Tuesday, 12 January 2016

The Story of Heinkel He111. Military variants. Part 3. German Dzib -Compiler-

Military variants

He 111 A - D

The initial reports from the test pilot, Gerhard Nitschke, were favourable. The He 111's flight performance and handling were impressive although it dropped its wing in the stall. As a result, the passenger variants had their wings reduced from 25 m (82 ft) to 23 m (75 ft). The military aircraft - V1, V3 and V5 - spanned just 22.6 m (74.1 ft). (17) The prototypes were equipped with 431 kW (578 hp) BMW VI 6.0 V12 in-line engines, succeeded by745 kW (999 hp) DB 600 engines. (17) The first prototypes were underpowered, as they were equipped with 431 kW (578 hp) BMW VI 6.0 V12 in-line engines. This was eventually increased to 745 kW (999 hp) with the fitting of the DB (Daimler-Benz) 600 engines into the V5, which became the prototype of the "B" series. (17)
A Chinese He 111A re-engined with Wright Cyclone radial engines.
Only 10 He 111 A-0 models based on the V3 were built, but they proved to be underpowered and were eventually sold to China. The type had been lengthened by 1.2 m (3.9 ft) due to the added 7.92 mm (.312 in) MG 15 machine gun in the nose. Another gun position was installed on top of the fuselage, and another in a ventral position as a "dustbin" exposed turret, which could retract. The bomb bay was divided into two compartments and could carry 680 kg (1,500 lb) of bombs. The problem with these additions was that the weight of the aircraft reached 8,200 kg (18,080 lb). The He 111's performance was seriously reduced; in particular, the BMW VI 6.0 Z engines were not now powerful enough. The increased length also altered the 111's aerodynamic strengths and reduced its excellent handling on takeoffs and landings. (22)
The crews found the aircraft difficult to fly, and its top speed was reduced significantly. Production was shut down after the pilot’s reports reached the Ministry of Aviation. However, a Chinese delegation was visiting Germany and they considered the He 111 A-0 fit for their needs and purchased seven machines. (22)
An He 111 Powerplant.
The first He 111B made its maiden flight in the autumn of 1936. The first production batch rolled off the production lines that summer, at Rostock. (22) Seven B-0 pre-production aircraft were built, bearing the Werknummern (Works numbers) 1431 to 1437. The B-0s were powered by DB 600C engines fitted with variable pitch airscrews. (22) The screws increased output by 149 kW (200 hp). The B-0 had a MG 15 machine gun installed in the nose. The B-0 could also carry 1,500 kg (3,310 lb) in their vertical cells. (22) The B-1 had some minor improvements. The installation of the revolving gun-mount in the nose and a flexible Ikaria turret under the fuselage.(23) After improvements, the RLM ordered 300 He 111 B-1s; the first were delivered in January 1937. In the B-2 variant, engines were upgraded to the supercharged 634 kW (850 hp) DB 600C, or in some cases, the 690 kW (925 hp) 600G. The B-2 began to roll off the production lines at Oranienburg in 1937. (24) The He111 B-3 was a modified trainer. Some 255 B-1s were ordered. (23)  However, the production orders were impossible to fulfill and only 28 B-1s were built. (23) Owing to the production of the new He 111E, only a handful of He 111 B-3s were produced. Due to insufficient capacity, Dornier, Arado and Junkers built the He 111B series at their plants in Wismar, Brandenburg and Dessau, respectively. (23) The B series compared favourably with the capacity of the A series.
A He 111E in Luftwaffe service, 1940. The early variants had a conventional, stepped cockpit
The bomb load increased to 1,500 kg (3,300 lb), while there was also an increase in maximum speed and altitude to 215 mph (344 km/h) and 22,000 ft (6,700 m) (10)(23)
In late 1937, the D-1 series entered production. However, the DB 600Ga engine with 781 kW (1,047 hp) planned for this variant was instead allocated to Messerschmitt Bf 109 and Bf 110 production lines. Heinkel then opted to use Junkers Jumo engines, and the He 111 V6 was tested with Jumo 210 G engines, but was judged underpowered. However, the improved 745 kW (999 hp) Jumo 211 A-1 powerplant prompted the cancellation of the D series altogether and concentration on the design of the E series.  (24)

