de Havilland DH.86
Разработанный и построенный в соответствии с требованиями правительства Австралии к многомоторному самолету для компании QANTAS (для полетов между Сингапуром и Австралией), DH.86 получил сертификат летной годности 30 января 1934 года - всего через четыре
месяца после начала проектирования. Самолет представлял собой двухстоечный биплан деревянной конструкции с полотняной обшивкой и шасси с хвостовым костылем. Основные стойки, установленные под внутренними мотогондолами, были закрыты большими обтекателями.
Первый полет DH.86 совершил 14 января 1934 года. Прототип и вторая аналогичная ему машина были приспособлены под управление одним пилотом. Вторая машина с 21 августа 1934 года использовалась "Railway Air Services" для работы на линии Кройдон - Глазго, с промежуточными посадками в Бирмингеме, Манчестере и Белфасте. Второй член экипажа (штурман-радист) сидел позади пилота.
Компании QANTAS и "Imperial Airways" потребовали, чтобы оба члена экипажа сидели бок о бок, и в августе 1934 года фирма доработала прототип, удлинив и расширив носовую часть.
Первый из 29 серийных самолетов получила австралийская компания "Holyman Airways" (четыре машины). Также самолеты получили компании QANTAS (6), "Imperial Airways" (5), "Jersey Airways" (6), египетская "Misr Airwork" (4), "Hillmans Airways" (3) и "Wrightways" (1).
DH.86A: этот вариант, созданный в 1935 году, отличался модифицированным ветровым козырьком, пневматическими амортизаторами шасси и хвостовой стойкой с колесом. Построили 20 самолетов, большая часть из которых была переделана в вариант DH.86B в 1937 году. RAF получили четыре самолета: два - школа радистов в Кранвелле и два - 24-я эскадрилья в Хендоне, другие машины были мобилизованы во время Второй мировой войны
DH.86B: конверсия DH.86A с концевыми шайбами на стабилизаторе, установленными после расследования катастрофы в Мартлешем Хит, происшедшей с одной из машин; вновь построенные DH.86B отличались горизонтальным оперением с законцовками увеличенной хорды и большими передаточными отношениями в проводке элеронов
de Havilland DH.86B
Тип: средний транспортный самолет с экипажем из двух человек
Силовая установка: четыре рядных двигателя de Havilland Gipsy Six мощностью по 200 л.с. (149 кВт)
Летные характеристики: максимальная скорость на оптимальной высоте 267 км/ч; крейсерская скорость на оптимальной высоте 229 км/ч; начальная скороподъемность 690 м/мин; потолок 5305 м; дальность полета 1287 км
Масса: пустого 2943 кг; максимальная взлетная 4649 кг
Размеры: размах крыльев 19,66 м; длина 14,05 м; высота 3,96 м; площадь крыльев 59,55 м2
Полезная нагрузка: до 19 пассажиров в закрытой кабине
Все четыре двигателя DH.86 были установлены в ряд на передней кромке нижнего крыла.
Flight, February 1934
SPEED WITH SAFETY
Built for Imperial Airways, Ltd. and Quantas Empire Airways to comply with the conditions of the Australian Government tender for the Empire Air Route extension from Singapore to Darwin and Cootamundra, the new De Havilland Express Four-engined Air Liner provides exceptionally fast and safe air travel
TO design and build a four-engined aeroplane and to obtain for it a certificate of airworthiness all in a period of four months is no mean feat, in fact, we venture to suggest that it must be quite unique; yet this is what the de Havilland Aircraft Co., Ltd., have done in their works at Stag Lane, and their "Express Air Liner," the first details of which we give in the following pages, is the result of wonderful keenness and co-operation by all departments of this company.
On September 28 last year we gave in FLIGHT the details of the conditions of tender issued by the Australian Government for the Singapore-Darwin-Cootamundra section of the England-Australia air mail service. It will also be remembered that some little time before that we published the result of a talk with Mr. Hudson Fysh, Managing Director, Queensland & Northern Territory Air Services, Ltd. Mr. Hudson Fysh was at that time in England concluding arrangements with Imperial Airways for collaboration between them and his firm for this tender.
