Zwilling Aircraft Projects

[Adler]

"Zwillings" are twin-fuselage variants of standard aircraft developed by Nazi Germany during World War II. They were constructed by joining two existing airframes with a central wing, and given a "Z" or "Zwilling" label following their conventional name.

List:

Aircraft Built:
DFS 332 (Initially designed with 2 fuselages, so not a true "Zwilling")
Heinkel He 111Z
Klemm Kl 25Z (testbed for the Messerschmitt Bf 109Z)
Messerschmitt BF 109Z-0 (Built but not flown; destroyed in a bombing raid)

Never-built Projects:
Arado E.530 (Initially designed with 2 fuselages, so not a true "Zwilling")
Blohm & Voss BV 250Z
DFS 230Z (Also DFS 203)
Dornier P 231Z (Also P 231 Enwurf II)
Dornier Do 335Z (Also Do 635/Heinkel P 1075)
Focke-Achgelis Fa 223Z
Focke-Achgelis Fa 325 "Krabbe" (1943 development of Fa 223Z)
Focke-Achgelis twin fuselage transport helicopter (1938 patent; unknown if based on any single fuselage design.)
Heinkel He 111Z-2 (He 111Z bomber variant)
Heinkel He 111Z-2 (He 111Z reconnaissance variant)
Junkers Ju 290Z
Junkers Ju 635 (Twin Do 335 with significant changes, partial or complete mockup was constructed)
Messerschmitt BF 109Z-1 (Bf 109 Z-0 production variant - heavy destroyer)
Messerschmitt BF 109Z-2 (Bf 109 Z-0 production variant - fast bomber)
Messerschmitt BF 109ZZ (Zwilling Zerstörer (Destroyer))
Messerschmitt Me 209Z (Also Me 409)
Messerschmitt Me 309Z (Also Me 609)
Messerschmitt Me 323Z (Speculated)

Speculative (likely fictional):
Blohm & Voss BV 222Z
Dornier Do 217Z
Focke-Wulf FW 190Z
Focke-Wulf Ta 152Z
Heinkel He 177Z
Junkers Ju 390Z

Fictional:
Focke Wulf Fw 200 Super Condor (1938 April Fools joke)

-----------------------

 

[Michel Van]

DFS 203 Zwilling transport Glider based on DFS 230 (build and tested)
the DFS 332 was completely new design aircraft

 

[Adler]

DFS 203 Zwilling transport Glider based on DFS 230 (build and tested)
the DFS 332 was completely new design aircraft

Thank you, I have updated the post.

 

[Michel Van]

Messerschmitt Me 323Z

There is no Me323Z however there is the Z/Me323-F
the Z stands for Zeppelin GmbH who build the F series of Me323
to make place for more projects at Messerschmitt
Like Me 609 study the Zwilling version of Me 509

seem the Z label on Z/Me323 let to mistake in some literature to Me323Z ?

Source:
Heinz J. Nowarra Die Deutsche Luftrüstung 1933-1945 Band 3

 

[Jemiba]

Would fully second Michel here, including his explanation, how this this designation came into being.
Have searched for the "Me 323 Z", too, and yes, it's mentioned in some sites, including Wiki, but I couldn't find it in the other publications I have, not to mention just a single photo, that could be regarded as a prove, that this version ever existed.
What is mentioned in nearly all sources, is the excessive effort demanded from the pilots to steer this aircraft, with sometimes up to 80 kg of pressure needed on the control wheel. In a twin version, this may not have been doubled, but it certainly wouldn't have been reduced, and it's hard to imagine, that power assisted controls would have been incorporated into, what would have been a flexing and wobbling vehicle.

 

[Adler]

There is no Me323Z however there is the Z/Me323-F
the Z stands for Zeppelin GmbH who build the F series of Me323
to make place for more projects at Messerschmitt
Like Me 609 study the Zwilling version of Me 509

seem the Z label on Z/Me323 let to mistake in some literature to Me323Z ?

Source:
Heinz J. Nowarra Die Deutsche Luftrüstung 1933-1945 Band 3

The ZMe 323F and Me 323Z are two different projects. The latter was a twin fuselage variant consisting of 2 E-1 airframes. It was reportedly constructed in the summer of 1944 as a carrier for a 17.7 tonne bomb. It made only one flight, and dropped a dummy of the weapon, which lead to an inflight breakup. There exist no photographs of it, so I will label it "speculated" in the post. Other sources claim it was a modified Me 323 with a He 111Z acting as a tug, which seems more plausible, but likewise unverifiable due to lack of documentation. The one and only way to confirm its existence is to obtain the Me 323 logs and records, which I do believe still exist, but have no idea where to access them.

Here are some other posts involving it:
https://www.secretprojects.co.uk/threads/german-17-7-ton-bomb.42159/https://www.secretprojects.co.uk/th...1-323-pre-and-follow-on-projects-zso-523.517/

 

[Justo Miranda]

The Messerschmitt Me 210 production was stopped on April 14, 1942.

