Dornier Do 335 Pfeil heavy fighter

The Dornier Do 335 Pfeil was a very special aircraft of unique design, claimed to be the fastest piston-engine aircraft of the Second World War. The idea of allocating two compounds engine- propeller in the same axis was intended to reduce the aerodynamic resistance of the aircraft in comparison with the conventional aircraft that had them installed in the wings. One of the propellers would be pulling the aircraft while the other would be pushing it. This idea, however, did not create a new school of thinking; rather, it could be considered as a tantrum from the jealous piston engines towards the future technology of turbojets, which in no time would surpass in efficiency any aeronautical application of the piston engines, no matter how witty it were. Actually the Dornier company had been investigating this propulsion system based in a tandem configuration for the engines since the end of the First World War; the Dornier Do 335 would be the definitive creation after 25 years of experience, but born in the worst moment possible. This tandem configuration allowed to fly in normal conditions with only one engine running, which in turn allowed for a maximum speed of only 563 kilometers/hour, given the considerable weight of this aircraft, which would include then the inactive engine, a true dead weight. This was the Achilles Heel of this aircraft, excessive weight and size that were not really justified by the excellent prestations, that moreover could be improved by using other techniques. The truth behind the flamboyant design was that most part of the turbojet fighters then in development could surpass the speed of the Dornier 335 - with the notable exception of the Gloster Meteor, situation that would not last much anyway -, in some cases with a notorious margin. Also some of the most advanced designs of single-engine piston fighters introduced towards the end of the conflict would be capable of reaching maximum speeds not far from the 765 kilometers/hour than the Do 335 could reach; and they could do this while carrying comparable firepower - which in the Do 335 was comparatively weak for an aircraft of such dimensions - in a rather smaller cell.

This unique design of fighter flew for the first time in the autumn 1943, starting the test flights the pre-series models A-0 at the end of the summer 1944. To these were united the A-1 to form a Kommando for tests in operations in the beginning of 1945. Total production reached only 37 exemplars. Let us see now a brief description of some of the different versions of the Do 335:

Do 335 V1/14: Prototypes. Progressive changes in the fuselage and since the V5 in the armament as well. 14 units built.

Do 335 A-0: Pre-series model. Fighter-bomber version. Engines DB 603A-2 1750 HP. 10 units built.

Do 335 A-1: Initial series model. Different engines. 11 units built.

Do 335 A-4: Long-range reconnaissance version, unarmed. Two cameras Rb 50/30 (18) in the bombs compartment. Engine DB 603G 1900 HP. Conversion from an A-0, not completed.

Do 335 A-6, A-10: Two-seat night fighter and training versions, respectively. Not completed (only prototypes V-10 and V-11).

Do 335 A-12: Two-seat training version. Engine DB 603E-1 1800 HP. 2 units built.

Do 335B: Tank destroyer version. Not completed (only prototypes V-13 and V-14).

Note from the author: In the two-seater version the rear cockpit was placed in a raised position in respect of the fore cockpit, in a configuration that reminds combat helicopters like the Mil Mi-24.




The Do 335 shown in this wartime photo was later exposed in the National Air and Space Museum in Washington DC. The only surviving exemplar, this aircraft was the second pre-series exemplar of the version A-0, denominated A-02, whose serial number is 240102 and the registry of the factory VG+PH. This exemplar was assembled in the Dornier facilities in Oberpfaffenhofen the 16th April 1945 and captured by the Allies the 22nd April in the same factory. Another exemplar with registry number FE-1012 was sent as well to United States for evaluation and its fate remains a mystery.

