Douglas DC-1 и DC-2

В авиакомпании TWA, оказавшейся перед необходимостью заменить устаревшие самолеты Fokker, обнаружили, что в очереди на получение новейших авиалайнеров Boeing Model 247 их обогнала авиакомпания "United Air Lines". Тогда было решено подготовить спецификацию на новый трехдвигательный пассажирский самолет цельнометаллической конструкции вместимостью не менее 12 пассажиров. 2 августа 1932 года она была разослана предприятиям авиапромышленности. Дональд Дуглас дал ответ в течение двух недель, а 20 сентября уже был подписан контракт. Правда, Дуглас убедил технического советника руководителя TWA Чарльза Линдберга в том, что требуемые характеристики могут быть обеспечены только при двухдвигательной силовой установке. Прототип нового самолета, названного DC-1 (Douglas Commercial № 1) и оснащенного двумя звездообразными двигателями R-1820, был выкачен из цеха 22 июня 1933 года и поднялся в воздух 1 июля того же года.
   Несмотря на возникшие поначалу проблемы с двигателями, испытания были успешно завершены, и самолет в декабре 1933 года передали TWA в муниципальном аэропорту Лос-Анджелеса. Однако DC-1 так и не поступил в эксплуатацию, а использовался в рекламных целях (например, в ночь с 18 на 19 февраля 1934 года совершил рекордный перелет между побережьями США, затратив на это 13 ч 4 мин).TWA подписала предварительное соглашение на закупку 25 серийных машин, отличавшихся от DC-1 более мощными двигателями и удлиненным на 0,61 м фюзеляжем, что позволило увеличить вместимость салона до 14 мест.
   Новая машина получила обозначение DC-2 и вскоре поступила в эксплуатацию и ряда других авиакомпаний - "American Airlines", "Eastern Air Lines", "General Air Lines", "Panagra" и "Pan American". Самолет также эксплуатировался в Европе компаниями KLM, "Lineas Aereas Postales Espanolas" (LAPE) и "Swissair". Наиболее известным из этих самолетов стал "Uiver", принадлежавший компании KLM и под управлением К. Д. Парментье и Дж.Дж. Молла в 1934 году ставшим победителем авиагонок на приз Мак-Робертсона (Великобритания - Австралия). По большому счету, их рекорд - 90 час 13 мин 36 с - побил другой участник, самолет de Havilland DH.88 Comet, который следовал по маршруту с грузом.
   ВМС США заказали в 1934 году один транспортный R2D-1, а позже еще четыре в целом идентичные машины. В 1936 финансовом году первые машины приобрел и авиакорпус Армии США - сначала были закуплены два 16-местных самолета, которые оценивались под обозначением XC-32 и поступили на вооружение как YC-34 (позже C-34), и 18 грузовых C-33, которые имели увеличенный киль и грузовую дверь. В 1937 году один C-33 был оснащен хвостовым оперением от DC-3 и получил обозначение C-33A (позже C-38), а позже на его базе был создан и C-39, получивший ряд других конструктивных элементов от DC-3, включая центроплан и шасси, а также двигатели R-1820-55 мощностью 975 л. с. (727 кВт). Последний вариант был заказан Армией США в количестве 35 машин - в эксплуатацию транспортных групп они поступили в 1939 году. Четвертый и пятый C-39 были переоборудованы еще на заводе в варианты C-41 и C-42: первый стал самолетом командующего авиакорпусом Армии США. Он был оснащен двигателями R-1830-21 мощностью 1200 л. с. (895 кВт) и имел взлетную массу 11 340 кг. Второй самолет, имевший аналогичную силовую установку и взлетную массу 10 716 кг, использовался для перевозок начальника Главного командования авиакорпуса Армии США (GHQ Air Force). Позже еще два C-39 были переоборудованы по стандарту C-42.
   На военной службе DC-2 эксплуатировался весьма активно на начальном этапе Второй мировой войны. Часть DC-2 была приобретена британскими ВВС и эксплуатировалась 31-й эскадрильей, находившейся в Индии. В общей сложности было выпущено 193 самолета Douglas DC-2 различных вариантов.


