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The Dornier Do 335 Pfeil: Hitler's Last Arrow

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It is an extraordinary fact that right up until almost the last days of the Second World War, German aircraft companies were coming up with cutting-edge designs for military aircraft and beginning to put these ideas into practice. Had the Western Allies and the Soviet Union not already been within sight of absolute victory over the Third Reich, these (or at least more highly developed versions of these) aircraft could have inflicted major damage and hindered or delayed the final defeat of Hitler and the Nazi regime. I have already written an article on the Forum about the Messerschmitt 163 Komet rocket interceptor, and the Germans were also pioneering combat use of a jet engined aircraft, the Messerschmitt Me 262, towards the end of the War. This topic is about yet another radical aircraft contending on Hitler’s side in his last ditch attempts to prevent the Allies from winning the War - the piston-engined Dornier Do 335 Pfeil (Eng. Arrow).

When it comes to aircraft performance, designers are always trying to maximise engine power and minimise drag, and a twin-engined layout with wing-mounted engines will only increase power over a single-engined design at the expense of reduced manoeuvrability and increased drag. An alternative arrangement that at least partially solves this problem is to place the engines in tandem, front and rear, along the aircraft centre-line, producing power in what is known as “centre-line thrust” The benefits of this engine arrangement include reduced frontal area, an aerodynamically clean wing, and the elimination of dangerous asymmetry in the event of one engine failing. Centre-line thrust was to be the raison d’être of the Dornier Do 335, featuring a conventional nose mounted engine with tractor airscrew together with a second engine located in the rear fuselage, driving a pusher propeller situated aft of the tail unit.

 

 

 

An instructive diecast model by Oxford of the only surviving Dornier Do 335 (see text for full details) - pics from rafmuseumshop.com:

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The origins of the centre-thrust layout implemented in the Dornier Do 335 actually go back to the First World War, when Dr/Prof Claude (Claudius) Dornier (1884-1969) designed a number of flying boats which typically featured a tandem engine arrangement; the engines were mounted back-to-back in pairs, with the forward unit powering a tractor airscrew and the rear-facing unit driving a pusher propeller. This arrangement was used in the successful Dornier Do Wal (Eng. Whale) flying boat of 1922. There was also inspiration from the Siemens-Schuckert Dr I triplane fighter of 1917 which utilised a “primitive” twin-engined centre-thrust design. In 1935, Dornier produced the Do 18, with a much improved version of the tandem engine system. In order to enable the pusher propeller to clear the trailing edge of the broad chord wing of the aircraft, an extension drive shaft from the rear engine was introduced. It wasn’t a difficult transition from this improvement to the idea of placing the pilot between the two engines in such an arrangement, and indeed, on 3 August 1937, Claude Dornier filed a patent (No. 728044) for an aircraft of just such a configuration, and it was on the basis of this patent that the Do 335 came into being. 

During 1939, Dornier was working on the P 59 high speed bomber project, which incorporated the tandem engine layout patented in 1937. However, the P 59 project was shelved by Reichsmarschall Goering in early 1940 on the over-optimistic assumption that the War would be over soon and thus all work that would not bear fruit within the next year or so should be cancelled. This blow did not end Dornier’s interest in his tandem-engine proposition, and he was soon working on another unarmed high speed bomber project - the P 231 - incorporating an internal bomb load of 2,200 lb and a similar configuration to that of the P 59. In May 1942, Dornier submitted a refined version of the P 231 design in response to a Technische Amt (Technical Department/Office) requirement for a single-seat high speed bomber. The Dornier proposal was selected as the winner after facing competition from rival designs by Arado and Junkers, and despite official resistance to the unconventional layout, a development contract was awarded under the RLM (German Aviation Ministry) designation Do 335.

