In late 1916 Idflieg (the German Inspectorate of Aviation Troops) issued the J type design specification for an armoured ground attack and army liaison aircraft. Junkers responded with one of the most revolutionary aircraft of World War One, the Junkers J.1.
Junkers were a pioneer in the construction of metal aircraft with their steel monoplane (confusingly also called the J.1) being completed in 1915. This was followed by an improved version called the J.2 and finally the J.3 made from the much lighter duraluminium (aluminium). This material was the natural choice for use in Hugo Junkers’ revolutionary J.4 designed to meet Idflieg’s J type specifications. This J.4, as Junkers referred to it, was confusingly designated the J.1 in service by Idflieg.
The Junkers J.1 (J.4) airframe was constructed entirely of duraluminium (dural) tubes almost completely sheathed in corrugated dural sheet. The front fuselage was constructed from 5mm armoured steel to protect the crew from enemy fire. Initially the rear fuselage, fin and rudder were covered with fabric but later production aircraft had the fin and rudder sheathed in corrugated sheet dural. Development was continued post armistice when even the rear fuselage was covered with corrugated sheet dural. This fully corrugated aircraft design would remain a Junkers feature well into the 1930s.
Nicknamed ‘the flying tank’ or ‘removal van’, the Junkers J.1 was the A-10 Thunderbolt of its day, designed to attack enemy ground targets while remaining impervious to ground fire. Despite being heavy, relatively slow and requiring a long take off and landing area, the J.1 was popular with its crews due to the protection provided by its armoured front section and all metal airframe.