Flight, August 1926

THE AVRO "AVIAN"
65 H.P. Armstrong-Siddeley "Genet" Engine

   IN designing a machine especially for the forthcoming Lympne Light 'Plane Competition for prizes offered by the Daily Mai! and others, there are two lines along which the problem of gaining the highest number of points may be attacked: one is to carry no more than the useful load of 340 lbs. stipulated as a minimum, and to use for the carrying of this load the smallest power plant which can be counted upon to get the machine around the 2,000 miles' course at an average speed of not less than 50 m.p.h., tuning the engine to use as little fuel as possible; the other consists in taking as a starting point the most powerful engine available within the maximum weight allowance of 170 lbs., and designing for it a machine which will carry considerably more than the 340 lbs. useful load. In between these two extremes there are, of course, a number of combinations possible. Mr. Chadwick, chief designer and engineer to A. V. Roe and Co., Ltd., has chosen to follow the latter course, partly as offering the best solution for the competition, but equally because in so doing a machine is, he considers, produced which is of a type likely to be practically useful to clubs, private owners, etc., quite apart from competition considerations.
   From the Lympne competition point of view, the Avro “Avian," as the new machine is called, is characterised by very low structure weight and great load-carrying capacity, while with future production in mind, the detail construction is of the simplest imaginable form without departing radically from normal practice. There are rumours of a new Ford "runabout" in which the fuselage is to be built up from stamped-out sides, tops and bottoms, and wings in which the top and bottom surfaces are also stamped out in one operation; but until the day comes when aeroplanes can be produced in thousands the plant necessary to do this is likely to be expensive, and Mr. Chadwick has not quite gone to this extent in his search for cheapness of production. As regards its suitability for "point-getting" at Lympne, it may be stated, although very accurate figures are not yet available, that the "Avian" has an estimated empty weight of round about 750 lbs., while its total loaded weight, within the airworthiness certificate, will be rather more than double that figure. As the longest distance to be covered in the competition without landing is something like 124 miles, the fuel to be carried must be sufficient for this distance plus a margin for head winds, etc. This means that the quantity of fuel to be carried will be fairly considerable, but a rough estimate indicates that the point-scoring load which the "Avian" will be able to carry may be somewhere in the neighbourhood of 750 lbs. To enable the machine to pass the take-off and pull-up tests in the eliminating trials with a total loaded weight of something like 1,580 lbs., wings of large area will, obviously, be necessary, and those of the "Avian" as used in the competition will have an area of no less than 294 sq. ft., which will give a wing loading of in the neighbourhood of 5-375 lbs./sq. ft., a figure which should allow the machine to "unstick" satisfactorily. For the same total loaded weight the power loading (based upon normal power) will be 24-3 lbs./h.p. As the "Genet" engine develops a maximum of 75 h.p. for short periods, the power loading for taking-off purposes is reduced to just over 21 lbs./h.p., so that with the relatively low wing loading the machine should clear the two 25-ft. barriers without difficulty.
   A ratio of empty weight to total loaded weight of less than 0-5 is, of course, extraordinarily good, and indicates very great care in detail design. Lest it should be thought by those not intimately acquainted with Avro standards of construction that such a ratio necessarily means a flimsy structure, we would point out that the factors of safety are such that the machine will be eligible for the "aerobatics" airworthiness certificate of the British Air Ministry, which fact may be accepted as sufficient proof of the strength of the machine.
   Before turning our attention to the details of the construction of the Avro "Avian," it may be of interest to mention briefly that the machine will be produced in three distinct forms after the competition. Firstly, there is the standard form, possibly with wings of somewhat smaller area than those used in the competition, but otherwise identical with the competition machine. For the Grosvenor Cup race, and for anyone wanting a faster machine than the normal, the "Avian" will be supplied as a low-wing monoplane, with a single strut bracing the wing to the top of the fuselage, as shown in a sketch. Finally, the machine will be "put on floats," when it will have the normal biplane wings. This form also is shown in a sketch. It will thus be seen that the Avro "Avian" should prove a low-powered aeroplane with many applications and suitable, by some very simple substitutions, for a. variety of uses. The detail construction is such as to make for cheap production, and we understand that after the Lympne meeting it is intended to market the "Avian" at a price which should appeal strongly not only to light aeroplane clubs, but also to private owners.

