines. This machine was originally designed as a passenger carrier, having all t he occupants, with the exception of the pilot, enclosed in a roomy cabin. By suitably arranging the wind screen the pilot can be very well protected outside. For the purpose of the Transatlantic journey the great amount of cabin space available will be used chiefly for housing the fuel tanks. It is estimated that she will have a range, when fitted with six tanks (containing 800 gallons of petrol) for the Transatlantic journey, of over 3,000 miles (in still air, of course), which should be ample for making the journey in either direction.
It is the intention of the firm to send two machines of this type to Newfoundland, and Maj. H. G. ffiske will take them over when they are ready, together with a staff of pilots and mechanics. The crew of the competing machine will number three, and has not yet been chosen.
Mr. J. D. North, the designer of the "B.P.," is confident that the machine can do the trip if she can be got ready in time. A special feature of the controls of the Boulton and Paul machine deserves to be mentioned. There is a locking device, mounted near the floorboards of the pilot's cockpit, by means of which the elevator and wing flaps are locked simultaneously in any desired position. The pull on the trigger at the same time automatically changes the rudder control over from the foot bar to the wheel which ordinarily operates the ailerons, the steering then being done exactly as in a motor car. This should relieve the pilot of a great amount of work, especially as the machine is very stable and will require little or no attention beyond that of keeping her on her course.
Flight, May 15, 1919.
THE TRANSATLANTIC CONTEST
IN our issue of April 10 we published scale drawings of the Sopwith and Short Transatlantic machines. At the time no further drawings were available, and other machines have been entered since then. This week we are able, through the courtesy of the various constructors who have given us facilities for obtaining particulars of their machines, to place before our readers scale drawings of three other entrants and a photograph of a fourth, as well as scale drawings of one of the American flying-boats which will attempt the crossing hors de concours.
The Boulton and Paul Napier-Machine
ONE of the most important features of the Boulton and Paul machine (an illustration of which appeared in our issue of April 17) is that after a short time in the air (about two hours for the amount of fuel carried for the Transatlantic flight) the machine is able to keep aloft on one engine only. The importance of this can scarcely be exaggerated. It will mean, looking at it in another way, that after two hours the two Napier engines need only be run at half their power. This should mean an enormous increase in their chance to "stick it" for the whole journey. It is further to be noted that at the "cruising speed" the speed of the machine is as high as 116 m.p.h. This is probably the highest cruising speed of any machine entered so far for the race. When flying at the cruising speed the range of the Boulton and Paul machine has been calculated to be about 3,850 miles, so that there is an ample margin in hand for the Transatlantic journey.
The fuel is carried in six separate tanks, each fitted with jettison valves operated by a lock control in the pilot's cockpit. These valves will discharge the whole of the fuel in 1 1/4 min. in case of emergency, and the tanks are so placed that when empty they will keep the machine afloat and right way up. The crew will consist of three, a chief pilot and two navigators, who will also be wireless operators and assistant pilots. The names of the crew have not yet been announced.
Two independent wireless sets will be fitted, a "spark" wireless for sending and receiving messages, and a "directional" for navigation purposes. A small hydrogen bottle and a balloon will be carried so as to make it possible to send up an "aerial" for sending wireless "S.O.S." even after the machine is on the sea, should that emergency occur.
The chief characteristics of the B.P. machine are as follow :-
Span 59 ft.
Length 40 ft.
Height 12 ft. 3 in.
Weight loaded 11,500 lbs.
Fuel capacity, petrol 800 gals.
Fuel capacity, oil 90 gals.
Cruising range 3,850 miles.
Engines Two 450 h.p. Napiers.
Maximum speed 148 m.p.h.
Cruising speed 116 m.p.h.
Flight, October 30, 1919.
THE BOULTON & PAUL COMMERCIAL MACHINE:
Two 450 h.p. Napier Lion Engines
GENERALLY speaking, the Boulton & Paul Commercial biplane may be said to be similar to the machine built by this firm for the Transatlantic flight. The deep fuselage extends right up to the top plane, thus giving ample accommodation inside for passengers or/and goods. Since, however, the main fuel tanks are mounted inside the body, the cargo or passenger space is divided into two separate compartments, one in front of the tanks and one aft of them. As at present fitted up, the machine is not provided with its full complement of seats, etc., as it is intended to obtain a certain amount of experience with her in the air before finally deciding upon the arrangement of seats. Also the arrangement will be largely dependent upon whether the machine is to be used for passenger flying, for carrying mails, or for a combination of the two. It will, therefore, be understood that this part of the design is still left open, so to speak, and is subject to alterations as requirements demand. Obviously there is a wide choice according to the use to which the machine will be put. For instance, by fitting relatively small tanks and installing a large number of seats, the P.8, as this machine is called on the B. & P. series list, will be able to carry a large load for a relatively short distance. On the other hand, the tank capacity may be increased and mails substituted for some of the passengers. Or, again, all passengers and mails may be left out, the whole carrying capacity being taken up by fuel, in which case the machine would have a very long radius of action.
