Flight, December 1936
A "MINOR" in METAL
Initial Effort by a New Concern: First Details of the C-W Cygnet Minor: Stressed-skin Construction: A Projected "Twin"
STRESSED-SKIN metal construction is no longer the expensive peculiarity of high-powered transports
and military types; there is a definite trend, particularly in America, toward light “private-owner” models built on this system. We may count ourselves fortunate that a few enterprising souls have had the foresight to study the possibilities of stressed-metal covering as applied to the smaller types, and among these Messrs. C. K. Chronander and J. I. Waddington, partners in C-W Aircraft, whose works are in Montrose Avenue on the Slough Trading Estate, are deserving of special commendation for producing Great Britain's first completely metal-covered light aeroplane.
As C-W Aircraft is a title not previously met with by readers, let us explain that policy is directed by Messrs. Chronander and Waddington, and that Mr. J. A. Heron is the chief engineer. These three are quite conversant with the most recent practice in stressed-skin construction, and hope to have the Cygnet flying in January. They are talking of delivery of production machines by Easter.
The Cygnet Minor ("Major" when any of the "Major" engines, such as Gipsy Major, Cirrus Major, Villiers-Hay Maya or Menasco Pirate are fitted) has been planned as a two-seater side-by-side machine for private operation or club training. A second passenger may be accommodated if the fuel load is reduced from 20 gallons to 8 gallons. The machine is fully aerobatic.
The low, cantilever wing has two main spars with booms of R.R. 56 alloy and light diaphragm ribs stiffened up with members of "bowler-hat" section. Torsional and shear leads are taken by the duralumin skin covering, but bending loads are taken by the spars. It is claimed that the wing, including ailerons, flaps and controls, weighs only 2 lb. per square foot. It is constructed in three sections: two outer panels and a centre section of seven-foot span and twenty-inch depth, which houses the fuel tanks. The comparative shallowness of this portion facilitates entry to the cabin. Attachment to the fuselage is effected by four bolts, the root-end fittings being straps of D.T.D.54 85-ton steel; there are no machined fittings.
With the centre-section spars as a basis, the sides of the cabin portion are built up. Fore and aft of this section are welded structures, the front one, of course, accommodating the engine mounting, and the rear one serving as an attachment for the rear end of the fuselage, which is of unusually small diameter. It is likely that in production models the welded portions will give place to monocoque sections.
A "Tadpole" Fuselage
Stringers of Z section and built-up frames feature in the after portion of the fuselage, to the rear end of which the tail unit is attached by eight bolts. The small cross-section of the rear part of the fuselage is said to confer aerodynamic and structural benefits, and merges with the wings through the medium of fillets of unorthodox design, the shape of which is seen to advantage in the accompanying drawings. This means that both in plan form and side elevation there is a very pronounced “slimming off.”
All control surfaces are metal-covered and of quite surprising lightness; the elevator weighs 3 1/2 lb., and the rudder 4 1/2 lb. The basic structure of the one-piece tailplane is similar to that of the wing.
The construction of the monocoque portions and the skinning of the wings has been simplified by the use of pop rivets and the employment of a special adaptation of a standard type of a riveting gun, which, it is claimed, enables the riveting to be done 20 per cent, faster than by normal methods. Countersinking features on the leading edges of wing and tailplane.
For riveting the skin on to members which cannot be drilled completely through a drill has been devised to make an "undercut" hole in the solid metal, enabling a pop rivet to be inserted and the head to be formed inside the undercut. A pantograph device has been developed (for the satisfaction of inspectors) which shows, four times actual size, the contours of the hole.
Flaps of high aspect ratio are incorporated having 24-gauge skin with triangulated ribs of light channel section. Operation is through a torque tube by a manual control with a spring servo device which automatically pulls down the flaps to 15 degrees for take-off. This spring bias also helps to keep the flaps closed in normal flight. The maximum depression is 60 degrees, permitting, it is estimated, a landing speed of 35 m.p.h.
A 6 1/2 in. travel is provided for in the Dowty single-strut undercarriage. The legs are carried in welded steel sockets attached to the front spars. The brakes are of the differentially operated Bendix type.