 

 

 

The only surviving Dornier Do 335 (see text for full details) - pic from indianamilitary.org - and, below, cutaway drawing of a typical (unspecified) Dornier Do 335 (pic from airpages.ru):

Do335OnDisplay-2.JPG

 

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The way was still not smooth in bringing the Do 335 concept to fruition. In the Autumn of 1942, with detailed designs progressing, the RLM informed Dornier that the advent of massive Allied bombing raids meant that the Do 335 as currently presented was no longer required. Instead, the aircraft would need to be rethought as a multi-role fighter of similar performance and capable of acting as a single-seat fighter-bomber, reconnaissance aircraft, heavy fighter, and two-seat night and all-weather interceptor. The redesign now went ahead but the Technische Amt delayed the issue of a formal contract such that Dornier eventually sought the intervention of Generalfeldmarschall Milch, the Inspector-General of the Luftwaffe. By the end of 1942, with the necessary redesign completed, the first metal cut had been made on the prototypes at Oberpfaffenhofen.

On 7 June 1943, with the growing seriousness of the war situation, Hitler himself intervened to expedite the Do 335 and the Me 262 programmes; prototypes of the Dornier plane were already in process of construction. However, Messerschmitt succeeded in persuading Hitler that their Me 262 would make a better high speed bomber than either the Arado Ar 234 or the Dornier Do 335, and on 7 September 1943, Hitler insisted that the Me 262 should receive sole priority. Milch’s advocacy of the two other types had been brushed aside, in spite of the fact that the Do 335 could carry twice the bomb load as the Me 262.

 

 

 

Youtube video of the Dornier Do Pfeil (Arrow) from youtube.com:

 

 

 

The initial prototype of the Dornier plane, designated Do 335 V1 (CP+UA), first flew on 26 October 1943 from Mengen, Württemberg, piloted by Flugkapitan Hans Dieterle and powered by Daimler-Benz DB603A-2 engines delivering 1750 hp at take-off. Handling trials at Oberpfaffenhofen were followed by official evaluation of the aircraft at the Rechlin Erprobungstelle. At high speeds, although some snaking and porpoising was found, the aircraft was generally well-recieved by the Rechlin test pilots. Favourable comments were made about the handling behaviour, manoeuvrability, acceleration and turning circle of the plane. Criticism was levied however at the poor rearward vision and fragile undercarriage. 

During the Winter and Spring of 1943-44, the V1 prototype was joined by  additional development aircraft. Prototypes Do 335 V2 and Do 335 V3 incorporated several minor changes; the oil cooler tank under the nose was shifted into an enlarged annular engine cowling, blisters were added to the cockpit canopy to house small rearview mirrors, and the main undercarriage doors were redesigned. These two protoypes were kept at Oberpfaffenhofen for further test flights. Do 335 V4 was intended as a prototype for the two-seat night and all-weather interceptor but it was cancelled while still under construction in the autumn of 1944.

 

 

 

The Do 335 V1 prototype with chin oil cooler and circular mainwheel doors, and the later V3 prototype with revised nose shape and mainwheel doors (photos from Dornier) - pics from aeroflight.co.uk:

d335-102.jpg

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In spite of the lateness in the day, if the Do 335 was ever to see combat, the prototypes kept on coming. Do 335 V5 (CP+UE) was the armament test prototype, fitted with an engine-mounted 30mm cannon and two 15 mm cannon mounted in the upper nose. Do 335 V6 (CP+UF) and Do 335 V7 (CP+UG) were retained at Oberpfaffenhofen for equipment trials, with V7 later being transferred to Junkers for ground tests using Jumo 213 engines. Do 335 V8 (CP+UH) was used as an engine test bed by Daimler-Benz. With mainstream construction of the new type now planned and intended to take place at Menzel, it was a harsh blow when a bombing rain in March 1944 destroyed much of the production tooling and forced Dornier to set up a new line at Oberpfaffenhofen. 