Constructionally, there are no great innovations to be found in the P8, most of the constructional details being of more or less standard type. It might be pointed out, however, that very extensive use has been made of tubular rivets in place of threaded bolts. This method of securing parts has been found very economical, both as regards strength for weight and in the actual use, the tubular rivets being quick to make once the proper tools for their manufacture have been installed, while replacements take little, if any, longer than would the replacement of a bolt. These tubular rivets are employed for securing the metal fittings to the fuselage longerons, and in many other places in the body and undercarriage. They make a very neat job, as there are no boltheads or nuts projecting, but only a thin bell mouth where the ends are flanged out. Apart from the use of these rivets, the fuselage is of standard construction, with longerons and struts of wood, the structure being cross-braced with standard tie rods. In the front part this simple arrangement is varied occasionally as local requirements demand, but, fundamentally, the fuselage structure is of the simple girder type. One feature of the fuselage design should be pointed out. The upper longerons do not run along the top corners of the body, but are placed some distance down the side. As a matter of fact, the top longerons run straight, in side elevation, thus forming a good datum line for rigging and trueing-up purposes. From this it will be seen that only the lower part of the fuselage is braced, the upper portion being merely a fairing made up of formers and longitudinal stringers. This can be clearly seen in one of the accompanying photographs, which shows the rear portion of the body, looking aft from the rear cabin.
As already pointed out, the main fuel tanks are mounted in the body, and as they are placed over the centre of pressure of the wings, so as not to alter the trim when the fuel is consumed, they divide the available space into two separate compartments. When fitted out as a passenger carrier, both front and rear cabins may be fitted with seats. Owing to the deep body and the possibility of placing the petrol tank high in the body, there is no need for any gravity tank, the main upper petrol tank performing this function. If more tanks are fitted for long duration work, some of them near the floor of the body, it will probably become necessary to provide means for transferring the fuel from these into the top tank, but at present the petrol system is simplicity itself, with gravity feed direct from the main tank.
In the fore part of the body, in front of the fore cabin, is the pilot's cockpit, the wind screen for which is so arranged that if desired the pilot can have his head projecting into the open without being in a direct draught, while if desired, he can close a small skylight and be totally enclosed, as are the passengers. From this position he retains quite a good view in practically all directions except straight back, and as the machine is very fast - about 150 m.p.h. - he need not worry overmuch about machines overtaking him. Lateral control is by means of a wheel, and a fore and aft movement of the wheel operates the elevator. Rudder control is normally by foot bar, but by a very ingenious arrangement it is possible during a long flight to lock the ailerons and elevator in position and steer the machine by the wheel. One of our sketches shows the control column and wheel. The changeover from foot bar to wheel steering is done with one movement. The wheel is so held that the ailerons and elevators are neutral and, with the wheel and column in this position, the locking lever shown near the bottom of the sketch is pulled. This locks the lateral and longitudinal control surfaces while at the same time disengaging the foot bar and connecting the rudder cables to the wheel. As the machine is expected to be very stable, this should be a considerable advantage on a very long journey. The controls are instantly returned to the normal by pulling the locking lever in the opposite direction, an operation requiring a fraction of a second only. For use when one engine is pulling slightly more than the other, there is an arrangement, also shown in the sketch, for taking the load thus imposed off the pilot's feet. This consists of a small wheel mounted on the right-hand side of the control column, near the top. Pressing the wheel inwards causes it to engage with the rudder control cables, and turning the wheel then puts one rudder cable under tension, the amount depending upon the number of turns given to the wheel. In this manner the pilot does not have to be pressing constantly with his right or left foot, according to which engine pulls the harder, and the springs incorporated with the control cables ensure that for steering the rudder is as easy to move as if it were central. In case of total failure of one engine, the turning effort made possible by this arrangement would be insufficient, and provision has been made for this contingency by pivoted fins above and below the tail plane, operated by a wheel on the starboard wall of the pilot's cockpit. The usual tail plane trimming gear is provided, also actuated by a hand-operated wheel.