After the failure of this multi-role aircraft, the Luftwaffe did not have anything to compete with the British D.H. Mosquito.

On October 20, 1942 the RLM´s Technical Department published a specification for a schnellbomber (fast bomber) with 1,000 kg payload, a penetration depth of 1,046 km (one third of the operational range) and a top speed of 700 km/h, later on increased to 1,000 km/h, flying at operational altitude.

The Messerschmitt Company was so keen to redeem its failure that it submitted six projects to the Schnellbomber contest:

-Me 265 (January 1942).

-Lippisch P 10-108 (May 1942).

-Me 329 (April 1942).

-Lippisch P 13 (November 1942).

-Bf 109 Z-2 (December 1942).

-Me 410 (December 1942).

Dornier proposed the project P 231/2 in November 1942.

Also in November Arado proposed the E 530, a single-seat high-altitude pressurized bomber designed to compete with the Bf 109 Zwilling for the DB 603 G engines and with the Junkers Ju 86 R-2 high-altitude bomber that had been banned from flying over England since October, to avoid being intercepted by the new high-altitude Spitfires.

The E 530 was expected to be able to fly at an altitude of 11,300 m and 760 km/h carrying an SC 500 bomb.

In order to carry out precision attacks in level bomb mode, Arado developed a new radio navigation system that guided the high-altitude bomber until 30 km from the target, at which point the pilot connected the three-axis Patin PKS autopilot and the Lofte tachometric bomb sight. Both devices acted together, driving the airplane according to the pilot movements over the bombsight. The bomb was automatically released when reaching the point predicted by the EGON system, controlled by a pair of Freya ground radar stations. A combination of the FuG 16 Zy, FuG 101 radio-altimeter computed the automatic bomb releasing.

In December 1942 the E 530 project was rejected in favour of the Me 410, but during a conference in Karinhall, on March 18, 1943, Göring warned the representatives of the aeronautical industry that he would not approve any new project until the requirement in the 1942 specification was met.

Arado E 530 technical data

Wingspan: 16 m, length: 13.9 m, height: 4.9 m, wing area: 35 sq. m, max weight: 10,200 kg, max speed: 760 km/h, service ceiling: 11,300 m, range: 1,850 km, power plant: two Daimler-Benz DB 603G, 12 cylinder inverted Vee liquid-cooled piston engines, each rated at 1,900 hp. with GM-1 power boost, armament: none, payload: one SC 500 bomb on external rack, electronics: FuG 16 Zy, BZA-1, Lofte 7K, Patin LKS 7, FuG 25a and FuG 101a.

 

[Justo Miranda]

Gotha P.55
​

It was a twin-boom expendable glider project, with a ballooned fuselage specially designed to contain a heavy load of explosives.

The anti-armour version of the P.55 could carry a warhead SHL 3500 Schwere Hohlladung (hollow charge) capable of destroying a capital ship. The SHL 3500, with 2 m of diameter and 3,500 kg weight, was also used by the Mistel composite-bombers. It contained 1,700 kg of explosive Füllung 95 activated by an extensible probe of 1.8 m called Elephantenrüssel (Elephant's trunk) with four impact fuses at its end.

The Pulkzerstörer version of the P.55 could carry up to 3,000 kg of HE possibly of the RDX type. The glider had to be towed by a He 177 bomber to the vicinity of the bomber stream and released between 1,000 and 1,500 m over the flight level of the enemy planes. The pilot drove the P.55 inward of a 'box' and triggered the cockpit ejection mechanism consisting of two Schmidding 109-543 solid fuel rockets 150 kp thrust each.

The capsule had a design based on the Personenabwurfgerät system developed by DFS for the release of agents into enemy territory. It was stabilized and slowed by a parachute located behind the pilot and could float for later recovery by a U-boat or seaplane. The warhead could be detonated by a radio signal from the He 177 mother plane by a Marder radio-fuse developed by the Orlich Institut for the air-to-air bombs Henschel Hs 293H. The explosion at a defined altitude could also be programmed by a barometric fuse type Baro-1 or an acoustic trigger Stimmgabel that was activated when the sound of the engines of the bombers reached certain intensity.

Technical data

​

Wingspan: 11.23 m, Length: 9.85 m, Maximum Speed (dive): 900 kph, Glide Ratio 1: 2

 

[Justo Miranda]

Daimler Benz Schnellbomberträger

​

In the winter of 1942-43, it was formed a joint study group for the development of the one long-range composite bomber that would be capable of attacking both the Soviet industrial plants beyond the Urals and the cities and naval bases in the east coast of USA. The study group was integrated by Dipl. Ing. Fritz Nallinger and Ober Ing. Übelacker of the Daimler Benz firm and Dipl.-Ing. Kurt Tank of Focke Wulf.