He 111 E

The pre-production E-0 series were built in small numbers. Fitted with Jumo 211 A-1 engines loaded with retractable radiators andexhaust systems. The variant could carry 1,700 kg (3,748 lb) of bombs giving it a take off weight of 10.300 kg (22,707 lbs). The development team for the Jumo 211 A-1 engines managed to increase engine power to 930 hp (690 kW), subsequently the He 111 E-1s bomb load capacity increased to 2,000 kg (4,410 lb) and a top speed of 242 mph (390 km/h). (25)
The E-1 variant with Jumo 211A-1 engines was developed in 1937, the He 111 V6 being the first production variant. The E-1 had its original powerplant, the DB 600 replaced with the Jumo 210 Ga engines. (26) The more powerful Jumo 211 A-1 engines desired by the Ministry of Aviation were not yet ready for installation. Another trial aircraft, He 111 V10 (D-ALEQ) was to be fitted with two oil coolers necessary for the Jumo 211 A-1 installation. (26)
The E-1s came off the production line in February 1938, in time for a number of these aircraft to serve in the Condor Legion during the Spanish Civil War in March 1938. (27) The Luftwaffe believed that because the E variant could outrun enemy fighters in Spain, there was no need to upgrade the defensive weaponry – which would prove a mistake from the Battle of Britain onward. (26)
The fuselage bomb bay used four bomb racks, in later versions eight modular standard bomb racks designed to carry one SC 250 kg (550 lb) bomb or four SC 50 kg (110 lb) bombs each in nose up orientation (which resulted in the bombs doing a flip as they were dropped out of the aircraft). These modular standard bomb racks were a common feature on the first generation of Luftwaffe bombers, but it turned out that they limited the ordnance selection to bombs of only two sizes. These racks were abandoned in later designs.
He 111E of the Legion Condor. Note the early variants' conventional "stepped" cockpit.
The E-2 series was not produced, and was dropped in favour of producing the E-3. with only a few modifications, such as external bomb racks. (25) Its design features were distinguished by improved FuG radio systems. (27) The E-3 series was equipped with the Jumo 211 A-3 for the duration of the series which packed 1,100 hp (820 kW). (27)
The E-4 variant was fitted with external bomb racks also and the empty bomb bay space was filled with an 835 L (221 US gal) tank for aviation fuel and a further 115 L (30 US gal) oil tank. This increased the loaded weight but increased range to 1,800 km (1,130 mi). The modifications allowed the He 111 to perform both long- and short-range missions. (28) The E-4s eight internal vertically aligned bomb racks could each carry a 250 kg (550 lb). (29) The last E Variant, the He 111 E-5, was powered by the Jumo 211 A-3, and retained the 835 L (221 US gal) fuel tank on the port side of the bomb bay. Only a few of the E-4 and E-5 were built. (27)
The RLM had acquired an interest in rocket boosters fitted for the sake of simplicity below the wings of a heavily loaded bomber to cut down the length of runway needed for takeoff. Once in the air the booster canisters would be jettisoned by parachute for reuse. The firm of Hellmuth Walter, at Kiel, handled this development. (30) The first standing trials and tests flights of the Walter HWK 109-500 Starthilfe liquid-fueled boosters were held in 1937 at Neuhardenberg with test pilot Erich Warsitz at the controls of Heinkel He 111E bearing civil registration D-AMUE. (31)

