В.Кондратьев Самолеты первой мировой войны
"ФОККЕР" D.VII / FOKKER D.VII
Победителя истребительного конкурса в Адлерсхофе - "Фоккер" D.VII принято считать лучшим германским истребителем Первой мировой войны и для этого есть веские основания. Самолет продемонстрировал высокую максимальную скорость, хорошую устойчивость и управляемость в сочетании с отличной высотностью и скороподъемностью.
Конструктивно машина, разработанная Антони Фоккером и Рейнольдом Платцем, представляла собой развитие типа D.VI со значительно увеличенной энерговооруженностью, которую обеспечил рядный шестицилиндровый двигатель водяного охлаждения "Мерседес" D-III мощностью 160 л.с. Начиная с июня 1918 г. самолет оснащался более мощным 185-сильным мотором BMW-IIIa (модификация D VIIF) или 180-сильным "Мерседесом" D-IIIau, с которыми его характеристики стали еще лучше.
Длина фюзеляжа и размах крыльев были увеличены в сравнении с D.VI, но их конструкция осталась прежней. Изменилось только оперение, в котором появился киль. Вооружение также оставалось стандартным - два синхропулемета LMG 08/15.
В феврале 1918 г. на заводах фирмы "Фоккер" и "Альбатрос" (OAW) развернулось массовое производство D.VII. Первые из них поступили на фронт в начале апреля. Всего до конца войны было построено по разным данным от 1700 до 2694 экземпляров (некоторые источники приводят даже цифру 3200, но это, скорее всего, число заказанных, а не фактически построенных машин).
В любом случае D.VII стал не только лучшим, но и самым многочисленным немецким истребителем того периода. К началу ноября в составе 48 истребительных эскадрилий западного фронта насчитывалось 775 D.VII, что составляло почти 3/4 самолетного парка германской истребительной авиации.
Летом и осенью 1918 г. немецкие пилоты на D.VII достигли выдающихся успехов в воздушных боях, сбив несколько сотен вражеских аэропланов. Зная об этом, представители стран Антанты на переговорах о заключении перемирия потребовали от Германии немедленно уничтожить или выдать победителям все самолеты данного типа.
Требование было выполнено. Немцам пришлось уничтожить более 900 истребителей, но Фоккер, вернувшись после войны в Голландию, успел вывезти туда 20 готовых D.VII и более 200 комплектов деталей и узлов, из которых в 1920 году возобновилась сборка самолетов для голландских ВВС и на экспорт.
В 1923 году 50 таких машин приобрел СССР. У нас они состояли на вооружении до конца 20-х гг. 19 "фоккеров" в 1919 году закупила Польша, применившая их в войне с Советской Россией. 142 трофейных D.VII американцы в том же году вывезли в США, еще 75 машин получила Бельгия в счет репараций. Отдельные экземпляры попали в Швейцарию, Данию, Финляндию, Испанию, Литву и Чехословакию.
ДВИГАТЕЛЬ: "Мерседес"D.III (160 л.с.) или аналогичный BMW - IIIa мощностью 185 л.с. (около 600 машин).
ВООРУЖЕНИЕ: 1 синхр. LMG 08/15 "Шпандау".
ЛЕТНО-ТЕХНИЧЕСКИЕ ХАРАКТЕРИСТИКИ ( с двигателем BMW-IIIa )
Размах, м 8,90
Длина, м 6,95
Площадь крыла, кв.м 20,50
Сухой вес, кг 670
Взлетный вес, кг 890
Скорость максимальная, км/ч 195
Время подъема на высоту
2000 м, мин.сек 4,0
Потолок, м 6400
В.Шавров История конструкций самолетов в СССР до 1938 г.
"Фоккер" D-VII с двигателем БМВ-IIIа в 180л. с. - одноместный истребитель, безрасчалочный биплан, крылья с полотняной обтяжкой. Иногда ставился двигатель "Мерседес" в 185 л. с. Этот самолет выпуска 1918 г. был у нас в нескольких десятках экземпляров.
Двигатель , марка||БМВ-IIIa
мощность, л. с.||185
Длина самолета, м||7
Размах крыла, м||8,9/7,0
Площадь крыла, м2||20,3
Масса пустого, кг||688
Масса топлива+ масла, кг||90+18
Масса полной нагрузки, кг||217
Полетная масса, кг||905
Удельная нагрузка на крыло, кг/м2||45
Удельная нагрузка на мощность, кг/лс||4,8
Скорость максимальная у земли, км/ч||190
Время набора высоты||
Потолок практический, м||7500
Продолжительность полета, ч.||2
А.Александров, Г.Петров Крылатые пленники России
Слава других германских истребителей сильно меркнет в соседстве с истребителями Фоккера. Одним из них и, по некоторым оценкам, лучшим во время первой мировой войны был "Фоккер Д. VII". После опытов, раздумий и бесед с друзьями-пилотами Энтони Фоккер пришел к выводу о необходимости применения свободно-несущего крыла с фанерной или полотняной обшивкой, которое могло избавить аппарат от многочисленных "цепляющихся" за воздух растяжек и облегчить конструкцию самолета в целом. 20 сентября 1917 г. (н. ст.), зная о запланированном на начало 1918г. конкурсе истребителей, Фоккер отдал распоряжение своей опытной мастерской готовить прототип новой машины - биплана под двигатель "Мерседес" 160 л. с. Работа увенчалась успехом и принесла заказ на экспериментальную партию в 50 аэропланов, приступив к выполнению которого Фоккер и его инженер Рейнольд Плац (Reinhold Platz) сделали все возможное, чтобы подготовить крупносерийное производство модели, чей фюзеляж включал в себя легкий и прочный сварной каркас из стальных труб, а коробка крыльев имела всего лишь 2 И-образные крайние стойки и несколько центральных. Удивительно, но при проведении сравнительных испытаний аппарат с крайними крыльевыми связями показал даже лучшие результаты, чем другой прототип без них. К сборке "Д-седьмых" подключились компании "Альбатрос" и "Остдойч Альбатрос" (Ostdeutsche Albatros Werke = OAW) и благодаря их совместным усилиям число фронтовых "Фоккеров" нового образца увеличилось с 19, на 30 апреля 1918 г., до 828 на 31 августа того же года (по новому стилю). Примерно треть из построенных экипировалась высотными двигателями БМВ IIIа 185 л. с, обеспечивавшими лучшие характеристики, тогда как вооружение состояло из стандартного набора из двух синхронизированных "Шпан-дау". "Фоккеры" служили в Германии, Турции, Болгарии и Австро-Венгрии, а после войны разлетелись по всему миру, достигнув в 1922 г. Советской России, чье правительство закупило 50 "семерок". Отправленные из Амстердама, самолеты с номерами 10, 20, 25, 30-33, 38, 40, 45,49-52, 54, 56-75, 82-88, 92-100 достигли Петрограда, где 17 аэропланов достались 1-й отдельной истребительной авиаэскадрилье и еще один - начальнику Петроградского военного округа, другие проследовали в Москву и Киев. В Петрограде "Фоккеры" собирались под руководством германского механика Ганса Шмидта (Hans Schmidt)" и, по всей вероятности, были впервые продемонстрированы общественности 2 августа 1922 г., на Комендантском аэродроме (79). До некоторых пор пулеметы на них не монтировались, да и водворение их на место заняло бы немного времени, так как вся соответствующая арматура оставалась на месте (80, а из коллекции ЦГАКФФД). Бортовые номера выполнялись в любопытном стиле (80, б из коллекции ЦГАКФФД), а на рулях поворота красовались занятные эмблемы типа виноградной грозди. Аэропланы ФД-VII, как они звались в отечественных документах, оставались в строю до начала 30-х годов.
O.Thetford, P.Gray German Aircraft of the First World War (Putnam)
Fokker V 11
This was the aircraft that was finally judged the best at the first D types Competition, and eventually, with a little modification, went into production as the D VII. The absence of vertical fin, the narrowness of the undercarriage vees and the shorter fuselage, as compared with the eventual production version, may be noted. The V 11 was powered with the 160 h.p. Mercedes D III engine. At the competition on 25th January 1918, flown by test pilot Grosse at a loaded weight of 874 kg. (1,923 lb.), it climbed to 5,000 m. (16,400 ft.) in 30.7 min. On the following day at 844 kg. (1,857 lb.) weight it took only 25.2 min. to make the climb.
Fokker V 18
Another step in the evolution of the D VII was the V 18, and the increased similarity, compared with the prior V 11, may be noted. A vertical fin was now added to improve directional stability. Power unit was again the 160 h.p. Mercedes D III. After a brief career, this prototype was destroyed in a collision with V 13 during the Fighter Trials at Adlershof. Loaded weight, 861.6 kg. (1,896 lb.). Climb, 1,000 m. (3,280 ft.) in 3 min., 5,000 m. (16,400 ft.) in 28 min. Ceiling, 6,400 m. (20,990 ft.).
Fokker V 21
V 21 was another D VII variant with tapered wings which participated in the second D types Competition in June 1918. It was fitted with a high-compression 160 h.p. Mercedes D III engine. Loaded weight was 853 kg (1,877 lb.), when it climbed to 1,000 m. (3,280 ft.) in 3 min. and to 6,000 m. (19,680 ft.) in 45 min. No photograph available.