The first design developed by the group in March 1944 was named ‘Projeckt A' number 01-891658 and consisted of a Trägerflugzeug upper element and a Schnellbomber lower element. The first was a giant transport aircraft powered by four HeS 021 turboprops, with 3,300 kp thrust each, mounted on pylons over the 60 m span wing. It was equipped with a huge fixed undercarriage with six 1880 x 680 wheels and enough ground clearance to carry a large load suspended under the fuselage. The Tragerflugzeug crew was of just two men; it weighed 135 tons and had a range of 17,000km. Its length was of 42 m, its height of 14 m and its wing area was of 555 sq m.



The lower element was a bomber of 83 tons, powered by two BMW 18 turbojets with 3,450 kp thrust each, 42 degrees swept wing, with 26.16 m span, and butterfly tail, capable of flying at 1,000 kph with a crew of two men and 5,000 kg of bombs. Its length was of 33.6 m, its height of 4 m and its wing area of 166 sq m.



In May 1944, the RLM ordered Daimler Benz to partner with the firm Heinkel in the construction of the HeS 021 turboprop that had been chosen to propel a long-range reconnaissance version of the Arado Ar 234. Problems with the starter motor and with the design of the reduction gearing for the airscrews delayed the project and the RLM choose to support the construction of the BMW 109-028 turboprop by mid-1944.

The cancellation of the HeS 021 also marked the end of the Projeckt A, but on February 7, 1945, the joint study group presented Projekt B number 0310256-03 to the RLM, a shortened version of Trägerflugzeug with a take-off weight of 122 tons and 73,500 kg payload, propelled by six DB 603N piston engines with 2,750 hp each. Projekt B was designed with a wingspan of 54 m, a length of 35 m, a height of 11.2 m, and a wing area of 500 sq m.



The Schnellbomber also evolved to suit the performances of the mother plane by reducing its size to a wingspan of 22 m, a length of 30 m, a height of 7.3 m. and a wing area of 140 sq m. On December 11, 1944, it was presented to the RLM in two versions - Schnellbomber and Aufklärer - under the name of Projekt C number 0310256-05. The bombing version retained the capacity to carry up to 5,000 kg of bombs at 1,000 kph, although its weight was reduced to 70 tons; their engines were replaced by a single DB 109-016 turbojet of 13,000 kp static thrust, adopting the undercarriage of a Ju 287.



To improve lateral stability the Schnellbomber was equipped with twin vertical tailfins that in the reconnaissance version were replaced by others of ‘butterfly’ type.

With 52 tons of J-2 fuel, Aufklärer could fly 9,300 km with a crew of two men and two photo-reconnaissance cameras Rb 75/30. To increase the range it was considered to use an axial-flow turbofan DB 109-007, specifically designed for a low specific fuel consumption of 1,720 kilograms per hour.



To fight against the Allies convoys in the Atlantic Ocean it was expected that the Trägerflugzeug could carry five Henschel Hs 295 antiship missiles; but in late 1944 the electronic jamming equipment of the allies could void the Germans radio guidance systems. On January 10, 1945, the OKL received a proposal to replace the missiles by a new type of S.O. Flugzeug (suicide airplane) called Projekt E number 0310256-04. In this project, each plane carried a hollow charge warhead SHL 2500 of 1.4 m diameter and 1,800 kg of K1 fuel for its turbojet engine HeS 011. It had 8.5 m of wingspan, 9.2 m. of length and 3.2 m of height. Its estimated range was of 2,000 km and it maximum speed of 1,000 kph.



There also existed a project of a more powerful version, first described in January 1946 as Projekt F in the R.A.F. Report No. 2383 A.I.2 (G) and as Projekt D or Lenkbomber by later German sources. It was a suicide bomber of 10.26 tons, powered by a DB 109-007 dorsal turbojet of 1,275 kp static thrust, with 4,000 kg of J2 fuel and provided with a hollow charge warhead SHL 3500 Holladungssprengbombe activated by a nose probe of 1.9 m, extendable to 2.6 m before impact. It could fly at Mach 0.82, reaching transonic speeds in terminal dive. Lenkbomber had 9 m of wingspan, 13 m of length, 3.10 m of height and 20 sq m of wing surface



Research on the DB 109-007 was paralyzed by the RLM in May 1944, suggesting an earlier date of design for the Lenkbomber.

 

[Justo Miranda]

Gotha projects

 

[Justo Miranda]

Dornier

 

[Justo Miranda]

Fake Focke-Wulf

 

[Justo Miranda]

Fw 189

 

[Justo Miranda]

Post-2

 

[Justo Miranda]

DFS

 

[Justo Miranda]

Messerschmitt

 

[Justo Miranda]

Post-2

 

[Justo Miranda]

Heinkel

 

[Justo Miranda]

Post-2

 

[Justo Miranda]

Fieseler

According to German air doctrine, the Luftwaffe should operate from poorly equipped frontline airfields to adapt to the rapid advances of the Wehrmacht during Blitzkrieg operations.