Варианты

   DC-2A: два гражданских самолета с двигателями Pratt & Whitney Hornet
   DC-2B: два самолета, приобретенных польской авиакомпанией LOT и оснащенных двумя звездообразными ПД Bristol Pegasus VI мощностью по 750 л. с. (559 кВт)
   C-32A: военное обозначение 24 гражданских самолетов DC-2, поступивших в ВВС Армии США в 1942 году; три транспортные машины не имели грузовых дверей


ТАКТИКО-ТЕХНИЧЕСКИЕ ХАРАКТЕРИСТИКИ

   Douglas DC-2

   Тип: транспортный самолет с экипажем из двух человек
   Силовая установка: два звездообразных ПД Wright SGR-1820-F52 Cyclone мощностью по 875 л. с. (652 кВт)
   Летные характеристики: максимальная скорость на высоте 2440 м - 338 км/ч; крейсерская скорость на высоте 2440 м - 306 км/ч; начальная скороподъемность 305 м/мин; практический потолок 6845 м; дальность 1609 км
   Масса: пустого 5628 кг; максимальная взлетная 8419 кг
   Размеры: размах крыла 25,91 м; длина 18,89 м; высота 4,97 м; площадь крыла 87,23 м2
   Полезная нагрузка: до 14 пассажиров

