Junkers J 2
Encyclopedia
The Junkers
J 2 was the first all-metal aircraft intended as a dedicated military aircraft design, the first all-metal aircraft meant to be a fighter aircraft
, and was the direct descendant of the pioneering J 1
all-metal aircraft technology demonstrator design of 1915.
s influential Prüfanstalt und Werft der Fliegertruppe ("Test Establishment and Workshop of the Aviation Troops") department, abbreviated "PuW", enough for Hauptmann Wagenführ to submit a contract to the Junkers firm for six all-metal monoplane
s, meant to be fighter prototype
s, with each to be powered with the Mercedes D.II inline engine
(as the J 1 had been), armed with one 7.92 mm (.312 in) Spandau lMG 08/15 synchronized machine gun
, and bearing IdFlieg serial numbers E.250/16 to E.255/16. The desired specifications were for an aircraft that had:
The IdFlieg contract for the ordered aircraft also specified that "the greatest maneuverability and nimbleness in flight must be achieved by the aircraft", a possible concern by the German governmental agency, over the usage of the heavy electrical steel
sheet metal that made up the earlier J 1's structure. Herr Junkers began wind tunnel
and design work promptly upon receipt of the contract paperwork, and eventually, by the end of the spring of 1916, an aircraft emerged from Junkers' Dessau
workshops that was much more streamlined in appearance than the J 1 had been.
that emerged from the Dessau workshops had an evolved appearance from the J 1, as the fuselage
nose now almost completely enclosed the Mercedes D.II engine, except for the open top of the cowling
. The J 2's fuselage structure had rounded dorsal and ventral contours, instead of the boxlike right angles of the J 1, possessed a narrower and deeper ventral "belly" radiator
enclosure, and used a horizontal stabilizer
planform shape that would become familiar on later, all-duralumin
Junkers monoplane designs to be built during 1917-18. The "all-moving" rudder
still possessed no fixed fin
, like the J 1. A faired-in headrest
was provided for, as well as a "roll bar" placed above the headrest for additional pilot protection in case of the aircraft flipping on its back during a crash landing. The J 2's landing gear
was of the usual vee-type, but a bit taller than the J 1's had been, with the upper ends of the legs anchoring not onto the fuselage "corners" as on the J 1, but on the first wing rib
"bay" beyond the wing root
, with a long tailskid that emerged from the lower rear fuselage directly below the stabilizer's leading edge
root location. The wings had at least three different airfoil changes running from root-to-tip, and had sections of them electrically roll-welded for stronger, more continuous bonding for greater strength. The resulting aircraft was intended to be smaller than the J 1 demonstrator, but with its steel structure, it almost equalled the J 1's completed weight.
One feature pioneered in the J 2, that would also be used in later all-metal monoplanes designed and built by Junkers in World War I, was a "unitized" forward fuselage structural concept, combining the framing of the engine mount, wing roots and cockpit framing into one central integral structure.
) on 2 July 1916, and started its IdFlieg-mandated static load testing. Otto Mader, one of the J 2's designers, then promised the IdFlieg agency that the following example, serialled E.251/16, would have even greater structural strength than the E.250's airframe possessed. Leutnant Theodor Mallinckrodt, the pilot that had first "hopped" the earlier J 1 some seven months previously, took the E.251/16 example up for the J 2 design's maiden flight on 11 July 1916. Mallinckrodt gave the E.251 example that he flew a good overall evaluation, judging it as "very maneuverable", with good turning qualities and safe aerodynamic behavior. A short time later, IdFlieg test pilots Unteroffizier
s Wendeler, and Max Schade, began "wringing out" the six examples of the J 2 as they arrived at Adlershof for their full range of flight evaluation tests.
Unteroffizier Schade would eventually take one of the test aircraft on a flight from Berlin (most likely from the government's Adlershof/Johannisthal facility) to Dessau later in the summer of 1916, achieving the then-high speed of 180 km/h (112 mph) with the aircraft, which was some 16 km/h (10 mph) faster than the contemporary French Nieuport 11
, but as the J 2 test aircraft still seemed to come up short in climbing performance tests, when evaluated against wood structure designs, like the then brand-new, Robert Thelen-designed Albatros D.I
aircraft, the steel structure of the J 2 made it just too heavy to be able to compete in air combat over the Front.