The weakness of the Messerschmitt Bf 109 undercarriage (with 1.98 m wide track only) caused numerous accidents and it was a constant source of concern for the Technisches Amt (Luftwaffe Technical Office).

In September 1935, the LC II development group issued a specification calling for a 2-3 seat multi-purpose communications STOL aircraft designed to exploit the latest aerodynamic high-lift devices developed for the Circuit Europe 1934 competition.

The essential features of such aircraft were held to be:

-Maximum view in all directions for the crew.

-Ability to take-off and landing on small, temporary airfields or strips.

-Good stability at minimum flight speed.

Three aircraft companies tendered for this contract: Klemm FWH Flugzeug Halle (Siebel) proposed its Si 201 project, Bayerische Flugzeugwerke AG (Messerschmitt) proposed the project P. 1051 (Bf 8-163) and Fieseler proposed the Fi 156.

Early in 1936 the RLM ordered the construction of three prototypes for STOL evaluation.

All of them used high-set wings fitted with high-lift devices: Handley Page leading-edge automatic slats, trailing-edge mounted Junkers Doppelflügel flaps synchronized to the ailerons and a new type of variable-incidence wing.

The winner of the contest was the Fi 156 which had a take-off run of 42 yards and landed in 140 yards only, under zero wind conditions.

Concurrently the RLM was extremely interested in the Focke-Wulf Fw 186, one special gyroplane with jump-start capability unlike the conventional short take-off run.

But during the flight tests conducted in July 1938 the prototype D-ISTQ showed aerodynamic and mechanical problems that could not be solved.

By this time the Luftwaffe was so satisfied with the STOL characteristics of the Fi 156 that further gyroplane development was discontinued and the Fw 186 test program was suspended in 1939.

In April 1937, the RLM issued the Schlachtflugzeug specification calling for an armored ground attack aircraft powered by two engines rated at 450-550 hp. each.

Focke-Wulf proposed an extensively modified version of the Fw 189 prototype D-OPVN fitted with armored cockpit.

Blohm und Voss proposed the Bv P 40, the ground attack version of the Bv 141 powered by one DB 600 engine.

Henschel proposed the “winged can-opener” Hs 129, with such heavy armour that it considerably affected its manoeuvrability and take-off run.

The Hs 129 was the winner of the Schlachtflugzeug competition, but the Technische Amt recommended the replacement of Argus engines with more powerful ones of French manufacture.

Two revolutionary STOL designs were also submitted to the Schlachtflugzeug contest: the Fieseler Fi 168 and the Junkers EF 50.

Wings fitted with slats and flaps provided the best solution for STOL flight.

In conventional aircraft, the wing stall occurs at the highest lift coefficient on an airfoil, when the airflow can no longer go around the leading-edge and separates from the upper wing surface.

To delay the stall, trailing-edge flaps mounted on the full span of the wing may be used to deflect the propeller slipstream downward, lifting an appreciable fraction of the aircraft weight.

Leading-edge slats also prevented the stall up to approximately 30-degrees angle of attack by picking up the air from below, pulling the air around the leading edge.

The disadvantage of this device was that the air accelerated in the slot venturi required energy which meant higher drag and could only be used on relatively slow aircraft.

An STOL aircraft can fly at low speed but cannot stay in hover at low altitude because of the turbulence generated by the propellers when deflected on the ground.

This phenomenon of aerodynamic interference was discovered on January 21, 1959, during flight tests of the Ryan VZ-3 prototype.

To best achieve STOL take-off, the wing high angle of attack must be achieved at the ground. With a tail dragger configuration, the long undercarriage legs meant that the landing gear is either weak or heavy.

Also, the tilted fuselage can severely limit the pilot’s forward visibility while taxiing and take-off. Good visibility is especially important in STOL aircraft. The high-wing configuration provides the best downward visibility to safely landing into unimproved areas, avoiding obstacles.

The Fi 168 Panzerjäger was a ground attack version of the Fieseler Storch powered by two Argus As 410 engines.

Construction of the prototype began on September 1, 1938, with the mock-up being inspected by RLM technicians in April 1939.

After the Hs 129 was chosen for mass production, the project was cancelled in September 1939.

Fieseler Fi 168 technical data

Type: two-seat tank destroyer, wingspan: 20.9 m, length: 12.55 m, height: 3.6 m, wing area: 58 sq. m, max weight: 4,630 kg, max speed: 246 km/h, range: 450 km, power plant: two Argus As 410, 12 cylinder, inverted-vee, air-cooled engines , each rated at 465 hp, armament: two nose mounted 20-mm MG FF/M cannons, two nose mounted 7.9-mm MG 17 machine guns and one 7.9-mm MG 15 rear firing machine gun.

 

[Justo Miranda]

Junkers

Hugo Junkers was so impressed by the capabilities of the Fieseler Fi 145 Storch that envisaged the study of an ultra-STOL armored Schlachtflugzeuge design parallel to the Fi 168 Panzerjäger, searching a solution for the ‘Air Flivver’ problem of stall/spin accidents.

