Dornier Do 335

Do 335 Pfeil
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Type	fighter/bomber
Manufacturer	Dornier Flugzeugwerke
Maiden flight	October 1943
Introduced	1944
Primary user	Luftwaffe
Number built	38

The Dornier Do 335 Pfeil ("Arrow", unofficially also Ameisenbär {"anteater"}), was a World War II heavy fighter built by the Dornier company. The Pfeil had performance much better than other twin-engine designs due to its unique centerline thrust layout. The Luftwaffe was desperate to get the design into squadron use, but delays in engine deliveries meant only a handful were delivered before the war ended.

Development

The origins of the Do 335 trace back to World War I when Claudius Dornier designed a number of flying boats featuring remotely-driven propellers and later, due to problems with the drive shafts, tandem engines. Tandem engines were used on most of the multi-engined Dornier flying boats that followed, including the highly successful Dornier Wal and the gigantic Dornier Do X. The remote propeller drive, intended to eliminate parasitic drag from the engine entirely, was tried in the innovative, but unsuccessful Dornier Do 14, and elongated drive shafts as later used in the Do 335 saw use in the rear engines of the tandem-engined Dornier Do 26 flying boat.

There are many advantages to this design over the more traditional system of placing one engine on each wing, the most important being power from two engines with the frontal area (and thus drag) of a single engine design, allowing for higher performance. It also keeps the weight of the twin powerplants near, or on, the aircraft centerline, increasing the roll rate compared to a traditional twin. In addition, a single engine failure does not lead to asymmetric thrust, and in normal flight there is no net torque so the plane is easy to handle. The choice of a full "four-surface" set of cruciform tail surfaces in the Do 335's design, allowed the ventral vertical fin/rudder assembly to project downwards from the extreme rear of the fuselage, in order to protect the rear propeller from an accidental ground strike on takeoff.

In 1939 Dornier was busy working on the P.59 high speed bomber project, which featured the tandem engine layout. In 1940, he commissioned a test aircraft to validate his concept for turning the rear pusher propeller with an engine located far away from it and using a long driveshaft. This aircraft, the Göppingen Gö 9. showed no unforeseen difficulties with this arrangement, but work on the P.59 was stopped in early 1940 when Hermann Göring ordered the cancellation of all projects which would not be complete within a year or so.

In May 1942, Dornier submitted an updated version with a 1,000 kg bombload as the P.231, in response to a requirement for a single seat high speed bomber/intruder (other entries included the Blohm & Voss BV 155). P.231 was selected as the winner after beating rival designs from Arado and Junkers, and a development contract was awarded as the Do 335. In the Autumn of 1942 Dornier was told that the Do 335 was no longer required, and instead a multi-role fighter based on the same general layout would be accepted. This delayed the prototype delivery as it was modified for the new role.

Fitted with Daimler-Benz DB 603A engines delivering 1,750 PS (1, 726 hp, 1,287 kW) at takeoff, the first prototype flew in October 1943. The pilots were surprised at the speed, acceleration, turning circle and general handling of the type; it was a twin that flew like a single. The only sore spots they found were the poor rearward visibility and weak landing gear. V2 and V3 incorporated several minor changes; the oil cooler under the nose incorporated into the annular engine cowling, blisters were added to the canopy with small rear view mirrors, and the main undercarriage doors were redesigned.

On 23 May 1944 Hitler ordered maximum priority to be given to Do 335 production. The main production line was intended to be at Manzel, but a bombing raid in March destroyed the tooling and forced Dornier to set up a new line at Oberpfaffenhofen. The decision was made to cancel the Heinkel He 219 and use its production facilities for the Do 335 as well. However, Ernst Heinkel managed to delay, and eventually ignore, its implementation.