At least one example (E.253/16) of the J 2 was fitted with slightly longer wings and matching longer ailerons, possibly in an effort to decrease the wing loading of the initial J 2 design, and another tested "upgrade" to the J 2s under test was to fit at least one of the aircraft with the then-new 119 kW (160 hp) Mercedes D.III
engine, and one of the J 2s so equipped achieved an amazing-for-the-time 200 km/h (124 mph) at full throttle in testing.
"As a result of the first (J 1) and second (J 2) aircraft, one would ascertain that the aerodynamic efficiency was very good. We thought we [the Junkers designers] were over the hill. This, unfortunately, was not the case. We had to start again from the very beginning. The reason was that in spite of the favorable horizontal speed, the aircraft could not meet the military climb specifications...we had to develop an aircraft that not only had low drag for ease of maneuver in the horizontal plane, but that could climb well-an aircraft with a low weight to power ratio...
...This could not be achieved with iron, and we had to choose a new material...light-weight metal. But not only the choice of iron had resulted in high weight. We had built too heavy because we wanted a safe aircraft and partially because we had not extracted the optimum structural strength from the material".
Unteroffizier Schade, after making the record Berlin-Dessau flight, would later lose his life in a crash, from entering a spin on 23 September 1916 in one of the J 2s, and this event, combined with the substandard climbing performance of the J 2 series of test aircraft, caused IdFlieg to withdraw any further governmental support (effectively ending the J 2's contract) for the Junkers firm's advanced monoplane designs until a lighter metal, such as duralumin, was selected for such designs. The first attempt to use duralumin for airframe construction by the Junkers firm was the never-completed J 3 mid-wing, rotary engine
-powered, aluminum tubing fuselage single-seat monoplane design, of which only the corrugated sheet duralumin-covered wing structures and "bare" tubular fuselage framing, primarily as an engineering exercise, were finished shortly before the end of 1916.
It is also thought that the contrasting promise of the advanced, low drag features of the Junkers monoplane aircraft designs, versus the Junkers firm's usage of experimental non-traditional sheet metal materials, and the firm's habit of almost constant experimentation obstructing any future hope of producing its advanced designs for the Luftstreitkräfte, compelled IdFlieg to create the Junkers-Fokker Aktiengesellschaft, abbreviated as Jfa and pronounced as if spelled "iefa" in German, on 20 October 1917, to allow Anthony Fokker
, who even flew one of the J 2 aircraft in tests late in December 1916, to improve the future producibility of the advanced designs of the Junkers firm.
Junkers
Junkers Flugzeug- und Motorenwerke AG , more commonly Junkers, was a major German aircraft manufacturer. It produced some of the world's most innovative and best-known airplanes over the course of its fifty-plus year history in Dessau, Germany. It was founded there in 1895 by Hugo Junkers,...
J 2 was the first all-metal aircraft intended as a dedicated military aircraft design, the first all-metal aircraft meant to be a fighter aircraft
Fighter aircraft
A fighter aircraft is a military aircraft designed primarily for air-to-air combat with other aircraft, as opposed to a bomber, which is designed primarily to attack ground targets...
, and was the direct descendant of the pioneering J 1
Junkers J 1
The Junkers J 1, nicknamed the Blechesel , was the world's first practical all-metal aircraft. Built early in World War I, when aircraft designers relied largely on fabric-covered wooden structures, the Junkers J 1 was a revolutionary development in aircraft design, being built and flown only 12...
all-metal aircraft technology demonstrator design of 1915.
Development
Only some two weeks after the last known recorded flight, on 18 January 1916, of the J 1 "technology demonstrator" design of 1915, the Junkers firm had impressed one Hauptmann Felix Wagenführ, head of IdFliegIdflieg
The Idflieg was the bureau of the German War Office that oversaw German military aviation prior to and during World War I....
s influential Prüfanstalt und Werft der Fliegertruppe ("Test Establishment and Workshop of the Aviation Troops") department, abbreviated "PuW", enough for Hauptmann Wagenführ to submit a contract to the Junkers firm for six all-metal monoplane
Monoplane
A monoplane is a fixed-wing aircraft with one main set of wing surfaces, in contrast to a biplane or triplane. Since the late 1930s it has been the most common form for a fixed wing aircraft.-Types of monoplane:...