Fokker V 22
Combining the best points of the V 11, V 18 and V 21, this machine became production D VII. It is seen here fitted with Jaray type airscrew. Engine, 160 h.p. Mercedes D III. Span, 8.9 m. (28 ft. 2 1/2 in.). Length, 7.0 m. ft. (22 ft. 11 5/8 in.). Height, 2.75 m. (9 ft. 0 1/4 in.). Weights: Empty, 700 kg. (1,540 lb.). Loaded, 850 kg. (1,870 lb.). Speed, 186.5 km.hr. (116.6 m.p.h.). Climb, 1,000 m. (3,280 ft.) in 3.8 min. Duration, 1 1/2 hr. Armament, twin fixed Spandau machine-guns.
Fokker D VII
Following the Triplane into production at the Fokker factory came the D VII, undoubtedly the most famous of all the German fighting scouts of the First World War. The D VII was another product of the fertile brain of designer Reinhold Platz, a figure whose work has become increasingly well known of recent years, mainly due to the researches of the late A. R. Weyl, F.R.Ae.S. Previously Anthony Fokker had managed to claim for himself the design of these machines, largely due to the reticence of Platz, a man without any desire for personal publicity. No doubt Fokker played a part in the evolution of the aircraft, though some of his ideas were wildly fanciful, but it was Platz who managed to bring the practical engineering qualities to bear and produce a worthwhile aeroplane. That Fokker was a brilliant pilot is beyond question, and once he had flown a prototype his flair for knowing instinctively what modifications would improve the machine was a great advantage. It was largely through his flying ability that he was on such good terms with many of the pilots of the German Air Force, particularly Bruno Loerzer.
Forerunner of the D VII was the V 11 prototype. First flights were encouraging, though Fokker discovered that the aircraft needed to be lengthened and required a vertical fin to damp down over-sensitivity, a characteristic which would probably have meant disaster in the hands of a less skilled pilot. After modifications the aircraft was entered in the first of the competitions for D class machines (i.e. single-seat fighting scouts) held at Adlershof airfield in January 1918. The decision of the Front Line pilots, invited to test the machines, was unanimously for the Fokker D VII, and large contracts were awarded to the firm. The irony of the contracts was that Fokker's great rival - Albatros - was ordered to manufacture the D VII under licence at both its Johannisthal factory (Fok. D VII Alb.) and at the Schneidemuhl works (Fok. D VII Oaw.). Each drawing office prepared their own drawings, and no attempt at complete standardisation was made. As a result, although all aircraft looked alike, there were detail differences, and not all components were interchangeable.
As a precaution against failure of steel supply, Albatros built an experimental D VII (541/18) with a wooden fuselage, but circumstances did not require it to go into production. Curiously enough, this aircraft weighed some 40 lb. more than a standard D VII.
The standard D VII was of basically similar construction to the Triplane, using the same formula of wooden cantilever wings and welded steel-tube fuselage. However, the wings differed in having two separate box-spars instead of a single compound spar; they also tapered in depth towards the tips. The same type plywood-covered leading edge and wire trailing edge was retained. A feature shared by the D VII and its Triplane predecessor was the "one-piece" lower wing, which was accommodated by a special cut-out in the lower longerons enabling the spars to go right through the fuselage. The wing was bolted in and a metal panel fitted below to fair off the bottom fuselage contour. Ribs were of three-ply, with narrow flanges tacked all round both sides of the perimeter, forming a sandwich. The top surfaces of the wings were perfectly flat and possessed no anhedral, as has often been shown in the past. The horn-balanced ailerons were of welded steel tube and tapered inversely from root to tip.
The fuselage was a braced box-girder welded from steel tube in the traditional Fokker manner, although forward of the cockpit, the structure became necessarily complex in order to provide adequate strength to support the engine. Metal panels covered the sides back to the leading edge of the lower wing and back to the cockpit on the top decking. Decking aft of the cockpit was in the form of a plywood panel over which the fabric was stretched. The characteristic triangular tailplane and fin, with their large, balanced and rounded, flight controls were also completely fabricated from light-gauge steel tube. All centre-section and interplane struts were of streamlined section steel tube, likewise the undercarriage vees and, as in the Triplane, an aerofoil lifting surface enclosed the axle, spreader bars and elastic-cord shock absorbers. Apart from the metal panels forward, the whole airframe was fabric covered.
Initially, the D VII was fitted with the 160 h.p. Mercedes D III engine, and the car-type radiator represented a new departure for a German production single-seater. Later in 1918 the new 185 h.p. B.M.W. engine went into D VIIs and gave improved performance.
The success of the Fokker D VII was attributable to the fact that it was a fairly easy, yet responsive, machine to fly, with an apparent ability to make a good pilot out of mediocre material; also it retained extreme controllability at its ceiling. With these points went an ability to "hang on its prop" to shoot at an opponent when other machines would have stalled into a spin. One of the first units to be equipped with D VIIs was Geschwader No. 1 (Jastas 4, 6, 10 and 11) in late April 1918, almost immediately after it had lost its legendary commander Baron Manfred von Richthofen, who was killed in a Triplane on 21st April 1918. Throughout the summer of 1918 D VIIs operated in increasing numbers: by early July there were 407 in service and by November a total of 775. The Geschwader No. 2 (Jastas 12, 13, 15 and 19) and Geschwader No. 3 (Jastas 2, 26, 27 and 36) were fully equipped as well as Jastas 5, 7, 8, 14, 16, 20, 22, 23, 24, 28, 29, 30, 32, 35, 37, 40, 44, 45, 46, 47, 48, 49, 51, 52, 53, 54, 56, 57, 58, 59, 66, 69, 71 and 79. These agile machines operated with tremendous success and wrought much havoc; the sight of "straight wings" approaching in a stepped-up gaggle struck anxiety into many a stout-hearted Allied pilot. Such was the regard of the Allied Powers for the capabilities of the Fokker D VII that it was specifically singled out for mention in the Armistice Agreement article which designated items that were to be handed over to the Allies "In erster Linie alle apparate D VII" (especially all first-line D VII aircraft). Some complete, but dismantled, aircraft were "organised" over the border and into Holland by Anthony Fokker, and they continued to be manufactured there and used by the Dutch Air Force until the late 1920s in the Netherlands East Indies.
Description: Single-seat fighting scout.
Fokker Flugzeug-Werke G.m.b.H. (Fok.).
Albatros Werke G.m.b.H. (Alb.).
Ostdeutsche Albatros Werke, Schneidemuhl (O.A.W.).
One 160 h.p. Mercedes D III 6 cylinder in-line water-cooled engine.
One 185 h.p. B.M.W. III 6 cylinder in-line water-cooled engine.
Dimensions (Mercedes version): Span, 8.9 m. (29 ft. 3 1/2 in.). Length, 7.0 m. (22 ft. 11 5/8 in.). Height, 2.75 m. (9 ft. 2 1/4 in.). Wing area, 20.5 sq.m. (221.4 sq.ft.).
Weights: Empty, 700 kg. (1,540 lb.). Loaded, 850 kg. (1,870 lb.). Captured aircraft: Empty, (1,622.5 lb.). Loaded, (1,936 lb.).
Performance: Maximum speed, 186.5 km.hr. (116.6 m.p.h.) at 1,000 m.(3,280 ft.). Captured aircraft: 182.5 km.hr. (1141 m.p.h.) at 2,000 m. (6,560 ft.). Climb, 1,000 m. (3,280 ft.) in 3.8 min. (Mercedes), 2.5 min. (B.M.W.); 5,000 m. (16,400 ft.) in 31.5 min. (Mercedes), 16.0 min. (B.M.W.). Captured aircraft: 1,000 m. (3,280 ft.) in 4.25 min. Ceiling, 22,900 ft. Duration, ca. 1 1/2 hr.
Armament: Twin fixed Spandau machine-guns synchronised to fire forward through airscrew.
Fokker V 24
With factory No. F 2612, the V 24 was virtually a standard D VII experimentally fitted with 200 h.p. Benz engine and served as the prototype for the later 185 h.p. B.M.W.-powered production D VII. Span, 8.9 m. (28 ft. 2 1/2 in.). Length, 7.0 m. (22 ft. 11 5/8 in.). Height, 2.75 m. (9 ft. 0 1/4 in.). Loaded weight, 1,006 kg. (2,213 lb.). Climb, 1,000 m. (3,280 ft.) in 3.1 min., 5,000 m. (16,400 ft.) in 23.5 min. Armament, twin fixed Spandau machine-guns.