He 111 F

The He 111 design quickly ran through a series of minor design revisions. One of the more obvious changes started with the He 111F models, which moved from the elliptical wing to one with straight leading and trailing edges, which could be manufactured more efficiently. (27) The dimensions of the new design had a wing span of 22.6m (74 ft 1¾in) and an area of 87.60m² (942.90 ft). (27)
Heinkel's industrial capacity was limited and production was delayed. Nevertheless, 24 machines of the F-1 series were exported to Turkey. (27) Another 20 of the F-2 variant were built. (32) The Turkish interest, prompted by the fact the tests of the next prototype, He 111 V8, was some way off, prompted the Ministry of Aviation to order 40 F-4s with Jumo 211 A-3 engines. These machines were built and entered service in early 1938. (24) This fleet was used as a transport group during the Demyansk Pocket and Battle of Stalingrad. (33) At this time, development began on the He 111J. It was powered by the DB 600 and was intended as a torpedo bomber. As a result, it lacked an internal bomb bay and carried two external torpedo racks. The Ministry of Aviation gave an order for the bomb bay to be retrofitted; this variant became known as the J-1. In all but the powerplant, it was identical to the F-4. (24)
The final variant of the F series was the F-5, with bombsight and powerplants identical to the E-5.[35] The F-5 was rejected as a production variant owing to the superior performance of the He 111 P-1. (32)

He 111 J

The He 111's low-level performance attracted the interest of Nazi Germany's Kriegsmarine. The result was the He 111J, was capable of carrying torpedoes and mines. However, the Navy eventually dropped the program as they deemed the four-man crew too expensive in terms of manpower. The RLM nevertheless continued production of the He 111 J-0. Some 90 (other sources claim 60 (34)) were built in 1938 and were then sent to Küstenfliegergruppe 806. (35) Powered by the DB 600Gshe engines, it could carry a 2,000 kg (4,410 lb) payload. But few of the pre-production J-0s were fitted with the DB 600G. Instead, the DB 600 was used, performance deteriorated and the torpedo bomber was not pursued. The J was used in training schools until 1944. (32) Some J-1s were used as test beds for Blohm & Voss L 10 radio-guided air-to-ground torpedo missiles. (36)

