Airspeed AS.10 Oxford

В 1936 году фирма "Airspeed" приняла участие в конкурсе, объявленном Министерством авиации, по созданию двухмоторного учебного самолета по спецификации (техническому заданию)Т.23/36. Проект был создан на базе удачного самолета AS.6 Envoy.
   Прототип AS.10 совершил первый полет 19 июня 1937 года, а уже в ноябре была поставлена партия из шести серийных машин. Четыре машины получила Центральная летная школа RAF, а еще два - 11-я летная школа. Oxford сохранил конструкцию своего предшественника. Изменениям подверглась силовая установка и внутренняя компоновка кабины. Кроме того, на Oxford Mk I была установлена турель Armstrong Whitworth с одним 7,7-мм пулеметом для обучения воздушных стрелков.
   Во время Второй мировой войны Oxford выпускался в больших количествах и широко использовался для подготовки авиаторов в рамках Имперской тренировочной программы (Empire AirTraining Scheme, EATS). В стандартной конфигурации он был трехместным, но наряду с сиденьями курсанта и инструктора на нем предусматривались рабочие места для обучения воздушного стрелка, бомбардира, штурмана и радиста. На всех серийных машинах было установлено сдвоенное управление, что позволяло использовать их в качестве учебно-тренировочных. Когда снимался комплект управления второго пилота, то на освободившемся месте мог разместиться в лежачем положении бомбардир. Учебные дымовые бомбы размещались в нишах центроплана. Также кресло второго пилота можно было откатить назад и поднять прикрепленный к борту фюзеляжа с помощью петель столик для тренировки штурманов. Повернутое назад кресло позади места второго пилота предназначалось для радиста. Кроме того, самолет мог оснащаться непрозрачным колпаком, позволявшим проводить обучение полетам по приборам.
   Самолеты модификаций Oxford Mk I (общего назначения, для подготовки бомбардиров и стрелков) и Oxford Mk II (для обучения пилотов, радистов и штурманов) были оснащены двигателями Armstrong Siddeley Cheetah X, мощностью по 375 л. с. Oxford Mk V, предназначенный для тех же задач, что и Oxford Mk II, оснащался парой моторов Pratt & Whitney R-985-AN-6 Wasp Juniors, мощностью по 450л.с. На Oxford Mk III, построенном в единственном экземпляре, стояли моторы Cheetah XV мощностью по 425 л. с. Oxford Mk IV, предназначенный для тренировки пилотов, так и не был построен. В порядке эксперимента один Oxford Mk II оснастили рядными моторами жидкостного охлаждения de Havilland Gipsy Queen, мощностью по 250 л. с. Кроме того, на один Oxford Mk I установили специальное шасси McLaren, основные стойки которого могли смещаться при взлете и посадке на определенный угол, в зависимости от силы ветра. А еще одну машину оборудовали двухкилевым оперением для проведения испытаний на штопор.
   Вторая мировая война создала огромный спрос на эти самолеты, использовавшиеся не только RAF, но и странами, участвовавшими в подготовке авиаторов по программе EATS. Несколько машин достались ВВС "Свободной Франции". Подразделения американских ВВС в Европе получили небольшое количество Oxford в рамках "обратного ленд-лиза". Много машин переоборудовали в санитарный вариант. Британские ВМС также использовали Oxford, сформировав в 1942 году 758-ю эскадрилью для обучения "слепым" полетам.
   Фирма "Airspeed", выпустившая 4961 Oxford, не могла в полной мере удовлетворить спрос на эти самолеты. Поэтому к их постройке были привлечены другие компании: "de Havilland" (построила 1515 машин), "Percival Aircraft" (1360) и "Standard Motors" (750). В общей сложности было построено 8586 самолетов этого типа. Последнюю машину "Airspeed" выпустила в июле 1945 года. Oxford использовались в летных школах RAF до 1954 года. После войны много этих машин было поставлено голландским ВВС.