A single central column between the occupants and twin sets of rudder pedals permit dual control, although for specialised training work the manufacturers visualise two complete sets of controls.
Bias on fore-and-aft trim is effected by a spring in the elevator circuit, one end of which can be moved on either side of a fulcrum so that plus or minus or zero bias can be obtained at will by the operation of a tell-tale knob on the control column. The aileron and elevator controls travel in conduits in the centre of the cabin, lids being provided for inspection.
The two sets of rudder pedals are linked with a parallel motion, so that only the pedals are normally visible. One set can be removed in a few seconds, leaving the passenger's space free from excrescences.
Production Cygnets will be upholstered by Rumbold in any colour or style desired. Doubtless, Mr. Rumbold will find his task of soundproofing considerably simplified by the absence of flat panels. Rhodoid panels of quite unusually large proportions, coupled with the good location of the seats in relation to the wing, should benefit outlook.
The seats are fully adjustable for height and leg-length. Smith's instruments are grouped on the centre and left of the facia board, where they are visible to pilot and passenger. To the left is a capacious locker and map tray. A patented design of exit, hinged about the front side members of the cabin enclosure, is incorporated.
The windscreen is of the forward-sloping variety, for which aerodynamic advantages and visual benefits in rain are claimed. It also facilitates entry and exit. Behind the seats is a large baggage space which can, as already mentioned, be used for the carriage of a second passenger. A large step is inset into the trailing edge of the wing, being spring-loaded to reassume the contour of the surface when not in use. Smoking will be permitted in the 50 cubic-foot cabin, the ventilation of which is controllable.
The prototype Cygnet Minor is being fitted with the new Cirrus Minor of 80-90 h.p., but an alternative unit is the Pobjoy Niagara III. As already mentioned, any of the "Major" series of engines can be fitted, giving a considerable increase in performance with, presumably, a certain reduction in range. A Pobjoy will actually be installed in the prototype after tests with the Cirrus.
It is hoped to market the Cygnet Minor with Cirrus Minor engine at about ?795.
In the light of experience gained during the construction of the Cygnet a small twin-engined monoplane known as the Swan has been planned. This model should prove suitable for feeder-line work or as a "luxury" private-owner's type. It is believed that, utilising a number of components (including the rear fuselage) of the Cygnet, this could be marketed at a very attractive price. The prototype has been designed round a pair of Villiers-Hay Mayas, but engines of a new model, manufactured by the same company and rated at about 170 h.p., will be alternatives, and would give a maximum speed of 180 m.p.h.
C-W CYGNET MINOR
Two-seater Cabin Monoplane 80/90 Cirrus Minor
Span 34 ft. 6 in.
Length 24 ft. 2 1/2 in.
Height 6 ft. 0 in.
Wing area 185 sq. ft.
Tare weight 850 lb.
Disposable load 600 lb.
Gross weight 1,450 lb.
Maximum speed 125 rn.p.h.
Cruising speed 110 m.p.h.
Landing speed (with flaps) 35 m.p.h.
Take-off run (with flaps) 75 yd.
Landing run (with flaps and brakes) 60 yd.
Standard range 600 miles
Ceiling 20,000 ft.
Service ceiling 18,000 ft.
Flight, September 1937
SWAN and CYGNET
Advance Details of the C. W. Swan Light Transport and the Production-type Cygnet
All being well the Swan should fly in about a year's time. Meanwhile Cygnet production is proceeding steadily, a batch of twenty of these intriguing little two-seaters having been ordered. All will be powered with the 130 h.p. Gipsy Major I and, embodying aerodynamic and structural refinements suggested during trials with the prototype, should be capable of 150 m.p.h. The upholstery will be by Abbey Coachwork. One of the more prominent alterations has been made in the seating arrangements: there is now a single bench-type seat and a central control column. If need be dual sticks can be easily arranged on the cross-shaft. There is space for two large, specially designed suit cases and accommodation for golf bags down the "tadpole" tail quite apart from other space behind the seat.
