Northrop Gamma / A-13 / A-16
Northrop - Gamma / A-13 / A-16 - 1932 - США
Страна: США
Год: 1932

Northrop Gamma
Northrop A-13, A-16, A-17 и A-33
Flight, February 1935
A 200 m.p.h. BOMBER

Northrop Gamma

В январе 1932 года Джон Нортроп и Дональд Дуглас основали на паях корпорацию "Northrop Corporation" как дочернее подразделение компании "Douglas Aircraft Со.". Первым самолетом новой компании стал Northrop Gamma - несколько машин были построены для совершения рекордных перелетов и исследований. Первые два самолета - Gamma 2A и Gamma 2B - были оснащены звездообразными двигателями Wright мощностью 785 л.с. и Pratt & Whitney Wasp мощностью 500 л.с., соответственно. Обе машины были поставлены в конце 1932 года: первый - компании "Texaco", передавшей его в аренду Фрэнку Хоксу для совершения рекордных полетов; второй - в аренду Линкольну Эллсворту, совершившему на нем трансантарктический перелет. Компания TWA в 1934 году приобрела три самолета Gamma 2D с двигателями Wright Cyclone мощностью 710 л. с. для использования в качестве одноместных почтовых самолетов. На втором был позднее установлен двигатель Wright мощностью 775 л. с. - самолет использовался компанией "Texaco" для измерения температуры масла и летал до тех пор, пока не был продан в авиакорпус Армии США, где получил обозначение UC-100.
   Несколько самолетов Gamma были поставлены частным покупателям, включая два самолета, проданных в Великобританию, самолет Gamma 2E передали в Экспериментальный центр авиации и авиационного вооружения британских ВВС, а последний построенный самолет Gamma 2L - компании "Bristol Aeroplane Со.", где он использовался в качестве летающей лаборатории для отработки двигателей Hercules. Правительство Китая заказало 24 самолета Gamma 2E для использования в качестве легких бомбардировщиков - они оснащались двигателями Wright мощностью 710 л. с. и могли брать на борт 726 кг бомб, а вооружение включало четыре 7,62-мм пулемета в крыле и один пулемет в задней кабине для обороны задней полусферы. Еще 25 самолетов Gamma 2E были собраны в Китае из комплектующих, поставленных компанией-разработчиком.

Northrop A-13, A-16, A-17 и A-33

На базе транспортного самолета Gamma в рамках инициативной работы был спроектирован легкий бомбардировщик-штурмовик Gamma 2C, который оснащался звездообразным двигателем Wright SR-1820F мощностью 735 л.с. В июне 1934 года самолет поступил в авиакорпус Армии США под обозначением YA-13. Впоследствии на нем был установлен двигатель Pratt & Whitney R-1830 Twin Wasp мощностью 950 л.с., после чего самолет получил обозначение XA-16 (Gamma 2F). После проведения испытаний самолетов YA-13 и XA-16 компания-разработчик получила контракт стоимостью 2 млн долларов на постройку 110 бомбардировщиков-штурмовиков под обозначением A-17.

Flight, February 1935

A 200 m.p.h. BOMBER
“Flight" Inspects the American Northrop 2E, Purchased by the Air Ministry and Now Undergoing Tests at Farnborough: Nearly 95 per cent, of its Own Weight Carried as Disposable Load: Range, with 1,100 lb. of Bombs, 1,500 Miles at 165 m.p.h.

