Flight, July 1921

THE BRISTOL COMMERCIAL TEN-SEATER BIPLANE

   A NEW commercial type aeroplane has recently been completed by the Bristol Aeroplane Co., and we give below some brief particulars of this machine, together with photographs and general arrangement drawings.
   This new Bristol is a large ten-seater single-engined tractor biplane, having an enclosed cabin for eight passengers and an open cockpit for pilot and mechanic.
   The 450-h.p. Napier "Lion" engine, with which this machine is fitted, is on a readily detachable mounting which also carries the nose radiator and oil tank. Complete access to the engine can be obtained by releasing six self-locking fasteners, no part of the cowl being removed from the machine. Electric starting is fitted, as well as hand turning gear operated from the ground.
   The fuselage is of deep rectangular section, with curved top deck, tapering to a shallow vertical knife-edge at the rear; the fuselage completely fills the gap between the planes. The saloon, or passengers' cabin, extends from the region of the front main wing spars well aft of the planes. Access to the cabin is by way of a door at the rear of the former, on the port side. Six of the passengers are located in separate seats, three a side, facing forward, and the other two passengers sit at the front end of the cabin facing aft. The seats are collapsible, and when folded project only five inches from the cabin sides, leaving a maximum of floor space should it be desired to carry cargo in lieu of passengers.
   Windows, which can be opened, are fitted the full length of both sides of the cabin, and heating is provided by means of hot air muffs round the exhaust pipes. For the convenience of passengers liable to air-sickness a small concealed self-emptying basin has been provided in close proximity to each seat. These fold against the side of the saloon and are readily accessible, the waste pipe discharging through the floor.
   In the roof of the machine a special emergency exit is provided, measuring 2 ft. 2 1/2 ins. by 2 ft. 2 ins. This is operated by a quick release gear should occasion arise.
   When it is desired to use the machine solely for the transport of cargo the space available is: length, 10 ft. 6 ins.; height at centre, 5 ft. 9 ins.; width, 4 ft.
   The pilot's and mechanic's cockpit is located high up in the fuselage at the leading edge of the top plane. An exceptionally fine range of vision is thus provided.
   Below the pilot's cockpit is a compartment 4 ft. 6 ins. long by 4 ft. wide by 2 ft. 6 ins. high, accessible through a trap door in the underside of the fuselage. This is intended for the conveyance of passengers' luggage or for other suitable cargo.
   Between the engine compartment and the pilot's cockpit is a steel fireproof bulkhead, and all control connections pass through glands. No petrol is carried in the body of the machine aft of this bulkhead.
   In the pilot's cockpit a complete wireless telephone and telegraph installation is installed, and has been fitted so as to be completely accessible to the mechanic. In order to allow of communication between the pilot and the passengers a small trap door has been provided to allow of messages being passed when required.
   Single control of the wheel type is fitted, all cable pulleys being five inches in diameter. The tail incidence can be varied by a lever and quadrant adjacent to the pilot, to trim the machine under all conditions of speed and load distribution. All control surfaces are unbalanced.
   The main planes are of equal span and chord, and are without stagger or sweepback, but are set at a pronounced dihedral angle. The lower planes are attached direct to the sides of the fuselage, and the top ones to small wing-roots in the roof of the cabin. There are two pairs of interplane struts each side, and the landing and lift bracing is by streamline wire. Ailerons are fitted to all four wings.
   The chassis is of the four-wheeled Oleo-elastic type, with wheels in tandem, brakes being fitted to the rear wheels and operated by a car type brake lever in the pilot's cockpit. A gate is provided for the brake lever so that the brakes may be operated together or singly as required. Elastic rings are used for suspension and the elastic carriers have been designed for ready renewal of these rings. The Oleo plungers are fitted with a special type of tapered needle valve to control the passage of the oil through the plunger to give constant oil pressure throughout the stroke of eight inches.
   The two main petrol tanks, of 50 galls, capacity each, are slung under the bottom planes at the inner interplane struts. Petrol is drawn from either of these tanks by two Vickers' centrifugal pumps coupled in series, and delivered through a Vickers' hand pump to the carburettors, any surplus passing to a 10-gall. gravity tank and overflowing back to the particular main tank in use. Smiths' capacity gauges for both main tanks are fitted on the instrument board.
   The principal characteristics of this machine are as follows :-
Dimensions
   Span 54 ft.
   Length, overall 42ft
   Height 11 ft

Weights
   As passenger machine -
   Machine empty with water 3,900 lbs.
   Wireless installation 63 lbs.
   Fuel and oil for 400 miles (100 galls. petrol, 6 galls, oil) 798 lbs.
   Crew (two) 360 lbs.
   Passengers (eight) 1,280 lbs.
   Baggage (50 lbs. per passenger) 400 lbs.
   Total 6,801 lbs.

   As cargo machine -
   Machine empty, with water 3,800 lbs.
   Wireless installation 63 lbs.
   Fuel and oil as above 798 lbs.
   Crew (two) 360 lbs.
   Cargo 2,079 lbs.
   Total 7,100 lbs.

Loading
   As passenger machine -
   Weight/h.p. (Napier "Lion" at 450 h.p.) 15.1
   Weight/sq.ft. 10.1
   As cargo machine -
   Weight/h.p. 15.8
   Weight/sq.ft. 10.6

Performances
   Full load. Half load.
Speed at ground level 122 m.p.h. 124 m.p.h.
,, 5,000 feet 118 m.p.h. 120.5 m.p.h.
,, 10,000 114 m.p.h. 117 m.p.h.
Time to climb to 5,000 ft. 9 mins. 7 mins.
,, 10,000 22 mins. 17 mins.
Ceiling 13,500 ft. 15,500 ft.