The screen (in two half-spheres with no flats - made of Plastilume-moulded acetate sheeting) and roof portion of the production machines will blend more smoothly with the general lines. A standard dash arrangement has been evolved; this has a central panel and two lockers. The panel is hinged at it's base for inspection of the leads. Special instruments or a Sperry panel can be arranged on the pilot's side in place of the locker.
The latest Cygnet has its flaps in two portions, there being no central section as on the prototype. Mechanical operation is specified. Another change is the introduction of double the dihedral (now 10 deg.), making for better stability. The rudder and wheels will be larger than on the prototype.
A South African trip has been arranged for the Cygnet demonstrator which should be finished in about three weeks.
The manufacturers are highly enthusiastic about the results they have obtained with Noral NA57S strain-hardened aluminium alloy for structural parts and skin surfaces. This material, produced by the Northern Aluminium Co., Ltd., is claimed to possess high resistance against corrosion, to have adequate strength combined with ductility and to be comparatively cheap.
Apart from their work on the Cygnets and the Swan, C. W. Aircraft are taking in some substantial sub-contracts at their new works in Oxford Avenue, Trading Estate, Slough.
Flight, February 1938
IN PRODUCTION FORM
The Final Version of the C.W.A. Cygnet Major : Special Luggage Arrangements : Air Impressions
By H. A. TAYLOR
SINCE the Cygnet is the first all-metal light aeroplane to be produced in this country, it is somewhat natural that emphasis should previously have been laid on structural considerations. Now that the final version has been flying for some time, and that delivery of the first of a production batch can be expected in April or May, one can forget the interesting internals and treat the Cygnet simply as a flying machine designed for use by the private owner, the charter firm, or the club.
In any case, there have been no changes in the essential structure, in which Alclad, by Northern Aluminium, plays a large part, since the machine first made its appearance last year. There has been a slight increase in the rudder area and in the dihedral, improvements in the control system, and the cabin top has been entirely redesigned with a convincing change for the better in the general appearance of the machine. A very real attempt has been made in the design of this cabin top to give the pilot and the passenger the maximum possible range of vision, and to this end almost the entire surface as far as the rear of the luggage compartment is transparent. The transparencies, with the new moulded windscreen, are the work of Plastilume Products.
The occupants sit well forward so that the landing and navigation view over the leading edge is excellent, while it is possible to see over the entire rearward horizon before the take-off. The only slight failure in the range of vision concerns the tail-down taxying view, which demands a certain amount of rubber-necking (or occasional deviations from the straight path) in order to make sure that there are no obstructions on the port side. In order that there shall be plenty of head room consistent with low drag, the occupants sit fairly low down, but even so the nose cowling, in cruising attitude, lies well below the level of the horizon.
The stowing of difierent shapes and sizes of suit cases and the necessity lor strapping them down firmly to make sure that they are not dislodged in bumps, is always something of a worry, and the designers of the Cygnet have dealt with the problem by the simple means of providing special suitcases of ample capacity which are placed firmly in recesses. In addition there is a long, narrow space behind the luggage compartment where, for instance, two sets of golf clubs may be stowed, and there is still ample room for all the odds and ends which are invariably added at the last moment. On both sides of the standard instrument panel are two sizeable lockers, each with a lid, and the one on the starboard side may be used, if necessary, for the disposition of any special blind-flying instruments, such as a Sperry panel, which the prospective owner may care to have fitted. The standard panel is supported on special vibration-proof Lord mountings which at the same time act as hinges, so that the entire panel may, on the removal of attachments at the top, be swung downwards in order that the connections may be inspected.
The arrangement of the controls includes normal dual rudder-bars with a single central control stick. Provision has. however, been made for the incorporation of two separate sticks, and it is possible that the standard version of the Cygnet will be so equipped. There are certain objections to a central position for this important item and the tendency is for the pilot to fly and land with the left wing down.
In order that the cabin proper shall not be unduly encumbered, the direct-operation flap-lever is arranged immediately beside the seat in a suitable recess, while the Bendix type of "walking-stick-handle" brake lever is conveniently reached but not in the way, placed as it is below the throttle quadrant. The compass is mounted on the floor between the two occupants and the fuel control is in full view immediately below the dashboard, so that there is no possible excuse for leaving this tap in "off" position. Certain changes may be made later to the instruments, though their general arrangement will be unaltered. At the moment the Korect Depth Gauge people are responsible for some of them and it is possible that in due course they will turn out the entire equipment in suitably matched form. Soundproofing. Ltd., have been responsible for the general furnishing and soundproofing arrangements, and these, I believe, form their first successful essay in such specialised work.