Flight, March 1934

THE DOUGLAS D.C.1

   A FLEET of twenty Douglas D.C.1 fourteen-passenger monoplanes is under construction for Transcontinental & Western Air, for use on the New York - Los Angeles service. The D.C.1 is a twin-engined low-wing cantilever monoplane of metal construction, carrying from 14 to 18 passengers.
   The low cantilever wing of the D.C.1 is tapered both in plan and thickness. It is of cellular multi-web construction, with smooth riveted skin covering. The chord varies from 170 in. at the root, where the aerofoil section is N.A.C.A. 2215, to 68 in. at the tip, where the aerofoil section is N.A.C.A. 2209. Alclad 24 S.R.T. is the chief material employed. This is a new extra light aluminium alloy having a thin coating of pure aluminium to give it high resistance to corrosion. A centre section which runs beneath the fuselage carries the two engine nacelles, the retractable landing gear and the fuel tanks. The attachment of the outer planes to the centre section in the case of this stressed skin wing, consists of a bolted flange running completely round the aerofoil. The ailerons are of metal construction, covered with fabric, and have trailing edge "tabs" which relieve the pilot of any load on the control wheel caused by conditions affecting lateral stability. Split trailing edge flaps are built into the lower side of the wing and continue beneath the fuselage from aileron to aileron. When fully lowered, they increase the lift by 35 per cent, and the drag by 300 per cent. The reduction in landing speed is approximately 10 m.p.h. The ailerons remain positive in action and are effective beyond the stalling point of the wing; the flap gear is operated by a hydraulic system controlled from the cockpit.
   The fuselage is of semi-monocoque construction with smooth riveted skin. Alclad 24 S.R.T. is used throughout. The entire interior from nose to tail is accessible, a hinged cover gives entrance to the nose compartment for access to the back of the instrument board, hydraulic brake cylinders, etc., while the floor of the passenger cabin, which is covered with a waterproof material, is removable for inspection of the control cables below. Aft of the rear baggage compartment is a door leading to the interior of the tail.
   Air flow over the empennage, which is built integral with the fuselage, is smooth owing to the provision of large fillets terminating in a cone which carries the tail light and trailing radio antenna. Both the fin and tail plane are fixed, trim being obtained by means of "tabs" on the rudder and elevators. The landing gear is in two independent units which retract upward and forward into the engine nacelles. Each wheel is carried in a fork member in a pair of hydraulic shock absorber struts. A hydraulic pump accessible to either the pilot or his assistant, raises the gear in 25 sec. and lowers it in 20 sec. Differentially controlled hydraulic brakes are fitted, and the brake operation remains positive with the wheels in the retracted position. As the axles come up against pillow blocks built into the nacelle structure, the aircraft may be landed on its wheels, which protrude approximately 9 1/2 in. below the nacelles, with gear retracted; only the airscrew tips would suffer damage. As the wheels, when in the retracted position, are even further forward of the centre of gravity than when they are extended, there is no tendency for the machine to nose over during a landing. The tail wheel is provided with a hydraulic shock absorber and a swivelling lock which keeps it aligned during flight.
   The D.C.1 is equipped with two engines of approximately 700 h.p. Either the Wright "Cylone" (710 h.p. at 1,950 r.p.m. at 7,000 ft. geared 16-11) or the Pratt & Whitney "Hornet" (700 h.p. at 2,150 r.p.m. at 6,500 ft. geared 3-2) may be fitted. Both engines use fuel of 87 octane rating. Each engine mounting, which is constructed of chrome molybdenum steel tubing, is a separate quickly detachable unit. All connections are broken and joined at the fireproof bulkhead with quickly detachable plugs or fittings.
   Port and starboard engine mountings are interchangeable. The engines are cowled with a three-piece N.A.C.A. cowling ring and the rear cowling of the nacelle is carefully faired into the wing. The adjustment of the engine mountings to the fireproof bulkheads is made through rubber bushings which greatly reduce the transmission of vibration to the rest of the aircraft. The exhaust collector outlets are below the wing to shield the cabin from noise and glare. Hamilton standard three-bladed, two position, controllable pitch airscrews are fitted. There are two main fuel tanks of 180 gallons capacity each and two auxiliary tanks of 70 gallons capacity each, making a total of 500 gallons maximum fuel supply. The main tanks are fitted with simultaneously opening dump valves controlled from the pilot's cockpit. After opening these valves, the pilot may watch the fuel gauge and close the valves again at will, thus discharging any desired amount of fuel. A carburetter air intake "preheater" which has a capacity sufficient to prevent the freezing of the carburetter during the coldest weather is fitted with a control valve and thermometer located in the cockpit. A pressure fire extinguisher system with a selector valve in the cockpit serves each engine.
   The cabin is 26 ft. 4 in. long, 5 ft. 6 in. wide and 6 ft. 3 in. high, and the entire length of the floor is free from structural obstacles. Normally the cabin is fitted to accommodate fourteen passengers in two rows of chairs spaced 40 in. apart and separated by a 16-in. central aisle. The chairs are adjustable for reclining or for reversing to face the passenger behind. Eighteen passengers may be carried with a slight reduction in the spacing of chairs and cargo space. Each seat has a separate window. Individual furnishings for each passenger include reading lamp, ashtray, magazine pocket, lunch tray, call button and ventilation control. The reading lamp is located in such a position that its light is directed over the shoulder of the user without annoyance to any other passenger. A hat rack is installed along each side of the cabin above the windows, with a hand' rail for passing up and down the aisle. Dome lights are provided for general illumination. Passengers enter the cabin through a large door on the port side of the fuselage and an emergency exit is provided on the starboard side. The mail loading door in the forward companionway may also be used. Under the direction of the Sperry Gyroscope Co. the cabin noise has been reduced to below 70 decibels above 1 millibar at cruising speed.
   A ventilating and steam heating system is provided. Air is admitted through a vent in the nose of the fuselage and is transmitted through ducts to the pilots' and passengers' compartments and to the lavatory. The system permits the entire air content of the cabin to be changed each minute, and a thermostat maintains the temperature at 70 deg. F. even when the outside air temperature is as low as 20 deg. below zero. The air is heated by passing it through the radiator under the floor served by steam pipes from a boiler installed in the port engine exhaust collector. This method of ventilation and heat control eliminates all possibility of noxious engine gases entering the ventilation system. Aft of the main door is a complete service buffet with drinking cups, built-in dry ice refrigerator and all facilities for serving meals while in flight. A lavatory is on the starboard side of the fuselage. A cargo compartment with a mail capacity of 1,000 lb. (76 cu. ft.) is just forward of the cabin on the starboard side of the fuselage. The door of this compartment opens into a companionway running along the port side of the fuselage between the pilot's cockpit and the cabin. The cargo is loaded through a special outside door provided in the left wall of the companionway directly opposite the cargo compartment doors. Aft of the cabin is the passengers' baggage compartment, with a capacity of 112 cu. ft., where additional mail may be stowed if desired. An exterior door on the side of the fuselage provides access to this compartment from the ground, and it may be reached in flight by stepping through a doorway from the lavatory.
   The pilots' roomy compartment has adjustable chairs and a wind shield designed for the elimination of reflection and glare. The movable non-splinterable glass panels which form the wind shield may be cleaned externally while in flight. The landing wheels may readily be seen from the cockpit when they are in the extended position. A complete set of controls is provided for each pilot and the control columns are offset to swing close to the side walls where they present no obstacle to the entering of the seats. A Sperry Gyroscopic Automatic Pilot (air-hydraulic type) can be installed by making a suitable rearrangement.
   A complete set of instruments is installed in group arrangement to facilitate rapid scanning, the instrument panel itself is mounted on flexible rubber bushings to minimise vibration. Indirect lighting with rheostat controls is provided. The D.C.1 may be fitted with two-way radio telephone equipment and directional beam receiver. A trailing antennae is extended through the fuselage tail cone.
   It was one of these airliners that carried out a remarkable flight across the American Continent on February 19 - the last day before the private commercial air mail lines handed over the transport of air mails to the U.S. Army pilots, under President; .Roosevelt's order cancelling all air mail contracts. Evidently with a view to showing what private commercial airlines could do, Transcontinental & Western Air, Inc., despatched the first of their new D.C.1's from Los Angeles, piloted by the well-known American pilot, Capt. Eddie Rickenbacker, and carrying 12 passengers, crew and a large quantity of mail - in fact, we understand that the machine carried an excess of full gross load. Making stops at Albuqerque, Kansas City and Columbus, Ohio, the machine covered the 2,653 miles to Newark, New Jersey, in 13 hours 4 minutes 20 seconds - or at an average speed of 205 m.p.h. For a greater part of the journey the Sperry Automatic Pilot relieved the pilot of the bulk of the piloting. After leaving Columbus they ran into a severe storm, and with the aid of the supercharged engines ascended to 20,000 ft. At this altitude the temperature outside the machine was some 75 deg. below zero, but this did not inconvenience the passengers (who, incidentally, were supplied with oxygen), thanks to the efficient heating arrangements of the cabin. When descending to lower altitudes a speed of 280 m.p.h. was maintained for an hour and a-half.