Flight, January 1922

THE "BRISTOL" 10-SEATER
400 H.P. Bristol

   IN our issue of July 7, 1921, we published an illustrated description of the "Bristol" 10-seater commercial biplane in its original form, with Napier engine and a four-wheeled undercarriage. This machine, it may be remembered, was designed by Mr. Reid, who has now succeeded Captain F. S. Barnwell as chief engineer and designer of the "Bristol" Aeroplane Company. Since the building of the original machine certain modifications have been made to component details, such as the undercarriage. As it was found that, even without the front wheels, the machine handled remarkably well on the ground, it was decided to do away with the extra weight of the two front wheels, which were consequently omitted. The machine has been to Martlesham for its type-tests, and has paid several flying visits to the Croydon aerodrome. It has been found to handle very well both on the ground and in the air, and it is expected that it will be put into actual commercial use on the airways in the coming spring and summer.
   Lately the machine has been re-designed to take the Bristol "Jupiter" radial air-cooled engine. The result is shown in the accompanying photograph. It might have been thought that fitting a radial in the nose of the machine, and the absence of a radiator would have resulted in spoiling the appearance of the machine. This, however, is not the case, as may be seen from the photograph. The manner in which Mr. Reid has run the covering from the comparatively small diameter at the front into the large section of the cabin leaves nothing to be desired as regards appearance, and also from the point of view of resistance the fuselage appears to have a very good shape. It may be remembered that the "Bristol" firm have carried out extensive experiments on engine mountings and fairings, and the present mounting represents the form found by experiment to be most efficient. This engine mounting was described and illustrated in our issue of October 13, 1921, and little need therefore be said about it here, beyond recalling that its distinctive feature is that it is swivelled or hinged along one side in such a manner that by undoing a few bolts the whole mounting can be swung laterally so as to give ready access to the rear of the engine without disturbing the petrol leads, which are so arranged that they run down along the hinged side and have sufficient flexibility to allow of a small amount of twisting and bending without requiring to be disconnected. The advantages of such a mounting for commercial work are obvious, as inspection is greatly facilitated. This should result in increased reliability, as it is well known that a part which is difficult to get at is often left alone, whereas a part that can be readily inspected usually receives its fair share of attention.
   Apart from the alterations necessitated by the installation of the "Jupiter" engine, the 10-seater remains practically the same as before. The cabin has accommodation for eight passengers, of whom six are seated in upholstered seats facing forward, the other two occupying a cross-seat along the front wall of the cabin and face aft. A ninth passenger, or a mechanic, can be carried in the seat in the pilot's cockpit. The chairs are designed to fold up when not in use, and should it be desired for a single journey to use the machine for carrying goods, the cabin is fairly clear when the seats are folded. When the seats are removed from the cabin, a space for cargo is left measuring 10 ft. 6 in. in length 5 ft. 9 in. in height (in the centre), and 4 ft. in width. The cabin is lighted by windows in the sides, and there is an emergency exit in the roof. For cold weather flying the cabin can be heated by means of hot air muffs round the long exhaust pipes. Aft of the cockpit there is a lavatory, and in front of the cabin, under the pilot's cockpit, is a luggage compartment reached through a trap door in the floor. This luggage compartment measures 4 ft. 6 ins. in length, 4 ft. in width, and 2 ft. 6 ins. in height.
   The pilot's cockpit is placed between the engine bulkhead and the front spar of the upper plane. From this position he obtains an excellent view forward and downward while, being practically on a level with the top plane, he can also see fairly well backwards. A wireless telegraph and telephone installation is provided for in the cockpit, and this is so placed as to be completely accessible to the engineer or navigator.
   As a safety precaution against fire, there is a steel bulkhead aft of the engine, between it and the pilot's cockpit, and all control connections pass through glands. No petrol is carried in the fuselage aft of the fireproof bulkhead. The petrol system consists of two main petrol tanks slung under the bottom plane, where they are in a position easy of access for filling. The tanks have a capacity of 45 gallons each, and petrol is drawn from either of these tanks by two Vickers centrifugal pumps coupled in series, and delivered through a Vickers hand pump to the carburettors, any surplus being returned through a 10-gallon gravity tank fitted high up on the fireproof bulkhead. Smith's capacity gauges for both tanks are fitted on the instrument board.
   As already mentioned, the undercarriage of the new machine is of the two-wheeled type. Rubber rings are used for suspension, and their carriers are so designed that the rings can be easily and quickly renewed. An oleo damper gear is incorporated, the special feature of which is the tapered needle valve so shaped as to give constant oil pressure through the whole stroke of the plunger (about 8 ins.).
   The main characteristics of the "Bristol" 10-seater are as follows: Span, 57 ft. 6 in.; length o.a., 40 ft. 6 ins.; height, 11 ft.; weight of machine empty, 4,000 lbs.; 90 gallons of petrol and 6 gallons of oil, 715 lbs.; crew (2), 320 lbs.; passengers (8), 1,200 lbs.; luggage, 350 lbs.; wireless, etc., 65 lbs.; total loaded weight, 6,650 lbs.; wing loading, 9-3 lbs./sq. ft.; power loading (Bristol "Jupiter" at 400h.p.), 16-6 lbs./h.p.; speed at ground level, 112 m.p.h.; speed at 5,000 ft., 110 m.p.h.; climb to 1,000 ft., 1 1/2 minutes to 5,000 ft., 13 minutes.