   HITHERTO, comparatively little has been known in this country about a particularly interesting American military aircraft, the Northrop 2E, but some months ago the British Air Ministry purchased a specimen, in accordance with the policy of acquiring examples of some of the more outstanding foreign types of aircraft from time to time. By the courtesy of the Ministry representatives of Flight were recently permitted to visit the Royal Aircraft Establishment, where the machine has been undergoing very searching tests, and the following notes and illustrations indicate some of the more interesting features of the design. The tests at the R.A.E. have included performance and strength tests, and these will be supplemented shortly by further flying tests at Martlesham Heath
   Although not by any means a new type, and, in fact, an obsolescent aeroplane as military aircraft go, the prototype having been built more than two years ago, the Northrop 2E gives an indication of what can be done by very skilful design The first machine of the type was built for Mr. Frank Hawks as a long-range high-speed "super-touring" aeroplane with a non-stop range of something like 2,000 miles. Known as the Sky Chief, this machine was described and illustrated in Flight of January 19, 1933. From this prototype aircraft were first developed the "Gamma" and "Delta" commercial aeroplanes, which differed mainly in the layout of the cabin and pilot's cockpit, one having the pilot right in front, ahead of the cabin, while in the other the pilot sat far back, behind the cabin. Yet a third variant on the same theme was the Northrop 2E long-range light bombardment type, or, as we should term it, light bomber.
   Fully detailed figures are not yet available, but it would appear from the Farnborough tests that the performance figures claimed by the manufacturers are, in the main, borne out in practice. For instance, with the bombs re moved, the machine has a maximum speed of 226 m.p.h at an altitude of 7,000ft./the height at which the Wright supercharged "Cyclone" engine is rated. So far it has not been possible to check the makers' claim for a full-load range of 1,500 miles at an average cruising speed of 165 m.p.h., but there seems to be little reason to doubt that the claim is substantially correct.
   Driving a Hamilton Standard two-bladed controllable-pitch airscrew, the nine-cylinder Wright "Cyclone" engine is rated at 715 b.h.p. at 7,000ft. and 1,950 r.p.m. As the machine weighs, fully loaded, 7,500 lb., a maximum speed of 226 m.p.h. must be regarded as remarkably good, and bears out the impression of "clean" aerodynamic design which one forms on inspecting the machine.
   Structurally, also, the Northrop 2E must be admitted to be well above the average in efficiency, the ratio of gross weight to tare weight being 1.948. There are many ways of judging efficiency, and no simple ratio such as that quoted can be expected to tell the whole story. So many things have to be taken into account, such as stiffness, strength, durability, and ability to stand manhandling. But assuming a given aircraft to be satisfactory in service, the percentage of its own weight which it will carry as disposable load does give an indication of the skill with which the designer has solved his many conflicting problems. In the case of the Northrop 2E the machine carries just under 95 per cent, of its own weight. Until quite recently an average figure for a very wide range of types has been 65 per cent, of the tare weight, so that it must be conceded that the designers have shown skill.
   In spite of the fact that the machine is a cantilever monoplane, the wing weight is under 2.4 lb./sq. ft. This figure includes machine-gun mountings, leading-edge landing lights, navigation lights, and aileron mass balances. An inspection of the structural methods employed does not reveal any very great refinements. For example, the wing covering is of one gauge throughout, and no attempt has been made to save weight by having a heavier gauge near the wing roots and a lighter gauge at the tips.
   The wing structure itself is of what might be termed the multicellular type. That is to say, the box-section spar to which we have become accustomed in this country is not used. Instead, the designers employ a number of plain channel members, to the flanges of which the wing covering is riveted. In between these channel-section members or spars the Alclad wing covering is stiffened by stringers of "Omega" section. The wing ribs are generally similar to the “spars” in that they are light channels with flanged circular lightening holes. They are, of course, riveted to spars and covering.
   An interesting feature of the wing design is the manner of attaching the outer wing portions to the centre-section. Instead of making the joint on the ends of the spars, a method which would have been rather difficult with a multi-spar construction, it is made with the aid of L-section strips in the plane of the wing chord. These strips have their horizontal flanges riveted to spars, stringers and skin. The vertical flanges of the centre-section are secured to those of the outer wing portions by bolts fairly widely spaced. The whole joint is covered in by a smooth capping strip secured at the trailing edge by a very neat quick-release fastening, as shown in one of the sketches.
   On theoretical grounds this joint is open to criticism, because of the offsetting of the securing bolts. In practice, however, it seems to be satisfactory, probably because the vertical flange of the L-section strips is quite thick.