W.Green, G.Swanborough The Complete Book of Fighters
FOKKER D VII Germany
Ordered on 20 September 1917 as a parallel development to the rotary-engined V 9 (from which was to be derived the D VI), the V 11, powered by a 160 hp Mercedes D III six-cylinder water-cooled engine, was the progenitor of the D VII, the most famous of all German World War I fighters. Of mixed construction like preceding Fokker fighters, the V11 flew in December 1917, but revealed some directional instability and other shortcomings. These were rectified by lengthening the fuselage, reducing the wing gap and stagger, etc, and the V 11 competed at Adlershof, together with the essentially similar V18, in the January 1918 D-type contest. Pronounced winning contenders by the Idflieg, these prototypes provided the basis for a fighter to which the designation D VII was assigned, contracts being placed with Fokker at Schwerin and the Albatros factories at Johannisthal and Schneidemuhl (OAW). Other prototypes comprised V 21, the 200 hp Austro-Daimler-engined V 22 - which was to be evaluated at Aspem in July 1918 - and the 185 hp BMW IIIa-engined V 24. This last served as the prototype of the similarly-powered D VIIF. Armed with two 7,92-mm LMG 08/15 guns, the D III-powered D VII began to reach the Front in April 1918, followed closely by the BMW IIIa-powered D VIIF, and licence production of the D VII with the Austro-Daimler engine was undertaken by MAG (Magyar Altalanos Gepgyar) in Hungary. In the event, MAG completed only 12 D VIIs, and these postwar. Fokker produced 877 series D VIIs (of which six were supplied to MAG as pattern aircraft together with the V 22), and 923 and 826 were built respectively by the Johannisthal and Schneidemuhl facilities of Albatros. Ninety-eight D VIIs were smuggled from Germany to the Netherlands after the Armistice, of which 22 went to the LVA (Luchtvaartafdeling), 20 to the MLD (Marine Luchtvaartdienst), six to the KNIL (Koninklijk Nederlands Indisch Leger) and the remaining 50 were sold to the Soviet Union. Eight D VIIs and two D VIIFs were acquired from the Allied Control Commission by the Swiss Fliegertruppe - one of these later being fitted with an Hispano-Suiza 8Fb engine as the D VIIS - which obtained a further six overhauled D VIIs in 1925 from the Swiss Alfred Comte concern, which went on to build eight D VIIs during 1928-29. A total of 142 D VIIs was shipped to the USA in 1919 for evaluation and use by the US Army’s Air Service, at least a dozen of these being used at McCook Field for experimental work with various engines, including the 230 and 290 hp Liberty, 200 hp Hall-Scott L-6 and 375 hp Packard 1A-1237. Several more D VIIs were purchased in 1920 for the Air Service from Fokker, and other countries to adopt the D VII post-World War I included Belgium, which received 75 from March 1919. Of these, 35 were delivered to the Army’s Aviation Militaire, remaining in service until 1931. The following data relate to the standard D III-powered D VII.
Max speed, 115 mph (185 km/h) at sea level, 116 mph (187 km/h) at 3,280 ft (1000 m).
Time to 3,280 ft (1000m), 5.8min.
Empty weight, 1,508 lb (684 kg).
Loaded weight, 2,006 lb (910 kg).
Span, 29 ft 2 1/3 in (8,90 m).
Length, 22 ft 9 3/4 in (6,95 m).
Height, 9 ft 0 in (2,75 m).
Wing area, 217.44 sq ft (20,20 m2).
G.Swanborough, P.Bowers United States Navy Aircraft Since 1911 (Putnam)
After the Armistice, the Army brought 142 Fokker D.VIIs into the United States. These were the finest German fighters in service at war's end, and were used in numbers throughout the Air Service as trainers for several years. Twelve were to have been transferred to the Navy for use by the Marine Corps, but only six (A5843-A5848) were used. These remained in the training role at Quantico, Virginia, until 1924. The first influence of the D.VII on subsequent US Naval aircraft design was to be noted in the Boeing FB-1 of 1925. Power plant was a 180hp Mercedes or 185 hp BMW. Span, 29 ft 3 in; length, 23 ft; gross weight, 1,993 lb; max speed, 124 mph.
L.Andersson Soviet Aircraft and Aviation 1917-1941 (Putnam)
Fokker D VII
Designed in 1917 by Reinhold Platz, the Fokker D VII was certainly one of the most successful aircraft of all time. This legendary single-seat fighter soon revealed outstanding agility and excellent controllability and became the mainstay of the German Luftstreitkrafte. The Fokker V 11 prototype was first flown in January 1918 and a batch of 400 was immediately ordered after a competition for single-seat fighters at Adlershof the same month. The D VII featured wooden cantilever wings with two box-spars and a welded steel-tube fuselage of rectangular cross section. Metal panels covered the sides of the fuselage forward of the lower wings and forward of the cockpit on the top decking. The triangular fin and tailplane were also made of steel tube. The ailerons, elevator and rudder were horn-balanced. The struts and the undercarriage were of streamlined steel-tube and an extra lifting surface was added to the axle between the wheels.
The Fokker fighter was at first fitted with the 160hp Mercedes D III engine driving a normal two-bladed wooden propeller, but this engine later gave way to the six-cylinder in-line water-cooled BMW IIIa rated at 185hp. A flat car-type radiator was fitted in front of the engine. Armament consisted of two fixed synchronised 7.92mm LMG 08/15 machine-guns with 500 rounds each, mounted on top of the fuselage in front of the cockpit.
The Fokker D VII was operational from April 1918 and by November nearly 800 were in service. Many were smuggled from the Fokker works at Schwerin in Germany to Holland in railway waggons in 1919. They were later sold and these aircraft and a number of ex-German machines saw service in Belgium, Holland, Lithuania, Poland, Rumania and the Soviet Union. A few also found their way to Denmark (two), Finland (three), Hungary, Latvia (three), Manchuria (three), Sweden (one) and Switzerland (four), and two were used by the Germans at Lipetsk. The last four of the Dutch machines were written off as late as 1938.
Fifty D VIIs were sold by Fokker to the Soviet Government in 1922. They were handed over in Amsterdam to representatives of the Russian Trade Commission in Berlin and their c/ns were; 10, 20, 25, 31-33, 38, 40, 45, 49-52, 54, 56-75, 82-88 and 92-100. One was test-flown by the German pilot Harry Rother in Amsterdam. Upon delivery to Leningrad in May 1922 they were assigned to the 1st Otdel'naya istrebitel'naya aviatsionnaya eskadril'ya at Gatchina, Leningrad, and the 3rd Otdel'naya istrebitel'naya aviatsionnaya eskadril'ya at Kiev. A German fitter named Hans Schmidt was sent out to erect the aircraft properly. In September 1922 the 1st Otdel'naya istrebitel'naya aviaeskadril'ya made a flight to Moscow with seventeen Fokker D VIIs. A single aircraft was assigned to the Commander of the Leningrad Military District and three to the 1st Higher School of Military Pilots in Moscow. One of these was destroyed when the commander of the school, N P Il'zin, collided in the air with a pupil flying a Nieuport 17 in September 1922.
Early in 1925 the D VIIs were replaced by Fokker D.XIs in the eskadrilii at Leningrad and Kiev and were handed over to the 1st Otdel'nyi morskoi istrebitel'nyi aviatsionnyi otryad, a naval fighter unit at Peterhof and to the 1st Otdel'nyi istrebitel'nyi aviatsionnyi otryad at Evpatoriya on the Black Sea. When these units became the 46th and 50th Aviaotryady in 1927, thirty-seven D VIIs remained. The 46th Aviaotryad received Grigorovich I-2s in 1928, and the 50th was disbanded in 1929. Single examples of the Fokker D VII were used for advanced training from about 1928 by the 1st, 2nd, 3rd and 8th Schools of Military Pilots, a couple of other flying schools, the 83rd (Training) Aviaotryad, the 73rd Aviaotryad and the 15th, 17th and 29th Aviaeskadrilii. Three of the eleven aircraft remaining in 1931 were handed over to Osoaviakhim, possibly for use as advanced trainers or aerobatic display aircraft. By the end of 1932 only four were on VVS charge and one was still left in December 1933. In the VVS the Fokker D VII was normally known as the FD-VII.
185hp BMW IIIa
Span 8.9m; length 6.95m; height 2.75; wing area 20.2irr
Empty weight 688kg; loaded weight 906kg
Maximum speed 198km/h; landing speed 90km/h; climb to 1,000m in 2.5min; ceiling 6,500m; endurance 1.8hr; range 425km
Flight, July 25, 1918.
A FOKKER BIPLANE OF RECENT TYPE.
ONE of the most interesting additions to the rapidly growing collection at the Enemy Aircraft View Rooms is a Fokker biplane of the D VII type, built, according to a pencilled date on one of the wing spars, in April of this year. The date is 24, IV, 18. The machine is thus one of the most recent to be exhibited, and is of interest on that account, as well as because of the originality of its design. Except for the fact that it is a biplane, the new Fokker product is very similar to the triplane described in our columns recently. The booty construction is the same, and the "wireless" wing design is very similar to that of the Fokker triplane. There is one notable departure, however; the engine fitted has evidently been a stationary water-cooled one, probably a 180 Mercedes.
