Flight, September 1931

S.A.B.C.A. S.XI

   DESIGNED and built by the Societe Anonyme Belge de Constructions Aeronautiques at Haren, Brussels, the S.A.B.C.A. S.XI is the first large commercial aeroplane to be produced by the well-known Belgian company, and in fact the first large machine of original design to be built in Belgium. It will doubtless be recollected that several years ago the S.A.B.C.A. acquired the rights to build Handley Page biplanes under licence, and a number of these machines have been produced and have, given very good service in Belgian Congo, where they have been in use for several years.
   At the moment it is not known whether the S.XI is intended for the African air routes of the S.A.B.E.N.A., or whether the new machines will be used on the European lines operated by that firm, such as, for example, the London-Copenhagen route. It seems likely that the machines will first be tried out on the European routes and then, if found satisfactory, be transferred to the Belgian Congo lines, where the all-metal construction should stand the climate rather better than do wood constructed aircraft, although these have, as far as can be gathered, given excellent service.
   The S.A.B.C.A. S.XI was designed by the chief engineer and designer of the company, M. Henri Jullien, and the initial test flights were made by the firm's chief test pilot, M. Charles Wouters, whom many British aircraft owners and pilots will have met on several occasions at meetings in Belgium and Holland. The first test was made on August 12, and indicated that no serious alterations were likely to be necessary, the machine handling well. We understand that accurate performance tests, etc., have not yet been made, and the performance figures given in the table on the next page are to be regarded as estimated figures.
   In general design the S.A.B.C.A. S.XI is a high-wing, semi-cantilever monoplane of all-metal construction, fitted with three "Jupiter" engines of 420 h.p. each, built in Belgium by the S.A.B.C.A. company under licence from the Gnome-Rhone company.
   Although mainly intended as a passenger-carrier, and normally equipped with seats for 20 passengers, the S.XI can also be used as a freighter, the seats being removable and the whole of the cabin space then being available for freight.
   That the S.XI is not a small machine may be gathered from an examination of the figures published in the table on the next page. For a wing span of 72 ft. 6 in. and a wing area of 1,042 sq. ft. the maximum permissible gross weight is 14,520 lb. It is classed by the manufacturers as a gros porteur, although in these days of really large machines the S.XI should, presumably, be regarded as a medium-sized aircraft.
   The tankage provided is large (634 gallons), but normally it is not intended that the machine should be used on stages so long as to require the whole of the tank capacity. The normal non-paying load (i.e., crew, etc.) is 352 lb. (160 kg.). For various quantities of fuel the range and pay load are as set out in the following table:
   Range (miles) 310 465 605 840
   Fuel and oil (lb) 1,540 2,200 2,860 3,960
   Pay load (lb.) 3,520 2,860 2,200 1,100
   In each case the cruising speed is estimated at 200 km./h. (124 m.p.h.). Even at the shortest range contemplated, it will be observed, the pay load is only 2.8 lb./h.p. based on maximum power. This does not appear to be a very high figure, but as the ratio of gross to tare weight is about the normal (1.59) it is to be assumed that the relatively low pay load is due to a considerable power reserve. This seems to be borne out by the figure for power loading, which is only 11.5 lb./h.p. It is likely also that the figures given refer to the machine equipped for passenger carrying, and that if the cabin were stripped of equipment, such as would be the case if the machine were used for carrying freight, the tare weight would be reduced and the pay load correspondingly increased.
   As already mentioned, the cabin has seating accommodation for 20 passengers. It is 19 ft. long, 8 ft. 6 in. wide, and 7 ft. 2 in. high, which gives a cabin volume of about 170 cu. ft. This is, of course, available for freight when the cabin equipment is removed. The seats are arranged in five rows of four, two seats on each side in each row, with a gangway down the centre. If desired the cabin can be equipped for night journeys, in which case there is room for 6 berths.
   The S.XI is of all-metal construction, the only exception being the fuselage covering, which is doped fabric.
   The semi-cantilever wing is built entirely of metal, the spars being of high-tensile steel and the ribs of Duralumin, which latter material is also used, in flat sheets, for the wing covering. The whole trailing edge of the wing, for a distance of more than 6 ft., is built as a detachable unit in order to facilitate transport.
   The fuselage is a welded steel tube structure, covered with fabric, and the tail surfaces are of Duralumin, including the covering. The wing bracing struts are of high-tensile steel stream-lined with Duralumin fairings.
   An undercarriage of the two-wheel type is fitted, and the wheels are provided with Bendix brakes.
   The cockpit is placed ahead of the wing, immediately behind the central engine, and has room for a navigator as well as for pilot and assistant pilot.
   To relieve the pilots on long flights, the tailplane is provided with a tail trimming gear, and the vertical fin is so arranged that it can be offset to left or right, thereby enabling the pilot to fly a straight course without a large load on the rudder when one wing engine is stopped.
   The main data relating to the S.A.B.C.A. S.XI are given in the following table :-
Dimensions
   Length o.a. 55 ft. 5 in. (16,9 m.).
   Wing span 72 ft. 6 in. (22,12 m.),
   Wing chord 14 ft. 9 in. (4,5 m.).
   Height o.a. 13 ft. 5 in. (4,1 m.).
   Wing area 1,042 sq. ft. (96,8 m.2).