Systematic experiments to determine STOL principles were conducted at the Junkers aero-dynamical institute in Aachen and one wind tunnel model was tested, under the project designation EF 50 (Entwicklungs-Flugzeug).

The new aircraft was designed to be powered by two Daimler-Benz DB 600 engines, driving two-blade, low-speed, five meters of diameter rigid propellers. That would result in a step angle while the aircraft standing on the ground.

Engine power was delivered to the propellers via two-speed gear boxes; the port propeller rotated in clockwise direction and the starboard propeller rotated counterclockwise, providing symmetric airflow over the entire wing surface.

The EF 50 configuration offered an exceptional low speed maneuverability to elude any fighter and the installation of rear-firing weapons was not considered necessary.

The square armored fuselage should provide good yaw stability and spin dampering due to its flat sides.

Leading-edge slats and double-slotted trailing-edge flaps (inspired by earlier 1930 Junkers Doppelflügel) were fitted to control the wings airflow at high angles of attack.

Junkers EF 50 technical data

Type: single-seat STOL project, wingspan: 11.5 m, power plant: two Daimler Benz DB 600, 12 cylinders, inverted Vee, liquid cooled engines, each rated at 900 hp, rotor diameter: 5 m.

 

[Jemiba]

Great stuff, but I think, we should stay with the original definition of „Zwilling“, given by Adler in his very first post : „… constructed by joining two existing airframes with a central wing“, contrary to twin boom aircaft.
„Zwillinge“ generally were a kind of a stop-gap measure, relatively quick to build, while twin-booms were constructed as such from the start.

 

[Dan Sharp]

"Zwillings" are twin-fuselage variants of standard aircraft developed by Nazi Germany during World War II. They were constructed by joining two existing airframes with a central wing, and given a "Z" or "Zwilling" label following their conventional name.

List:

Aircraft Built:
DFS 332 (Initially designed with 2 fuselages, so not a true "Zwilling")
Heinkel He 111Z
Messerschmitt Me 323Z (Speculated)
Messerschmitt BF 109Z (Built but not flown; destroyed in a bombing raid)

Never-built Projects:
Arado E.530 (Initially designed with 2 fuselages, so not a true "Zwilling")
Blohm & Voss BV 222Z
Blohm & Voss BV 250Z
DFS 230Z (Also DFS 203)
Dornier P 231Z (Also P 231 Enwurf II)
Dornier Do 335Z (Also Do 635)
Heinkel He 111Z-2 (He 111Z bomber variant)
Heinkel He 111Z-2 (He 111Z reconnaissance variant)
Junkers Ju 290Z
Messerschmitt BF 109ZZ (Zwilling Zerstörer (Destroyer))
Messerschmitt Me 209Z (Also Me 409)
Messerschmitt Me 309Z (Also Me 609)

Speculative (likely fictional):
Dornier Do 217Z
Focke-Wulf FW 190Z
Focke-Wulf Ta 152Z
Junkers Ju 390Z

-----------------------

I've got more information on most of these proposals, but too much to put into one post. Please ask me below if you need anything.

Using the definition of a 'Zwilling' having to consist of two fuselages of existing aircraft, I believe the list looks like this:

Aircraft built:
Heinkel He 111Z

Never-built projects:
DFS 203 (DFS 230 fuselages)
Blohm & Voss P 167 (BV 250 Zwilling)
Messerschmitt Bf 109 Z
Messerschmitt Bf 309 Z
Heinkel P 1075 (Do 335 Z)
Junkers Ju 290 Z
Junkers Ju 635 (this used bits of Do 335 fuselages, rather than complete fuselages, but still)


Broadening the definition of 'Zwilling' to include twin-fuselage designs based on non-production model fuselages, we can add the following:

Aircraft built:
DFS 332

Never-built projects:
Arado E 530
Blohm & Voss P 166
Dornier Do P 231 'Entwurf 2'
Heinkel unnamed twin-fuselage project of October 8, 1942
Hirth Hi 23
Jacobs-Schweyer Jas P 5
Junkers EF 109

To address the other designs mentioned individually:
Messerschmitt Me 323Z - no evidence for this.
Messerschmitt Bf 109 Z actually being built - no evidence for this either.
Blohm & Voss BV 222Z - no evidence.
Messerschmitt Me 209 Z - mentioned by Milch in a GL meeting as something that might be desirable but no evidence that Messerschmitt ever worked on it. The Schnellbomber contest had been won by the Do P 231 before the Me 209 fully succeeded the Me 309.
Me 409 - a Bf 109 with DB 628 engine.
Me 609 - code name for Me 262s built at Regensburg.
Dornier Do 217Z - no evidence.
Focke-Wulf FW 190Z - no evidence.
Focke-Wulf Ta 152Z - no evidence.
Junkers Ju 390Z - no evidence.