Constructional Features

   From the fact that it is designed for cheap production one expects the Avro "Avian" to be a very straightforward piece of construction, and during a visit to the Avro works at Hamble last week we were able to determine that this is indeed a fact. So much so, that one might easily fall into the error of dismissing the machine as being perfectly simple and normal, and therefore of no particular interest. In doing this one would not only be unfair to the machine but one would miss an opportunity to appreciate the extent to which the simplicity evident everywhere is due to the very greatest care and thought in design. A close inspection of the details of the construction leaves one with the feeling that the designer had made up his mind at the start that every member was to be as simple and as light as possible, and that such few metal fittings as are used should be of a form that could be produced at an absolute minimum of cost.
<...>

Power Plant

   The Armstrong-Siddeley "Genet" engine is mounted on an extremely light engine plate of Duralumin, the form and details of which are shown in one of our sketches. Owing to the fact that most of the engine accessories in the "Genet" are placed in front, there is little need to get at the back of the engine, although the engine plate used enables this to be done with great ease if necessary. As the petrol tank is in the top fairing, direct gravity feed can be used, with consequent simplicity of the petrol system. For the competition the "Genet" will be fitted with a single magneto, as the addition of a second would bring the total weight up to more than the 170 lb. stipulated as a maximum. After the competition, however, dual ignition will be fitted as standard, the necessary provision for this having been made in the engine.
   The main dimensions of the Avro "Avian" are shown on the general arrangement drawings on p. 535. It is only necessary to add that the weight empty is in the neighbourhood of 750 lb., while the total loaded weight is approximately 1,580 lb. Concerning performance no information can be given for obvious reasons, but in spite of its large area the “Avian" is a clean design and should do well.

Flight, September 1926

British Light ‘Plane Development & Lympne Meeting

THE 1926 MACHINES

No. 9. The Avro "Avian" (Armstrong-Siddeley "Genet")

   In many ways this machine may be said to be the most interesting of those taking part in the forthcoming Lympne meeting. It is an entirely new design, and is remarkable for its extraordinarily low empty weight and its high useful load. The former is, approximately, 680 lbs., while the total loaded weight under the certificate of airworthiness is 1,550 lbs. Whether the machine will be loaded up to its full permissible weight at Lympne is not quite certain. A machine in which the useful weight is 60 per cent, of the gross weight, or in other words, the load 1-4 times the weight of the machine bare, is something very much out of the ordinary, and there can be little doubt that the "Avian" will prove a formidable opponent in the competition. Concerning the machine itself, this was described and illustrated in FLIGHT on August 26, 1926, and it will suffice if we recall that it is chiefly remarkable for its very large wings, the total area being no less than 294 sq. ft. The total wing span is 32 ft., in spite of which, however, but a single pair of interplane struts is used on each side, the long, unsupported span being made possible by using a fairly thick wing section. In the Grosvenor Cup race after the competition the "Avian" will probably be fitted with a single wing, turning it into a low-wing monoplane, with a single strut bracing each side.

