Flight, July 1931

THE ARROW "ACTIVE
A new all-metal low-power single-seater biplane, designed for transitional training and fighter practice, including advanced aerobatics. The engine is a Cirrus-Hermes type IIB inverted four-cylinder air-cooled of 115 h.p. The machine starts at scratch in King's Cup Race.

   DURING the last year or so several British aircraft firms have turned their attention to the production of aircraft types intended to form an intermediate step between the dual-control training machine and the high-power single-seater fighter, which a large percentage of service pilots will later be called upon to fly. A feature of all these machines has been low power, with consequent low first cost and very low operating cost in service, which enables an air service using such types to train its fighter pilots and give them constant practice at very small cost indeed.
   To the list of British aircraft of this type has now been added the Arrow "Active," with 115-h.p. Cirrus-Hermes II.B inverted engine. This machine has been designed and built by Arrow Aircraft (Leeds), Ltd., the managing director of which company is Mr. A. C. Thornton. Mr. Thornton, it may be remembered, was at one time on the technical staff of the Blackburn Aeroplane & Motor Co., Ltd., and was responsible, under Major Bumpus, for the design of the original "Bluebird," and also to some extent, we believe, for the Lynx-engined Blackburn "Lincock." Possibly this fact may explain certain points of similarity between the "Lincock" and the "Active," a similarity which is somewhat elusive but is unmistakeably present.

Constructional Features

   In the construction of the Arrow "Active," metal has been used exclusively, except for the wing covering, which is doped fabric.
   The fuselage consists of three separate units: the engine mounting, the central part of the fuselage from engine plate to back of cock-pit, and the rear part of the fuselage. The first of these units, the engine mounting, will be referred to when we come to deal with the engine installation.
   The fuselage centre structure is practically a monocoque, consisting of a skin of duralumin sheet riveted to steel channel longitudinals, carried on frames of tubular and channel members and duralumin box bulkheads. In section the fuselage is pear-shaped, being very narrow at the bottom. The lower wing roots are built integral with the fuselage, the box frames being of very substantial construction.
   The rear fuselage primary structure is of triangular section, and consists of three tubular longerons, with the single tube at the bottom. No welded joints are used, a special standardised fuselage joint of extruded tubular and flanged section being employed. All tubular bracing members have socket ends. The fairing members are all of metal, strongly built and faired to give a good fuselage shape, the lines merging smoothly into the centre structure. The covering of this part of the fuselage is doped fabric.
   The biplane wings are arranged as a "sesquiplan," the lower wings being of much smaller span and chord than the upper. In addition, the stagger is fairly pronounced, so that the view is particularly good, further assisted by the downward slope of the deck fairing from windscreen to propeller boss, the inverted engine showing up to great advantage in this respect.
   In both upper and lower wings main spars of high-tensile steel are used, the spars being of "figure of eight" section. The end attachment fittings are machined sockets, the sockets and spar fittings being in many cases secured by high-tensile ferrules screwed on high-tensile rods. These ferrules provide large bearing surfaces, and are used in considerable numbers in order to distribute stresses. Drag bracing is by high-tensile swaged tie rods and steel struts of square section.
   The wing ribs have booms of drawn duralumin sections, with diagonal braces of tubular section and large area duralumin diaphragms for stiffening. These ribs have been subjected to static loading tests and to 100 hours' vibration tests, and show very large reserve strength factors.
   But a single interplane strut is used on each side. This is in the form of a streamline section steel tube, and the ends of the strut are received in special reinforced end fittings of strong box formation, with lug attachments to the internal box ribs between front and rear spars. These box ribs are attached to the main spars by saddle-plate fittings with reinforcing plates attached, and have long bearing surface engagement with their respective spars, being multi-ferruled and bolted to the spars.
   The external wing bracing is by streamline wires, and by the use of single interplane struts no incidence wires are used.
   The top plane centre-section rests direct on the ridge of the fuselage deck fairing, and with this arrangement a single centre-section strut on each side suffices. This means a considerable reduction in the number and length of struts and wires in the airscrew slipstream, and helps materially to produce a "clean" machine.
   A cantilever tailplane is employed, having two continuous tubular spars of high tensile steel and large diameter. The tailplane is provided with incidence adjustment, and is well stabilised at its four points of attachment to the fuselage. The two elevators are built up on a continuous spar tube, and are hinged to the rear spar of the tailplane at five points. The crank levers are box formation. The whole elevator unit "is readily detachable.
   The fin unit is a cantilever built on a main fin post tube, the lower end of which telescopes into a reinforced sleeve which forms part of the rear fuselage stern fitting. The forward fin member is stayed to the fuselage by a triangular arrangement of tubes inside the fairing, and provides an adjustment whereby the fin unit may be offset in relation to the centre line of the aircraft. The rudder consists of a forward main spar tube and a subsidiary spar tube, to which are secured ribs built up from drawn duralumin boom sections, all ribs in the tail unit being of this type. The outer framing and trailing edge members are made from streamline section steel tube. The rudder is hinged to the fin tube by machined fork fittings. The lower portion of the rudder is shaped in a particular manner to increase the rudder control during such manoeuvres as spinning.