At the same time the de Havilland Aircraft company submitted a proposal for a four-engined airliner with a high performance and a wide margin of safety in the event of engine failure. It was seen that the proposed type was not only capable of conforming to the Australian requirements but that it would exceed the minimum performance needs handsomely. A contract was therefore placed by Imperial Airways on behalf of the newly formed firm, Quantas Empire Airways, for one of these aeroplanes to be built and used as a basis for their tender to the Australian Government. A condition of the tender was that the aeroplane submitted had to possess a certificate of airworthiness on the closing date for the tenders, which was January 31, 1934. The task, however, though great, proved not to be beyond the resources of the factory, and the C. of A was obtained on January 30. It will be remembered that we published some of the first flying pictures of this machine on January 18. Not only had every detail of the machine to be designed and manufactured in this period, but the "Gipsy Six" engine, which was then only in its early stages of development, had to be brought through its teething troubles and to obtain its Air Ministry Type Test; moreover, four engines had to be completed for installation in the new machine.
Everything went according to programme. The machine was first flown by the firm's test pilot, Capt. H. S. Broad, on January 14, and during the following week the D.H.86, as she is officially known, passed through the Aircraft Experimental Establishment at Martlesham for airworthiness and handling trials.
It will be seen from the artist's impression that the cabin space is particularly large, naturally, therefore, permitting a variety of arrangements. As shown, accommodation is provided for ten passengers, with a lavatory and luggage compartment, and when Rumbold's have finished the upholstery it will be a very comfortable job. It is probable, however, that for the England-Australia service, should the tender be accepted, the lavatory will be brought forward and a large mail compartment built behind it, thus decreasing the passenger accommodation by two. This sketch also shows the deep long windows which are built either side of the fuselage, making the cabin light and pleasant, a feature which is enhanced by the two top lights normally provided in the roof of the cabin through two emergency exit panels. There is generous head, room as the average height of the cabin is 6 ft. 3 in. (1,9 m.), and the total cubic capacity in the machine available for the carriage of load is 594 cu. ft. (16,82 m3.). A fully controllable fresh-air ventilator system, which ventilates without causing draught, and a cabin-warming equipment is, of course, fitted.
The machine has not got dual control in its present form, but the pilot sits right forward in a cabin separated from the passenger compartment by a bulkhead and door. In this position he has a well-nigh perfect outlook, and the slope of the windscreen, combined with the speed of the machine, should obviate any obstruction of the glass due to snow or rain. Nevertheless, the two large side panels are single pieces of Triplex glass which may easily be lowered, to give a clear and unobstructed outlook forward and to the side. The second member of the crew is accommodated on the starboard side of the pilot and behind him, in which position there is ample room for a full wireless equipment as well as a chart table and stowage for the navigating equipment generally.
Structurally the "86" is interesting, as it is the first machine incorporating a new method of using plywood and spruce. Our artist's sectional sketch shows that the fuselage is primarily a three-ply box, but it has this great difference from the normal type, in that the fuselage is built with the plywood inside the box, and with the spruce longerons, struts and stringers, outside it. Outside this again is a complete fabric covering, doped, as are the other covered units, with Titanine, giving a weatherproof and durable finish. This method of forming the fuselage provides clear walls, floor and roof, and also conserves space, as the sound proofing material, in this case Cabot quilting, can be packed between the plywood and the fabric in the space made by the longerons and stringers. Aft of the main planes sheet Elektron guards are placed over the corners of the fuselage, serving both to give a better shape to the fuselage and to obviate taking the fabric over the otherwise sharp corner.
The tail units are, in general, normal de Havilland design and construction. Their shape is, of course, typically "D.H.," and their construction is of spindled spruce spars, fairly substantial spruce ribs, and a covering of 0.8 mm. plywood. Over the whole there is a covering of fabric and then the usual dope. The elevators (and the ailerons) are not aerodynamically balanced and are controlled by straightforward dual cables between the control column and top and bottom steel horns on the centre of the elevator spar. The tail plane is adjustable throughout a wide range by a vertically mounted square cut screw acting on the leading edge and controlled by an endless cable from a handwheel in the pilot's cockpit. The fin is particularly interesting, because it, also, has its leading edge mounted on a similar screw, allowing it to be offset either side, thus counteracting the unbalanced thrust in the case of engine failure. The rudder is also balanced by means of a small movable surface inset into its trailing edge. This, being attached to the fin by means of cables either side of the rudder, automatically produces a balancing force when the rudder is operated by the main controls. The attachment point on the fin is mounted on a vertical rotatable tube having at its lower end a fore and aft horizontal slotted lever with a pin fixed to the fuselage through the slot. When the fin is offset by its own trimming device the tube will' rotate, operate the balance, and compensate the rudder for the effect of the offset thrust. The fully castoring tail wheel is fitted with rubber blocks in compression to absorb the shock of landing.