Flight, March 1928

THE AVRO "AVIAN III”
A.D.C. "Cirrus II" Engine

   THE first Avro "Avian" was, it may be recollected, designed and built for the Daily Mail competition held at Lympne in 1926, and was then fitted with the new Armstrong-Siddeley “Genet" engine. Outstanding features of the prototype were: Very low structure weight, wings of large area, and exceptional ratio of loaded weight to tare weight. Thus the tare weight of the competition machine was 695 lb., and the loaded weight 1,600 lb., the load being made up of 77 lb. of petrol and oil, and 828 lb. of useful load (including pilot). A detailed illustrated description of the original "Avian” was published in FLIGHT of August 26, 1926.
   Since 1926, the "Avian" has been put into production, and the type which we are about to describe is known as the "Avian" Mark III, which is fitted with the Mark II A.D.C "Cirrus" engine. The latest model differs considerably from the prototype, and among other changes may be mentioned the decrease in wing area, the large area of the 1926 machine being used in order to enable the machine to carry a large useful load and thus score heavily for competition purposes. Incidentally, it is the original machine which Hinkler used on his recent magnificent flight to Australia in 15 1/2 days. The wings, however, are of much smaller area than those used in the competition.
   The production type "Avian" has been strengthened a good deal so as to enable it to withstand the varied handling which it may receive from beginners in flying, and when used for school work. The lines have been improved considerably, and the machine now has a remarkably "clean" appearance, the long slender fuselage terminating in front in a neat engine fairing, and merging cleanly into the spinner over the propeller boss.
   The fuselage is of the flat-sided three-ply covered type, and the details of its construction are shown in a set of sketches on page 155. The form of construction adopted is simplicity itself, and has the advantage over the wire-braced girder type of construction that it does not require any trueing-up after prolonged service. In front a fire-proof bulkhead separates the cockpits from the engine, which is supported on a very simple mounting of steel tubes, the arrangement of which is illustrated by a sketch. The engine cowling is so arranged as to be entirely detachable, thus leaving the engine exceptionally accessible, the more so as there is little or no bracing to get in the way. What adds further to the facility with which inspection and adjustment of the engine can be carried out is the special type of undercarriage, invented by "Bert" Hinkler, which lowers the machine a good deal when the wings are folded, the top hamper of the engine thus being within easy reach.
   The two cockpits are arranged one behind the other in the customary manner, and dual controls are provided, so that the machine may be used for instructional purposes. The "joy stick" in the front cockpit is detachable so as not to be in the way when a non-piloting passenger is being carried.
   The controls are, generally speaking, of normal type, but as one of our photographs will show, they are mounted on a complete unit which is independent of the main fuselage structure except in so far as its very simple mounting is concerned. The foot bars are provided with T-shaped pedals, and these, which are made of tubing, are mounted in sockets and provided with bolt holes so that the pedals may be adjusted to suit pilots of different length of legs.
   The undercarriage is, as already mentioned, quite different from that fitted on the prototype machine. The original "Avian" (G-EBOV) has an undercarriage of similar type, rigged up by "Bert" Hinkler, its inventor, but the "Avian Mark III" has a slightly modified form, although incorporating the same general principle. The new undercarriage is of the "divided" type, i.e., there is no axle running across from side to side. Instead, the two separate wheel axles are hinged on the centre line of the bottom of the fuselage and bent to a horizontal direction near the wheels. The shock absorbing, or telescopic member is the front "leg" of the chassis Vee, which incorporates rubber block compression rubbers. The rear chassis leg is taken to a point on the lower rear wing spar.
   As regards the lower wing, two short wing roots are attached permanently to the fuselage. These roots are triangular in plan view, with the base of the triangle formed by the leading edge and the apex at the rear spar hinge. To brace the root against the undercarriage loads a short diagonal strut runs to the top longeron. When the wings are folded they swing, of course, around the hinge. The point of attachment of the rear chassis strut being situated some little distance out from the hinge, when the wings are folded the upper end of the rear strut moves back with the wing, and in so doing pulls the wheel back with it, and at the same time the wheel moves upward slightly. The combined effect is to lower the machine and to relieve the load on the tail skid. Thus, with the wings folded., the machine can be wheeled along quite easily by one man.
   The divided undercarriage has other advantages, such as a wide wheel track which renders possible taxying the machine in a strong cross wind without risk of it being blown over on to a wing tip. The absence of a horizontal axle also lessens the risk of nosing over in long grass or corn, in case of a forced landing.
   Telescopic jury struts are used to separate the inner ends of the wings when the latter are folded. When the wings are spread the jury struts are "telescoped" and rest in clips under the top plane.
   The wing construction of the Avro "Avian" is of perfectly normal two-spar type. The wings are but slightly staggered in relation to each other, but the gap is large and the biplane arrangement is probably very efficient.
   The top plane centre-section contains the petrol tank, which has a capacity of 20 gallons. An interesting feature is that one of the centre-section struts is used as the petrol gravity pipe, the flexible petrol tubing being joined to the lower end of this strut. This is indicated in the side elevation below. The high position of the petrol tanks ensures an ample head of petrol even during a steep climb, and, of course, the petrol system is greatly simplified by using direct gravity feed.
   When fitted with the standard "Cirrus" Mark II engine, the tare weight of the "Avian III" is 875 lb. The normal loaded weight of the machine is 1,360 lb., and the certificate of airworthiness covers up to a gross weight of 1,450 lb. for "aerobatics," and up to 1,600 lb. for ordinary straight flying. In other words, if it be desired to use the "Avian" for long-distance non-stop flights, a large tank can be fitted in the front cockpit, and the machine may be loaded up to 1,600 lbs. without exceeding its C. of A. for "non-aerobatic" flying.
   The main dimensions of the "Avian III" are given on the general arrangement drawings. The main performance figures are as follows, and apply to the loaded weight of 1,360 lb.: Top speed at ground level 105 m.p.h. (170 km./h.). At 5,000 ft. the top speed is 100 m.p.h. The absolute ceiling is 17,000 ft. (5,180 m.), and the stalling speed, 40 m.p.h. (65 km./h.) Power loading, 17 lbs./h.p. Wing loading, 5-57 lbs./sq. ft. “Wing Power," 0-328 h.p./sq. ft. (3-53 h.p./sq. m.).
Everling Quantities.
   "High-speed Figure": 26
   "Distance Figure": 4-9
   "Altitude Figure" (Ceiling): 7-6
   All these figures are high, and well above the average.