He 111 P

The He 111P incorporated the updated Daimler-Benz DB 601A-1 liquid-cooled engine and featured a newly designed nose section, including an asymmetric mounting for an MG 15 machine gun that replaced the 'stepped' cockpit with a roomier and more aerodynamic glazed stepless cockpit over the entire front of the aircraft. This smooth glazed nose was first tested on the He 111 V8 in January 1938. These improvements allowed the aircraft to reach 475 km/h (295 mph) at 5,000 m (16,400 ft) and a cruise speed of 370 km/h (230 mph), although a full bomb load reduced this figure to 300 km/h (190 mph). (24) The design was implemented in 1937 because pilot reports indicated problems with visibility. (24) The pilot's seat could actually be elevated, with the pilot's eyes above the level of the upper glazing, complete with a small pivoted windscreen panel, to get the pilot's head above the level of the top of the "glass tunnel" for a better forward view for takeoffs and landings. The rear-facing dorsal gun position, enclosed with a sliding, near-clear view canopy, and for the first time, the ventral Bodenlafette rear-facing gun position, immediately aft of the bomb bay, that replaced the draggy "dustbin" retractable emplacement became standard, having been first flown on the He 111 V23, bearing civil registration D-ACBH. (37)
Radio equipment mapping on the He 111 H6
One of Heinkel's rivals, Junkers, built 40 He 111Ps at Dessau. In October 1938, the Junkers Central Administration commented:
Apparent are the externally poor, less carefully designed components at various locations, especially at the junction between the empennage and the rear fuselage. All parts have an impression of being very weak.... The visible flexing in the wing must also be very high. The left and right powerplants are interchangeable. Each motor has an exhaust-gas heater on one side, but it is not connected to the fuselage since it is probable that ... the warm air in the fuselage is not free of carbon monoxide (CO). The fuselage is not subdivided into individual segments, but is attached over its entire length, after completion, to the wing centre section. Outboard of the powerplants, the wings are attached by universal joints. The latter can in no way be satisfactory and have been the cause of several failures. (38)
The new design was powered by the DB 601 Ba engine with 1,175 PS (24) The first production aircraft reached Luftwaffe units in Fall 1938. In May 1939, the P-1 and P-2 went into service with improved radio equipment. The P-1 variant was produced with two DB 601Aa powerplants of 1,150 hp (860 kW). It had self-sealing fuel tanks. (39) The P-1 featured a semi-retractable tail wheel to decrease drag. (39) Armament consisted of a MG 15 in the nose, and a sliding hood for the fuselage's dorsal B-Stand position. Installation of upgraded FuG III radio communication devices were also made and a new ESAC-250/III vertical bomb magazine was added. The overall takeoff weight was now 13,300 kg (29,321 lb). (40)
He 111P dropping bombs over Poland, September 1939
The P-2, like the later P-4, was given stronger armour and two MG 15 machine guns in "waist" mounts on either side of the fuselage and two external bomb racks.[27] Radio communications consisted of FuG IIIaU radios and the DB601 A-1 replaced the 601Aa powerplants. The Lotfernrohr 7 bombsights, which became the standard bombsight for German bombers, were also fitted to the P-2. The P-2 was also given "field equipment sets" to upgrade the weak defensive armament to four or five MG 15 machine guns. (40) The P-2 had its bomb capacity raised to 4 ESA-250/IX vertical magazines. (40) The P-2 thus had an empty weight of 6,202 kg (13,272 lb), a loaded weight increased to 12,570 kg (27,712 lb) and a maximum range of 2,100 km (1,305 mi). (40)
The P-3 was powered with the same DB601A-1 engines. The aircraft was also designed to take off with a land catapult (KL-12). A towing hook was added to the fuselage under the cockpit for the cable. Just eight examples were produced, all without bomb equipment. (39) The P-4 contained many changes from the P-2 and P-3. The jettisonable loads were capable of considerable variation. Two external SC 1800 kg (3,960 lb) bombs, two LMA air-dropped anti-shipping mines, one SC 1,800 kg plus four SC 250 kg; or one SC 2,500 kg external bomb could be carried on an ETC Rüstsatz rack. Depending on the load variation, an 835 L fuel and 120 L oil tank could be added in place of the internal bomb bay. The armament consisted of three defensive MG 15 machine guns. (39) later supplemented by a further three MG 15s and one MG 17 machine gun. The radio communications were standard FuG X(10), Peil G V direction finding and FuBI radio devices. Because of the increase in defensive firepower, the crew numbers increased from four to five. The empty weight of the P-4 increased to 6,775 kg (14,936 lb), and the full takeoff weight increased to 13,500 kg (29,762 lb) owing to the mentioned alterations. (39)
The P-5 was powered by the DB601A. The variant was mostly used as a trainer and at least twenty-four production variants were produced before production ceased. (32) The P-5 was fitted with meteorological equipment, and was used in Luftwaffe weather units. (39)
Many of the He 111 Ps served during the Polish Campaign. With the Junkers Ju 88 experiencing technical difficulties, the He 111 and the Do 17 formed the backbone of the Kampfwaffe. On 1 September 1939, Luftwaffe records indicate the Heinkel strength at 705 (along with 533 Dorniers). (41)
The P-6 variant was the last production model of the He 111 P series. In 1940, the Ministry of Aviation abandoned further production of the P series in favour of the H versions, mostly because the P-series' Daimler-Benz engines were needed for Messerschmitt Bf 109 and Bf 110 fighter production. The remaining P-6s were redesignated P-6/R2s and used as heavy glider tugs. (42) The most notable difference with previous variants was the upgraded DB 601N powerplants. (38)
The P-7 variant's history is unclear. The P-8 was said to have been similar to the H-5 fitted with dual controls. (38) The P-9 was produced as an export variant for the Hungarian Air Force. Due to the lack of DB 601E engines, the series was terminated in summer 1940. (38)

He 111H and its variants

A Heinkel He 111H bomber, which was abandoned by the Luftwaffe during the retreat after the Battle of El Alamein.
He 111 H-1 to H-10