   With a wing loading of more than 20 lb./sq. ft. the landing speed would be intolerably high were it not for the fact that split trailing-edge flaps are used. These do not extend over the entire wing span but only over about two-thirds of the span of the outer wing portions, their inner ends being at the wing joint. It may, perhaps, be remembered that in Frank Hawks' machine the split flaps were larger and that ailerons of the “park bench” type were placed above the wing. In the 2E slotted ailerons of the normal Handley Page type are fitted. These, incidentally, are fabric covered, presumably because of mass-balancing, and are the only surfaces on the machine to be so covered. The mass balances are in the form of lead strips placed inside the leading edge.
   The trailing-edge flaps are single-surfaced, and look rather light for their work. A notice in the pilot's cockpit points out that they are not to be used at speeds above 100 m.p.h. They are stiffened internally by channels parallel with the span, and externally by fore-and-aft channels. The flaps are operated by toggles - short links rather like turnbuckles, and adjustable for length in a similar way - running from a sliding tube inside the wing to eyebolts on the front internal channel on the flap. The sliding tube is actuated hydraulically by a cylinder and pump in the cockpit.
   In the construction of the fuselage an ingenious system has been adopted. Fore-and-aft "planking" is used, and instead of stringers riveted to the skin, one edge of each "plank" is turned inwards and then curled over to form a stiffening member. The fuselage formers, which are of very simple section, are pierced near the skin to allow the turned-over edges of the planking to pass through as continuous stringers. The system is ingenious, but does not appear to be particularly cheap from a manufacturing point of view. The centre-section of the wing is built integrally into the bottom of the fuselage, the wing spars being riveted to the fuselage formers. Needless to say, fillets are used in the corners between upper wing surface and fuselage sides.
   The tail surfaces are of a form of construction similar to that used in the wing. The elevators are mass-balanced by lead weights carried on arms projecting forward from the hinge-line, and the weights are enclosed in the tail plane at all except large elevator angles.
   Tail-trimming would be complicated with the shape of fuselage used, owing to the difficulty of making a neat sliding joint between tailplane spar and the curved sides of the fuselage. Instead, trimming "tabs" on the trailing edge of the elevator are used.
   With the multi-spar wing construction adopted there is little space inside the wings for stowing any large objects, and, presumably, partly for that reason, a "trousered" undercarriage has been used instead of a retractile one. The wheel forks are cantilevered from specially strengthened centre-section spars, and it was noticed that the designers had avoided "handing" the wheels, both of which are of the same "hand," so that on the port undercarriage leg the brake is on the inside, while on the starboard it is on the outside. In this way only one type of wheel need be stocked as a spare.
   The 715 h.p. "Cyclone" engine is enclosed in a long-chord N.A.C.A. cowling. An oil cooler is placed under the engine mounting, just aft of the rear edge of the cowling, and air under forced draught is led to the cooler by two large-diameter tubes the forward ends of which are led out between the lower cylinders.
   Fuel is carried in tanks housed in the centre-section of the wings, the total capacity being 362 U.S. gallons. When the machine is cruising at 165 m.p.h. it is claimed that this suffices for a range of 1,500 miles. A bomb load of 1,100 lb. is still available at that range.
   Turning a civil into a military aeroplane must always necessitate a compromise. In the Northrop this has taken the form of carrying the bombs under the centre-section, where their extra drag reduces the performance to a degree which cancels the advantages of the originally clean aerodynamic design. In fact, with the bombs in place, the speed is no greater than that of comparable British types. To give the bomber any view at all a retractile bombing station is built into the floor of the gunner's cockpit. This has a window facing forward, and one suspects that after a very short time this window becomes covered with oil and fairly useless for accurate work.
   A machine gun is provided in the rear cockpit. It covers an arc of less than 180 degrees, i.e., it cannot be fired quite broadside. Two guns are provided for the pilot. They are placed one in each wing, a location which has the advantage that, as the guns are outside the propeller disc, no interrupter gear is required. On the other hand, a jamb cannot be cleared. To give the crew a reasonable view and yet keep them out of the slipstream, a "conservatory" roof has been built on to the cockpits. This roof is in sections, one or more of which can be opened by sliding them along.
   Of the qualities of the Northrop 2E as a military machine it is difficult to form a decided opinion. That it will have to depend on straightforward speed rather than on aerobatics appears to be indicated by a warning in the cockpit pointing out that the machine must not be dived at speeds in excess of its normal maximum.
"THE HUMAN BULLET": Frank Hawks, of "Texaco," and his all-metal Northrop "Gamma" Sky-Chief, on which he made his 200 m.p.h. flight across Canada.
First Northrop Gamma
Gamma 2D использовался для экспериментов на больших высотах, чтобы выяснить возможность авиалайнеров обходить грозовые фронты.