Further details on the Hirth Hi 23, Jacobs-Schweyer Jas P 5 and Junkers EF 109 - including scans of period drawings - can be found in my (Dan Sharp) Luftwaffe - Secret Projects of the Third Reich bookazine of 2019.

A scan of the only known drawing of the Heinkel twin-fuselage design of October 8, 1942, can be found on p38 of my Luftwaffe - Secret Wings of the Third Reich bookazine of 2018.

A photograph of the Me 409 mock-up can be found on p268 of The Secret Horsepower Race by Calum Douglas.

Details of the Me 609 designation's clear association with Regensburg-built Me 262s can be found in my 2022 book Messerschmitt Me 262 Development & Politics, along with archival references. Similar information can also be found in Alexander Kartschall's 2020 book Messerschmitt Me 262 Geheime Produktionsstaetten and also, much earlier, in The History of German Aviation: Willy Messerschmitt - Pioneer of Aviation Design by Ebert, Kaiser and Peters, published in 1999.

 

[Dan Sharp]

Great stuff, but I think, we should stay with the original definition of „Zwilling“, given by Adler in his very first post : „… constructed by joining two existing airframes with a central wing“, contrary to twin boom aircaft.
„Zwillinge“ generally were a kind of a stop-gap measure, relatively quick to build, while twin-booms were constructed as such from the start.

There was a brief time, during the autumn of 1942, when the Zwilling was considered to be the ideal form for a fast bomber. Then Junkers came up with the EF 111 and the ideal form switched to being a single fuselage with tandem engines. The Do P 231, while ostensibly being based on the Do P 59 of 1937, actually incorporated some design elements of the EF 111 which the Do P 59 hadn't possessed.

The DFS 332 was constructed as a twin fuselage design mainly because it was the best configuration for testing different wing designs using the centre section.

 

[hesham]

Messerschmitt Bf 109 Z actually being built - no evidence for this either.

Thank you my dear Dan for this explanation,

but for Bf.109Z,there are many evidences about it,

https://www.secretprojects.co.uk/th...5-projects-prototypes.9036/page-6#post-711327

 

[Dan Sharp]

Thank you my dear Dan for this explanation,

but for Bf.109Z,there are many evidences about it,

https://www.secretprojects.co.uk/th...5-projects-prototypes.9036/page-6#post-711327

Messerschmitt Bf 109 Z actually being built - no evidence for this either.

 

[Dan Sharp]

There is no Me323Z however there is the Z/Me323-F
the Z stands for Zeppelin GmbH who build the F series of Me323

There was a ZMe 323 F, ZMe 323 G, ZMe 323 H and lastly the Z SO 532.

But there is no evidence whatsoever for an Me 323 Z. No mention in any primary source.

 

[Adler]

Using the definition of a 'Zwilling' having to consist of two fuselages of existing aircraft, I believe the list looks like this:

Aircraft built:
Heinkel He 111Z

Never-built projects:
DFS 203 (DFS 230 fuselages)
Blohm & Voss P 167 (BV 250 Zwilling)
Messerschmitt Bf 109 Z
Messerschmitt Bf 309 Z
Heinkel P 1075 (Do 335 Z)
Junkers Ju 635 (this used bits of Do 335 fuselages, rather than complete fuselages, but still)


Broadening the definition of 'Zwilling' to include twin-fuselage designs based on non-production model fuselages, we can add the following:

Aircraft built:
DFS 332

Never-built projects:
Arado E 530
Blohm & Voss P 166
Dornier Do P 231 'Entwurf 2'
Heinkel unnamed twin-fuselage project of October 8, 1942
Hirth Hi 23
Jacobs-Schweyer Jas P 5
Junkers EF 109

To address the other designs mentioned individually:
Messerschmitt Me 323Z - no evidence for this.
Messerschmitt Bf 109 Z actually being built - no evidence for this either.
Blohm & Voss BV 222Z - no evidence.
Junkers Ju 290Z - no evidence
Messerschmitt Me 209 Z - mentioned by Milch in a GL meeting as something that might be desirable but no evidence that Messerschmitt ever worked on it. The Schnellbomber contest had been won by the Do P 231 before the Me 209 fully succeeded the Me 309.
Me 409 - a Bf 109 with DB 628 engine.
Me 609 - code name for Me 262s built at Regensburg.
Dornier Do 217Z - no evidence.
Focke-Wulf FW 190Z - no evidence.
Focke-Wulf Ta 152Z - no evidence.
Junkers Ju 390Z - no evidence.

Further details on the Hirth Hi 23, Jacobs-Schweyer Jas P 5 and Junkers EF 109 - including scans of period drawings - can be found in my (Dan Sharp) Luftwaffe - Secret Projects of the Third Reich bookazine of 2019.

A scan of the only known drawing of the Heinkel twin-fuselage design of October 8, 1942, can be found on p38 of my Luftwaffe - Secret Wings of the Third Reich bookazine of 2018.