Flight, October 1934

THE SUCCESSFUL MACHINES
Points of Interest in the Specifications of the De Havilland "Comet,” Douglas D.C.2 and Boeing Transport

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The Douglas D.C.2.
  
   Designed and built by the Douglas Aircraft Company, Inc., of Santa Monica, California, the D.C.2 piloted by Parmentier and Moll was probably the aeroplane which caused the greatest admiration at Mildenhall during the days before the start of the race. Not only was the clean aerodynamic design appreciated, but the workmanship and finish of the all-metal construction came in for very favourable comment by all the technical experts who saw the machine. What has undoubtedly helped to make this very fine piece of aircraft engineering possible is the fact that initially an order was placed for sixty machines. This gave the Douglas works a chance to get down to manufacture on a quantity production basis. In Great Britain, unfortunately, aircraft constructors do not receive orders for large commercial aeroplanes on any such generous basis, the largest order ever placed being for eight machines.
   In the construction of the Douglas D.C.2 use has been made of what is known as the "stressed skin" system. This expression is used to denote a form of structure in which the outer covering is not a mere fairing used to give the desired form, but actually also takes part of the stresses. In the Douglas the metal covering (light aluminium alloy) is applied in fairly small panels riveted to the internal framework. A very smooth skin has resulted, and the actual riveting has been very carefully done, so that it is impossible to find a rivet which has not been clenched properly, or which has been clenched too hard, thereby bruising the metal skin.
   With an empty weight of 12,200 lb., the Douglas D.C.2 carries a disposable load of 5,880 lb., bringing the total loaded weight up to 18,080 lb. The disposable load can, of course, be varied in accordance with the service to be operated. For the Australia race the machine was flown in its standard form as a fourteen-passenger transport, with a crew of four. During the race three passengers only were carried, but the standard cabin equipment was retained.
   With normal tankage the D.C.2 has a range of about 600 miles when carrying fourteen passengers, but when only eight passengers are carried the tankage suffices for about 1,200 miles at a cruising speed of 170 m.p.h.
   Two American Wright "Cyclone" engines of 700 h.p. each are mounted in nacelles projecting forward from the leading edge of the wing. They drive three-bladed Hamilton controllable pitch propellers with duralumin blades. The advantage of this type of propeller is that its pitch can be set to a fine angle for maximum revs, and power when taking off and to a coarse angle, corresponding to "top gear" for speed, once the machine is in the air.
   Retractable undercarriages are provided, and, when raised, the wheels are housed inside the engine nacelles.
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Flight, November 1934

EFFICIENCY
Some Facts and Features of a Machine which has Been Shown to be Outstanding in its Class. Speed and Comfort Combined in America's Latest - the Douglas D.C.2.

