Rare WWII Engineering Marvel: The Unusual Heinkel He 111Z ‘Zwilling’ Towplane

World War II produced no shortage of strange and ambitious experiments in aviation. From rocket-powered interceptors to jet bombers, aircraft designers across the warring nations often pushed the boundaries of what was technically possible. Among these curiosities, few were as visually striking—or as mechanically daring—as the Heinkel He 111Z “Zwilling.”

Created by literally fusing two He 111 bombers together with a fifth engine mounted between them, the He 111Z was designed for one purpose: to haul enormous gliders into the air. In one rare and remarkable photograph, the ungainly twin-fuselage aircraft is shown towing not just one, but two massive Go 242 assault gliders in tandem—a sight that underscores just how unusual this “twin” aircraft truly was.

The Origins of the “Zwilling”

By 1940–41, German planners recognized a looming problem. Their military strategy increasingly relied on large gliders, such as the Messerschmitt Me 321 “Gigant,” to carry troops, vehicles, and even light tanks into battle. But these gliders were massive, ungainly, and difficult to launch.

The Me 321 alone required three Messerschmitt Bf 110 fighters in a risky “troika” arrangement, or a single specially modified He 111 using rocket-assisted takeoff boosters. These methods were inefficient and dangerous. What Germany needed was a dedicated heavy towplane.

Heinkel’s solution was ingenious, if unconventional: take two of its reliable He 111 twin-engine bombers, join them together with a new wing section and an extra engine, and create a five-engine monster powerful enough to haul even the largest gliders. The result was the He 111Z—Zwilling, meaning “twin” in German.

Design and Construction

At first glance, the He 111Z looked like something out of science fiction:

Two complete He 111 fuselages, each with its own cockpit, joined by a new central wing section.

Five Junkers Jumo 211F engines, with one mounted in the center wing.

A strengthened wing spar to handle the stress of towing giant gliders.

Crew of seven, distributed across both fuselages but primarily controlled from the left cockpit.

The modifications created an aircraft with a wingspan of nearly 115 feet (35 meters), making it one of the largest piston-engine aircraft of the Luftwaffe.

Though ungainly, the design had advantages. By reusing the proven He 111 airframes, Heinkel could quickly build the Zwilling without starting from scratch. And the five engines gave it the raw pulling power needed to get even a fully loaded Me 321 off the ground.

Operational Role

The He 111Z was built almost exclusively as a glider tug. Its main mission was to tow:

Me 321 “Gigant” gliders — huge transports capable of carrying tanks or 200 troops.

Go 242 gliders — smaller assault transports used for airborne troops.

In some cases, the Zwilling was tasked with towing two Go 242s at once, a dangerous undertaking but one that highlighted its unusual capabilities.

The He 111Z was also tested with bombs, long-range fuel tanks, and reconnaissance equipment, but its ungainly design and limited numbers meant it never evolved into a true multipurpose aircraft.

Strengths and Weaknesses

The He 111Z was, in its own way, an engineering marvel. But like many of Germany’s more unusual wartime designs, it suffered from severe limitations.

Strengths:

Tremendous towing capacity compared to conventional bombers.

Efficient use of existing He 111 airframes and parts.

Provided a practical solution to the problem of launching giant gliders.

Weaknesses:

Extremely vulnerable in combat. Its size and sluggish performance made it an easy target for Allied fighters.

Small production numbers—only about 12 were built.

Specialized role meant limited flexibility.

Range and endurance issues when towing massive, drag-inducing gliders.

In Action

The He 111Z entered service in 1942, just in time to participate in several German airborne operations and supply efforts.

Eastern Front: Used to tow gliders carrying supplies and reinforcements, particularly during critical moments such as the Battle of Stalingrad.

Mediterranean Theater: Supported attempts to supply German forces in Tunisia and Sicily.

Defensive Operations: As the tide of war turned, Zwillings were sometimes used to ferry supplies to besieged garrisons.

Reports indicate that several He 111Zs were lost to Allied fighters, as their size and slow towing speed made them easy prey. Their operational impact, while interesting, was ultimately marginal.

Legacy and Rarity

The He 111Z was never more than a niche aircraft. Only about a dozen were constructed, and by 1944 most had been destroyed or grounded due to fuel shortages and lack of spare parts. None survived the war.

Yet the Zwilling occupies a unique place in aviation history. It represents a creative—if desperate—solution to a logistical problem, and an example of German ingenuity in repurposing existing designs to meet new demands. Its bizarre twin-fuselage silhouette stands alongside aircraft like the Messerschmitt Me 262 jet fighter and the Heinkel He 162 “Volksjäger” as evidence of how experimental German aviation became during the war.

A Comparison: Twin-Fuselage Aircraft

The He 111Z was not the only twin-fuselage aircraft ever built. Designers in several countries experimented with the concept:

North American F-82 Twin Mustang (USA): A postwar long-range escort fighter made by joining two P-51 Mustang fuselages.

Savoia-Marchetti SM.92 (Italy): A WWII Italian twin-fuselage heavy fighter prototype.

Modern Examples: Aircraft like Scaled Composites’ White Knight space launch plane continue the concept today.

What set the He 111Z apart was its sheer size and specific mission of hauling enormous gliders—something no other twin-fuselage design attempted.

Conclusion

The Heinkel He 111Z Zwilling remains one of World War II’s strangest engineering marvels. By joining two bombers and bolting on a fifth engine, German designers created a massive towplane unlike anything else in the skies.

Though only a handful were built, and their combat impact was limited, they represented the kind of bold, unconventional thinking that wartime necessity often inspires.

Photographs of the He 111Z towing two Go 242 gliders in tandem capture the spirit of this era—an extraordinary hybrid design born out of desperation, innovation, and a willingness to attempt the unusual in pursuit of military advantage.

In the end, the He 111Z was less a war-winner and more a symbol of wartime ingenuity. Strange, rare, and unforgettable, it stands today as one of the oddest creations ever to take flight under the banner of the Luftwaffe.