The prototypes were still being constructed and tested - a situation that was to continue with various prototype variants until the end of hostilities - and the Do 335 V9 (CP+UI) was the prototype for the Do 335A-0 pre-production model. Fitted with a strengthened undercarriage, full armament, and DB603A-2 engines, it was delivered in May 1944 to the Rechlin Erprobungstelle for further official trials. Hitler, at this point, facing the likelihood of an Allied invasion of France at any moment, decided to give maximum priority to the production of the Do 335. It was also  decided to cancel the Heinkel He 219 and use its production facilities to build Do 335s but Ernst Heinkel resisted this move and managed to delay, and eventually ignore, its implementation. 

 

 

 

The two-seater Do 335A-12 - picture from a kit model and photograph of the actual variant (pics from i.ytimg.com and, below, i.pinimg.com/originals):

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Do 335 V9 was quickly followed on the Oberpfaffenhofen production line by the first Do 335A-0 (VG+PG) fighter-bomber. In all, ten of these aircraft were produced, several being used by Erprobungskommando 335 (EK335), formed in September 1944 for the service evaluation and development of operational tactics for this new type. These were part of an order by the RLM which also included 14 prototypes, eleven production A-1 single-seaters and three A-10 and A-12 two-seat training aircraft. Finally, in late 1944, the Do 335A-1 superseded A-0 on the production line, becoming the first combat-ready production model of the aircraft. It was similar to the Do 335A-0 but with the uprated DB603E-1 engines and two underwing hard points for additional bombs or drop tanks. 

Delivery of the Do 335A-1 commenced in January 1945, and immediately impressed. Capable of a maximum speed of 474 mph at 21,325 ft with MW boost, or 426 mph without boost, and able to climb to 26,250 ft in only 14.5 minutes, the Do 335A-1 could easily outpace any Allied fighters in the vicinity; it could also carry a bomb load of 1,100 lb for 900  miles. The aircraft was nicknamed “Pfeil” or “arrow” by Dornier test pilots on account of its speed, but service pilots were less fulsome and called it “Ameisenbär” (Eng. Anteater) because of its long nose. The Do 335A-1 was armed with one 30 mm Mk103 cannon (with 70 rounds) firing through the nose of the propeller hub, and two 15 mm MG-151/15 cannon (with 200 rounds per gun) firing from the top cowling of the forward engine. An internal bomb load of 500 kg (1,100 lb) could also be carried.

 

 

 

Interesting Youtube video showing original footage of the Do 335 in flight (from youtube.com):

 

 

 

 

The Do 335 was an advanced machine in a number of ways and not only in its engine configuration. Pilot safety in an emergency was given some priority, with the result that a pneumatic ejector seat was incorporated which when fired, pushed the pilot away from the aircraft with a force of about 20 G. In addition, the chances of a pilot safely escaping the aircraft were enhanced by the use of exploding bolts that when detonated would jettison the pusher three-blade propeller and dorsal fin. Another innovative design feature was the tricycle landing gear. It has to be said, however, that the Do 335 was not without its faults. Weak landing gear that was prone to failure has already been mentioned, but there was also a tendency for the rear engine to overheat. The D0 335A-1 was also very large for a fighter, with a length of 13.85 m (about 45 ft 6 in), and wing span of 13.8 m (about 45 ft 3 in). It was heavy when loaded, at 9,600 kg (21,000 lb) and stood so high (at 5 m or about 16ft 5 in) that an adult of average height could walk beneath it. Nevertheless, its performance characteristics were such that there might have been mileage in both using the Dornier Do 335 in certain fighter operations and continuing to develop the centre-line thrust concept further. Unfortunately (or fortunately for us), time ran out for the Wartime Luftwaffe.