ТАКТИКО-ТЕХНИЧЕСКИЕ ХАРАКТЕРИСТИКИ

   Airspeed AS.10 Oxford Mk V

   Тип: трехместный учебный самолет
   Силовая установка: два мотора воздушного охлаждения Pratt & Whitney R-985-AN-6 Wasp Junior, взлетной мощностью по 450 л. с. (335,5 кВт)
   Летные характеристики: максимальная скорость 325 км/ч на высоте 1250 м; скороподъемность у земли 610 м/мин; время набора высоты 3050 м - 6 минут; потолок 6400 м; дальность полета 1127 км
   Масса: пустого снаряженного 2572 кг; максимальная взлетная 3269 кг
   Размеры: размах крыла 16,26 м; длина 10,52 м; высота 3,38 м; площадь крыла 32,33 м

Flight, April 1937

UP FOR SCHOOLS
The Airspeed Oxford: A Twin-engined Trainer for the Service

   "OXFORD" is the name chosen for the Airspeed twin-engined, advanced training monoplane now in large-scale production for the R.A.F. Essentially, the machine resembles the Envoy, and its military or "Convertible" variation, but it incorporates a number of innovations, notably in the nose portion, where greater width permits dual control.
   Not only will the Oxford be an admirable intermediate type for the training of pilots destined to fly high-performance multi-engined machines, but its layout permits instruction and practice in navigation, gunnery and bombing. An Armstrong-Whitworth gun turret is fitted.
   The engines of the production Oxford will be Armstrong Siddeley Cheetah IXs, rated at 310 h.p. at 6,000ft. (350 h.p. maximum). These units will be of the newest type, adapted to drive De Havilland variable-pitch airscrews.
   The first production Oxford should soon be flying.

Flight, June 1938

MODERN TRAINER
The Airspeed Oxford with Two Cheetah X engines : Flying Qualities and Layout : Quantity production

   AS the Expansion Scheme began to swing into its stride the Air Ministry decided to order a large number of twin-engined monoplane trainers which would reproduce to a large degree the characteristics of contemporary high-performance first-line machines. The type chosen was the Airspeed Oxford, which, apart from functioning as a transitory medium for flying instruction (including instrument flying), was designed to provide for instruction in navigation, night flying, wireless, direction finding, gunnery, and vertical photography. Incidentally, it would make a first-rate general-purpose machine, or could be used for over-water reconnaissance.
   The manufacturers were fortunate in having behind them constructional and operational experience with the Envoy, upon which the design of the Oxford was based. Planning the Convertible Envoy in its military form also helped pave the way for the new machine.
   Before very long Oxfords will be in production not only at the Airspeed Portsmouth works, which have already delivered a useful number, but at the De Havilland and Percival plants.
   For a good many years it has been the habit of civil pilots and of transport pilots in particular to jeer at the flying equipment in, and general layout of, military aeroplanes. In the days when such jeering was really justified the powers that be probably felt that such things as v.p. air-screws, retractable undercarriages, flaps, and, for that matter, proper blind-flying instruments, were neither necessary nor desirable in military machines. During the past year or two things have been changing, but, even so, there has been a good deal to criticise, at least in the flying equipment of a great many modern types.
   It would probably not be an exaggeration to say that in the Airspeed Oxford a really modern array of controls and instruments has been planned in complete detail and, as a whole, almost for the first time. This is only right and proper since the Oxford is intended primarily as a twin-engined trainer in which pilots who are eventually going on to the modern type of aeroplane will learn how to make the best use of all the equipment which they are likely to find in such a type. The planning of the control cabin itself is such as would please even the pilots who are familiar with some of the much-praised American transport aeroplanes. In fact, if production considerations permitted, the Oxford, in suitably modified form, would make an excellent training machine for the use of probationary pilots in the larger transport operating companies. The only items which are missing in the present-production Oxfords are those relating to the blind-approach technique. No doubt later machines of the same type will be suitably equipped for such approach practice when more Service aerodromes have been supplied with the necessary ultra-short-wave beacons and marker beacons - presuming these to be standard.
   Recently we had a chance of flying with Mr. G. B. S. Errington, the Airspeed test pilot, on an acceptance test flight. During the course of this flight the machine was put through all its nor­mal paces, and it was interesting to realise that it was one straight from the factory, and, consequently, a representative example of production. It had not previously been flown at all, yet the corrections to be made were few and of a minor nature. For instance, the machine flew right wing low, so that aileron tab adjustment would be necessary, and one of the engines was not giving quite full boost.
   One’s first impression on entering the pilot’s compartment is that the view, in practically all essential directions, is as nearly perfect as possible, and a great deal better than that to which one is accustomed in the ordinary civil aeroplane. The roof extends well to the rear of the seats, so that with the tail down it is possible to scan the rear sky properly before taking off. The screen itself is entirely unobstructed, the two large side windows can be slid open, and there are small sections which can be opened without unreasonable draught for use in bad weather conditions. The only blind spots are those inevitably made by the engine cowlings.
   With the fore-and-aft trimming wheel (which is mounted on the starboard side of pleasantly sensitive and approximately a neutral given full throttle, lifts its own tail and, on a smooth aerodrome, would quite well fly itself off. Once the machine is properly on the move there is little or no swing, and this, it appears, can be held on the rudder alone. For the take-off the automatic mixture control lever is set at the rear of its gate to provide an over-rich mixture for, say, two minutes during the take-off and climb. At 1,000ft. the lever is moved to a central position, which provides a "normal" automatic mixture, and the rest ol its travel is designed primarily for use at considerable altitudes. The pilot is, therefore, relieved of the necessity for continuous mixture adjustment. The effect of moving the lever forward to the normal position is rather similar to that of changing airscrew pitch. The initial batch of Oxfords, at least, are fitted with fixed-pitch airscrews, though there is a lever below and to the left of the control bank all ready for v.p. or c.s. control. Beside this latter lever are two others operating the undercarriage and flaps respectively; these are actuated by hydraulic jacks, the power for which is provided by a pump driven by the starboard engine. This engine also drives an air compressor for the braking system and a vacuum pump for the gyroscopic instruments, while the port engine drives an electric generator. Also on the main control bank are levers for carburettor temperature adjustment and for the twin landing lights mounted in the port wing, while at the base of the bank there is a trimming crank for rudder bias adjustment which, apart from its normal uses on a long flight, goes a considerable way towards relieving the rudder pressure if it is necessary to fly at any time on one engine alone.
   The flaps, an indicator for the position of which is mounted beneath an hydraulic pressure gauge in the centre of the dashboard, are not normally used for the take-off. Though a fifteen-degree position shortens the run to a slight degree, the additional drag after the take-off outweighs this small advantage.
   The normal full-power take-off boost figure is about 2 1/2 lb., the engines being moderately supercharged to provide maximum cruising power at about 8,000ft. In case of an emergency the throttles can be moved past a wired-up section of their gates. In this position the engines are giving much more than their normal rated horse-power at ground level. The maximum speed at rated altitude is 192 m.p.h. On this particular machine, with one engine slightly down in performance, the indicated speed at this height was 170 m.p.h., which, corrected for altitude (7,000ft.) means that the machine was flying at 185 m.p.h. or so.