The body of the Fokker biplane is built throughout of steel tubing, the method of joining the struts and cross members to the corner rails being the same as in the Fokker triplane, and the tubular quadrants serving as an anchorage for the cross-bracing wires being also exactly of the same type as in the previous machine. The wire bracing, as before, is simply doubled over the terminals, and only a single strainer being employed in each double wire. The tail plane and elevator are similar in shape and construction to those of the triplane, to the description of which we would refer our readers for details. The rudder is balanced, as in the triplane, but is preceded by a triangular vertical fin, which has probably been necessitated by the larger water-cooled engine, which gives a deeper body in front. The vertical fin is chiefly remarkable on account of the fact that it has its front attachment slightly off-set to the left, probably to counteract the tendency, caused by the torque, to turn to the left.
The pilot's seat is similar to that of the triplane, and is provided with the same wing nuts for quickly adjusting its height to suit individual pilots. In the machine exhibited, the control lever is missing, but from the parts remaining in place it would appear that there has been a forked lever pivoted on a longitudinal rocking shaft, which in turn carried the cranks for the aileron control cables, which pass over pulleys in the top plane in the manner illustrated in our description of the triplane.
The engine, which, as we have already pointed out, has been of the water-cooled type, is mounted on a structure built entirely of steel tubes. The two engine bearers are large diameter tubes, supported from the corner rails by small diameter tubes apparently of very light gauge. The tanks are placed immediately behind the engine, the right-hand compartment of the large main tank carrying the oil, and the left-hand compartment the petrol. A Vee-type radiator of honeycomb formation is built into the nose of the body, and is provided on the inside with a shutter for adjusting the cooling.
The under carriage is of very similar design to that of the triplane, the axle being enclosed in a wing section of three-ply wood. The shock absorbers are of the spiral spring type, and are covered, in by a woven casing. A feature of the Fokker construction, both as exemplified in the triplane and in the present machine, is the large amount of welding employed, and the manner of employing it. After an examination of the biplane, one is apt to come to the conclusion that the designer of the Fokker biplane places implicit faith in has welders, and, we are bound to admit with very good cause. The welding is excellently done throughout the machine, but the way the designer has seen fit to employ the welded joints is not above criticism. Thus, on examining the undercarriage, one finds that the lug - a simple forked arrangement - to which the cross bracing cables of the front bay are attached, is simply welded to the wall of the chassis strut without any internal reinforcement. The result, as regards one of the lugs, has been that in the shock of landing the lug has pulled out bodily a large triangle of the strut wall. The welded joint itself has remained intact, but it appears probable that the welding process has weakened the metal of the strut wall so that under the sudden stress of a rough landing this part gave way first, leaving the joint itself intact. This speaks well for the welder, but less so for the designer.
With regard to the wings of the Fokker biplane, these have been designed on the "wireless" principle, as in the case of the triplane. There is this difference, however, that whereas in the triplane the two spars were placed so close together as to form a single box, they are quite separate in the biplane, owing, no doubt, to the greater chord, which with its consequent greater travel of the centre of pressure, made it necessary to place the spars farther apart than could conveniently be done with the single-box arrangement. Each of the spars is built up of spruce flanges, connected on front and rear faces by three-ply webs, the whole forming a box. Both spars taper in a vertical as well as in a horizontal plane. The spars of the upper wing are of uniform width and depth over the portion between the body struts, and taper, from the point of attachment of these struts, to the wing tip, both in front elevation and in plan. The lower wing spars are of uniform section for the width of the body, and hence taper with a straight taper to the tips. The wing section appears to be similar to, but an enlarged edition of, that employed in the triplane. It is extremely deep compared with any modern standard, about 9 1/2 ins. being the maximum thickness of the top plane. The bottom plane, which is of smaller chord, appears to be a geometrical reduction of the top one, and is of considerably smaller chord. The actual dimensions have not yet been ascertained, as the machine in question is very considerably damaged, but we hope to refer to it in more detail at a later date. As far as can be; ascertained at present, the chord of both wings was uniform from root to tip, which fact would appear to indicate that the section from point to point varies from one of very great depth and thickness in the centre to one of more orthodox section near the tips. The aerodynamic effect of this would be of interest, and we cannot in this connection refrain from again urging, as we have repeatedly done in the past, the advisability of having tests made on all available enemy aerofoil sections and the results published. A section like the Fokker is not generally credited with any very high efficiency, but the mere fact that it has been retained in a design, examples of which have been built not more than three months ago, would certainly appear to indicate that it has not been found in practice to be so inferior as to outweigh any other advantages that may attend its employment.
The wing ribs of the Fokker biplane are somewhat similar to those of the triplane, but a difference was noticed in the construction of the flanges. In the triplane the thin three-ply web was accommodated in a narrow groove in the top and bottom flanges, but so narrow was the web that quite 50 per cent, of the tacks missed the web altogether and simply served to weaken the flanges. In the biplane it is not, therefore, surprising to find that an attempt has been made to eliminate this defect. This attempt has taken the form of the employment of a two-piece flange instead of the old grooved one-piece flange. Instead of vertical tacks the two halves of the two-piece flanges are held together and to the thin web by transverse tacks driven through alternately from right and left, and riveted over.
The manner of supporting the top plane is somewhat different from the method employed in the triplane. No wire bracing whatever is used, the necessary transverse rigidity being provided by the arrangement of the body struts. Sloping outwards from the body is a system of struts, all stream line steel tubes. One strut runs from the lower corner rail of the body to the rear spar. A set of three struts unite in a welded joint secured to the top spar by a single bolt. Each of these three struts is welded to a portion of the body, so that when the top plane is removed, a pyramid of steel tubes remains in place on the body, sloping upwards and outwards from the sides. The front one of these struts is welded to the tubular engine bearer, projecting through an opening in the metal body covering. The middle strut is welded to the bottom corner rail at the point where is, attached the front strut of the undercarriage, and the third strut is also welded to the bottom -corner rail, or, more correctly speaking, to a rail running above the spars of the lower wing, at the point where it is crossed by the front spar. The upper front spar is thus rigidly secured, whereas provision has been made for an adjustment of the angle of incidence by fitting into the end of the strut running from the rear spar to the lower body rail a threaded eye bolt fitting into a socket on the lower rail. Incidentally it might be mentioned in this connection that the upper plane is marked "Anstellwinkel 0·" (angle of incidence 0·.) Whether or not the bottom plane is also set at no angle of incidence we have not yet been able to ascertain. The mounting of the bottom plane is slightly different to that of the bottom plane of the triplane. In the latter provision was made for a slight adjustment of the angle of incidence, but in the biplane no such arrangement is to be found, the spars being rigidly attached to the body corner rails.
Only one pair of inter-plane struts connect the upper and lower wings on each side. These are in the form of an N, the joints between the members being welded. The joints between the legs of the N and the wing spars are in the form of ball and socket joints, those for the front top spar and rear bottom spar being fixed, while threaded bolts screwed into the end of the struts meeting the upper rear and lower front spars provide means for adjusting the incidence. No lift or landing wires are fitted, the deep spars being relied upon to resist the bending moments without external aid. Internally the wings are drift-wired with solid circular section steel wire, of 'heavy gauge, but not in duplicate. It was noticed that one of the lugs to which a drift wire was attached had sheared through, but we should hesitate to say that this necessarily indicates that here was a weak point regarded from the point of view of flying stresses, as the wing had evidently been badly damaged by the machine turning over on landing.
The armament of the Fokker biplane consists of two Spandau guns mounted on top of the body and synchronised in the usual manner to fire "through" the propeller.
As regards the covering of the Fokker biplane this is chiefly remarkable, in the specimen under review, on account of the colours in which it is painted. The front portion of the body and the top surface of the top plane are painted a deep vermilion, while the rear portion of the body is painted white. The lower surfaces of the top plane and the bottom plane are camouflaged in the usual German manner by a printing in different colours of lozenge-shaped figures.
The tail plane and elevator are painted black, with the exception of a parallel portion of the top surface, which is painted white like the body.
As already mentioned one of the wing spars bears the date 24.IV. 18, and another spar is branded "Gebr. Perzius, Flugzeug Abteilung." Painted in red stencil on the rear face of the bottom spar is the wording D VII Fl. No. 1450.
Flight, October 3, 1918.
THE FOKKER BIPLANE, TYPE D VII.
