Flightline: 188 - Junkers Ju 188
Developed from the Ju 88, the 188 was produced in too few numbers to affect the outcome of WWII.
As Nazi Germany began its semi-clandestine rearmament campaign in the 1930s, the Luftwaffe developed the Schnellbomber doctrine, calling for bombers that traded defensive guns for speed. Junkers Flugzeug- und Motorenwerke AG ("Junkers Aircraft and Motor Works") responded with their Ju 88 twin engine design, which served throughout WWII as a schnellbomber, dive bomber, torpedo bomber, night fighter and heavy fighter, with more than 15,000 examples produced.
A Ju 88 of 2nd Squadron, Bomber Wing 28, in flight. | Photo: German Federal Archives
In July of 1939 the Reichsluftfahrtministerium (RLM, "Ministry of Aviation") issued specifications for the 'Bomber B', which would fly faster and higher than the Ju 88 while carrying a higher bomb load. A maximum speed of 600kmh was called for, along with a bomb load of 4,000kg and the range needed to reach any part of England from bases in France or Norway. The specification also called for a pressurized cockpit and remotely controlled defensive turrets. Junkers submitted their Ju 288 design, which was derived from the Ju 88, which would be powered by the Junkers Jumo 222 multi-bank engine. Issues with the engine and landing gear delayed the 288 however, and Junkers proposed a modified Ju 88 as a stop-gap aircraft until the problems were ironed out.
Design & Variants
Orthograph of the Ju 188 | Illustration: Kaboldy
What became the Ju 188 was first proposed as the Ju 88B, a variant rejected for being both too radical and unimpressive. The Ju 88B would have altered the original stepped cockpit, replacing it with an egg-shaped design composed of 36 curved panes in a greenhouse frame, which was smoothly fared into the ventral Bola defensive unit. This new nose and cockpit reduced the drag of the Ju 88B, making it marginally faster than other variants while at the same time improving crew visibility. The RLM considered the Ju 88B's gains were outweighed by the difficulty in production, and declined to procure the aircraft. When the Jumo 222 ran into trouble, delaying the Ju 288 and Fw 191 'Bomber B' programs, and with existing schnellbombers falling to improved RAF, USAAF and VVF fighter designs, Junkers resubmitted the Ju 88B, now designated the Ju 188.
The 188 was based on the Ju 88 A-1, adding in the 88B's cockpit design. The squared-off wingtips were now longer and pointed, which also reduced drag and improved performance. Junkers intended powerplant was their Jumo 213, which had reached the bench-test phase and was expected to develop 1,100kW (1,500hp), but the RLM stipulated that the design accept the BMW 801 engine in a Kraftei ("power-egg") unitized installation. The Kraftei, used on other twin- and multi-engine German aircraft, consisted of either a radial or inline piston engine, complete with all of the ancillary equipment, typically already enclosed in a cowling and equipped with quick-change attachment points and connectors for electrical, coolant and fuel lines. This allowed crews to swiftly remove and replace engines for maintenance as well as simplifying construction.
Two prototype Ju 188s were converted from existing Ju 88s, one Ju 88 E-O was modified with the projected defensive fit, two 13mm MG 131 and two 7.92mm MG 81Z in the Bola gondola, and the second, modified from a Ju 88 A-4, was designated the Ju 188 V1 and featured the larger tail fin that would be standard on later model Ju 88s and the Ju 188. A second V1 was completed in January 1943, this aircraft had the external bomb shackles moved inboard of the engines for improved handling and performance. Both V1s began test flights for the dive-bombing system, also installed in the Ju 88 A-4, in February.
The 188 was 14.948m long, with a wingspan of 22m and a height of 4.45m. Empty weight was 9,900kg, max TO load was 15,300kg with 3,000kg of bombs internally or two 1,000 external loads. Maximum speed was 499kmh at 6,000m altitude, while cruise speed was 375kmh at 5,000m. Service ceiling with a 2,000kg load was 9,300m.