Good Controls

   The controls appear to be everything that they should be, and the aileron control in particular is a good deal more pungent than is usually expected in comparatively large aeroplanes; their effect is equally vigorous at comparatively low gliding speeds, and does not seem to differ one way or the other when the flaps are in the fully down position. Students of airflow will find a singularly interesting effect on the Oxford, this effect showing that the change of flow caused by the flaps is noticeable not only around the fuselage but several feet above it. The wire­less aerial whistles or is silent, as the case may be, when the flaps are up or down. The flaps steepen the approach quite sufficiently to simplify approach judgment, but not so much that the hold-off and landing needs to be made in one swift, firm movement. From a speed of about 75 m.p.h. there is quite a useful period during which the machine's height above the ground can be adjusted before the final stall.
   Needless to say, the Oxford is equipped with the standard Service blind-flying panel, incorporating an A S.I., a sensitive altimeter, an artificial horizon, a directional gyro, a rate of climb indicator and the necessary turn indicator. Incidentally, the modern vertical velocity, or rate of climb, indicator is extremely quick in action, and that in this particular Oxford appeared to have a lag of rather less than two seconds. One of the ingenious little details of the control layout is the arrangement of the rudder pedal adjustment for the first pilot. The pedals themselves can be brought towards or away from the pilot by the simple means of turning the cylindrical pads with the feet.
   In the bomb-aimer’s compartment, if so it can be called, there is an additional instrument panel incorporating an A.S.I., an altimeter and a watch, while on the electrical panel on the port side of the fuselage there is an additional altimeter. The second pilot’s part of the main dash­board carries essential flying instruments, including a second compass. This seat is normally taken by the navigator trainee, and it can be moved sufficiently far back on its runners to enable the occupant to make use of a chart board and navigating instruments. Elsewhere in the fuselage there is accommodation for these instruments and, additionally, for a tail drift-sight.
   The radio equipment (which may be assumed to be of the Marconi A.D.77/6872 type), mounted behind the centre section, is of the normal two-way type, with the equipment mounted vertically in a single frame, the operator facing rearwards. Above and behind this seat is he hand-turning gear for the loop aerial. The detachable handle for this is used for rotating the aerial in order to obtain bearings, or, when placed in another socket, retracts the loop into a recess in the roof. When retracted, the loop is quite flush with the top of the fuselage.
   Among the many uses of the Oxford is that of blind-flying training, and a special hood has been devised for use over the first pilot's seat. When ex­ended, this hood completely cuts out all view except that of the instruments themselves, and it can be folded backwards and swung sideways so that it is completely out of the way when not in use.

