Arado Ar 240

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Ar 240
Model of an Ar 240
Role Zerstörer (Destroyer) prototype
National origin Germany
Manufacturer Arado Flugzeugwerke
First flight 10 May 1940
Primary user Luftwaffe
Number built 15

The Arado Ar 240 was a German twin-engine, multi-role heavy fighter aircraft, developed for the Luftwaffe during World War II by Arado Flugzeugwerke. Its first flight was on 10 May 1940,[1] but problems with the design hampered development, and it remained only marginally stable throughout the prototype phase. The project was eventually cancelled, with the existing airframes used for a variety of test purposes.

Design and development

The Ar 240 came about as the response to a 1938 request for a much more capable second-generation heavy fighter to replace the

Reichsluftfahrtministerium (RLM/German Aviation Ministry) was nevertheless interested enough to order prototypes of both designs.[2]

Prior to this point, Arado had invested heavily in several lines of basic research. One was the development of the "Arado travelling

fatigue for any flight above about 4,500 m (14,760 ft). Finally, they had also invested in a technically advanced remote-control defensive gun system, which they had been experimenting with for several years. The system used a gunsight located in the rear cockpit, operated by the navigator/gunner, which had optics on both the top and bottom of the aircraft, allowing aim in any direction. The gunsight was hydraulically connected to well-streamlined pancake-shaped, remotely-operated turrets
on the top and bottom of the aircraft. For the Ar 240 design, the Arado engineers combined all this research into a single airframe.

For outright performance, they used as small a wing as reasonable, thereby lowering

leading edge slats for high low-speed lift. When the flaps were extended, the upper portion of the ailerons
would remain in place while the lower portion extended rearward, essentially increasing the wing area.

A Jumo 222-powered Junkers Ju 288 prototype with ducted spinners, of a similar type to that intended for the Ar 240.

The

Ta 154
) also benefitted from the simpler setup of an annular radiator just forward of the engine.

The fuel cells in the wings were provided with a newly developed self-sealing system that used thinner tank liners, allowing for more fuel storage. The liners could not be easily removed as they stuck to the outer surface of the tank, so in order to service them, the wing panelling had to be removable. This led to a complex system for providing skinning stiff enough to be handled in the field, complicating construction and driving up weight.

As with all German multi-use aircraft designs of the era, the aircraft was required to be a credible dive bomber. The thick wing panelling was not suitable for piercing for conventional dive brakes, so a "petal"-type brake was installed at the extreme rear of the fuselage — appearing much like what had been trialled with the Dornier Do 217 — which, unlike the Do 217's vertically-opening "petals", opened to the sides instead when activated. When closed the brake looked like a stinger, extending beyond the horizontal stabilizer and twin fins.

Finally, the cockpit was fully pressurized. This would not have been easy if the armament had to be hand-operated by the gunner, as it would have required the guns to penetrate the rear of the cockpit canopy. However, the remote control system allowed them to be located in turrets in the unpressurized rear of the fuselage.

All of this added weight, and combined with the small wing, led to a very high wing loading of 330 kg/m2 (221 lb/ft2), compared to an average of about a 100 for a single-seat fighter.

Operational history

Testing and evaluation

Technical specifications were first published in October 1938, followed by detailed plans later that year. In May 1939, the RLM ordered a batch of six prototypes. The first Ar 240 V1 prototype, DD+QL, took to the air on 25 June 1940, and immediately proved to have poor handling in all axes, also tending to overheat during taxiing.

The handling was thought to be the result of the ailerons being too small, given the thick wing, so the second prototype was modified to have larger ones, as well as additional vertical fin area on the dive brakes to reduce yaw. In addition, small radiators were added to the landing gear legs to improve cooling at low speeds, when the gear would normally be opened. Ar 240 V2, KK+CD, first flew on 6 April 1941, and spent most of its life at the factory in an experimental role.

Ar 240 V3 followed, the first to be equipped with the FA 9 rear-firing armament system, developed jointly by Arado and DVL, armed with a 7.92 mm (.312 in) MG 81Z machine gun. Ar 240 V4 was the first to include an operational dive brake, and flew on 19 June 1941. Ar 240 V5 and the V6 followed in December and January, including the upgraded FA 13 system, using two 13 mm (.51 in) MG 131 machine guns in place of the MG 81Z for a considerable boost in firepower.[2] Ar 240 V7 and V8 acted as prototypes for the planned Ar 240B, which was to use two Daimler Benz DB 605As, while Ar 240 V9, V10, and V11, and V12 served as prototypes of the Ar 240C.[4]

The Ar 240's excellent performance quickly led to the V3, V5 and V6 being stripped of their armament, including the defensive guns, and used as

JG 5 'Eismeer', based in Finland, received two, 1. and 3.(F)/100 on the Eastern Front (World War II) received one each and 1.(F)/123 in Italy received one.[1]

Variants

Arado Ar 440
Ar 240A-0
Four preproduction aircraft.
Ar 240B
Proposed version
Ar 240C-1
Heavy fighter version.
Ar 240C-2
Night fighter version.
Ar 240C-3
Light bomber version.
Ar 240C-4
High-altitude reconnaissance version. The project was abandoned in favour of the Ar 440.
Ar 440
Ar 240 V10 was earmarked as the Ar 440 prototype; second prototype not built.
MK 108 cannons, plus 1,000kg bomb load. First flown in early Summer 1942, it proved far superior to the Ar 240. Production was eventually rejected in favour of the Dornier Do 335.[1]

Specifications (Ar 240A-01)

Data from [6]

General characteristics

  • Crew: two
  • Length: 12.81 m (42 ft 0 in)
  • Wingspan: 13.34 m (43 ft 9 in)
  • Height: 3.95 m (13 ft 0 in)
  • Wing area: 31.3 m2 (337 sq ft)
  • Aspect ratio: 5.68
  • Empty weight: 6,200 kg (13,669 lb)
  • Gross weight: 9,450 kg (20,834 lb)
  • Max takeoff weight: 10,297 kg (22,701 lb)
  • Powerplant: 2 ×
    Daimler-Benz DB 601E
    inverted V-12 liquid-cooled piston engine, 876 kW (1,175 hp) each
  • Propellers: 3-bladed constant speed metal propellers

Performance

  • Maximum speed: 618 km/h (384 mph, 334 kn)
  • Cruise speed: 555 km/h (345 mph, 300 kn)
  • Range: 2,000 km (1,200 mi, 1,100 nmi)
  • Service ceiling: 10,500 m (34,400 ft)
  • Rate of climb: 9.083 m/s (1,788.0 ft/min)
  • Time to altitude: Climb to 6,000 m (19,700ft): 11 min
  • Wing loading: 302 kg/m2 (62 lb/sq ft)
  • Power/mass: 0.19 kW/kg (0.11hp/lb)

Armament

See also

Aircraft of comparable role, configuration, and era

Related lists

References

  1. ^ a b c Munson 1978, p. 26.
  2. ^ a b Gunston 1989, p. 157.
  3. ^ Ju 288 nacelles for Jumo 222 engines, showing the flow-through ducted spinners
  4. ^ "Luftwaffe Lovers: Multirole aircraft - Arado Ar240". 4 June 2016.
  5. ISBN 9781783034192
    , unpaginated.
  6. ISBN 978-1-900732-06-2
    .

Bibliography

External links

Wikimedia Commons has media related to Arado Ar 240.
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