The Do335A-2 and A-3 were proposed developments with improved canon armament but were never built. One Do 335A-0 became the prototype for the Do 335A-4, an unarmed long-range reconnaissance model with two Rb50/30 cameras in the weapons bay and DB603G engines. Ten A-4s were ordered for production but none were completed. The same fate was to befall the Do 335A-6 radar-equipped two-seat night-fighter variant, prototyped by the Do 335 V10 (CP+UK). In this variant, a second cockpit for the radar operator was positioned above and behind the normal cockpit, and the weapons bay replaced by a redesigned fuel tank. Radar antennae were attached to the wing leading edges and flame dampers fitted to the exhausts. The prototype V10 was never actually fitted with the FuG217 radar and although production of the A-6 was transferred to Heinkel in Vienna, none were assembled. A number of dual-control control trainers were produced interspersed with production of the A-1; these were variants Do 335A-10 and Do 335A-12 which had their respective prototypes. The instructor occupied the second cockpit (though without an ejector seat due to shortages). 

 

 

 

A Dornier Do 335A-1, work number 107, at the factory in Oberpfaffenhofen. This example was taken over by American troops and examined by US intelligence (pic from airpages.ru):

do335_12.jpg

 

 

Original Dornier handbook pages for the Do 335A-1 (pic from airpages.ru):

do335_15.jpg

 

 

 

As the war situation further deteriorated, development efforts switched from the A-series fighter-bomber to the more heavily armed B-series heavy fighter. Time was running out for Hitler, however, and the B-series aircraft were to be represented only by two single prototype machines - a Do 335 V13 (RP+UA) for the Do 335B-1 and a Do 335 V14 (RP+UB) for the B-4. The V13 featured a revised nose undercarriage arrangement, a V-shaped armoured windscreen, DB603E  engines, an additional fuel tank in the weapons bay, and the replacement of the two 15 mm MG151 cannon in the nose by 20mm MG151s. The B-4 prototype had this armament supplemented by two 30 mm Mk103 cannon mounted on the inner wing leading edges. Further developments were still under construction, including some with two-stage supercharger DB603LA engines capable of 2,100 hp.

 

Two of the sources used for this topic are pretty clear that no pilots flew Do 335s in combat, at least not serving with a fully operational unit. However, this may be an over-simplication of the exact situation, and here I quote from the Aeroflight (2016) article:


“Plagued by mechanical unreliability and lack of aviation fuel, the operational career of the Do 335 is rather obscure. Do335A-0 and A-1 aircraft are thought to have flown a number of operational missions with EK335. Some were also used by III/KG2 in the Spring of 1945. French fighter ace Pierre Clostermann’s book ‘The Big Show’ mentions an encounter with a Do 335 in April 1945, during which the German aircraft easily outpaced the pursuing Hawker Tempests and escaped. Such events were very rare, so it seems likely that most operations were high speed interdiction missions - many taking place at night.”

 

When the US Army overran the Oberpfaffenhofen factory in late April 1945, only 11 Do 335A-1 single-seat fighter-bombers had been completed as well as two Do 335 A-12 conversion trainers. There were another nine A-1s, four A-4s and two A-12s in final assembly, with components and assemblies ready for 70 more aircraft. Heinkel at Vienna had not been able to build any Do 335A-6 night-fighters. At the end of the War, it transpired that a number of planned developments of the Do 335 were in progress on the drawing board, including several big-winged high altitude fighters, the Do 535 with a rear jet engine, the Do 635 (later Ju 635) long-range reconnaissance aircraft with twin fuselages joined by a common wing centre section, and the P 256 jet fighter. 

 

 

 

Two prototypes including the V13 prototype for the B-1 series designed for heavy day-fighter roles (pic from airpages.ru)

do335_20.jpg

 

 

 

