Ju 188A & E
The Ju 188 was designed to be fitted with either the 1,750 PS (1,290 kW, 1,730 hp) Jumo 213A or 1,700 PS (1,250 kW, 1,680 hp) BMW 801 G-2 engines without any changes to the airframe. It was originally intended that both would be known as A models, but the naming was later changed: the Ju 188A model powered by the 213, and the Ju 188E by the 801.

The first three production Ju 188 E-1 machines were delivered with the BMW engines in February 1943, another seven in March, and eight in April. A conversion testing unit was formed up in May, and after testing were attached to an operational unit, with the first mission, an attack by three Ju 188E-1s on a factory in Lincoln, Lincolnshire taking place on 18 August 1943. By the end of the year, 283 Ju 188s had been delivered (including Ju 188Fs), and two new factories were added to the production effort. Most operational machines differed from the prototypes only in having a 20 mm MG 151/20 cannon in the nose and dorsal turrets in place of the 13 mm (.51 in) MG 131. The MG 131 I was intended to be used in the Ju 188 E-1 or the G-2. But the heavy armament in the A and E series was the MG 151/20. The Ju 188 E-2 was built as a torpedo-bomber, but was identical to the Ju 188 A-3.

A Ju 188A-3 of Kampfgeschwader 6 being loaded with bombs. Western Europe, 1944
(Source: Bundeszrchiv)

Ju 188C
It was planned all along to skip over a "B model" to avoid confusion with the original Ju 88 B, but in the original planning the A and E models would both be called A's. The Ju 188 C would thus be the next model in line.

Junkers Ju 188C
(Source: unknown)

The C series was built to the extent of a single example, by modifying one of the few A-1 machines. To this, they added the new power-operated FA 15 turret in the tail. The turret mounted two 13 mm MG 131s, aimed with a double-periscope (top and bottom) system mounted in the cockpit.

This modification would have greatly improved defensive firepower, always lacking on German designs, but reliability was so poor it was decided to abandon the system.

Ju 188D & F
In early 1944, it was decided to focus on reconnaissance versions of the A and E models The airframe was modified with the removal of the bomb aimer and the forward gun, and additional fuel cells were added to extend the range to 3,400 km (2,110 mi). The Ju 188 D-1 was otherwise similar to the A-1, and the Ju 188 D-2 fitted nose radar for naval reconnaissance. Similar conversions of the E models were the Ju 188 F-1 and Ju 188 F-2.

Junkers Ju 188D-2
(Source: unknown)

Ju 188G & H
One problem with the Ju 88 that carried into the 188 was the lack of internal room for bomb storage. Both carried the majority of their bombload on the outside of the plane on racks under the wing, where it greatly affected performance. This was to have been addressed in the G and H models, which extended the fuselage downward for more room with the addition of a wooden pannier.

Junkers Ju 188G-0
(Source: unknown)

This modification also left enough room at the tail to fit a manned turret in place of the C model's remote-control one. However this system proved to be just as limited as the remote-control FA 15, being so small that only gunners could fit into it, and had basically no ability to escape in an emergency. The RLM rejected the manned design and planned on mounting the FA 15 even if it were unreliable. Oddly, the designs still had the nose area extended under the plane for a rear gunner, when this would no longer be needed and its removal would have greatly cleaned up the lines of the plane.

With the Jumo 213s now being sent to fighter production, the Ju 188 G-2 was to use the BMW 801 only, with the reconnaissance conversion known as the Ju 188 H-2. Neither entered production before the war ended.

Ju 188R
In the summer of 1944, three E models were modified as night fighters with the addition of radar and either four 20 mm MG 151/20s or two 30 mm (1.18 in) MK 103 cannons in the nose. However, the added visibility of the 188 was not useful in the night role, and because the added drag of the radar washed out any speed difference, the Ju 188 R-0 was not ordered.

High-altitude versions
High-altitude versions In 1943, it was planned to upgrade the entire lineup with even more wing area and a pressurized cockpit for high-altitude work. A single basic airframe would be offered in three versions, the Ju 188J heavy fighter, Ju 188K bomber, and the Ju 188L reconnaissance version. All three did away with the under-slung gunner's compartment, leading to a cleaner nose profile, and the bomber and recce versions mounted their loads in a long pannier under the middle of the plane instead of the deeper fuselage of the G and H models.

Simpler versions of these with no defensive armament and even longer wings became the Ju 188S fighter and Ju 188T intruder. With Jumo 213E-1 engines 2,050 PS (1,510 kW, 2,020 hp) at take-off and 1,690 PS (1,240 kW, 1,670 hp) at 9,500 m (31,400 ft), the Ju 188T could reach 700 kph (440 mph). Operating at this altitude, the Ju 188S could carry only 800 kg (1,760 lb) of bombs.

Before any of these could start production, the entire lineup was renamed the Ju 388, the vastly improved performance warranting this change in name.

Gunston, Bill & Wood, Tony - Hitler's Luftwaffe , 1977, Salamander Books Ltd., London
Wikipedia - Ju 188