The H variant of the He 111 series was more widely produced and saw more action during World War II than any other Heinkel variant. Owing to the uncertainty surrounding the delivery and availability of the DB 601 engines, Heinkel switched to b820 kW (1,100 hp) Junkers Jumo 211 powerplants, whose somewhat greater size and weight were regarded as unimportant considerations in a twin-engine design. When the Jumo was fitted to the P model it became the He 111 H.
The He 111 H-1 was fitted with a standard set of three 7.92 mm (.312 in) MG 15 machine guns and eight SC 250 250 kg (550 lb) or 32 SC 50 50 kg (110 lb) bombs. The same armament was used in the H-2 which started production in August 1939. (43) The P-series was gradually replaced on the eve of war with the new the H-2, powered by improved Jumo 211 A-3 engines of 820 kW (1,100 hp). (43)
 A count on 2 September 1939 revealed that the Luftwaffe had a total of 787 He 111s in service, with 705 combat ready, including 400 H-1 and H-2s that had been produced in a mere four months. (44) Production of the H-3, powered by the 895 kW (1,200 hp) Jumo 211 D-1, began in October 1939. Experiences during the Polish Campaign led to an increase in defensive armament. MG 17s were fitted whenever possible and the number of machine guns was increased to seven. The two waist positions received an additional MG 15 or 17, and on some variants a belt-fed MG 17 was even installed in the tail. (43)
He 111H on a torpedo training exercise, 10 October 1941
After the Battle of Britain, smaller scale production of the H-4s began. The H-4 was virtually identical to the He 111 P-4 with the DB 600s swapped for the Jumo 211D-1s. (45) This variant also differed from the H-3 in that it could either carry 2,000 kg (4,410 lb) of bombs internally or mount one or two external racks to carry one 1,800 kg (3,970 lb) or two 1,000 kg (2,210 lb) bombs. As these external racks blocked the internal bomb bay doors, a combination of internal and external storage was not possible. A PVR 1006L bomb rack was fitted externally and an 835 L (221 US gal) tank added. The PVR 1006L was capable of carrying a SC 1000 1,000 kg (2,210 lb) bomb. Some H-4s had their PVC racks modified to drop torpedoes. (45) Later modifications enabled the PVC 1006 to carry a 2,500 kg (5,510 lb) "Max" bomb. But 1,000 kg (2,200 lb) "Hermann" or 1,800 kg (3,970 lb) "Satans" were used more widely. (46)
The H-5 series followed in February 1941, with heavier defensive armament. (47) Like the H-4, it retained a PVC 1006 L bomb rack to enable it to carry heavy bombs under the fuselage. The first ten He 111 H-5s were pathfinders, and selected for special missions. The aircraft sometimes carried 25 kg flashlight bombs which acted as flares. The H-5 could also carry heavy fire bombs, either heavy containers or smaller incendiary devices attached to parachutes. The H-5 also carried LM A and LM B aerial mines for anti-shipping operations. After the 80th production aircraft, the PVC 1006 L bomb rack was removed and replaced with a heavy-duty ETC 2000 rack, enabling the H-5 to carry the SC 2500 "Max" bomb, on the external ETC 2000 rack, which enabled it to support the 5,000 lb (2,300 kg) bomb. (48)
Some H-3 and H-4s were equipped with barrage balloon cable-cutting equipment in the shape of cutter installations forward of the engines and cockpit. They were designated H-8, but later named H8/R2. These aircraft were difficult to fly and production stopped. The H-6 initiated some overall improvements in design. The Jumo 211 F-1 engine of 1,007 kW (1,350 hp) increased its speed while the defensive armament was upgraded with one 20 mm MG FF cannon in the nose position, one MG 15 in the ventral turret, and in each of the fuselage side windows (optional). Some H-6 variants carried tail-mounted MG 17 defensive armament. (49) The performance of the H-6 was much improved. The climb rate was higher and the machine could reach a slightly higher ceiling of 8,500 m (27,200 ft). When heavy bomb loads were added, this ceiling was reduced to 6,500 m (20,800 ft). The weight of the H-6 increased to 14,000 kg (30,600 lb). Some H-6s received Jumo 211F-2s which improved a low-level speed of 226 mph (365 km/h). At an altitude of 6,000 m (19,200 ft) the maximum speed was 270 mph (435 km/h). If heavy external loads were added, the speed was reduced by 21.75 mph (35 km/h) (50)
Other designs of the mid-H series included the He 111 H-7 and H-8. The airframes were to be rebuilds of the H-3/H-5 variant. Both were designed as night bombers and were to have two Jumo 211F-1s installed. The intention was for the H-8 to be fitted with cable-cutting equipment and barrage ballon deflectors on the leading edge of the wings. The H-7 was never built. (51)
The H-9 was intended as a trainer with dual control columns. The airframe was a H-1 variant rebuild. The powerplants consisted of two JumoA-1s or D-1s. (51) The H-10 was also designated to trainer duties. Rebuilt from an H-2 or H-3 airframe, it was installed with full defensive armament including 13 mm (.51 in) MG 131 and 7.92 mm (.312 in) MG 81Z machine guns. It was to be powered by two Jumo 211A-1s, D-1s or F-2s. (51)