[From the Technical Department, Aircraft Production, Ministry of Munitions, we have just received an official report on the Fokker biplane. Except for extreme pressure on our columns the first instalment of our own description of this machine would h<...> appeared in last week's issue of "FLIGHT," the greater part of the material for this article being made-up ready for publication. After carefully perusing the official report we have decided to adhere to our original intention of publishing our own description of this machine, preceded by certain items in the official report compiled from sources not available to the general Press. At the same time we feel obliged to point out certain discrepancies between the official report and our own. These occur mainly in scale drawings of the machine. Thus in the side elevation the inter-plane struts are shown, in the official drawing, as approximately parallel whereas as a matter of fact they are very far from being so. This mistake has apparently been caused by placing the front side of the lower plane too far forward, bringing it into line with the chassis strut attachment, while, as a matter of fact, it is placed slightly farther aft in the recess in the body, as clearly indicated in "FLIGHT'S" side view. Fig. 1. In the same manner the rear spar of the bottom plane appears to have been placed too far aft. Turning our attention to the front elevation of the official general arrangement-drawing, it is found that the top wing is represented as having its top surface set at a negative dihedral and its lower sur<...> at a positive dihedral angle. This does not tally with our own measurements, which show that the top surface of the top plane is perfectly straight, the lower surface sloping up to it. Again, the taper of the top spars is shown in the official drawing to ex<...> right from centre line to tip. This is not correct. The top spars are parallel between the points of attachment of the struts slop<...> outward from the body, tapering from these points to the tip. This may appear only a small matter and one not worth drawing attention to. It should be remembered, however, that a change in the particular example referred to might, and in all probabi<...> would considerably affect the stability and manoeuvreability of the machine, and the matter may not, therefore, be of as <...> consequence as might be imagined. In the official plan view of the Fokker there are one or two points which are not strictly accu<...> such as showing the upper wing tip with a sharp corner at the leading edge instead of rounded off, and a straight leading edge instead of one slightly swept back. With this, however, we are not quarrelling, as the rounded corner woud be of m<...> importance, and the sweep-back, as pointed out in our description, may be intentional, or, on the other hand, may have be caused by straining the wings badly. We have no desire to find fault merely for the sake of it, but when it comes to such serious item as the off-setting of the vertical fin, which is shown in the official plan view as being on the centre line, while a matter of fact its front end is off-set to port, we do think this is inexcusable, especially as it is quite correctly pointed out in the text of the report that the biplane "has a triangular fin with foremost point is fixed an inch or two to the port side of the centre line of the machine," and a sketch, Fig. 12, has been drawn to illustrate this feature.
The text of the official report is quite accurate, as jar as have been able to judge, and the respective sketches are excellent with one exception. Fig. 15 in the official report is intended to show the engine bearers and their mounting. Whether it does with any great success or not does not greatly matter to <...> argument, but what does matter is that important tubes form part of the bearer and body structure have been omitted. <...> to illustrate our point we are publishing the official <...> well as our own (page 1114). - ED.]
THE following data, relating to the performance of this t<...> of machine and the detailed particulars of the weights, wh<...> are reproduced from the official report, should be of considerable interest. It will be seen that these data have been compiled from various sources, some being obtained from the machine described, while others have been based upon figures relating to machines captured by the French :-
The British No. of the machine is G/2B/14, and the German No. is Type D7 F.N. 1,450; maker's No. 2,455.
It was brought down north of Hazebrouck on June <...> 1918, by a British S.E.5a, and is a single-seater fighter.
This aeroplane presents features of very grea<...> whether viewed from the standpoint of aerodynamic ties or of actual construction. The machine which has been the subject of investigation was unfortunately rather extensively damaged, thus making absolute accuracy of description difficult, and trials of performance impossible.
A similar machine, however, has been tested for performance by the French authorities, who have issued the following report :-
Altitude. Time of climb. Speed at this height,
metres feet m. s. m.p.h.
1,000 3.281 4 15 116.6
2,000 6,562 8 18 114.1
3,000 9.843 13 49 109.7
4,000 13.124 22 48 103.5
5,000 16,405 38 5 94.9
The following data regarding weights is taken from a French source :-
Weight of fuselage, complete with engine, &c 1,322.2 lbs.
Weight of upper wing with ailerons 167.2
Weight of lower wing 99.0
Weight of fin and rudder 6.6
Weight of fixed tail plane 17.6
Weight of elevators 9.9
[The schedule of principal weights given below is the result of weighing the actual components mentioned, which were taken from the aeroplane allotted G/2B/14]
A different French report gives the following figures, which are taken from inscriptions found on one of the Spandau <...> captured Fokker of the same type :-
Weight, empty 1,540 lbs.
Permissible load (useful load and fuel) 396 lbs.
Schedule of Principal Weights. lbs. oz.
Upper wing, complete with ailerons, pulleys, bracing
wires, fabric and strut fittings 156 0
Lower wing (no ailerons fitted), complete with strut
fittings and fabric 97 0
N strut between wings 6 9
Straight strut, between fuselage and trailing spar of
upper wing 2 8
Aileron frame, with hinge clips, without fabric 4 8
Rudder frame, with hinge clips, without fabric 4 11
Fin frame, without fabric 1 14
Tail planes (complete in one piece), without fabric 12 6
Elevators (complete in one piece), without fabric 11 2
Radiator, empty 48 0
Undercarriage strut, each 2 10
Undercarriage axle, with shock absorber bobbins 18 2
Bobbin, each 0 7
Shock absorber, each 3 9
Undercarriage (complete), without wheels and tyres,
and without plane, but including struts 29 4
Aluminium tube, forming rear spar of undercarriage
plane 1 8
Wheel, without tyre and tube 11 8
Tyre and tube 9 4
Tail strut 1 15
Fabric, per square foot, with dope 0 1
Bottom plane compression rib 0 15
Bottom plane, ordinary rib 0 11
Top plane ordinary rib, at centre of plane 1 0
Bracket, with bolts, attaching top plane to fuselage
struts 1 11
Main spar, top plane, including fillets for ribs, per
foot run in centre 1 12
Owing to tapering ends the average weight per foot of the spars will be slightly less than this figure.
Fabric and Dope.
The fabric is coarse flax, coarser and less highly calendered than the type usually met with, and a good deal heavier.
It is colour-printed in the usual irregular polygons. The bright red paint, mentioned below, is removable by alcohol, but not soluble in it, coming off as a skin under the treatment.
Under the paint is a dope layer - an acetyl cellulose. Neither paint nor dope presents unusual features.
Paint 92.0 gms. per sq. m.
Dope 68.1 "
Fabric 143.6 "
Strength 1,772 k/m.
Extension 7.0 per cent.
Where the wings are not painted, the fabric is covered with a thin layer of dope only.
[With these comments upon and extracts from the official report, we now commence our own description, in its original form, of the Fokker biplane.]
[Of the machines now on view at the Enemy Aircraft View Rooms, Agricultural Hall, Islington, few are of greater interest than the Fokker biplane, D VII. This is mainly due to the fact that this machine is of recent manufacture (the wings bear the stamp 24. IV. 18) and is at present employed in considerable numbers on the Western Front, but also on account of the unusual design of some of its more important component parts. In our issue of July 25th, 1918, we published a more or less diagrammatic perspective drawing of this machine, the set of wings then available for inspection being in a very damaged and incomplete condition. At the same time we gave a brief description of the main characteristics, which will, therefore, be familiar to readers of "FLIGHT." A complete set of main planes is now available, and by the courtesy of the authorities we have been permitted to inspect the machine and to prepare the following drawings, sketches, and description. - ED.]
As its class letters (D VII) indicate, the Fokker biplane is of the single-seater fighting type of machine. As distinct from all previous types of Fokker machines it is fitted with a large water-cooled engine, with the radiator mounted in the nose of the body. As regards its wings the Fokker biplane forms a compromise between the one-and-a-half- plane originated by the Nieuport firm and the ordinary single-strutter machine with both planes of the same span and chord. In the Fokker the upper plane is considerably greater in area than the lower, while the difference between the two is not quite so pronounced as in the Nieuport type. The single pair of interplane struts form the link of similarity to what we have termed the ordinary single strutter, inasmuch as they are not of the Nieuport Vee type, but follow general practice with the one exception that they are braced by a single diagonal tube instead of the more usual incidence wires.
From the general arrangement drawings it will be seen that the upper plane is mounted comparatively low in relation to the top of the fuselage, thus giving a fairly good view forward. Owing to the method of mounting the top plane there are no bracing wires running across the top of the body, interfering with the two machine guns, which are mounted above the body. As pointed out in our preliminary report on this machine, it is of the "wireless" type as regards its wing truss, no lift wires or landing wires being provided, although internal drift wires are fitted in the wings. This feature has been made possible by choosing an extremely deep wing section, very similar to that of the Fokker triplane described in our issue of May 30th, 1918, which gives ample room for a spar deep enough to take the wing loads without the external aid of lift wires. The construction of the wings will be dealt with in detail later, but at the present juncture a few words regarding the aerodynamic side of the question may not be amiss.
When describing the Fokker triplane we expressed a doubt as to whether all things considered, the deep wing section was "worth while." One has become accustomed to regard such a deeply cambered section as liable to have a high resistance factor, although its lift coefficient may be, and probably is, high. At the time we strongly urged that the N.P.L. should carry out wind tunnel tests on a model of the section to ascertain what, exactly, are its lift and drag coefficients and other characteristics. Up to the time of writing we have no information to the effect that such tests have been made. Nor are we prepared to express the opinion that tests would necessarily reveal any astonishing and unexpectedly good features. When, however, we see such a section employed in a machine of so recent manufacture as April of this year, we confess that we do think there is reason to suppose that the section cannot be so very inferior; otherwise why continue to employ it? Surely the scientific German mind would not tolerate its retention just to please a designer of a "freak" machine? One is therefore forced to the conclusion that the enemy has found that the wireless, wing truss with the (possibly) larger resistance section has its advantages over low-resistance sections plus their wire bracing.
That the particular spheres of flying in which the section scores may be climbing and a high ceiling we should be the last to deny, but even so the enemy must, after weighing the cons and pros, have come to the result that these two attributes are of more importance than mere speed, if the latter is obtained at the cost of the former. Without the wind tunnel tests, or actual tests of a full size machine, one does not even know whether or not the Fokker biplane does have a comparatively low maximum speed. We would therefore again urge that tests be carried out in the wind tunnel, and that the results be made known to British manufacturers and designers.
