Junkers J.I

The Junkers J.I was a German sesquiplane format warplane of World War I, developed for low-level observation and ground attack. It is especially noteworthy as being the first all-metal aircraft to enter mass production. It was a slow aircraft, but its metal construction and heavy armour, which comprised an extremely advanced, single-unit armored structure that ran from just behind the propeller, to the rear crew position, and acted both as the main fuselage structure and engine mounting setup in one unit, was an effective shield against anti-aircraft defensive fire.

Junkers J.I
Class Aircraft
Type Attack
Manufacturer Junkers
Origin Germany
Country Name Origin Year
Germany 1917
Country Name Operational Year Retirement Year
Germany 1917 View
ManufacturerName Production From Production To Quantity
Junkers 227 View

In an extremely advanced design, a single-unit steel "bathtub" that ran from just behind the propeller to the rear crew position acted not only as armour, but also as both the main fuselage structure and engine mounting in one unit, engine access being provided by twin vertically-hinged, aft-swinging triple-piece armor-steel panels, one on either side of the nose. The armour was 5 millimetres (0.20 in) thick and weighed 470 kilograms (1,040 lb). It protected the crew, the engine, the fuel tanks, and radio equipment (when fitted). The flight control surfaces were connected to the aircraft's controls by push–rods and bellcranks — not with the usual steel cable control connections of the era — as push-rods were less likely to be severed by ground fire.

There was a significant size difference between the upper and lower wings - the upper wing had a total area of 386.3 square feet (35.89 m2), over double the total area of the lower wing - 147.2 square feet (13.68 m2). This is a form of biplane known as a Sesquiplane.

The aircraft had two fuel tanks with a total capacity of around 120 litres (32 US gal). The main tank (divided into two parts for redundancy) was supplemented by a smaller, 30-litre (7.9 US gal) "gravity tank". This was intended to supply fuel to the engine by Gravity feed in the event of an engine fuel pump failure; it contained enough fuel for thirty minutes on full power. There was a manual fuel pump for use when the gravity tank became exhausted.

The aircraft could be disassembled into its main components: wings, fuselage, undercarriage, and tail, to make it easier to transport by rail or road. A ground crew of six to eight could re–assemble the aircraft and have it ready for flight within four to six hours. The wings were covered with 0.19 millimetres (0.0075 in) thick aluminum skin which could be easily dented so great care had to be taken when handling the aircraft on the ground.

The J.I was well liked by its crews, although its ponderous handling earned it the nickname "furniture van". The aircraft first entered front service in August 1917. They were used on the Western Front during the German Spring Offensive of 1918.

The aircraft could be fitted with two downward firing machine guns for ground attack, but they were found to be of limited use because of the difficulty of aiming them. The J-Is were mainly used for army co–operation and low–level reconnaissance. They were also used for dropping ammunition and rations on isolated or cut–off outposts that could not be easily re-supplied by other means.

The production at Junkers works was quite slow, because of poor organization. Only 227 J.Is were manufactured before production ceased in January 1919 (production continued until just after the end of the war). At least one was lost to ground fire - shot down by a French anti-aircraft machine gun that was firing Armour-piercing rounds. Although this was apparently an isolated event as some sources state, none were lost in combat. A few were lost in landing accidents, and other mishaps.

Role Observation and liaison aircraft
Manufacturer Junkers
Designer Otto Mader
First flight 28 January 1917
Introduction 1917
Retired 1918
Primary user Luftstreitkräfte
Number built 227

General characteristics

  • Crew: Two, pilot and observer
  • Length: 9.1 m (29 ft 10 in)
  • Wingspan: 16.00 m (52 ft 6 in)
  • Height: 3.4 m (11 ft 2 in)
  • Wing area: 49.4 m (531 ft)
  • Empty weight: 1,766 kg (3,893 lb)
  • Gross weight: 2,140 kg (4,718 lb)
  • Powerplant: 1 x Benz Bz.IV, 149 kW (200 hp)


  • Maximum speed: 155 km/h (97 mph)
  • Range: 310 km (193 miles)
  • Service ceiling: 4,000 m (13,120 ft)


  • 2 x fixed, forward-firing 7.92 mm LMG 08/15 machine guns
  • 1 x trainable, rearward-firing 7.92 mm Parabellum MG14 machine gun

End notes