 Later H variants, H-11 to H-20
A formation of He 111Hs, circa 1940

In the summer of 1942, the H-11, based on the H-3 was introduced. With the H-11, the Luftwaffe had at its disposal a powerful medium bomber with heavier armour and revised defensive armament. The drum-fed 7.92 mm (.312 in) MG 15 was replaced with a belt-fed 13 mm (.51 in) MG 131 in the now fully enclosed dorsal position (B-Stand); the gunner in the latter was now protected with armoured glass. The single MG 15 in the ventral C-Stand or Bola was also replaced, with a belt-fed 7.92 mm (.312 in) MG 81Z with much higher rate of fire. The beam positions originally retained the single MG 15s, but the H-11/R1 replaced these with twin MG 81Z as well; this latter arrangement was standardized in November 1942. The port internal ESAC bomb racks could be removed, and an 835 L (221 US gal) fuel tanks installed in its place. (52) Many H-11s were equipped with a new PVC rack under the fuselage, which carried five 250 kg (550 lb) bombs. Additional armour plating was fitted around crew spaces, some of it on the lower fuselage and could be jettisoned in an emergency. Engines were two 1,000 kW (1,340 hp) Junkers Jumo 211F-2, allowing this variant to carry a 2,000 kg (4,410 lb) payload to a range of 2,340 km (1,450 mi). Heinkel built 230 new aircraft of this type and converted 100 H-3s to H-11s by the summer of 1943. (52)
The third mass production model of the He 111H was the H-16, entering production in late 1942. Armament was as on the H-11, with some differences. The 20 mm MG FF cannon was deleted, as the H-16s were seldom employed on low-level missions, was replaced with a single MG 131 in a flexible installation in the nose (A-Stand). On some aircraft, designated He 111 H-16/R1, the dorsal position was replaced by a Drehlafette DL 131 electrically powered turret, armed with a single MG 131. The two beam and the aft ventral positions were provided with MG 81Zs, as on the H-11. The two 1,000 kW (1,340 hp) Jumo 211 F-2 provided a maximum speed of 434 km/h (270 mph) at 6,000 m (19,690 ft); cruising speed was 390 km/h (242 mph), service ceiling was 8,500 m (27,900 ft). (53) Funkgerät (FuG) radio equipment. FuG 10P, FuG 16, FuBl Z and APZ 6 were fitted for communication and navigation at night, while some aircraft received the FuG 101a radio altimeter. The H-16 retained its eight ESAC internal bomb cells; four bomb cells, as on previous versions could be replaced by a fuel tank to increase range. ETC 2000 racks could be installed over the bomb cell openings for external weapons carriage. Empty weight was 6,900 kg (15,210 lb) and the aircraft weighed 14,000 kg (30,860 lb) fully loaded for take off. German factories built 1,155 H-16s between the end of 1942 and the end of 1943; in addition, 280 H-6s and 35 H-11s were updated to H-16 standard. (53)
The last major production variant was the H-20, which entered into production in early 1944. It was planned to use two 1,305 kW (1,750 hp) Junkers Jumo 213E-1 engines, turning three-blade, Junkers VS 11 wooden-bladed variable-pitch propellers. It would appear this plan was never developed fully. Though the later H-22 was given the E-1, the F-2 remained the H-20s main power plant. Heinkel and its licensees built 550 H-20s through the summer of 1944, while 586 H-6s were upgraded to H-20 standard. (54)(55)
In contrast to the H-11 and H-16 the H-20, equipped with two Jumo 211F-2s, had more powerful armament and radio communications.
The defensive armament consisted of one MG 131 in an A-Stand gun pod for the forward mounted machine gun position. One rotatable Drehlafette DL 131/1C (or E) gun mount in the B-stand was standard and later MG 131 machine guns were added. (56) Navigational direction-finding gear was also installed. The Peil G6 was added to locate targets and the FuBI 2H blind landing equipment was built in to help with night operations. The radio was a standard FuG 10, TZG 10 and FuG 16Z for navigating to the target. The H-20 also was equipped with barrage balloon cable-cutters. The bomb load of the H-20 could be mounted on external ETC 1000 racks, or four ESAC 250 racks. The sub variant H-20/R4 could carry 20 50 kg (110 lb) bombs as external loads. (56)
The He 111H had to be kept in production until 1944 because the Ministry of Aviation failed to provide a successor: the He 177A Greif heavy bomber was plagued by engine problems, and the Bomber B program was eventually abandoned. The vast majority of the 7,300 He 111s produced were the H models, largely identical to the first H introduced in 1939.