CONSTRUCTION AND EQUIPMENT

   COMPREHENSIVE jigging has permitted creditable rapidity of construction, though the output of the Airspeed factory, which has not yet reached its peak, is not for publication at Air Ministry request.
   The fuselage of the Oxford is a typical Airspeed semi-monocoque with spruce longerons and stiffeners beneath the plywood covering. The joint between front and rear sections is made at the rear bulkhead; an interesting point is the special reinforcement of the forward bulkhead to withstand the shock in the event of the machine turning over during landing.
   The fuselage sides are made on separate jigs alongside each other.
   One requirement of training machines for the Royal Air Force is the ability to be transported easily by road when dismantled. Consequently, the wing of the Oxford is in three parts. It is, of course, a stressed skin ply-covered structure with spars which have spruce flanges and three-ply webs. The spars are positioned on one jig, others being provided for positioning the leading and trailing edges. The three-piece ribs have braced webs and spruce booms. The sturdy centre-section is of similar construction to the outer panels. There are interesting drilling jigs for the centre-section spars with a system of colouring for the various sizes of holes to be drilled. The spars are positioned by horizontal and vertical datum lines.
   Split flaps extend from aileron to aileron, and are normally operated hydraulically by pressure from an engine-driven pump, though for emergencies there is a hand-operated pump.

The Tail Unit

   The elevator is fabric-covered and is built up from a wooden spar and ribs. The fin is of similar construction, the fin post being built into the fuselage and faired with fabric covering and spruce stringers. Aerodynamic and mass balances are provided for the rudder. Although the skin of the main planes is applied at 45 deg., this measure is not considered worth while for the tailplane.
   The retractable undercarriage is of Airspeed design, and features a broken radius rod mechanism acting on a braced twin oleo leg chassis and retracting rearward into each nacelle. Although actuation is normally by an engine-driven pump, manual gear is provided to pump the wheels down in the case of engine failure.
   The brakes on the Avery wheels are operated pneumatically by a lever on each control column. Normal movement of the rudder gives differential action by means of the Dunlop relay system. A B.T.H. compressor is driven from the right-hand engine, and maintains a pressure of 200 lb. /sq. in. in a reservoir in the centre section. There are two main fuel tanks, each of 49 gallons capacity, between the centre-section spars; they are interconnected with two auxiliary tanks each holding 29 gallons. Fuel is drawn by the engines from the main tanks, the auxiliary tanks feeding into the main ones by gravity. Oil is carried in two tinned steel tanks (84 gallons each) in the engine nacelles. An oil-cooler of Airspeed design and Gallay construction is used, the cooler being integral with the tank. Cooling air is taken through an inlet inside the engine cowling and conducted by a pipe to the tank of the cooler.
   The standard power plant of the Oxford is two Arm­strong Siddeley Cheetah X seven-cylinder air-cooled radials geared 1:1 and with a supercharger gear ratio of 6.5:1, giving a normal output of 340 h.p. at 2,300 r.p.m. and 7,000ft. Maximum and take-off powers are respectively 350 h.p. at 2,425 r.p.m. and 7,500ft. and 375 h.p. at 2,300 r.p.m. The engines are designed to use the size 2,000-De Havilland variable-pitch airscrews, though these are not yet available in quantity. Machines now being delivered have wooden airscrews. Constant-speed De Havillands can be accommodated.
   Welded steel construction is used for the nacelles, which are attached to the centre section at four points by means of Lord rubber insulated joints.
   Claudel Hobson’s "M"-type carburettors with variable datum boost control and automatic mixture control are
specified. The control pedestal has two throttle control levers and one lever for adjusting mixture strength. This has three positions: "Automatic weak," "automatic rich" and "over-ride."
   When rapid accelerations are expected, the lever is put in “automatic rich”; the “automatic weak” position is for economical cruising. For take-off the “over-ride” position is used, this actuating an enrichment jet to prevent detonation and to keep the engine at a safe temperature. Electric starters, auxiliary hand-turning gear and dual engine-driven fuel pumps are specified. The port engine drives a 500-watt generator, and its twin is responsible for the pump for the hydraulic system, the compressor for the brakes and the vacuum pump for the blind-flying instruments.
   The equipment includes piping, with attachments and mountings for three oxygen regulators, a flowmeter, three bayonet unions and three high-pressure oxygen cylinders of 750 litres capacity.
   When the Williamson camera is installed in place of the wireless, remote electrical control is arranged for the pilot and bomb aimer.
   Provision is made for the installation of a gun turret in the upper portion of the fuselage. This, for the time being at least, is of the Armstrong Whitworth manually operated type, which accommodates a single Lewis gun. Sixteen 11 1/2 lb. practice bombs are carried internally in the centre section. Two bomb-release switches are installed - one for the pilot and one at the bomb-aimers’ station. The pilot has control of the selector and jettison.
   A protected tube behind the first pilot's seat is used for firing the Very pistol through the floor. Other tubes are provided in the rear fuselage for two parachute flares released by remote control from the cockpit.
   The question of inspection has been very carefully studied, suitable panels being provided below the pilot's cockpit for access to the flying controls, hydraulic gear and electrical leads, and in the outer wing panels for inspection and control.
   Five Oxfords are being delivered to the Royal New Zealand Air Force for advanced training and general-purpose work. Other countries are showing marked interest, though the demands of the expansion scheme limit the possibilities for the machine in the export market.