s, meant to be fighter prototype
Prototype
A prototype is an early sample or model built to test a concept or process or to act as a thing to be replicated or learned from.The word prototype derives from the Greek πρωτότυπον , "primitive form", neutral of πρωτότυπος , "original, primitive", from πρῶτος , "first" and τύπος ,...
s, with each to be powered with the Mercedes D.II inline engine
Inline engine (aviation)
In aviation, an inline engine means any reciprocating engine with banks rather than rows of cylinders, including straight engines, flat engines, V engines and H engines, but excluding radial engines and rotary engines....
(as the J 1 had been), armed with one 7.92 mm (.312 in) Spandau lMG 08/15 synchronized machine gun
Machine gun
A machine gun is a fully automatic mounted or portable firearm, usually designed to fire rounds in quick succession from an ammunition belt or large-capacity magazine, typically at a rate of several hundred rounds per minute....
, and bearing IdFlieg serial numbers E.250/16 to E.255/16. The desired specifications were for an aircraft that had:
- a top speed of 145 km/h (90 mph)
- a flight duration of 90 minutes
- a climb rate to 3,000 m (9,840 ft) altitude within 20 minutes.
The IdFlieg contract for the ordered aircraft also specified that "the greatest maneuverability and nimbleness in flight must be achieved by the aircraft", a possible concern by the German governmental agency, over the usage of the heavy electrical steel
Electrical steel
Electrical steel, also called lamination steel, silicon electrical steel, silicon steel, relay steel or transformer steel, is specialty steel tailored to produce certain magnetic properties, such as a small hysteresis area and high permeability.The material is usually manufactured in the form of...
sheet metal that made up the earlier J 1's structure. Herr Junkers began wind tunnel
Wind tunnel
A wind tunnel is a research tool used in aerodynamic research to study the effects of air moving past solid objects.-Theory of operation:Wind tunnels were first proposed as a means of studying vehicles in free flight...
and design work promptly upon receipt of the contract paperwork, and eventually, by the end of the spring of 1916, an aircraft emerged from Junkers' Dessau
Dessau
Dessau is a town in Germany on the junction of the rivers Mulde and Elbe, in the Bundesland of Saxony-Anhalt. Since 1 July 2007, it is part of the merged town Dessau-Roßlau. Population of Dessau proper: 77,973 .-Geography:...
workshops that was much more streamlined in appearance than the J 1 had been.
Advanced design features
The J 2 airframeAirframe
The airframe of an aircraft is its mechanical structure. It is typically considered to include fuselage, wings and undercarriage and exclude the propulsion system...
that emerged from the Dessau workshops had an evolved appearance from the J 1, as the fuselage
Fuselage
The fuselage is an aircraft's main body section that holds crew and passengers or cargo. In single-engine aircraft it will usually contain an engine, although in some amphibious aircraft the single engine is mounted on a pylon attached to the fuselage which in turn is used as a floating hull...
nose now almost completely enclosed the Mercedes D.II engine, except for the open top of the cowling
Cowling
A cowling is the covering of a vehicle's engine, most often found on automobiles and aircraft.A cowling may be used:* for drag reduction* for engine cooling by directing airflow* as an air intake for jet engines* for decorative purposes...
. The J 2's fuselage structure had rounded dorsal and ventral contours, instead of the boxlike right angles of the J 1, possessed a narrower and deeper ventral "belly" radiator
Radiator (engine cooling)
Radiators are used for cooling internal combustion engines, mainly in automobiles but also in piston-engined aircraft, railway locomotives, motorcycles, stationary generating plant or any similar use of such an engine....
enclosure, and used a horizontal stabilizer
Tailplane
A tailplane, also known as horizontal stabilizer , is a small lifting surface located on the tail behind the main lifting surfaces of a fixed-wing aircraft as well as other non-fixed wing aircraft such as helicopters and gyroplanes...
planform shape that would become familiar on later, all-duralumin
Duralumin
Duralumin is the trade name of one of the earliest types of age-hardenable aluminium alloys. The main alloying constituents are copper, manganese, and magnesium. A commonly used modern equivalent of this alloy type is AA2024, which contains 4.4% copper, 1.5% magnesium, 0.6% manganese and 93.5%...