 He 111Z
An He 111Z towing a Me 321 glider

The He 111Z Zwilling was a design that entailed the merging of two He 111s. The design was originally conceived to tow the Messerschmitt Me 321 glider. Initially, four He 111 H-6s were modified. This resulted in a twin-fuselage, five-engine aircraft. They were tested at Rechlin in 1941, and the pilots rated them highly. (57) A batch of 10 were produced and five were built from existing H-6s. The machines were joined by a center wing formed by two sections 6.15 m (20 ft) in length. The power plants were five Jumo 211F engines at 1,000 kW (1,340 hp) each. Total fuel capacity was 8,570 L (2,260 US gal). This was increased with the addition of four 600 L (160 US gal) drop tanks. (34) It could tow a Gotha Go 242 glider or Me 321 for up to 10 hours at cruising speed. It could also remain airborne if the three central power plants failed. The He 111 Z-2s and Z-3s were also planned as heavy bombers carrying 1,800 kg (3,970 lb) of bombs and having a range of 4,000 km (2,500 mi). The ETC extensions allowed for a further four 600 L (160 US gal) drop tanks to be installed.
The He 111 Z-2 could carry four Henschel Hs 293 anti-shipping guided missiles, which were guided by the FuG 203b Kehl III missile control equipment. (58) With this load the He 111Z had a range of 1,094 km (680 mi) and a speed of 314 km/h (195 mph). Its maximum bomb load was 7,200 kg (15,870 lb). To increase power the five Jumo 211F-2 power plants were to be fitted with Hirth TK 11 superchargers. The armament was the same as the H-6 with the addition of one 20 mm MG 151/20 in a rotating gun-mount on the centre section. The variant did not display any convincing (stable) flight performance. (58)
The layout of the He 111Z had the pilot and his controls in the port fuselage only. Only the controls themselves and essential equipment remaining in the starboard section. The aircraft had a crew of seven; a pilot, first mechanic, radio operator and gunner in the port fuselage, and The Z-3 was to be a reconnaissance version and was to have additional fuel tanks increasing its range to 6,000 km (3,730 mi). Production was due to take place in 1944, just as bomber production was being abandoned. The long-range variant designs failed to come to fruition. (59) The He 111Z was to have been used in an invasion of Malta in 1942 and as part of an airborne assault on the Soviet cities Astrakhan and Baku in the Caucasus in the same year. During the Battle of Stalingrad their use was cancelled due to insufficient airfield capacity. Later in 1943 it helped evacuate German equipment and personnel from the Caucasus region and during the Allied invasion of Sicily attempted to deliver reinforcements to the island. (60)
Allied reconnaissance of an He 111Z at Regensburg, 1944.
During operations, the He 111Z did not have enough power to lift a fully loaded Me 321. The He 111s in RATO (rocket assisted takeoff) units were supplemented by rocket pods. Two were mounted beneath each fuselage and one underneath each wing. This added 500 kg (1,100 lb) in weight, but gave additional thrust to the engines. The pods were then released by parachute after takeoff. (34)

The He 111Z's operational history was minimal. One such machine was caught by RAF fighter aircraft over France on 14 March 1944. The He 111Z was towing a Gotha Go 242, and was shot down. (61) Eight were shot down or destroyed on the ground in 1944. (62)