Undercarriage

   The undercarriage is of the "split" type, the axles having machined socket fittings hinged to a machined spool on the bottom longeron or keel tube. The two telescopic legs are of the oil and spring type, the landing shock being first absorbed by oil discharging through a diaphragm orifice. There are no welded fittings in the undercarriage, and all sockets are machined and of ample proportions. Grease nipples are provided at all pivot points.
   The tail skid is a hinged tubular lever, pivoted in a machined forked fitting, which swivels in bronze bushes carried in a housing which forms part of the bottom end of the main stern post. Shock absorption is by a spring working in compression.

Controls

   The flying controls are of normal type, with a duralumin tube control column and adjustable rudder bar provided with parallel action movement. Direct lines of tie-rod controls are employed throughout, and these are guided by felt pad supports mounted in metal box fittings, the felt pads retaining the lubricant.
   Engine controls are operated by levers provided with Ferodo friction discs, and are interconnected at the quadrant for the return to normal of the altitude adjustment. Arens units are employed in the engine controls, and are of relatively large size.

Engine Installation

   As already mentioned, the power plant fitted as standard in the Arrow "Active" is the inverted Cirrus-Hermes type IIB. It is mounted on resilient engine feet on a tubular structure which gives good accessibility to the rear of the engine. The main structural members are fitted with machined sockets having chamfered barrels to graduate the change of section. Under running conditions the structure is particularly free from vibration. The engine mounting may be completely dismantled.
   Simple gravity feed is employed in the petrol system, a tinned steel tank being mounted in the upper centre-section. A short length of Superflexit pipe line connects with the carburettor through a quickly-detachable filter on the engine mounting. A dirt trap is provided in the tank sump. An oil system of normal type is fitted, with delivery and scavenge pumps connected by short Superflexit pipes to a tinned steel tank mounted on resilient pads on the engine bearers. The tank is provided with cooling tubes and air scoops. An oil thermometer and oil-pressure gauge are provided in the system.

Cockpit

   By the particular type of fuselage construction adopted, it has been possible to cut down the sides of the cockpit coaming considerably, so that the pilot may get a particularly unobstructed view. The seat is arranged to take the seat-type parachute, and the seat back is detachable. A very complete set of instruments are provided, and the compass is placed centrally in front of the pilot, above the control column.
   Following is a list of the instruments fitted: Compass, airspeed indicator, inclinometer, altimeter, oil thermometer, oil-pressure gauge, and revolution counter.
   The equipment further includes: Petrol filter, double-pole engine switch, oil filters, safety belt (Air Ministry approved type), and a set of jury struts for folding the wings.