One of the accompanying sketches shows the engine controls. These consist of two sets of duplicate levers. The rear set is for ordinary engine control, the right-hand lever being the throttle for the starboard engine, the left-hand one for the port engine. The front pair is for altitude control. From the way the levers are mounted, it will be seen that both engines may be throttled together or separately, by moving the two levers together or singly.
As will be seen from the general arrangement drawings and photographs of the machine, the engines are enclosed in neat aluminium casings, giving a very low resistance. This has been made possible by fitting the radiator in the fuselage. To vary the cooling the radiator is mounted on two vertical worms which can be rotated from the pilot's seat by means of a wheel via chains and cables. A header tank is placed in the top plane, connected to the radiator by means of a flexible rubber pipe. This pipe is arranged in a series of zig-zags so as to allow of the raising and lowering of the radiator without getting kinks in the tube. Although the single radiator is not partitioned off, the water system of either engine can be cut off during flight. The manner in which this is accomplished will be understood from reference to the diagram of the water system. The water pumps on the engines draw the water from the bottom of the radiator, force it through the water jackets and hence up to a small tank in the top plane. From this it runs down a pipe to the side of the radiator. Here the water is not allowed to mix at once with that already in the radiator, but has to flow over the top of a small partition near the side of the radiator. The pipes leading from the radiator to the engine, and the return pipes from engines to radiator, are provided with cut-off valves, placed under the bottom of the fuselage and connected to controls in the pilot's cockpit. The actual cut-off valves are shown in one of the accompanying photographs.
The main planes, of which the top one has a chord of 8 ft., while the bottom plane chord is 6 ft. 6 ins., are of standard construction. The spar fittings are very substantial, as may be gathered from two of our sketches, which show the front and rear fittings at the points where occur the attachments of front and rear chassis struts, inter-plane struts, diagonal engine bed struts, etc. All the struts, it will be seen, are pin jointed. Balanced ailerons are fitted to both top and bottom planes.
The 450 h.p. Napier Lion engines are mounted on the bottom planes, the engine beds being of light although very strong design. The vertical supports of the engine bearers are in the form of a framework of wood, covered with three-ply. From the engine bearers diagonal tubes run outwards and downwards, providing a perfect system of triangulation, which is extended inwards by tubes running from the bottom plane spars to the upper longerons of the fuselage. The whole engine mounting has been very well thought out, care being taken to ensure that there are no offset moments. The consequence is that there is a marked absence of vibration under all conditions.
One of our photographs shows the starboard engine in three-quarter rear view. It will be seen that the oil tank is mounted behind the engine. Mounted on the trailing portion of the bottom plane, behind the oil tank, is a hand-operated starting magneto for starting the engine when the machine is on the ground. The engine housing is in the form of sheet aluminium, and may be seen in the photographs of the complete machine.
The undercarriage is in the form of two simple "Vees" of wood, hinged laterally to the bottom wing spars. The two axles are of the bent type, hinged at their inner ends to the bottom longerons of the fuselage, and carrying at their outer ends the Palmer Cord wheels. Springing is partly by shock absorbers of rubber and partly pneumatic, the cylinder being shown in one of the photographs.
The control surfaces are of standard type, the rudder being balanced. The tail plane, as already mentioned, is of the variable incidence type for purposes of trimming the machine, and the only respect in which the tail differs from usual practice is in the fitting of two pivoted fins, above and below the tail plane, which serve to balance the turning moment set up when one engine is out of commission.
The aerodynamical features of the P.8 have been thoroughly tested in the wind tunnel of Messrs. Boulton & Paul's experimental department, especial care being taken to ensure good stability, as this is a very important point in a commercial machine designed for long-distance flights. Special apparatus have been designed to facilitate the determination of rotary derivatives, and a great amount of stability work is being done by the B. & P. wind tunnel staff. When, therefore, this firm places a machine on the market it may be taken for granted that every effort has been made to ensure that she is absolutely "right," having that degree of stability which relieves the pilot of the greater part of his work on a long flight, without having the excessive stability that may cause a machine to "take charge" at a time when manoeuvrability is required.
The main particulars of performance, etc., are as follows :-
Weight, empty 4,000 lbs.
" loaded 7,000 "
Speed at 10,000 ft. 149 m.p.h
15,000 ft 142 "
Climb to 10,000 ft. 8 mins.
Climb to 15,000 ft 15 mins.
Ceiling 25,000 ft.
Load/sq. ft 8.4 lbs.
Load/h.p 7.7 "
At the time of writing the Boulton & Paul P.8 has just been finished, and her preliminary trials are due to take place any time. After them the machine will probably be heard of shortly, but of the exact nature of the flight we are not permitted to speak at present.