Flight, October 1928

British Exhibits At The Berlin Aero Show 1928

THE MACHINES

A. V. ROE AND CO., LTD.

   THERE are two Avro "Avians" at the Exhibition, one fitted with a "Cirrus Mk. II" engine, and the other with an Armstrong-Siddeley "Genet," Mk. II engine. Both machines are standard. It is interesting to note that this type of light aeroplane is being despatched in batches of fifties every six months to A. V. Roe and Co.'s agents in America. This production type "Avian" has been strengthened a good deal so as to enable it to withstand the varied handling which it may receive from beginners in flying, and when used for school work. The lines have been improved considerably and the machine has a remarkably "clean" appearance.
   The fuselage is of the flat-sided three-ply covered type, and the form of construction adopted is simplicity itself, having the advantage over the wire-braced girder type of construction that it does not require any trueing-up after prolonged service. In front a fire-proof bulkhead separates the cockpits from the engine, which is supported on a very simple mounting of steel tubes. The engine cowling is very neat and so arranged as to be entirely detachable, thus leaving the engine exceptionally accessible, the more so as there is little or no bracing to get in the way. What adds further to the facility with which inspection and adjustment of the engine can be carried out is the special type of undercarriage, invented by "Bert" Hinkler, which lowers the machine a good deal when the wings are folded, the top hamper of the engine thus being within easy reach.
   The two cockpits are arranged one behind the other in the customary manner, and dual controls are provided, so that the machine may be used for instructional purposes. The "joy stick" in the front cockpit is detachable so as not to be in the way when a non-piloting passenger is being carried.
   The new undercarriage is of the "divided" type, i.e., there is no axle running across from side to side. Instead, the two separate wheel axles are hinged on the centre line of the bottom of the fuselage and bent to a horizontal direction near the wheels. The shock absorbing, or telescopic member is the front "leg" of the chassis Vee, which incorporates rubber block compression rubbers The rear chassis leg is taken to a point on the lower rear wing spar.
   As regards the lower wing, two short wing roots are attached permanently to the fuselage. These roots are triangular in plan view, with the base of the triangle formed by the leading edge and the apex at the rear spar hinge. To brace the root against the undercarriage loads a short diagonal strut runs to the top longeron. When the wings are folded they swing, of course, around the hinge. The point of attachment of the rear chassis strut being situated some little distance out from the hinge, when the wings are folded the upper end of the rear strut moves back with the wing, and in so doing pulls the wheel back with it, and at the same time the wheel moves upward slightly. The combined effect is to lower the machine and to relieve the load on the tail skid. Thus, with the wings folded, the machine can be wheeled along quite easily by one man.
   Telescopic jury struts are used to separate the inner ends of the wings when the latter are folded. When the wings are spread the jury struts are "telescoped" and rest in clips under the top plane.
   The wing construction of the Avro "Avian" is of perfectly normal two-spar type. The wings are but slightly staggered in relation to each other, but the gap is large and the biplane arrangement is very efficient.
   The top plane centre-section contains the petrol tank, which has a capacity of 20 gallons. An interesting feature is that one of the centre-section struts is used as the petrol gravity pipe, the flexible petrol tubing being joined to the lower end of this strut. The high position of the petrol tanks ensures an ample head of petrol even during a steep climb, and, of course, the petrol system is greatly simplified by using direct gravity feed.
   When fitted with the standard "Cirrus" Mark II engine, the tare weight of the "Avian III" is 875 lbs. The normal loaded weight of the machine is 1,360 lbs., and the certificate of airworthiness covers up to a gross weight of 1,450 lbs. for "aerobatics," and up to 1,600 lbs. for ordinary straight flying. In other words, if it be desired to use the "Avian" for long-distance non-stop flights, a large tank can be fitted in the front cockpit, and the machine may be loaded up to 1,600 lbs. without exceeding its C. of A. for "non-aerobatic” flying.
   The main performance figures are as follows, and apply to the loaded weight of 1,360 lbs. : top speed at ground level, 105 m.p.h. (170 km./h). At 5,000 ft. the top speed is 100 m.p.h. The absolute ceiling is 17,000 ft. (5,180 m.), and the stalling speed 40 m.p.h.