Flying Qualities

   The following extracts from the official Air Ministry report on the flying qualities of the Arrow "Active" may be of interest :-
   "Aerobatic loading at full weight. - Flight tests with centre of gravity both in extreme forward and rearward positions. The aircraft was put through all normal aerobatics at this weight and centre of gravity positions, and was excellent to handle.
   "The controls are light, effective and well harmonized throughout the whole speed range. With the centre of gravity in both extremes, two spins to the left and two to the right were carried out, each of eight turns. The aircraft goes into a spin comfortably and spins smoothly with nose well down, recovery being easily effected by centralisation of controls. The aircraft recovers level flight after a small loss of height. All aerobatics can be easily carried out. Turns to right and left in inverted flight are also easily carried out.
   "At this centre of gravity position a controlled stall glide can be executed if the rudder is used to prevent the aircraft dropping a wing. Control at the stall is good.
   "The take-off presents no difficulties, control is quickly picked up, and there is no tendency to swing. Landing is easy, there being excellent control at low speeds of approach. The aircraft can be side-slipped easily.
   "The aircraft has been inspected for constructional detail in accordance with routine for certificate of airworthiness trials. The aircraft appears to comply in every respect with the requirements for certificate of airworthiness in as far as constructional detail is concerned."
   The main dimensions, areas, etc., of the Arrow "Active" are given on the general arrangement drawings. The weight of the machine empty is 853 lb., and the permissible gross weight for the Aerobatics Category Certificate of Airworthiness is 1,210 lb. Application has not yet been made for a Certificate of Airworthiness in the "Normal" category, but it is likely that this may be granted, if desired, for a gross weight of 1,500 lb. which would be a far greater weight than could be put into the machine, except, perhaps, for very special work.
   Performance figures are not yet available. This may have some connection with the fact that the Arrow "Active" has been entered for the King's Cup Race, in which the handicappers have placed it scratch. They evidently have a high opinion of the maximum speed. And presumably Captain Dancy has access to the Martlesham figures!
   Readers who desire further information about this little machine should communicate direct with Arrow Aircraft (Leeds), Ltd., Little Russell Street (off Whitehall Road), Leeds. Telephone: Leeds 23124.

Flight, November 1932

British Aircraft

Arrow Aircraft (Leeds), Ltd.
Little Russell Street, Leeds, Yorkshire

   MR. A. C. THORNTON was, until he formed his own company under above title, on the technical staff of the Blackburn Company at Brough, Yorkshire. His first, and so far his only type of aircraft is the little "Active", which is designed and produced to incorporate, on a small and economical scale, the features found on modern single-seater high-performance aircraft.
   The Arrow "Active," intended as an intermediate or transitional training scout machine, is an all-metal sesquiplan biplane for all stages of advanced flying training and aerobatic practice. The engine fitted can be either the Gipsy III, Hermes II.B, Hermes IV or any similar engine. In addition to serving for flying and aerobatics training, machine gun training, etc., it can be used for high-speed practice bombing, and will carry a. series of nine to twelve 8 1/2 lb. (3,9 kg.) practice bombs.
   The machine has been designed to comply with the British Air Ministry's load factors for "aerobatic" flying, and includes factors of 7.5 with the centre of pressure in the forward position, 1.5 for the terminal velocity nose diving case, and 5 for inverted flight. The official tests have included all aerobatic manoeuvres, such as looping, rolling, spinning, diving, and inverted flying. Pilots report the controls to be responsive, light in action, and sufficiently sensitive to develop the correct sense of touch.
   The fuselage incorporates two forms of construction. The front part is a metal monocoque, with light Duralumin formers and stringers and covered with Duralumin sheet plating. The rear fuselage portion is a steel tube structure, with three longerons, the whole made streamline shape by light stringers and fabric covering. Bracing is by diagonal tubes, so that no rigging is required in use.
   All-metal construction (with the exception of the fabric covering) is employed, the main wing spars being round steel tubes formed into a "figure of eight" section. The constructional material used is high-tensile steel. The external wing bracing is in the form of streamline wires, and the upper and lower planes are separated by single "I" struts.
   A "split" type of undercarriage is fitted, the telescopic struts having shock absorbing components in the form of coil springs and oil.
   The petrol tank is mounted in the top centre section, a position which gives direct gravity feed to the carburetter.
   Controls of orthodox type are employed, and the "Active" has been reported on by several pilots as being very pleasant to fly, the controls being effective and well harmonised.
   No data relating to weight, etc., are available, but the following performance figures (relating to the Gipsy III model) may be quoted :-
   Maximum speed 144 m.p.h. (232 km,/h.)
   Cruising speed 128 m.p.h. (206 km./h.)
   Landing speed 50 m.p.h. (80,5 km./h.)
   Take-off speed 48 m.p.h. (77 km./h.)
   Climb to 10,000 ft. (3 048 m.) 12 1/2 mins,
   Service ceiling 20,000 ft. (6098 m.)
   Duration at full throttle 2 3/4 hours
   Duration at cruising speed 3 1/4 hours