The initial production A model was designed to use either the BMW 801 or Jumo 213, but in practice the Jumo-powered aircraft were designated 188A while those with 801s were known as the 188E. Similarly, delays in the 213 project caused A models to be delivered after their E model compatriots, and at a slower rate of production. Both the A and E models were identical to the V1 except in having the MG 131s replaced by heavier hitting MG151/20s. The first three Ju 188 E-1 were delivered in February 1943, with another seven the following month and eight more the month after that. A training and conversion group was formed in May, with the first operational mission, an attack on a factory in Lincolnshire, was carried out by three 188Es on 18 August 1943. Deliveries of the A model picked up towards the end of 1943. Beginning in 1944 the 213 was available in a methanol-boosted version; aircraft fitted with this engine were designated the Ju 188 A-2.
A Ju 88 E in Wellenmuster ("wave pattern") camouflage and carrying air-drop cannisters. | Photo: German Federal Archives
A separate torpedo bomber variant of both the A and E models was produced, with the 213 powered version designated the A-3 and the 801 powered models known as E-2s. Otherwise identical, the torpedo bomber versions mounted a low-UHF-band FuG 200 Hohentwiel sea-search radar under the nose and was refitted with shackles for air-dropped torpedoes. By the time production of the A and E models concluded in 1944, approximately 500 examples were completed.
A Ju 188 A-3, armed with two torpedoes, prepares for a mission. | Photo: German Federal Archives
Junkers intentionally skipped the B designator to avoid confusion with the Ju 88B, so the next model planned was the Ju 188C, which was to have a remotely-operated turret in the tail, designated the FA 15, which would have had two 13mm MG 131 aimed by two periscopes, one dorsal and one ventral, mounted in the cockpit. While this would have increased the defensive firepower of the 188 line, poor reliability of the FA 15 saw the C model abandoned after one example.
It was decided in 1944 to concentrate production on a reconnaissance variant of the 188, which differed from the A and E models in the removal of bomb aiming equipment as well as the forward-firing gun. Cameras and additional fuel tanks were installed, bringing the range up to 3,400km. Four models were built, with the D-1 and F-1 being photo recon variants powered by the Jumo 213 and BMW 810 respectively, and a naval recon variant fitted with sea-scan radar, with the D-2 powered by the 213 and the F-2 powered by the 810.
Ju 188F-2 Rächer with two external 200 liter tanks. | Photo: German Federal Archives
One of the main issues with the 188 was a lack of internal space for weapons, which forced the planes to carry most of their bombs on underwing shackles, erasing whatever gains made over earlier planes. Junkers proposed solving this problem by making the fuselage taller, increasing the possible bomb and fuel load. This would also have added space for a manned turret in the tail, but this idea was rejected as only the smallest would have fit in the space provided. The RLM instead intended to use the FA 15 remote installation tested on the 188C, which, it was hoped, could be made more reliable. This enlarged 188 would have been produced in two versions, the G-2 bomber and H-2 recon model. The Jumo 213 production having been earmarked for fighters only by this time, the 188 G-2 and H-2 would have been fitted with BMW 801 engines. While construction of a few G model prototypes had started, allied bombing disrupted production to the point that none were completed.
In the summer of 1944 three E model aircraft were modified as prototypes for the 188 R night fighter. Armament was planned to be either four 20mm MG 151/20s or two 30mm MK 103 cannon. Trials found that the radar installation produced too much drag and the presence of better night fighters like the Uhu saw the 188 R cancelled.
A separate program was to add a pressurized cockpit and larger wing to the 188 line, producing the 188J heavy fighter, 188K bomber and 188L recon aircraft, while the even more extreme 188S and 188T intruder variants did away with defensive installations and added even longer wings, increasing the service altitude to a maximum of 9,500m and the top speed to 700kmh. The extensive changes needed saw the RLM redesignate this model as the Ju 388, but less than 100 K and L models were produced before Germany capitulated in 1945.
At least two Ju 188s, one each of the A-2 and A-3 models, were captured by the RAF and tested at the end of the war before being scrapped. Prior to the end of WW2, approximately 12 Ju 188 were ordered by the Vichy French government, these aircraft continued to serve in the French Air Force and Aviation Navale afterwards, but were retired in 1951. Of the roughly 1,200 Ju 188 of all marks built, none are known to survive.