Junkers monoplane designs to be built during 1917-18. The "all-moving" rudder
Rudder
A rudder is a device used to steer a ship, boat, submarine, hovercraft, aircraft or other conveyance that moves through a medium . On an aircraft the rudder is used primarily to counter adverse yaw and p-factor and is not the primary control used to turn the airplane...
still possessed no fixed fin
Vertical stabilizer
The vertical stabilizers, vertical stabilisers, or fins, of aircraft, missiles or bombs are typically found on the aft end of the fuselage or body, and are intended to reduce aerodynamic side slip. It is analogical to a skeg on boats and ships.On aircraft, vertical stabilizers generally point upwards...
, like the J 1. A faired-in headrest
Headrest
In an automobile, head restraints are attached or integrated into the top of the seats in each seating position to limit the rearward movement of an adult occupant's head relative to his torso in a crash, so as to reduce the danger of whiplash or other injury to the cervical vertebrae...
was provided for, as well as a "roll bar" placed above the headrest for additional pilot protection in case of the aircraft flipping on its back during a crash landing. The J 2's landing gear
Undercarriage
The undercarriage or landing gear in aviation, is the structure that supports an aircraft on the ground and allows it to taxi, takeoff and land...
was of the usual vee-type, but a bit taller than the J 1's had been, with the upper ends of the legs anchoring not onto the fuselage "corners" as on the J 1, but on the first wing rib
Rib (aircraft)
In an aircraft, ribs are forming elements of the structure of a wing, especially in traditional construction.By analogy with the anatomical definition of "rib", the ribs attach to the main spar, and by being repeated at frequent intervals, form a skeletal shape for the wing...
"bay" beyond the wing root
Wing root
The wing root is the part of the wing on a fixed-wing aircraft that is closest to the fuselage. On a simple monoplane configuration, this is usually easy to identify...
, with a long tailskid that emerged from the lower rear fuselage directly below the stabilizer's leading edge
Leading edge
The leading edge is the part of the wing that first contacts the air; alternatively it is the foremost edge of an airfoil section. The first is an aerodynamic definition, the second a structural one....
root location. The wings had at least three different airfoil changes running from root-to-tip, and had sections of them electrically roll-welded for stronger, more continuous bonding for greater strength. The resulting aircraft was intended to be smaller than the J 1 demonstrator, but with its steel structure, it almost equalled the J 1's completed weight.
One feature pioneered in the J 2, that would also be used in later all-metal monoplanes designed and built by Junkers in World War I, was a "unitized" forward fuselage structural concept, combining the framing of the engine mount, wing roots and cockpit framing into one central integral structure.
Operational history
The first production example of the J.2, with IdFlieg serial number E.250/16, was delivered to Adlershof (near Berlin, the home of Germany's first airfieldJohannisthal Air Field
The Johannisthal Air Field, located 15 km southeast of Berlin, between Johannisthal and Adlershof, was Germany's first airfield. It opened on 26 September 1909, a few weeks after the world's first airfield at Rheims, France .-Overview:...
) on 2 July 1916, and started its IdFlieg-mandated static load testing. Otto Mader, one of the J 2's designers, then promised the IdFlieg agency that the following example, serialled E.251/16, would have even greater structural strength than the E.250's airframe possessed. Leutnant Theodor Mallinckrodt, the pilot that had first "hopped" the earlier J 1 some seven months previously, took the E.251/16 example up for the J 2 design's maiden flight on 11 July 1916. Mallinckrodt gave the E.251 example that he flew a good overall evaluation, judging it as "very maneuverable", with good turning qualities and safe aerodynamic behavior. A short time later, IdFlieg test pilots Unteroffizier
Unteroffizier
Unteroffizier is both a specific military rank as well as a collective term for non-commissioned officers of the German military that has existed since the 19th century. The rank existed as a title as early as the 17th century with the first widespread usage occurring in the Bavarian Army of the...
s Wendeler, and Max Schade, began "wringing out" the six examples of the J 2 as they arrived at Adlershof for their full range of flight evaluation tests.