The wing construction, as regards the outer portions, is more or less standard "Dragon," the heavily tapered aerofoil section being R.A.F.34 modified. The spars are of spruce, spindled to "I" section. The ribs are of spruce fixed to the spars with the "D.H." capping clips of light alloy. The drag bracing is, for the most part, of double piano wire with steel drag struts. The leading edge is completely covered with plywood which is carried right back to the rear spar round about the region of the single interplane strut separating the top and bottom planes in the outer bay. This strut is a streamline steel tube and in subsequent models of this machine the aileron interconnecting gear will, instead of being cables as at present, consist of a tube running up inside this strut. The interplane main bracing is by dual streamline wires in the front bay only. The ailerons are of the same construction as the tail unite and are completely covered with 0.8 mm. plywood. They are actuated, as are all the flying controls, by Bruntons "Tru-Lay” cable running over large pulleys without the use of fibre blocks at any point, thus providing a control system with extremely little frictional loss. To facilitate inspection of the controls to the tail units, the fabric in the bottom of the fuselage is brought together with a "Zip" fastener so that it can be opened at any time without difficulty. The inner bays of the main planes are, of course, very interesting structurally, as the bottom one carries all four engines and the undercarriage. Our artist's sketch shows one of the inner engine mountings, built up of welded steel tubes, and incorporating the cantilever undercarriage. In the sketch this undercarriage has dual compression legs either side, but we understand that for subsequent models it has been found, by Mr. Dowty, of Aircraft Components Co., Cheltenham, who has designed this undercarriage, that a considerable saving in weight will be made by having only a single leg either side. Between the points of attachment of the two inner engines the wing spars are continuous underneath the fuselage and are steel tubes of circular section. Those between the roots and the top main planes are the same. The engine mountings are all similar, those of the inner engines carrying behind them fuel tanks of 57 gall, each, each tank sufficing for the two engines on that side. The oil tanks are slung below the engine mountings in the case of the inner engines and behind in the case of the outer engines. The engine cowlings and the fairings over the rear portion of the mounting are all of sheet Elektron, which is chromated before being painted as an anticorrosion measure. It is interesting to note that, throughout the whole machine, where sheet light alloy is used, as the fairings over the wheels, the frames of the windows and doors, Elektron is used.
The engines have already been described in FLIGHT (January 25, 1934), and there is therefore no need to go into detail here. In this machine they drive Fairey metal airscrews and are fitted with Eclipse direct acting electric starters fed from a 20 ampere electric battery (Caple electric inertia starters can be fitted if required). This seems small, but we are told that 70 engine starts have been obtained from this battery without recharging. Fuel is fed from the tanks to each engine by dual Amal pumps, a type which is now being manufactured by D.H.'s themselves. The fuel cocks will be operated on subsequent machines from the pilot's cockpit, as will be the altitude controls to the carburetters, by Simmonds-Corsey controls. The revolution counters are of the Record electrical type operating neat vertical dials either side of the dashboard. The two Claudel-Hobson carburetters of each engine take fresh air through a Vokes flame trap during slow running, and the throttle control is operated by an endless cable over pulleys from normal levers close to the pilot's left hand. The Bendix wheel brakes, acting in Dunlop wheels with low-pressure tyres, are differentially connected to the rudder bar and controlled by a hand lever in the same way as other "D.H." aircraft.
In the pilot's cockpit the control column is of the spectacle type. The seat can readily be raised for landing. The dashboard, which is very neat though carrying instruments for four engines, swivels forward allowing ready access to the wiring behind it. The trail trim wheel comes readily to the pilot's left hand and the fin trim to his right. A Smith's electric fuel gauge is placed behind, and to the left hand of, the pilot.