Weights
   Power plant 3,300 lb. (1 500 kg.).
   Air frame 5,800 1b. (2 633 kg.).
   Tare weight 9,100 lb. (4 137 kg.).
   Disposable load 5,420 1b. (2 463 kg.).
   Max. permissible gross weight 14,520 lb. (6 600 kg.).

   Wing loading 13-9 lb./sq. ft. (68,2 kg./m.2).
   Power loading 11-5 lb./h.p. (5,24 kg./CV).
   "Wing power" 1-21 h.p./sq. ft. (13 CV/m2).

Performance
   Max. speed near ground 137 m.p.h. (220 km./h.).
   Cruising speed 124 m.p.h. (200 km./h.).
   Landing speed 62 m.p.h. (100 km./h.).
   Everling "High-speed Figure" 14-5

Flight, December 1931

THE S.A.B.C.A. S.XII

   A SMALL three-engined machine of the "feeder-line" type, the S.XII, designed and built by the Societe Anonyme Belge de Constructions Aeronautiques is a high-wing braced monoplane of mixed construction. Designed for a gross weight of 2,800 kg. (6,160 lb.) the S.XII is fitted with three Renard radial air-cooled engines of 120 h.p. each, one engine being mounted in the nose of the fuselage and the other two outboard under the wings. The cabin has accommodation for four passengers. At the moment of writing the official performance figures are not available, but the estimated top speed is 185 km./h. (115 m.p.h.) and the cruising speed at 80 per cent, of maximum power, 170 km. /h. (105 m.p.h.). The estimated landing speed with full load is 100 km./h. (62 m.p.h.), and by using the trailing edge flaps it is thought this will be reduced to 85 km./h. (53 m.p.h.).
   The lay-out of the S.A.B.C.A. S.XII is shown in the general arrangement drawings and photographs. It will be seen that the outboard engines are placed close under the wings, a position which in this country is not usually considered very efficient aerodynamically. The wing is strut-braced, the front wing struts being round steel tubes with electron fairings, while the rear struts, also steel tubes, have wooden fairings. The wings do not fold. The wing has wooden spars and ribs.
   The fuselage is of welded steel construction, with fabric covering.
   All engine mountings are of welded steel tube construction, and engine cowls and petrol tanks are of electron.
   The undercarriage is of wide track, and of the "split" type, each half consisting of a single wheel 800 X 150 fitted with Bendix brakes, and mounted on the usual tripod of axle, radius rod and compression strut. The compression struts do not run to the wing but to the front wing bracing struts, from which point a short strut is taken diagonally to the side of the fuselage, there to be anchored to a stout bulkhead in the plane of the front spar. A tail wheel is used instead of a skid.
   To get good controllability without fatiguing the pilot, the elevators are horn-balanced, while rudder and fin are placed aft of the horizontal tail to give them greater leverage and also to avoid "blanketing" of the rudder and fin at large angles of incidence. Like the elevators, the rudder is horn-balanced, and the rudder chord is large at the bottom.
   The ailerons, it will be seen, extend over the whole wing span. The inner portions can be operated by the pilot to act as variable camber gear, leaving the outer portions to perform the function as ailerons.
   Two seats are provided in the cockpit, although normally it is intended that one pilot should suffice. The cabin has seats for four passengers, with plenty of room for them to get in and out without getting in each other's way. Many of the instruments are of the vertical scale type, and the instrument board has been arranged to make a survey of all the different dials as easy as possible.
   Normally it is intended that the machine should have a range at cruising speed of 600 km. (370 miles), and the load is then divided up as follows: Tare weight, 2 014 kg. (4,430 lb.); fuel and oil, 270 kg. (594 lb.); crew of one, 80 kg. (176 lb.); pay load, 4 passengers and freight 500 kg. (1,100 lb.); gross weight, 2 864 kg. (6,300 lb.).
   The wing span is 18.10 m. (59 ft. 5 in.), and the wing area 43 sq. m. (463 sq. ft.), which gives a wing loading of 13.6 lb./sq. ft. The power loading (based on 3 X 120 b.h.p.) is 17.5 lb./h.p. Official performance figures are not yet available.