The comparison chart below shows the characteristics of the Do 335 along with other prominent aircraft of that time, they all German with the exception of the American P-80. In 1939 Fritz Wendel had achieved the highest speed ever in a piston-engine aircraft; he reached 754.8 kilometers/hour aboard a Messerschmitt Me 209 V1. The Do 335 was capable of surpassing that speed while not being an aircraft designed for the sole purpose of beating a speed record, but a complete war machine. However, traditional piston-engine propulsion was already giving the maximum that it could; we can take as reference the record set in August 1989 by a modified Grumman F8F Bearcat known as Rare Bear, which reached a speed of 850.24 kilometers/hour. This happened 45 years after the first Do 335 had flown, and the increase in speed had been less than 90 kilometers/hour, while in the time of the Do 335, the babbling turbojet engines were already able to surpass such speed of 850 kilometers/hour. The Me 262, the He 162 or the P-80 were able to reach such speed, but certainly they were not heavy fighters as the Do 335. However this one was comparatively armed like a normal fighter of the late wartime and it is hard to tell what exactly the Luftwaffe needed then of such an aircraft. Due to the piston-engine typology it seems clear that this aircraft would not age well in the hypothetic case of a prolonged war. A few advanced piston-engine fighters were already capable of reaching speeds above 700 kilometers/hour with only one engine; the Ta 152H was really close to catch the Do 335 in this regard. The Do 335 could have been a powerful adversary during few years, until the number of turbojet fighters - for example the P-80 - in the battlefield would grow in intolerable numbers or other simpler and cheaper piston-engine designs of similar performance - for example the Ta 152H - would have rendered the Do 335 as not profitable. It is also notable that the version of the bomber Ar 234 equipped with four BMW 003A-1 turbojet engines could reach 875 kilometers/hour, far away from the standard version fitted with two engines.



Structure of the Do 335

Even if not in every of its dimensions, it seems factible to think in the Do 335 as the most voluminous fighter, in general terms, produced during the Second World War. The landing gear in fore tricycle contributed to accentuate the impression of a behemoth fighter. The fuselage was of entirely metallic construction, although the vertical fins had wooden leading edges. Pilots were generally enthusiastic about the characteristics of the Do 335, commenting favorably on its general handling behavior and maneuverability, and in particular, on its acceleration and turning circle. The instruments and controls in the cockpit were the standard in any German aircraft of its kind; the front panel instrumentation, with twin indicators for the engines to the right, and the side control consoles, had certain resemblance with the ones installed in the Me 262. There was a primitive ejection seat and there were explosive charges ready to detach the rear tails and propeller from the aircraft in the event of an emergency ejection, along with the canopy. The Do 335 had the world's first ejection seat; it was vital due to the rear propeller, albeit this seat could cause terrible injuries. Backwards visibility from the cockpit was deficient however, due to the anormally thick aft fuselage that had to shelter the rear engine. The engines were two in-line Daimler- Benz DB 603E-1, liquid-cooled, with twelve pistons in inverted V. They were quite powerful but not specially; there were more powerful engines in use already in other countries. The development of this engine had started already before 1939, but it was not ready until 1942. As a curiosity, it may be worth saying that one of the prototypes of this engine was intended to be installed in the automobile Mercedes-Benz T80 created to set a speed record; it was stimated that it could reach 750 kilometers/hour, which is hard to believe. Nonetheless, the outbreak of the war cancelled the attempt. There was a huge fuel tank (1280 liters) behind the pilot's cabin, or below the operator's cabin, in the case of the two-seater version; it is improbable that the crew would appreciate such placement for the fuel tank. Just after this deposit was installed the rear engine, which was connected to the rear propeller by a long transmission shaft; there was a ventral air intake in the aft fuselage to refrigerate this engine. To protect the rear propeller during takeoff a ventral tail was installed symmetrically to the dorsal tail. Wings had a certain arrow shape, but not so notorious as in the Me 262; there were not guns installed in them, but pods in the lower surface, allowing to mount cannon pods, bombs or fuel tanks as needed. The wings also provided stowage space for the master compass, the armored hydraulic fluid reservoir and compressed air bottles. A 30-millimeter cannon shared space with the fore engine, firing through the propeller cone, while two 15 -millimeter machine guns were installed above the engine, synchronized with the rotation of the propeller.



Specifications for Do 335A-1

Categories: Aircraft - World War Two - 20th Century - [General] - [General]

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Article submitted: 2014-11-10