A photograph of the Me 409 mock-up can be found on p268 of The Secret Horsepower Race by Calum Douglas.

Details of the Me 609 designation's clear association with Regensburg-built Me 262s can be found in my 2022 book Messerschmitt Me 262 Development & Politics, along with archival references. Similar information can also be found in Alexander Kartschall's 2020 book Messerschmitt Me 262 Geheime Produktionsstaetten and also, much earlier, in The History of German Aviation: Willy Messerschmitt - Pioneer of Aviation Design by Ebert, Kaiser and Peters, published in 1999.

Hello and thank you. Mr. Dan, would you happen to have any more information on the DFS 203 and BV P.167? I could not find any documents relating to the former, whereas the BV P.167 is only referenced in a single drawing attached below. (Originally posted by @kiradog in https://www.secretprojects.co.uk/threads/blohm-und-voss-bv-238-drawings.4712/ )

 

[Dan Sharp]

Hello and thank you. Mr. Dan, would you happen to have any more information on the DFS 203 and BV P.167? I could not find any documents relating to the former, whereas the BV P.167 is only referenced in a single drawing attached below. (Originally posted by @kiradog in https://www.secretprojects.co.uk/threads/blohm-und-voss-bv-238-drawings.4712/ )

DFS 203 - this is covered in Luftwaffe - Secret Projects of the Third Reich.

Blohm & Voss P 167 - there's a lot of primary source information available about a lot of obscure Blohm & Voss projects, but not this one. The only known evidence of it is that drawing. I did, however, scan it from the microfilm myself with a bit more clarity. Even then, the original is just too faded to get any more detail out of it.

Interesting that the nose of the port fuselage appears to be different from the nose of the starboard one, making it asymmetrical.

 

[Justo Miranda]

Can you imagine the torsional loads on the central section of the wing when one of the hulls takes off and the other is still subjected to water suction?

 

[Adler]

Can you imagine the torsional loads on the central section of the wing when one of the hulls takes off and the other is still subjected to water suction?

That was a proposal for the BV 250, not the BV 238. The BV 250 was a conceptualized land-based variant of the BV 238.

 

[Justo Miranda]

That was a proposal for the BV 250, not the BV 238. The BV 250 was a conceptualized land-based variant of the BV 238.

You're right, but that wing design would also split during a poorly coordinated takeoff between both fuselages. It's a horrible idea.

 

[Ravinoff]

The Me 323Z is very related to the story of the German "17.7-ton bomb" I've been (very casually) digging into lately. You can read about that over in its thread, but here's the abridged version: the 323Z seems to originate in the book Last Talons of the Eagle: Secret Nazi Technology Which Could Have Changed the Course of World War II by Gary Hyland and Anton Gill. Being overly interested in this whole thing I finally just set up an account on archive.org as the book in question is available for their stupid one-hour loan thing. And here's what I've got:

A single test flight was apparently made by an Me 323Z at the Karlshagen test grounds sometime in the latter half of July 1944, carrying a dummy of a 17,700kg (there it is again!) bomb that was successfully dropped. However, the aircraft had been damaged in the days prior to the test by Allied strafing, and insufficient repairs caused it to catastrophically break up in midair. Construction-wise it was built the same as the He 111Z, with two fuselages joined by a common wing section, and powered by nine BMW 801 engines in place of the four or six Gnome-Rhône 14Ns of the regular 323. That would be a notable increase in power, 801s were rated at 1550-1950hp compared to the 1100 of the Gnome-Rhône, and might have been enough to get a Gigant-Zwilling off the ground. No mention is made of whether it actually was able to take off without assistance. And if any photos of the 323Z were taken, none are known to survive.

 

[Jemiba]

Yes, the 323Z seems to be indivisibly linked to that equally unproven 17.7-ton bomb. A bit strange to me, that a book with the subtitle "Secret Nazi Technology Which Could Have Changed the Course of World War II", so implying, that this regime was at least in some parts better, and more efficient, than it obviously was in reality, comes up with a project, that in my opinion, makes the Nazis look quite dumb.
The RAF built their Grand Slam bomb, just about 10 tons, and needing a specially modified Lancaster to carry it. The RAF had a lot of those bombers, targets, and actually chances of reaching them. The Luftwaffe had neither in 1944 ...
The Me 323 always was in short supply, its missions extremely dangerous, but often the only way to bring supplies to cut-off forces. But nevertheless, the Luftwaffe obviously happily agreed to modify two of them into an aircraft, that maybe could carry this bomb, but to my opinion, would have never had the slightest chance of reaching any worthwhile target with it ... Honestly, though being a German, and having had a Grandfather, who not only had this party membership book, but until the end of his live believed in it, I will never understand the Nazis !

 

[dan_inbox]

A bit strange to me, that a book with the subtitle "Secret Nazi Technology Which Could Have Changed the Course of World War II", so implying, that this regime was at least in some parts better, and more efficient, than it obviously was in reality, comes up with a project, that in my opinion, makes the Nazis look quite dumb.