An examination of the plan view of the Fokker biplane will show that ailerons are fitted to the top plane only, and that even so are of an area which would appear to be wholly inadequate, as compared with those of machines of more orthodox design. Yet from what one can learn from pilots who have seen the actual machines at close quarters they appear to be very quick on the lateral control. Why is this? Again, one can only come to the conclusion that in some way the peculiar wing section must be responsible for the efficiency of the ailerons. Whether this be due to the deep section as such, or whether to the fact that the wings are very much tapered in thickness from root to tip is difficult to say. It appears probable that it may be in some measure due to both factors. The fact remains that sufficient lateral control is apparently provided by ailerons of ridiculously small area.
It has already been mentioned that the wing spars of the Fokker biplane taper from root to tip. The form this taper takes will be to a certain extent apparent from the front elevation of the machine, but a more detailed reference to it may be of assistance. The upper wing spars, front as well as rear, have their top surfaces perfectly straight. The bottom surfaces are parallel to those of the top for a length extending between the points of attachment of the outward sloping body struts. From this point to the tip the lower surfaces of the spars slope upwards. The effect of this arrangement is to give the lower surface of the top plane a dihedral angle, the top surface being straight.
As regards the lower wing spars, their taper appears to be approximately symmetrical, that is to say. Both surfaces of the spar are parallel for the short length resting inside the body, while from the side of the body to the wing tip the upper surface of the spar appears to slope down to about the same extent as the lower surface slopes up. In the machine under review both wings appear to have a sweep back of about one degree or so, but whether this was present originally or whether produced by excessive strain we have not been able to ascertain. The remaining component members of the machine do not present anything particularly unusual, and we can therefore now turn our attention to the :-
Body. - As in the case of the triplane, the body of the Fokker biplane is built of steel tubing throughout. The general arrangement and most of the details will be clear from the side elevation and plan, Fig. 1. The four corner tubes or longerons vary considerably in section as one progresses from nose to stern. Their outside diameter at any point is indicated in the drawings, but we have not been able to ascertain the thickness of the tube walls, as this would have necessitated cutting a great number of rails and struts. Apparently the tubes are of very light gauge, and are joined, a larger to a smaller, at the points where occur the body struts. The struts are attached to the longerons, as in the triplane, by welding, the joint being particularly well made. As a matter of fact it is only this excellent workmanship that mates this construction feasible. Whether the welding has been done by the oxy-acetylene method, by oxygen and hydrogen, or by electricity is impossible to say. The construction points unmistakably to the body framework having been welded in place over jigs, and as one spoiled joint would ruin the whole framework it appears probable that a considerable amount of control of the temperature of the flame used would be an advantage. Possibly, therefore, the welding has been done by electricity. Whatever the method, there can be no doubt that the welding is excellently done, and, unless an entirely new method has been evolved by the enemy, could only have been entrusted to highly skilled workmen.
It is not only in joining the struts of the body to the longerons that welding has been employed, but also to a great extent for securing members which do not, strictly speaking, belong to the main body framework. For instance, the three stream line steel tube struts which connect the front spar of the top plane with the body are welded at their lower ends to various portions of the body frame. The front one of these struts is welded to the tubular engine bearer, while the other two are welded to the upper and lower longerons respectively. Thus when the wings are dismantled these struts remain in place on the body, a fact which would, one imagines, render them liable to damage during transportation In order to give an idea, of the amount of skilful welding necessary in the Fokker body we show, in Fig. 2, a complexity of welds, all occurring at one joint. There are no less than seven members joined here by welding, not counting the socket for the front chassis strut, which might, as a matter of fact, have been included as it is attached to the longerons by welding.
In conformity with the rest of the design of the body of the Fokker biplane, the engine bearers and the framework connecting them with the fuselage are in the form of steel tubes. Of these there are a considerable number, some plain, straight tubes and others bent to the shape of a letter U. The arrangement of these bearers and their supports is shown from two points of view in Fig 3. The inset shows one of the split collars or slips by means of which the engine is secured to the two bearers.
Fig. 4 shows some constructional details of the body and tail planes of the Fokker biplane. The fixed tail plane as well as the divided elevator are built up of steel tubes, the general arrangement being shown in Fig. 1. In the general sketch of Fig. 4 the ribs of the tail plane have been omitted so as to show more clearly other details. Like the tail plane and elevator, the rudder and its fin are built of steel tubing. The fin has the peculiarity that its front end is slightly offset to port, probably to counteract a tendency, caused by the torque, to turn to the left. This offsetting of the fin would probably result in a tendency to turn to the right with the engine switched off, but with regard to this we have no data, as the machine has not been flown by any of our pilots, being in a too damaged condition to make this expedient. The attachment of the front end of the fin to the front transverse tube of the tail plane is shown at A, Fig. 4. The detail at B shows a hinge that is very extensively used on the Fokker biplane, both for the elevator and rudder, and also for the ailerons. The construction of the hinge will be easily understood from a reference to the sketches. A sheet aluminium plate has a portion stamped out as shown to form the front half of the bearing, the remaining two strips forming the rear half. Into the space thus formed is forced a bush that provides the bearing surface for the rudder or elevator tube. The whole hinge impresses one as being very neat and simple, and the only objection that might be raised against its employment is that each hinge has to be pushed into place before the elevator or rudder ribs are welded to the tubular leading edge. As, however, everything is, apparently, done over jigs this is a matter that is easily managed while building up the control organs. The sketch at D shows the split collars used for securing the two diagonal tubes which reinforce the body frame at the point where occurs the handle by means of which the rear portion of the body is lifted when handling the machine on the ground.
The body of the Fokker biplane terminates at the rear in a sort of false stern post of wood, the last vertical tube of the body being placed some little distance farther forward. This tube, which is welded at its ends into the angle formed by the converging longerons at this point, has mounted on its upper end the attachment for the tail plane. This is in the form of a simple bolt, which does not appear to provide any adjustment for the angle of incidence of the tail plane, although it might easily be extended to do so. The front attachment of the tail plane to the top longerons is by means of two bolts passing through short lengths of tube welded to the inside of the longerons. At its lower end the vertical tube referred to above carries the attachment for the tail skid, the details of which are shown at F. The upper end of the tail skid is sprung by coil springs and the amount of travel is limited by a cable as shown at E. The sketch at G shows the tubular quadrant to which the bracing wires of the body are attached. As in the triplane these wires are simply doubled over the quadrant, and are thus not strictly speaking in duplicate. Only a single wire strainer is incorporated with each double wire, the method of locking the strainer being as shown in the sketch.
(To be continued.)
Flight, October 10, 1918.
THE FOKKER BIPLANE, TYPE D VII.
(Continued from page 1116.)
IN our last instalment the construction of the Fokker biplane body was dealt with in detail. Before turning our attention to the wings, it may be as well to refer briefly to some of the equipment and accessories which, although being attached to or mounted in it, do not form a part of the main body structure.
In principle the controls of the Fokker biplane are very similar to those of the triplane described in our issue of May 9th, 1918, but some of the details are somewhat different. Fig. 5 is a perspective view of the controls. A longitudinal rocking shaft is carried in two bearings, formed by clips bolted to transverse tubes in the bottom of the body. The control column, which is a steel tube tapering towards its upper end, fits into a tapering socket that is in turn welded to the collar surrounding the longitudinal rocking shaft. The downward projection of the column is similarly welded to the bottom of the collar. It will thus be seen that a welded joint is relied upon for the main elevator cables, a feature which places great reliance on the excellence of the welded joint.
The longitudinal rocking shaft has a forward projection, on which are carried the two crank arms operating the aileron cables. These two cranks are formed of sheet steel bent over so as to form a stream-line section with its sharp edge pointing downwards. They are placed at an angle of about 100· to one another, and are, in addition, staggered, the port arm being in front of the starboard one. The rudder bar, as in the Fokker triplane, is in the form of a steel tube secured to its collar as shown in the sketch and pivotting on a vertical tube secured at its lop to one of the fuselage cross struts, and at the bottom to one of the bottom cross struts via a fork formed by two short tubes as shown, in order to clear the longitudinal shaft. The pilot's feet are prevented from slipping off by the tubular guards welded to the foot bar. The method of anchoring the rudder cables to the foot bar is interesting. On each side a short tube is welded to the side of the foot bar, and through this tube is passed a bolt which also goes through the arms of the stirrup or shackle that forms the final attachment for the rudder cables. Here again the controls put the -welded joints under tension. In the triplane the shackles passed over the foot bar, the vertical tubes being welded to the front of the bar, thus avoiding the tension on the welded joint. The method of making the shackles is very simple, as shown in the detail sketch of Fig. 5. A short length oа tube of small diameter has its ends slotted and flattened out, holes being provided in the flat portion for the vertical bolt. The tube is then bent and the shackle is finished. In Fig. 5. the floor boards have been omitted on the starboard side to show the controls, but under the left foot guard will be seen a segment of aluminium which serves to protect the floor against the constant rubbing of the pilot's heel. Another such guard is, needless to say, fitted under the right foot.