Flight tests

File:Do335a-0 1945 USN Patuxent River test center.jpg

Do 335 tested in the USA

The first 10 Do 335 A-0s were delivered for testing in May. By late 1944, the Do 335 A-1 was on the production line. This was similar to the A-0 but with the uprated DB 603 E-1 engines and two underwing hard points for additional bombs, drop tanks or guns. Capable of a maximum speed of 474 mph (763 km/h) at 6,500 m (21,300 ft) with MW 50 boost, or 426 mph (686 km/h) without boost, and able to climb to 26,250 ft (8,000 m) in under 15 minutes, the Do 335 A-1 could easily outrun any Allied fighters it encountered. Even with one engine out it could reach about 350 mph (563 km/h).

Delivery commenced in January 1945. When the U.S. Army overran the Oberpfaffenhofen factory in late April 1945, only 11 Do 335 A-1 single seat fighter-bombers and two Do 335 A-12 conversion trainers had been completed.

In his book The Big Show, French ace Pierre Clostermann claims the first Allied combat encounter with a Pfeil in April 1945. Leading a flight of four Hawker Tempests from No. 3 Squadron RAF over northern Germany, he intercepted by chance a lone Do 335 flying at maximum speed at treetop level. Detecting the British aircraft, the German pilot reversed course to evade. In spite of the Tempest's considerable speed, the RAF fighters were not able to catch up or even get into firing position.

Variants

• Do 335A-0 : Ten pre-production aircraft.
• Do 335A-1 : Single-seat fighter-bomber aircraft.
• Do 435 : Proposed Two-seat night-fighter version. Not built.
• Do 535 :Proposed turbojet powered version. Not built.
• Do 635 : Proposed long-range reconnaissance version. Not built.

Survivors

File:100 3125.JPG

The only surviving Do 335 (VG+PH) at the Steven F. Udvar-Hazy Center near Washington, DC

Only one Do 335 survives today. The aircraft was the second preproduction Do 335 A-0, designated A-02, with construction number (Werknummer) 240102, and factory radio code registration, or Stammkennzeichen, of VG+PH. The aircraft was assembled at Dornier's plant in Oberpfaffenhofen (southern Germany) on 16 April 1945. It was captured by allied forces at the plant on 22 April 1945. The aircraft was test flown from a grass runway at Oberwiesenfeld, near Munich, to Cherbourg, France while escorted by two P-51s. The Do 335 was easily able to out distance the escorting Mustangs and arrived at Cherbourg 45 minutes before the P-51s. VG+PH was one of two Do 335s to be shipped to the United States aboard the Royal Navy ship HMS Reaper, along with other captured German aircraft, to be used for testing and evaluation under a USAAF program called "Operation Sea Horse." One Do 335, with registration FE-1012, went to the USAAF and was tested in early 1946 at Freeman Field, Indiana. Its fate is a mystery.

VG+PH went to the Navy for evaluation and was sent to the Test and Evaluation Center, Patuxent River Naval Air Station, Maryland. Following testing from 1945 to 1948, the aircraft languished in outside storage at Naval Air Station Norfolk. In 1961, it was donated to the Smithsonian's National Air Museum, though it remained in deteriorating condition at Norfolk for several more years before being moved the National Air & Space Museum's storage facility in Silver Hill, Maryland. In October 1974, VG+PH was returned to the Dornier plant in Oberpfaffenhofen, Germany (then building the Alpha Jet) for a complete restoration. In 1975 the aircraft was restored by Dornier employees, many of whom had worked on the airplane originally. They were amazed to find that the explosive charges built into the aircraft to blow off the tail fin and rear propeller in the event of an emergency were still on the aircraft and active 30 years later.

Following restoration the completed Do 335 was displayed at the Hanover, Germany Airshow from 1 May to 9 May 1976. After the air show, the aircraft was loaned to the Deutsches Museum in Munich where it was on display until 1986, when it was shipped back to Silver Hill, Maryland. VG+PH can be seen today in the Steven F. Udvar-Hazy Center of the National Air & Space Museum alongside other unique late-war German aircraft such as the Arado Ar 234B-2 "Blitz," and the only surviving Heinkel He 219A "Uhu" (currently only the fuselage is on display, the wings are still undergoing restoration as of March 2007).