   TO what can one attribute the exceptional performance of the Douglas D.C.2? This was a general question the other week at Mildenhall, where K.L.M.'s new machine proved such a magnet to everyone present, including some of our most capable aircraft designers.
   One might summarise and give two reasons. First, aerodynamic efficiency resulting from a clean structure and absence of interference between adjacent and adjoining members, and, secondly, the incorporation of ideas in accordance with modern American practice in commercial aircraft, as, for example, geared and supercharged engines - operating in low-drag cowlings, using fuel of high octane value and driving variable pitch airscrews - retractile undercarriages and trailing edge flaps.
   On examining the aircraft in detail, features are noticed which simplify both production and maintenance. The multicellular wing and the semi-monocoque fuselage are notable examples. Little, if any, comfort has been sacrificed to performance, and from the passengers' viewpoint the machine is one of the quietest in operation, and displays few uncomfortable characteristics such as are sometimes noticed in high-speed machines flying in rough weather.
   When the prototype, the D.C.1, was built to T.W.A. specifications, few experts believed that the requirements would be met. Actually, they were exceeded by about 30 per cent.
   Stressed skin multi-cellular construction is used for the cantilever wing, which tapers in both plan form and thickness. Great torsional rigidity is claimed. In this type of construction, which was developed by the Northrop Corporation, a subsidiary of the Douglas Aircraft Co., Inc., there is a large number of members taking the loads with no heavy concentrations. The skin varies in thickness from .02 in. to .029 in. and is reinforced by numerous longitudinals, riveted at intervals of about 4m., which resist bending, and by ribs. Actually, the skin covering is No. 24 SKT "Alclad," which may be regarded as a sandwich of duralumin between two sheets of aluminium. Three webs, with heavy flanges riveted to the skin, carry the vertical shear loads. Torsion is taken by the skin, and frequent ribs preserve the contour and divide the structure up into a number of small cells. The upper surface of the centre part of the wing is composed of heavy corrugated sheet under the flat covering, and the nacelles are riveted to this sheet, making an integral unit. Along the centre section of the wing between the two ailerons is a hydraulically operated split trailing edge flap which may be lowered in about one minute at an air speed of 80 m.p.h. All tail surfaces other than the rudder are of multi-cellular construction.
   In the D.C.2 used by T.W.A. and K.L.M. Wright "Cyclone" F.3 geared and supercharged nine-cylinder radials, rated at 710 h.p. at 7,000 ft., are fitted. Alternatively, Pratt and Whitney "Hornets" of similar power may be used. The engine mountings are of welded steel tubes, the entire nacelle forward of the fire wall being quickly detachable. Both nacelles are interchangeable, and an engine may be changed in fifteen minutes. N.A.C.A. cowlings, made in three sections, and easily removed by one man, are fitted. Two main tanks, holding 150 gallons each, and two auxiliary tanks of 62 gallons capacity each, are located in the wing. The two main tanks are fitted with simultaneously opening dump valves.
   When retracted the wheels of the undercarriage move forward and upward. A small portion of wheel is left protruding to allow an emergency landing.
   Of semi-monocoque construction, the fuselage, like the wing, is covered with riveted skin. The entire interior is accessible from nose to tail. A hinged cover gives entrance to the nose compartment for inspection of the back of the instrument board and of the hydraulic brake cylinders. The floor of the passenger cabin is covered with a waterproof material and is removable for inspection and service of the control cables below. Movable shatterproof glass panels, which may be cleaned externally while in flight, are fitted to the pilots' cabin, which is rainproof and as near draughtproof as possible, and is designed to eliminate reflection and glare. Complete dual flying controls are installed. The controls for the trimming "tabs" are accessible to both pilots, each of whom has a brake operating lever at his disposal. If desired, the navigation instruments may be so placed that the hands will be horizontal at the cruising speed determined by the buyer. Electrical instruments are grouped on a separate panel in a shielding box.
   Fourteen chairs are placed in two rows along each side of the cabin. Individual furnishings for each seat include reading lamp, ash tray, literature pocket, lunch tray, call button, ventilation control, and air sickness container. Dome lights provide general illumination. Hat racks are installed above the windows. The seats are 19in. wide, are adjustable to a reclining position, and are reversible, so that the passenger may sit facing aft if desired. The aisle between the seats is 16in. wide. Aft of the cabin is a buffet with ice box, refuse receptacle, and space for two half-gallon thermos flasks and for fourteen lunch boxes. The lavatory is also located behind the cabin.
   It is possible to maintain a temperature of at least 70 degrees F. in the cabin, the air temperature being controlled by a thermostat. Vents are provided for adequate ventilation. At cruising speed the passenger cabin has a sound level below 72 decibels, this result being attained by the complete sealing of the compartment, treatment of walls and floors with a combination of sound-absorbing materials acting for different noise frequencies, and the installation of a sound filter in the ventilation intake.
   Two cargo and baggage compartments are provided, one being located in the plane of the engines and airscrews, holding 1,000 lb. of baggage, and the other behind the cabin. Aft of this latter is a door leading to the tail.