  
AIRSPEED OXFORD.
Twin-engined Advance Trainer
Two Armstrong Siddeley Cheetah X Engines - 350 h.p. (max.) at 7,500ft.

Dimensions.
   Span 53ft. 4in.
   Length 34ft. 6in.
   Height 11ft. 1in.
Performance.
   Max. rate of climb at sea level 1,340 ft./min.
   Max. speed sea level 169 m.p.h.
   Max. speed, 8,000ft. 192 m.p.h.
   Cruising speed at 5,000ft. 100 m.p.h.
   Fuel consumption at 10,000ft. (62 1/2 % power) 13.4 gal./hr./engine.
   Service ceiling 23,550ft.
   Single-engine ceiling 6,000ft.
   Endurance (2,100 r.p.m., 10,000ft.) 5 1/4 hr. + 1/4 hr. at full throttle.

Flight, November 1939

Britain's Military Aircraft
A Survey of Our Service Machines

AIRSPEED

   THE main resources of the Airspeed concern are now concentrated on the production of Oxford twin-engined military trainers.
   The Oxford, although based on the design of the successful Envoy transport machine, which was at one time one of the fastest civil types in the world, is, from the military viewpoint at least, an entirely new design. It was planned to meet the requirements of an Air Ministry specification for a twin-engined trainer incorporating the majority of features common to modern multi-engined military aircraft.
   Structurally, the Oxford is a fine example of what can be done with wood. The wings are made in three sections to facilitate transport and repair. The centre section carries the two Armstrong Siddeley Cheetah X seven-cylinder radial engines, the retractable undercarriage and the main fuel tanks. On the sharply tapered outer panels and beneath the fuselage are split trailing edge flaps.
   Of semi-monocoque wooden construction, the fuselage has a ply covering applied at an angle of 45 deg. to the datum line. Separating the cabin from the pilot’s cockpit is a specially reinforced bulkhead for taking the loads of an overturn landing.
   In the cockpit the instruments are mounted on two panels. The blind-flying panel carries a sensitive altimeter, an airspeed indicator, a rate of climb indicator, an artificial horizon and directional gyro and a turn and bank indicator.
   For gunnery training a manually-operated turret similar to that fitted on the earlier types of Armstrong Whitworth Whitley bombers is fitted. This will accommodate a Lewis, a Vickers K, or a Browning gun. In the bomb well there is accommodation for sixteen 8 1/2 lb. practice bombs, though racks can be supplied for carrying eight 12 kg. or two 100 kg. bombs.
   Fittings for wireless, navigational, photographic and oxygen equipment are provided and there is stowage for a Very signal pistol which fires through a protected tube behind the pilot's seat. Aft of the gun turret is provision tor two parachute flares.
   With fixed-pitch wooden airscrews the Oxford attains a maximum speed of 192 m.p.h. at 8,000ft., and will cruise at 164 m.p.h. at 10.000ft., flying at a gross weight of 7,500 lb. Dimensions are: Span, 53ft. 4in.; length, 34ft. 6in.; and height, 11ft. 1in.
   Also in production for the R.A.F. at the Airspeed works is the Queen Wasp wireless-controlled target machine. This is a biplane with sharply tapered wings and fitted with an Armstrong Siddeley Cheetah engine. When operating as a target the machine is usually fitted with a float undercarriage, though wheels can be used if desired.

Airspeed (1934), Ltd., The Airport, Portsmouth.