In late 1916, the demand for a durable observation aircraft capable of performing ground attack missions led to the introduction of the Junkers J.I. Developed in early 1917, it was the world's first all-metal aircraft produced in quantity. Eliminating the need for external bracing wires, the fuselage, wings and tail were constructed of Duralumin while the engine and two-man crew were protected by a nose-capsule of 5-mm chrome-nickel sheet-steel. Although this unique design resulted in a strong and durable aircraft capable of surviving the effects of enemy ground fire, the Junkers J.I was heavy, cumbersome and took forever to get off the ground.
The Junkers CL.I was a ground-attack monoplaine aircraft developed in Germany during World War I. Its construction was undertaken by Junkers under the designation J 8. as proof of Hugo Junkers' belief in the monoplane, after his firm had been required by the Idflieg to submit a biplane (the J 4) as its entry in a competition to select a ground-attack aircraft.
The J 8 design took the J 7 fighter as its starting point, but had a longer fuselage to accommodate a tail gunner, and larger wings. The prototype flew in late 1917 and was followed over the next few months by three more development aircraft.
The Idflieg was sufficiently impressed to want to order the type, but had misgivings about Junkers' ability to manufacture the aircraft in quantity and considered asking Linke-Hoffmann to produce the type under licence. Finally, however, Junkers was allowed to undertake the manufacture as part of a joint venture with Fokker, producing a slightly modified version of the J 8 design as the J 10. Like the other Junkers designs of the period, the aircraft featured a metal framework that was skinned with corrugated duralumin sheets. 47 examples were delivered before the Armistice, including three built as floatplanes under the designation CLS.I (factory designation J 11). After the war, one or two CL.Is were converted for commercial service by enclosing the rear cockpit under a canopy.
The Junkers D.I (factory designation J 9) was a fighter aircraft produced in Germany late in World War I, significant for becoming the first all-metal fighter to enter service.
What really set the Junker D.I apart from any previous aircraft
was it's cantilevered low-wing design and corrugated duralumin skin.
Duralumin, the same metal used for Zeppelin construction, was light yet
strong. The Junkers monoplane was rugid, fast, and agile. The D.I was
every fighter pilots' dream. The design was a decade ahead of its time
appearing a year too late.
The prototype, a private venture by Junkers designated the J 7, first flew on 17 September 1917. Demonstrated to the Idflieg early the following year, it proved impressive enough to result in an order for three additional aircraft for trials. However, the changes made by Junkers were significant enough for the firm to redesignate the next example the J 9, which was supplied to the Idflieg instead of the three J 7s ordered.
During tests, the J 9 was felt to lack the maneuverability necessary
for a front-line fighter, but was judged fit for a naval fighter, and a
batch of 12 was ordered. These were to have been supplied to a naval
unit by September 1918, but instead equipped the same unit redeployed to
the Eastern Front after the Armistice. One survives in a French Museum.