Flight, June 1929

BRITISH AIRCRAFT AT OLYMPIA

A. V. ROE & CO., LTD.

   OWING to the fact that the material dealing with the exhibits of A. V. Roe & Co. reached us very late, it has not been possible to include the article describing the Avro show machines in its proper place, alphabetically, and we have, perforce, had to place it here, at the end of our advance show report. While regretting the fact, we had no choice in the matter, as it was necessary to go to press with this week's issue of FLIGHT a good deal earlier than usual, and the makeup of the Olympia Show Report could not be deferred until the last minute.
   At least four complete aircraft are expected to be shown on the Avro stand; An Avro 10, an Avro 5, an "Antelope," and a metal "Avian" with "Genet Major" engine. This engine is an entirely new type, produced by Armstrong Siddeley Motors, Ltd., and will make its public appearance for the first time at Olympia.
<...>
   The Avro "Avian" light 'plane two-seater is a machine with a number of famous flights to its credit, among them being Bert Hinkler's flight from Croydon to Australia in 15 1/2 days last year. This performance has not since been beaten, or even equalled, by an aircraft of any power.
   The "Avian" is now supplied with three distinct power plants: The "Cirrus III," the Armstrong Siddeley "Genet," and, quite recently, the Armstrong Siddeley "Genet Major" engine of 100 h.p. The performance of the machine naturally varies according to the power plant fitted, but in other respects the machine itself remains almost unchanged, so that the following notes may be taken to refer to all types.
   The "Avian," in all its variations, is a tractor biplane with accommodation for pilot and passenger. It may be used for school work or by the private owner, and may be purchased either as a landplane or as a seaplane. In its latest form the "Avian" is partly of metal construction in that its fuselage is of welded steel tube construction, of the same general type as that used in the Avro 10 and Avro 5 machines. The longerons and struts are of circular section and are joined by welding. In the side panels the bracing is by diagonal struts, while in top and bottom panels wire bracing is employed. The stringers of the deck and side fairings are of wood.
   The "Avian" wings are mainly of wood construction, with wooden spars and ribs, although the top centre-section is a welded steel tube structure containing the streamline petrol tank, which has a capacity of 24 gallons. The wings are made to fold.
   A new type of undercarriage has been produced recently for the "Avian." Previously a type of undercarriage was fitted in which, when the wings were folded, the wheels moved back slightly, thus reducing the load on the tail when the wings were folded. The new undercarriage has radius rods and bent axles hinged to the centre line of the bottom of the fuselage, while the telescopic leg is taken to the top longeron of the fuselage. The shock absorbers in the telescopic legs consist of rubber pads, integrally moulded with metal friction plates and separated by metal washers. The stroke of the leg is long, so that quite large shocks can be effectively absorbed. The wheel track is very wide (6 ft.) for the span of the machine, and the "Avian" can be taxied in a strong cross wind without risk of overturning.
   As regards accommodation and equipment, the "Avians" of all types have the usual tandem seating arrangement, with adequate windscreens, dual controls, safety belts and all the usual instruments such as revolution counters, altimeters, airspeed indicators and oil-pressure gauges.
   We regret that, owing to the fact that the "Avian" with "Genet Major" engine has but recently been completed, we have no figures of weights and performance of this machine. The standard "Cirrus Avian" landplane has the following dimensions: Length o.a., 24 ft.; wing span, 28 ft.; width, folded, 9 ft. 6 in.; overall height 8 ft. 6 in.
   The tare weight of the "Cirrus Avian" landplane is 935 lbs. The load is made up as follows: Pilot, 165 lbs.; passenger, 165 lbs.; 20 gallons of petrol, 155 lbs.; 1 1/2 gallons of oil, 15 lbs. Loaded weight, 1,435 lbs. Total permissible weight (Aerobatics C. of A), 1,450 lbs. Total permissible weight (normal C. of A.), 1,600 lbs.
   At a gross weight of 1,435 lbs. the performance of the "Cirrus Avian" is as follows: Full speed at ground level, 102 m.p.h.; maximum speed at 5,000 ft., 98 m.p.h.; cruising speed at 1,000 ft., 87 m.p.h.; stalling speed, 40 m.p.h. Length of run to take off, 70 yards. Length of run after landing, 90-100 yards. Rate of climb at ground level, 750 ft./min. Time to 5,000 ft., 8 min.; to 10,000 ft., 21 min. Absolute ceiling, 18,000 ft. Range, 400 miles.
   The "Cirrus Avian" seaplane has the same dimensions as the landplane, but the length is 25 ft. The tare weight is 1,053 lbs. and the loaded weight 1,553 lbs. The total gross weight for "normal" C. of A. is 1,600 lbs.
   Maximum speed at sea level, 97 m.p.h.; at 5,000 ft., 93 m.p.h.; cruising speed at 1.000 ft., 82 m.p.h.; stalling speed, 42 m.p.h. Time to take off in still air, 8-10 secs. Rate of climb at sea level, 480 ft./min.; time to 5,000 ft., 14 mins., to 10,000 ft., 39 minutes. Absolute ceiling 13,000 ft. Range, 400 miles.