The grip in which the control column terminates at its upper end is quite different from that found on the Fokker triplane. In the present machine the grip consists of a small piece of wood, shaped to fit the fingers of the right hand, and having a slight hollow at the top for the thumb. The triggers for the machine guns are not pushed by the thumb as in the majority of other machines, but are pulled by the fingers towards the grip. On the port side of the control lever is mounted a Bowden control for the throttle. The handle of this had been knocked off in the machine examined, so it has been impossible to ascertain its exact shape. It has therefore been shown dotted in the sketch. This lever does not operate the throttle direct, but is connected to the proper throttle lever mounted on the port side of the body by Bowden cables. The object evidently is to enable the pilot to work the throttle from the control lever during a fight, instead of having to shift his hand and possibly fumbling about for a few seconds before getting hold of the main throttle lever. It will be noticed that no provision has been made in the biplane for locking the elevators in position, the necessity for doing this having apparently been avoided by the arrangement of the gun and engine controls.
Before leaving the subject of controls reference may be made to the lateral control system of the Fokker biplane, which is somewhat unusual. In order to facilitate an explanation of the principle on which the aileron control is based, we have prepared a diagram. Fig. 6, which shows, in purely diagrammatic form, the paths followed by the aileron cables over the various pulleys. It will be noticed that the lower plane has not been included in the diagram. This is due to the fact that nowhere do the aileron control cables pass over or through the bottom plane, as is usually the case in German machines, specially when the typically German aileron crank levers, working in slots in the top plane, are fitted. In the Fokker biplane the crank levers are vertical as in British machines. So far as one is able to judge, the object which the designer had in mind when working out this control system was to provide positive control, not only to the aileron that is being pulled down, but also to that being pulled up. The manner in which this object has been attained in the Fokker, will be understood by a reference to Fig. 6. In the explanation to follow we shall refer to the cable pulling down the ailerons as a positive cable, and to that pulling up the ailerons as the return cable. In the diagram the two sets of cables have been drawn differently, the positive cable being shown by a chain dotted line, while the return cables are indicated by a plain dotted line From the crank on the longitudinal rocking shaft in the fuselage the positive cable runs through a guide on the top longerons (not shown), over a pulley mounted on the top rear spar, along the spar, around another pulley, and hence to the lower aileron crank. The return cable from the same crank arm in the body runs through the same guide on the top longeron, to a pulley at the side of that for the positive cable, along the spar in the opposite direction to that of the positive cable, over another pulley and hence to the top crank of the aileron. The arrows in the diagram will help to make the arrangement clear. Thus, when the control lever is pulled to port, the positive cable pulls down the starboard aileron, and the return cable pulls up the port aileron.
As far as we have been able to ascertain, all the tanks carried on the Fokker biplane have been incorporated in one single tank of brass. The oil tank occupies the extreme starboard side of the tank, then comes a small reserve tank, and on the port side, partitioned off from the reserve tank, the main tank, which, judging from the lines of rivets visible on the outside, is divided up into two compartments communicating with one another. From external measurements the capacity of the various tanks is approximately as follows: Oil tank, 3 gallons; petrol, 20 gallons. These figures are only approximate. Both petrol tanks work under pressure, supplied by two pumps, one driven by the engine and the other hand operated. As shown in Fig. 7, the mounting of the tank is rather unusual, there being no supporting bands passing underneath the tank, which is slung from the top cross tubes of the body by means of brackets and bolts, as shown.
The instrument board of the Fokker biplane is not a very elaborate affair, the "gadgets" being few in number, compared with the instrument boards of some of our own machines. Especially noticeable in all German machines, with the exception of some of the later Gothas, is the absence of speed indicators. In the case of the Fokker it is possible that some of the instruments may have been removed, although there are no indications that more have been fitted than those now in place on the machine. On the port side of the instrument board is the hand magneto, surmounted by its switch. In the centre are the two petrol pressure indicators, and underneath them the petrol and pressure cocks. In the top right-hand corner is a grease pump for the water pump. Mounted on the starboard body struts is the hand-operated petrol pump and the compass. The mounting of the latter is somewhat unusual, as shown in Fig. 8. A small piece of three-ply wood is clipped at its upper end to one of the body bracing wires and at its lower end to the bottom longeron. Mounted on this is the bracket that carries the compass. The base plate is provided with a curved slot which allows of adjusting the placing of the compass in relation of the centre line of the body. A brass bar of square section projects downwards from the base plate, and on this are mounted the adjusting magnets. These are evidently placed initially by experts, and the pilot is not permitted to interfere with them in any way, as they are locked in position and sealed with a lead seal. One would imagine that in an all-steel body like that of the Fokker, the size and number of the adjusting magnets necessary would be considerable; yet this does not appear to be the case.
The throttle and ignition control levers are placed at the pilot's left hand. As already pointed out when describing the main controls, the throttle lever is connected up with Bowden cables to a throttle lever on the control column. The main throttle lever operates the throttle via a series of rods and cranks. The ignition is similarly controlled.
The armament consists of two Spandau machine guns, provided with the usual interrupter gear for firing between the blades of the airscrew. The mounting of the machine guns is indicated in Fig. 9. Each gun is provided with two supports, and a certain measure of rigidity is added by running a tube from the front support rearwards and outwards to the end of one of the top cross struts. As in other German machines, the rear gun support allows of vertical adjustment, while the front support provides for a slight adjustment laterally. The cartridge boxes are of sheet aluminium, and do not present any features of particular interest.
The honeycomb radiator, which is unusual for a German machine, in that it is placed in the nose of the fuselage, is of Vee shape as seen in plan. The apex of the Vee is cut off, however, forming a flat of approximately 4 ins. width down the extreme front of the radiator. The left half of the curved top of the radiator forms a small water tank, while the right half is simply a curved fairing. Provision has been made for varying - although apparently to a very small extent - the cooling by placing a small door or shutter over the starboard side of the radiator. This door, which is placed on the inside, behind the radiator, is normally allowed to trail in the line of flight, but can be pulled against a spring by means of a cable so as to lie fiat against the back of the radiator. When closed this door only covers a small portion of the radiator, less than one-third, so one does not imagine that the amount of control over the cooling is very great. The mounting of the radiator will be fairly clear from Figs. 1 and 4 in our last issue.
The undercarriage of the Fokker biplane is of the simple Vee type, with stream-line steel tube struts. At their upper ends the struts terminate in balls fitting into sockets welded to the fuselage members, and are prevented by a short bolt from coming out of the socket. At the lower end the undercarriage struts are welded to a sheet steel box, in which is a slot for accommodating the travel of the axle. This sheet steel box also serves as a support for the short stubs to which are anchored the shock absorbers. These are of the coil spring type, enclosed in a woven covering after the fashion of rubber cord. An aluminium box, formed of sheet, connects the port and starboard boxes and serves as the main spar of the fairing, or wing section, surrounding the axle. This section was severely damaged in the machine examined, and its exact shape is therefore a matter of surmise, but it appears probable that in section it was very similar to the wings. From what little remains of it this section appears to have been covered top and bottom with three-ply wood. In addition to serving as a fairing for the axle this section probably gives a not inconsiderable amount of lift, especially when landing, when there would be a "cushioning" effect due to the proximity of the section to the ground. The diagonal bracing of the undercarriage is in the form of stranded cable in the front bay only. The cables are attached at the lower end to a forked lug welded to the wall of the struts One of these lugs, as pointed out in our preliminary description of the Fokker biplane, had pulled a triangular portion of the -strut wall out, although the weld itself appeared undamaged. At the upper end, the bracing cables of the undercarriage are simply passed around the bottom longerons and spliced. This feature was shown, incidentally, in Fig. 2 in last week's issue of "FLIGHT."
(To be continued.)
Flight, October 17, 1918.
THE FOKKER BIPLANE, TYPE D VII.
(Concluded from page 1144.)
As already mentioned the wings of the Fokker biplane form one of the most interesting features of the design, both aerodynamically and structurally. In Fig. 11 are shown four typical sections, taken at various points in the planes. The top section in the illustration is taken in the centre section of the top plane. Underneath this is a section taken on the top plane rib occurring a short distance inside the attachment of the inter-plane struts. These two sections give a good idea of the manner in which the planes of the Fokker biplane taper in camber towards the tips. It will be seen that both upper and lower surfaces of the section are flattened out towards the tip. The other two sections shown in Fig. 11 represent the lower plane rib at the root and inside the attachment of the inter-plane struts respectively. Here, it will be seen, there is no flattening out of the bottom camber, in fact it appears that the maximum bottom camber of the thinner section is slightly greater than that of the section at the root... In both upper and lower plane sections it will be observed that the distance from centre line of front spar to leading edge diminishes slightly as the tip is approached. This accounts for the sweep back referred to in a previous instalment of this article.
Constructionally the ribs are built up of solid webs of thin three-ply wood. The flanges of the ribs are attached in a somewhat unusual manner to the webs. Instead of having the flanges in one piece and grooved for the web, the flanges in the Fokker biplane are in two halves, the three-ply web passing between the two halves of the flanges and extending the full thickness of the section. The flanges are tacked together and to the web by horizontal tacks driven through and riveted over.
