Arado Ar 240

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L'Ar 240 sur Wikipedia de langue anglaise :

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The Arado Ar 240 was a [Vous devez être inscrit et connecté pour voir ce lien] twin-engine multi-role [Vous devez être inscrit et connecté pour voir ce lien] aircraft developed for the [Vous devez être inscrit et connecté pour voir ce lien] during [Vous devez être inscrit et connecté pour voir ce lien] by [Vous devez être inscrit et connecté pour voir ce lien].

Its first flight was in [Vous devez être inscrit et connecté pour voir ce lien], but problems with the design hampered development and it remained only marginally stable through the [Vous devez être inscrit et connecté pour voir ce lien] phase.

The project was eventually cancelled, with the existing [Vous devez être inscrit et connecté pour voir ce lien] 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generation heavy fighter to replace the [Vous devez être inscrit et connecté pour voir ce lien], which was becoming outdated.

Both Arado and [Vous devez être inscrit et connecté pour voir ce lien] responded. Messerschmitt's response, the [Vous devez être inscrit et connecté pour voir ce lien], was a totally new design, but thanks to Messerschmitt's experience with the Zerstorer ("Destroyer") concept, it would be able to enter service quickly.

Arado's design was considerably more ambitious for the smaller firm, a dream project of Arado's chief designer, Walter Blume, since the mid-1930s.

While it would take some time before deliveries of the Arado design could begin, the [Vous devez être inscrit et connecté pour voir ce lien] (German War Ministry, RLM) was nevertheless interested enough to order prototypes of both designs.

Prior to this point, Arado had invested heavily in several lines of basic research.

One was the development of the "[Vous devez être inscrit et connecté pour voir ce lien]" which offered excellent low-speed lift performance.

Another was ongoing work into the design and construction of [Vous devez être inscrit et connecté pour voir ce lien], which dramatically lower pilot [Vous devez être inscrit et connecté pour voir ce lien] 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 [Vous devez être inscrit et connecté pour voir ce lien] located in the rear cockpit, operated by the [Vous devez être inscrit et connecté pour voir ce lien]/[Vous devez être inscrit et connecté pour voir ce lien], 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 [Vous devez être inscrit et connecté pour voir ce lien] 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 [Vous devez être inscrit et connecté pour voir ce lien] (at the expense of greater [Vous devez être inscrit et connecté pour voir ce lien]).

Normally this would make the plane have "impossibly high" landing speeds, but this was offset by the use of a huge travelling flap and [Vous devez être inscrit et connecté pour voir ce lien] for high low-speed lift.

When the flaps were extended, the upper portion of the [Vous devez être inscrit et connecté pour voir ce lien] would remain in place while the lower portion extended rearward, essentially increasing the wing area.

The [Vous devez être inscrit et connecté pour voir ce lien] were conventionally installed and equipped with a three-blade fully-adjustable [Vous devez être inscrit et connecté pour voir ce lien].

The [Vous devez être inscrit et connecté pour voir ce lien] were somewhat unique however, quite similar to those fitted to the [Vous devez être inscrit et connecté pour voir ce lien] which pioneered them, consisting of an annular block located in front of the engine, but with the Ar 240 partially covering each of them in an oversized propeller spinner, with the air entering through a large hole in the front of the spinner and exiting out the [Vous devez être inscrit et connecté pour voir ce lien] flaps.

As with the Jumo inline-powered versions of the Ju 88, this made the plane look as if it was mounting a [Vous devez être inscrit et connecté pour voir ce lien], and the Ar 240, like later Jumo inline-powered fighter aircraft from the Focke-Wulf firm (the Fw 190 D, Ta 152
and twin engined Ta 154) also benefitted from the simpler setup of an annular radiator just forward of the engine.

The [Vous devez être inscrit et connecté pour voir ce lien] in the wings were provided with a newly developed [Vous devez être inscrit et connecté pour voir ce lien] 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 [Vous devez être inscrit et connecté pour voir ce lien].

The thick wing panelling wasn't suitable for piercing for conventional [Vous devez être inscrit et connecté pour voir ce lien], so a "petal"-type brake was installed at the extreme rear of the [Vous devez être inscrit et connecté pour voir ce lien] which opened to the sides when activated.

When closed the brake looked like a stinger, extending beyond the [Vous devez être inscrit et connecté pour voir ce lien] and twin [Vous devez être inscrit et connecté pour voir ce lien].

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 [Vous devez être inscrit et connecté pour voir ce lien].

However, the remote control system allowed for them to be located in turrets in the unpressurized rear of the fuselage.

All of this added weight combined with the small wing led to a very high [Vous devez être inscrit et connecté pour voir ce lien] of 330 kg/m² (221 lb/ft²), compared to an average of about a 100 for a single-seat fighter.

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, and it also tended to overheat during[Vous devez être inscrit et connecté pour voir ce lien].

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 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 as a test plane.

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) [Vous devez être inscrit et connecté pour voir ce lien].

Ar 240 V4 was the first to include an operational dive brake, and flew on 19 June 1941.

Ar 240 V5 and V6 followed in December and January, including the upgraded FA 13 system using two 13 mm (.51 in) [Vous devez être inscrit et connecté pour voir ce lien] in place of the MG 81Z for a considerable boost in firepower.

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 [Vous devez être inscrit et connecté pour voir ce lien] aircraft over [Vous devez être inscrit et connecté pour voir ce lien], where no other two-seater could venture by 1942.

Mitrailleuse MG 131

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Variants


Ar 240 A-0

Four pre-production aircraft.


Ar 240B

Proposed version


Ar 240 C-1

Heavy fighter version.


Ar 240 C-2

[Vous devez être inscrit et connecté pour voir ce lien] version.


Ar 240 C-3

[Vous devez être inscrit et connecté pour voir ce lien] version.


Ar 240 C-4

High-altitude reconnaissance version. The project was abandoned in favour of the Ar 440.


Ar 440

Improved variant with the fuselage stretched by 0.9m (35.5 in) and powered by the 1900hp (1417kW) DB 603G, the production aircraft would have had two 2000hp (1491kW) DB 627A/B engines.

Prototype converted from a prototype Ar 240, total of four built in 1942.
The type did not enter production and the programme was cancelled in 1943.

Specifications (Ar 240 A-0)

Data from German Aircraft of the Second World War

General characteristics

• Crew: Two
  
• Length: 12.8 m (42 ft 0⅓ in)
  
• [Vous devez être inscrit et connecté pour voir ce lien]: 13.33 m (43 ft 9 in)
  
• Height: 3.95 m (12 ft 11½ in)
  
• Wing area: 31.3 m² (337 ft²)
  
• Empty weight: 6,200 kg (13,669 lb)
  
• Loaded weight: 9,450 kg (20,833 lb)
  
• Powerplant: 2× Various Daimler-Benz [Vous devez être inscrit et connecté pour voir ce lien],