In terms of examples that survived the immediate aftermath of war, two A-0 single-seaters were shipped back to the USA on the British carrier HMS Reaper for evaluation by the US Navy and Air Force. An airworthy A-12 two-seater was flown to the UK and flight tested at the Royal Aircraft establishment (RAE) Farnborough, but an A-1 also destined for Britain force-landed at Merville in France en route and was abandoned. A further incomplete B-series Do 335 airframe also made it to Britain. The A-12 was test flown only three times before crashing and killing the test pilot in January 1946. Some interesting observations have been made by Captain Eric “Winkle” Brown who undertook initial flight testing of the Do 335 A-12, including a tendency for the brakes to overheat and even catch fire; a problem suffered generally by Luftwaffe aircraft. Fortunately, this was partly compensated for by the reversible-pitch tractor propeller which could reduce landing distance by 183 metres (600 ft). Brown says that once the aircraft had reached high speeds, the controls were responsive and well-harmonised, and he praised the powered ailerons and stability of the plane. Brown concluded that although later Allied fighters would have been able to match it when out in the open, as an all-weather and night-fighter, the Do 335 would have been a formidable opponent. He draws specific attention to the speed of the Do 335 and the fact that the Mustang or Spitfire would have had a job nailing it.

 

 

 

The original Do 335A-12 taken to Britain and tested at RAE Farnborough - see text for details and, below, front view of a Dornier 335 V3 prototype showing the wide track of the main wheels. A third picture, bottom, of a Dornier 335 shows the characteristic cruciform tail of the type (pics from airpages.ru):

do335_45.jpg

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do335_08.jpg

 

 

 

 

There is now only a single surviving Dornier Do 335, which is on display at the Steven F. Udvar-Hazy Center (the Smithsonian Air and Space Museum at Dulles Airport, Virginia, USA). This aircraft, the second Do 335A-0 built and originally designated VP+GH and A-02 (Wk No. 240102), had been evaluated at the US Navy’s Patuxant River Test Center from 1945-48. Subsequent to testing, the plane was left in open storage for no less than 27 years, in the grounds of Naval Air Station (NAS) Norfolk before being transferred to the storage facility of the National Air and Space Museum (NASM) in 1961. Finally, the decaying airframe was flown back to Munich, in 1974, for restoration and preservation by the Dornier company the following year, at Oberpfaffenhofen (then in the process of building Alpha Jets). During the restoration process, crafts-people from the Dornier company, of whom many had worked for the firm since World War Two, were surprised to find still attached to the aircraft the explosive bolts designed to blow off the tail fin and the rear propeller. Dornier displayed the preserved plane at the May 1976 Hannover Airshow before moving it to the Deutsches Museum in Munich. Then, in 1986, it was returned to the Paul E. Garber Facility for storage. It is currently on display in the Boeing Aviation Hangar (NASM) at the Steven F. Udvar-Hazy Center in Chantilly, Virginia, USA (Inventory Number A19610129000).

 

 

 

Depiction of a Dornier Do 335 Pfeil in flight (pic from img1.goodfon.com):

dornier-do-335-ww2-war-art.jpg


 

 

 

Among the sources used in the research and writing of this topic, the following are to be particularly acknowledged; in descending order of importance:

“Dornier Do 335 Aircraft Profile” Article last updated 26 June 2016 by admin; Aeroflight:the Website for Aviation Enthusiasts (aeroflight.co.uk/aircraft/types/type-details/dornier-do-335/htm

“Flying the Arrow”, by Guiseppe Picarella/London, 21 December 2004; article for Flight Global (flightglobal.com/flying-the-arrow/58253.article)

“Dornier Do 335 A-0 Pfeil (Arrow)”; Smithsonian National Air and Space Museum, undated topic incl. display details (airandspace.si.edu/collection-objects/dornier-do-335-A-0-pfeil-arrow/nasm_A19610129000)

“The World’s Strangest Aircraft” by Michael Taylor: published in 1996 by Grange Books, London.


 

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very good show ! i have a photo of a 1938 dornier " flying boat".   tied up in New York harbor with one engine pod of 6 (i think) removed for repair.  vin 

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Thanks Honour. I think only 37 of them were built, but it indicated that the NAZI's where resourceful, but Hitler had flawed forethought.

I'm glad he did.:wink:

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Yet another great and worthwhile read.

:thumbsup:

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