The wing spars are of the box type of construction, as indicated in Fig. 12, which shows the sections of all four spars in the centre, i.e., where the maximum dimensions are found. The flanges, it will be noticed, are not solid, but are built up of two laminations each. The top flanges of all four spars are so shaped as to form an approximately rectangular space between them and the bottom flanges. At the points of attachment of the spars, such as to body or to inter-plane struts, this space is filled with a distance-piece in the form of a piece of wood. The distance-piece does not, however, touch the flanges direct, a piece of wood tapering towards the ends, which are forked, being interposed between the distance-piece or packing block and the flanges. The object of this arrangement appears to be connected with shear stresses on the spars, which are disposed of gradually instead of suddenly in this manner. The rib flanges are made of pine, and are connected by thin webs of three-ply, about 1.5 mm. thick, which are glued to the flanges. The tops and bottoms of the spars are afterwards covered with a strip of fabric, which extends over the sides of the spar to past the edge of the flanges, thus acting as a protection for the glued joints. The leading edge, as in the Fokker triplane, is in the form of very thin three-ply wood, which extends back to the front spar, where it finishes off in a serrated edge having its points tacked to the spar. This feature is shown in Fig. 13. This sketch also shows the vertical triangular-section pieces of wood which reinforce the rib webs, as well as the manner of attaching the ribs to the wing spars. The trailing edge is in the form of a wire, and its attachment to the ribs is shown in another sketch in Fig. 13. The end rib of the wings of the Fokker biplane is different to that of the triplane, which had, it may be remembered, a tip formed by an ordinary wing rib laid on its side. In the biplane the wing tip is formed by a piece of wood of U-section, which is attached to the ends of the spars as shown in the sketches at the bottom of Fig. 13. Between the spars, and between trailing edge and rear spar, the ribs are strengthened by tapes running alternately over and under the ribs. A short distance in front of the trailing edge there is a further reinforcement in the form of a long strip of wood of square section running through all the rib webs.
The attachment of the wings to the body has already been briefly referred to. The front spar of the top plane is attached to the top of the tripod formed by the tubes rising from and welded to the body, which were described at the time of dealing with the fuselage. The rear spar is similarly attached to a single strut. The details of the attachment are shown at A and B, Fig. 14. A thin strip of steel is bent over the spar and passes down the sides of the spar to the bottom corners. Another piece of sheet steel - this of heavy gauge - is bent to form two forks, the upper of which fits over the sides of the spar, to which it is attached by two horizontal bolts, while the other fork projects downwards and inwards and serves as an anchorage for the bolt that passes through the head of the rear centre section strut. The attachment of the bottom plane to the fuselage is shown in sketches C and D, Fig. 14. The general principle is similar to that employed for the upper plane attachment, and the details will be easily understood from an inspection of the sketches. The manner in which the bottom plane, which is built in one piece, is dropped out of the body when the bolts have been removed is briefly indicated in the sketch D. The lower false longerons are cut at this point, and a trap door formed by a framework of steel tubing is bolted in place under the wing. By undoing these bolts the door can be swung out of the way and the bottom plane dropped through. The absence of wing bracing wires facilitates the dismantling and erecting of the wings.
The inter-plane struts of the Fokker biplane are of streamline steel tube. The manner of attaching them to the wing spars is illustrated in the sketch E of Fig. 14, which, although representing the front spar attachment particularly, is typical of the other attachments as well. Vertical piercing of the spars is avoided by employing a base plate having forked members passing down the side of the spar and secured to it by two horizontal bolts. Through this base plate is inserted a socket of the shape shown at F, Fig. 14. This socket is machined out of the solid with a large base plate of circular shape, provided, however, with flats preventing it from turning. The base plate of the socket is of ample area, thus minimizing the tendency of the socket to tilt on the spar owing to any angularity of the inter-plane struts.
Reference to the aileron controls has already been made and a diagram published of the path followed by the aileron control cables. The remaining sketches of Fig. 14 show the details of the arrangement of the various pulleys and guides for the aileron cables. At A is shown the method of mounting the pulleys on the rear top spar. A forked lug is secured to the spar by a horizontal bolt passing through the spar, and has welded to it a tubular guide for one of the aileron cables. The two pulleys are enabled to swing freely by pivoting the sheet steel framework carrying them on a bolt passing through the fork of the lug referred to above. A reference to the diagram (Fig. 6), published last week, will show where these pulleys occur.
Before reaching the aileron crank levers the cables pass over another set of pulleys, also mounted on the rear top spar, but immediately in front of the crank levers. These pulleys and the method of mounting them form the subject of the sketches at G, Fig. 14.
The ailerons of the Fokker biplane are built up of steel tubing, as shown at H. It will be noticed that with the exception of the balanced portion of the aileron the trailing edge is formed by a wire. The attachment of this wire to the framework is shown at I. A stiffener or false trailing edge is formed by a tube running through the aileron. This tube is welded into the angle between the tubular ribs of the aileron as shown at J. The aileron crank levers are welded direct to the tubular leading edge without the intermediary of a collar, as in the case of the elevators. The shape of the crank levers is shown at K. The hinges of the ailerons are exactly similar to those of the elevator and rudder, which were described and illustrated in a previous instalment of this article.
Flight, November 21, 1918.
"HANGING ON THE PROP."
THERE are few evolutions in the air of which the modern aeroplane is not capable when handled by a skilful pilot. The loop, the "apple turn-over," the spiral nose-dive, the spin, the Immelmann turn, the dead leaf fall, and a host of others will be familiar to many readers of "FLIGHT," as they are to be seen almost any day from one or more of London's suburbs. There is one stunt, however, which has not yet become familiar on this side of the Channel, although it will probably not be long before that also is numbered among the service pilot's stock-in-trade. The evolution we have on mind, and which was, we understand, originated by pilots if Fokker biplanes at the Front, has become known as "hanging on the prop." The title is very descriptive, conveying as it does the idea that the machine is held up by the propeller only. This would be exactly the impression of another aviator watching from an aeroplane travelling at ordinary speeds, although in point of fact it appears very doubtful whether the machine is stationary. It is far more likely that it is moving along, but at so comparatively slow a rate that to an observer watching from another machine moving along at a speed well above 100 m.p.h. it does indeed appear to be "left standing."
In the accompanying sketch we have endeavoured to convey an impression of the attitude which the Fokker biplane assumes when performing this new "stunt." As a matter of fact, it may be doubtful whether the machine actually assumes a position so near the vertical, but when preparing the drawing it was found that if the angle was less, the drawing did not convey the impression desired but rather one of a modern high power machine climbing at a steep angle.
From what we can gather from pilots who have seen the Fokker go through this evolution it appears that this machine is able, not only to assume this attitude, but to maintain it for long periods, the latter being the feature of the stunt which impresses pilots most. It is, we think, generally agreed that the majority of machines, if placed in such an attitude, would be very prone to come out of it in a side slip or a tail slide. This does not appear to be the case with the Fokker which, as already pointed out, seems to be able to maintain this extraordinary position practically indefinitely.
As to the advantages of this stunt, these would appear to be a steady platform from which to fire, and the ability of firing up at a machine passing overhead, i.e., in a position where it is precluded from returning the fire.
Aerodynamically the why and wherefore of this remarkable performance can scarcely be accurately stated without the most complete data of the machine, engine and propeller. Broadly speaking, what would appear to happen is this: The machine is travelling along an approximately horizontal flight path, probably at the same time climbing slightly. This would mean that the machine was very cabre not only relatively to the horizontal but also to its flight path. The propeller axis therefore forms an angle with the relative wind, the component of which that is parallel to the propeller axis being small. This would mean that the translational speed of the propeller (along its axis) would be small, and furthermore that the conditions obtaining would be rather different from those of a machine travelling slowly but with its propeller axis parallel or nearly so to the flight path. In the case of the Fokker, it would appear that the propeller, owing to its oblique path through the air, is acting less as a fan than is a propeller moving slowly through the air with its blades revolving in a plane practically at right angles to the relative wind. This would probably mean that although the efficiency would be very low, the thrust would be comparatively high, not high enough, of course, to absolutely sustain the machine, but high enough to do so in conjunction with the air pressure on the wings, body and tail of the machine.
The air pressure would, of course, as the machine is assumed not to be quite vertical, have a resultant having an upward slope, and between the resultant of the air pressure on the machine, which would have an upward and rearward direction, and the propeller thrust, which would have an upward and forward direction, the machine is sustained. The resultant of these two components would have a forward slope, as the machine is supposed to be travelling along horizontally.
Another "explanation" might be that the machine is actually dropping all the time, the propeller thrust merely serving to retard the fall sufficiently to give the impression that the machine is "hovering," As has been pointed out, without having full data of the machine, engine, and propeller, it is hardly possible to give a correct explanation of what takes place, and in the foregoing we have only endeavoured to indicate briefly the principles involved. If any readers should have a fuller, or a different, explanation, we shall be pleased to open our columns to a discussion of the aerodynamic side of the problem.