Northrop 2D Gamma NC13758 before its modification for use in Tomlinson’s high-altitude research programme. All three examples of the 2D Gamma were purchased by TWA for a high-speed mail service that never fully materialised in the wake of the 1934 Air Mail Emergency, when the US Army took over the transport of the nation’s air mail - temporarily, as it turned out.
This side view of the Gamma clearly shows the rectangular turbocharger installation on the port side of the engine cowling. Despite the type’s chronic shortcomings in terms of the view from the cockpit, the Gamma was classically brawny in the American tradition, and was reportedly much-loved by its pilots, who found it strong and steady.
Tomlinson shares a smoke with fellow TWA pilot Frank Busch, who later became the airline’s General Manager of Operations and Vice-President of Flight Operations. Smoking around aircraft was clearly not an issue at the time! Note the legend on the Gamma’s fuselage, which reads ‘‘Overweather Experimental Laboratory”.
The starboard side of the Gamma’s fuselage incorporated the heating duct from the engine to the observer’s compartment and cockpit. Note also the direction-finding radio loop on the forward fuselage and the spinner for the three-bladed propeller.
Pioneer high-altitude pilot Daniel W. "Tommy” Tomlinson beside the Northrop Gamma in which he conducted numerous invaluable research flights during 1936-37.
Tomlinson wearing one of several oxygen masks he tested while flying the Gamma.
The mail compartment ahead of the cockpit was extensively modified as an observer's station by adding small windows on each side of the fuselage
The Cyclone-engined Northrop Gamma of Bernarr MacFadden. This machine, with Conqueror engine, was entered for the MacRobertson Race but came to grief.
OFF TO THE ANTARCTIC : The Northrop machine. Polar Star, which will be used by the Lincoln Ellsworth Expedition for flights over the South Pole, being shipped at Dunedin en route for Deception Island.
After testing the Model 2C, the Air Corps suggested some changes, including a revised tail assembly. The aircraft was then purchased and designated YA-13.
В целях улучшения характеристик YA-13 на него установили двигатель Pratt & Whitney R-1830-7 мощностью 950 л. с. и трехлопастный воздушный винт. Новый вариант получил обозначение XA-16 - самолет сфотографирован во время летных испытаний в авиакорпусе Армии США в 1935 году.
Another unusual type in British markings was K5053, the Northrop 2E attack bomber. It was tested at Martlesham and Farnborough in 1934-35.
The YA-13 was re-engined with a Pratt & Whitney R-1830 Twin Wasp and redesignated XA-16.
YA-13 вначале проходил испытания с гражданской регистрацией X12291. Как видно, бомбы подвешиваются на держателях между обтекателями шасси.
The Gamma Model 2E was the export variant of the Model 2C. Several of them were purchased by China. Note the ventral gunner station.
The prototype tested by Wroath during his time at Martlesham: Northrop 2E K5053.
The Northrop 2E K5053 was delivered to Britain in November 1934 and flown by Clouston during ice formation experiments at Farnborough. Interestingly the next serial number, K5054, was allocated to the prototype Spitfire.
The Northrop being issued to certain attack units of the U.S. Army Air Corps is structurally similar to the bomber version, an example of which was purchased by the British Air Ministry. The Wright Cyclone engine is specified and the maximum speed is about 220 m.p.h.
The addition of the "conservatory" roof above and a bomber's position below somewhat mars the clean lines.
Running-up the engine: The Northrop 2E outside the hangars at Farnborough
The Fairey "Hendon" night bomber in its new guise - with a nose "conservatory" and three-bladed airscrews. In the background is the Northrop bomber from Farnborough.
Легкий бомбардировщик Нортроп "Гамма" 2EC
Легкие бомбардировщика Валти V-11 и Нортроп 2E китайских ВВС
The flying test-bed for the Bristol Hercules engine is a Northrop monoplane. Note the long-chord cowling with controllable cooling gills. The position of the air intake above the cowling is interesting.
Built at Santa Monica in California, Northrop Gamma 2L G-AFBT was the only example on the British register, and was imported by Bristol in September 1937 for use as an engine test bed. After use in early flight trials of the Hercules, as seen fitted here, the aircraft was dismantled at Filton and stored throughout the war, before being broken up in November 1945.
The tail unit: Note the trimming "tabs" on the elevators, and the mass balance which disappears into the tailplane.
The upper member of the cruciform stern piece is twisted in order to reduce yawning due to the rotating slipstream.
The Northrop's flaps. On the left the split trailing-edge flap is shown closed, and the slotted aileron in the "down" position. On the right the flap is open and the aileron "up." Operation is hydraulic.
Protection is afforded to the crew of the Northrop by sliding roof windows, one or more panels being closed or opened at will.
The bomber's sighting nacelle, shown retracted and lowered. On the right is a front view, showing the window.
Structural details of the Northrop 2E. The form which the multiple spars and stringers take is shown on the left, while the general "theme" of the fuselage construction is illustrated on the right.
An example of a multi-spar wing, the American Northrop. Although good structurally, this type makes installation of tanks and bombs difficult.
The wheels are carried on cantilever forks from the wing spars.
The outer wing portions are secured to the centre-section by flanged joints, as shown. On the right are details of the neat steps fitted on the sides of the fuselage; when not in use these steps disappear into the fuselage.
This sketch indicates the locations of the bombs and machine guns.