Unteroffizier Schade would eventually take one of the test aircraft on a flight from Berlin (most likely from the government's Adlershof/Johannisthal facility) to Dessau later in the summer of 1916, achieving the then-high speed of 180 km/h (112 mph) with the aircraft, which was some 16 km/h (10 mph) faster than the contemporary French Nieuport 11
Nieuport 11
|-See also:-References:NotesBibliography* Angelucci, Enzio, ed. The Rand McNally Encyclopedia of Military Aircraft. New York: The Military Press, 1983. ISBN 0-517-41021-4....
, but as the J 2 test aircraft still seemed to come up short in climbing performance tests, when evaluated against wood structure designs, like the then brand-new, Robert Thelen-designed Albatros D.I
Albatros D.I
|-See also:...
aircraft, the steel structure of the J 2 made it just too heavy to be able to compete in air combat over the Front.
At least one example (E.253/16) of the J 2 was fitted with slightly longer wings and matching longer ailerons, possibly in an effort to decrease the wing loading of the initial J 2 design, and another tested "upgrade" to the J 2s under test was to fit at least one of the aircraft with the then-new 119 kW (160 hp) Mercedes D.III
Mercedes D.III
The Mercedes D.III, or F1466 as it was known internally, was a six-cylinder, liquid cooled inline aircraft engine built by Daimler and used on a wide variety of German aircraft during World War I. The initial versions were introduced in 1914 at 160 hp, but a series of changes improved this to...
engine, and one of the J 2s so equipped achieved an amazing-for-the-time 200 km/h (124 mph) at full throttle in testing.
Shortcomings of an "iron aircraft"
Despite the attempts to improve the J 2's performance and handling, by late in the summer of 1916 Hugo Junkers had come to the realization that the continued use of sheet electrical steel was no longer practical for aircraft construction, writing in his diary that:"As a result of the first (J 1) and second (J 2) aircraft, one would ascertain that the aerodynamic efficiency was very good. We thought we [the Junkers designers] were over the hill. This, unfortunately, was not the case. We had to start again from the very beginning. The reason was that in spite of the favorable horizontal speed, the aircraft could not meet the military climb specifications...we had to develop an aircraft that not only had low drag for ease of maneuver in the horizontal plane, but that could climb well-an aircraft with a low weight to power ratio...
...This could not be achieved with iron, and we had to choose a new material...light-weight metal. But not only the choice of iron had resulted in high weight. We had built too heavy because we wanted a safe aircraft and partially because we had not extracted the optimum structural strength from the material".
Unteroffizier Schade, after making the record Berlin-Dessau flight, would later lose his life in a crash, from entering a spin on 23 September 1916 in one of the J 2s, and this event, combined with the substandard climbing performance of the J 2 series of test aircraft, caused IdFlieg to withdraw any further governmental support (effectively ending the J 2's contract) for the Junkers firm's advanced monoplane designs until a lighter metal, such as duralumin, was selected for such designs. The first attempt to use duralumin for airframe construction by the Junkers firm was the never-completed J 3 mid-wing, rotary engine
Rotary engine
The rotary engine was an early type of internal-combustion engine, usually designed with an odd number of cylinders per row in a radial configuration, in which the crankshaft remained stationary and the entire cylinder block rotated around it...
-powered, aluminum tubing fuselage single-seat monoplane design, of which only the corrugated sheet duralumin-covered wing structures and "bare" tubular fuselage framing, primarily as an engineering exercise, were finished shortly before the end of 1916.
It is also thought that the contrasting promise of the advanced, low drag features of the Junkers monoplane aircraft designs, versus the Junkers firm's usage of experimental non-traditional sheet metal materials, and the firm's habit of almost constant experimentation obstructing any future hope of producing its advanced designs for the Luftstreitkräfte, compelled IdFlieg to create the Junkers-Fokker Aktiengesellschaft, abbreviated as Jfa and pronounced as if spelled "iefa" in German, on 20 October 1917, to allow Anthony Fokker
Anthony Fokker
Anton Herman Gerard "Anthony" Fokker was a Dutch aviation pioneer and an aircraft manufacturer. He is most famous for the fighter aircraft he produced in Germany during the First World War such as the Eindecker monoplanes, the Fokker Triplane the and the Fokker D.VII, but after the collapse of...
, who even flew one of the J 2 aircraft in tests late in December 1916, to improve the future producibility of the advanced designs of the Junkers firm.