Why would those authors not use Marketing BS ™ to the hilt?
This is the proper way in our Western Free Enterprise world...

Unless one has enough pride to refuse to wallow his name so low, that is.
But who does anymore?

 

[Dan Sharp]

Discussion of the Me 323Z belongs in the 'Theoretical, Fake and Generic Projects' thread.

Building a twin-fuselage Me 323 would be a substantial undertaking, requiring funds, manpower and materials, the allocation of which would generate a paper trail. And such paper trails exist for every other built aircraft. But there is no evidence for it ever having happened, let alone evidence for the Me 323Z being completed and flown (which would then generate a second paper trail - if it was damaged in an attack, that would be included in a report on the attack; if it broke up in mid-air there would be an accident report and possibly an investigation etc.).

The Blohm & Voss P 167 exists as a single drawing (and it also appears on both versions of the company projects list) and it would still be more believable to say that the P 167 was built and flown - because there is at least some evidence that it was 'real'.

 

[Adler]

Extract from "Last Talons of the Eagle", page 119.

This is the only section in the book concerning the Me 323Z, and seemingly the origin of all the information regarding it found on the web. The book refers to the project as a "drawing board "special"", and affirms that there is no evidence for its existence. Important to note that "Last Talons of the Eagle" as well as other works by Gary Hyland overexaggerate Nazi technological advancements and touch upon Nazi mysticism and Ufology. While we can not say for certain that the Me 323Z was never on the drawing board, this seems like sufficient evidence to say it was never flown nor built.

 

[Ravinoff]

Extract from "Last Talons of the Eagle", page 119.

This is the only section in the book concerning the Me 323Z, and seemingly the origin of all the information regarding it found on the web. The book refers to the project as a "drawing board "special"", and affirms that there is no evidence for its existence. Important to note that "Last Talons of the Eagle" as well as other works by Gary Hyland overexaggerate Nazi technological advancements and touch upon Nazi mysticism and Ufology. While we can not say for certain that the Me 323Z was never on the drawing board, this seems like sufficient evidence to say it was never flown nor built.

...why I didn't think of taking a screenshot and posting it I have no idea, thanks.

Yes, the 323Z seems to be indivisibly linked to that equally unproven 17.7-ton bomb. A bit strange to me, that a book with the subtitle "Secret Nazi Technology Which Could Have Changed the Course of World War II", so implying, that this regime was at least in some parts better, and more efficient, than it obviously was in reality, comes up with a project, that in my opinion, makes the Nazis look quite dumb.
The RAF built their Grand Slam bomb, just about 10 tons, and needing a specially modified Lancaster to carry it. The RAF had a lot of those bombers, targets, and actually chances of reaching them. The Luftwaffe had neither in 1944 ...
The Me 323 always was in short supply, its missions extremely dangerous, but often the only way to bring supplies to cut-off forces. But nevertheless, the Luftwaffe obviously happily agreed to modify two of them into an aircraft, that maybe could carry this bomb, but to my opinion, would have never had the slightest chance of reaching any worthwhile target with it ... Honestly, though being a German, and having had a Grandfather, who not only had this party membership book, but until the end of his live believed in it, I will never understand the Nazis !

Well supposedly (again, this is from one of Frederich Georg's books, so take with a gain of salt), the planned candidate - or one of them at least - for the 17.7 was the Ju 290 E, which itself is another rather dubious drawing board concept for a night bomber that...you actually commented a bit on ten years or so back in this thread.

 

[Justo Miranda]

Hi

 

[Dan Sharp]

I can only reiterate that there is no evidence at all for the existence of an Me 323Z, even as a drawing board project. If any moderators are reading this, discussion of it belongs in the 'Theoretical, Fake and Generic Projects' thread.

There is the barest shred of evidence to support Thomas Hitchcock's Ju 290 E, as outlined in Monogram Close-Up 3. This comes from the well-known report A.I.2(G) Report No. 2383 German Aircraft: New and Projected Types by Horace King, dated January 1946.

This gives only the most minimal description of the Ju 290 E as "a night bomber likewise based on the C and having a large bomb bay under the fuselage" - see below. Whether Hitchcock extrapolated his description and drawing from that, or whether he had some independent information on it is unknown.

The closest I can get to it is some Junkers graphs dated June 1944 showing what the performance of the Ju 290 might have been like with four Jumo 222 E/Fs (earlier graphs, from March 1944, show projected performance with Jumo 222 A/Bs). These graphs don't mention a C, D or E designation.

Incidentally, it would seem that there were numerous other Ju 290 variants that have never been reported on before as far as I'm aware, such as a six-engined Ju 290 (small wing area) and two different wings for the Ju 390. The last variant I could find evidence on, from February 1945, was a Ju 290 A (sub-type unspecified) fitted out to carry either two or three Re 4 piloted flying bombs.