Since the first of the production machines made its appearance the weather has not been suitable either for speed tests over a measured course or for such tests as those for rate of climb. In its unfinished form the machine covered a two-way course on full throttle at about 146 m.p.h., and the smoothness of the final finish should add 2 or 3 m.p.h. to this figure. The pitot head had not, when I flew the machine, been tested for position error and the readings could not be taken too seriously. However, after giving the machine plenty of time to gather speed these were 120 at 2,100 r.p.m. and a little less than 140 m.p.h. on full throttle. The runs were made in air which was far from smooth at 3,000ft., and the corrected figures, for what they are worth, would be 126 and 146 m.p.h.
The bumps, which were directly caused by a fairly strong and gusty wind at lower levels and by the usual currents near the 4,000-foot cloud level, prevented any serious attempts at hands and/or feet off flying. The machine would fly with comparative accuracy on the stick alone, but the bumps caused a yawing motion which could not be immediately corrected. However, Mr. Wynne-Eyton, who has carried out all the more recent test flying, says that in smooth air the machine flies quite well without use of the rudder. At cruising revolutions a certain amount of rudder correction is required and it will be necessary to fit a rudder bias before the machine could be left to fly entirely happily by itself.
This wind, which was blowing at about 10 or 15 m.p.h. at ground level, also militated against any estimation of a takeoff run. In the circumstances this run, when the machine was flown either two or one up, seemed to be well below the 120 yards which is officially given, and the machine can safely be pulled oh the ground at or near the stall and will afterwards gather speed at quite a considerable climbing angle. I found that, contrary to usual low-wing characteristics, the machine would fly itself off if the take-off was made without lifting the tail too high. For the shortest possible length of run it would probably be better to hold the tail well up and to pull the Cygnet off the ground when the needle moved beyond the 40 m.p.h. mark.
The controls are smooth and nicely balanced and only at very high speeds were the ailerons at all heavy in operation. I did not fly the machine in its original form, but I am told that, though considered quite satisfactory at the time, the controls have undergone an all-round improvement.
Half-hearted stalling experiments at a very safe height (the machine has not yet been put through its spinning tests) showed that this stall, with flaps either up or down, was quite harmless and, if carried to its logical conclusion, resulted only in a momentary drop of the nose and, sometimes, of one wing. Aileron and rudder control faded out at practically the same moment, apparently a few miles an hour above the actual stalling speed.
A virtually infinite variety of positions is provided for the flap lever, and if the machine is not too near the ground or flying very slowly, this variety of positions can be used to adjust the approach angle without using the motor. The flaps do not extend right across but are in two separate portions, and, while being amply powerful for steepening the approach angle, are not so powerful that the pilot is left with little time to make an accurate hold-off or that the change of angle is dangerously great.
The process of landing is simplicity itself. The elevator control is gentle in its effect and there is a sufficiently marked lag to prevent any pump-handling. It is possible, by a very full movement at the last moment, to effect a tail-first touchdown, and after the first landing, which was slightly “one-two,” I found that the most satisfactory landings could be made without using the entire elevator movement. The differences in elevator load between full throttle and closed throttle, with the flaps up or down, is very slight and, after setting the trimmer so that the machine flew level correctly at cruising revolutions, I did not use it again. In its present form the control, which consists of a small knurled knob working on a quick thread to tighten a spring, is inconveniently-placed. This, however, is to be altered in due course.
It is almost impossible to make any fair judgment in the matter of noise, and most of that heard in the Cygnet cabin appears to be caused by the airflow. It is, however, possible to converse at the cruising speed without unduly raising the voice, and the arrangement of stops will prevent the windows from opening very slightly and thus increasing the volume of sound. On the ground the rear of the fuselage acts as a kind of amplifying trumpet for the noises made by the tail wheel and, until one becomes accustomed to them, it is difficult to resist the temptation to get out and look to see if the wheel is still there At the present time Hanworth, where I flew the Cygnet, is very rough in parts, but the ample movement of the undercarriage legs smoothes things out once the tail is off the ground.
The price of the Major-engined C.W. Cygnet has not yet been definitely settled, but it is likely to be in the immediate vicinity of £1,200
130 H.P. Gipsy Major Engine.
Length 24 ft. 3 in.
Span 34 ft. 8 in.
Weight empty 1,200 lb.
All-up weight 1,000 lb.
Maximum speed 150 m.p.h.
Cruising speed 130 m.p.h.
Stalling speed 45 m.p.h.
Rate of climb at sea-level 850 ft./min.
Range 650 miles.
Makers : C.W. Aircraft, Ltd., Trading Estate, Slough, Bucks.
Flight, March 1938
British light aircraft
IT is unfortunate that, for the moment at any rate, C-W. Aircraft do not fine it possible to proceed with the production of the Cygnet, which has a special interest as the first all-metal light aeroplane to appear on the British market. In its latest form, with a Gipsy Major engine and redesigned windscreen and cabin top, the Cygnet has distinctly handsome lines, and its general performance is well up to that of similar types.
A great deal of care has been expended on the cabin and luggage arrangements, and, following minor modifications to the controls of the prototype, the machine has really pleasant flying qualities. The occupants sit side-by-side in a roomy cabin with ample transparent areas in essential places, and special suitcases have been designed in "built-in" form. Additionally, there, is plenty of space alt for the stowage of golf bags and the like, a large area behind the seats for smaller bags and oddments, and locker accommodation on either side of the instrument panel. Full dual control is provided
The flap gear is now manually operated and the "braking" area, while being ample to steepen the glide at reasonable speeds, does not kill the float too quickly from, say, 55 m.p.h. In its characteristics the Cygnet is very similar to any other low-winged machine of the same general layout, and the flaps-down stall is as innocuous as it should be.
The company also have on the drawing board a high-efficiency twin-engined machine which could be used for feeder line, charter or luxury private-owner work. Its development, of course, rests upon what, we hope, are the temporary difficulties also concerned with the full production of the Cygnet for which, incidentally, the Slough works are stated to be ready tooled.
SPECIFICATION: Span. 34ft. 6in.; length, 24ft. 3in.; all-up weight, 1,900 lb.; weight empty, 1,200 lb.; maximum speed, 150 m.p.h.; cruising speed. 130 m.p.h.; landing speed, 45 m.p.h.; initial rate of climb, 830ft./min.; range, 650 miles; price. £1,200. Makers: C-W. Aircraft, Oxford Avenue, Trading Estate, Slough, Bucks.
Flight, October 1938
British Sport and Training types
EARLIER this year General Aircraft took over the manufacturing rights for the C.W. Cygnet two-seater cabin monoplane, which is still this country’s only all-metal, stressed-skin light machine. The company has decided to develop the machine into one in which stability and ease of handling will be the outstanding features. Already the tail has been modified to take twin fins and rudders, and in due course a tricycle undercarriage will be fitted.
The existing machine is powered with a Gipsy Major engine, but provision will be made for the fitting of a Cirrus Major or a Menasco C4S unit, according to the wishes of the purchaser. The structure of the Cygnet offers excellent opportunities for drop-hammer production, and by this means it is planned to manufacture a machine at a competitive price. The figures below refer to the prototype with the normal undercarriage and single fin and rudder.
The Cygnet’s cabin has a transparent top extending to a low waist-line, and the screen is of the one-piece moulded type giving a wide range of vision. Split flaps are, of course, fitted.
Cygnet data:- Span, 34ft. 6in.; length, 24ft. 3in.; all-up weight, 1.800 lb.; weight empty, 1,305 lb.; wing-loading, 10 Ib./sq. ft.; power-loading, 15 lb./h.p.; maximum speed, 148 m.p.h.; cruising speed at 70 per cent, power, 130 m.p.h.; stalling speed, 48 m.p.h.; rate of climb, 900 ft./min.; service ceiling, 16,000ft.; and cruising range, 460 miles.