Arado Ar 240

Ar 240

Model of an Ar 240
Role	Zerstörer (Destroyer) prototype
Manufacturer	Arado Flugzeugwerke
Designer	Walter Blume
First flight	25 June 1940
Primary user	Luftwaffe
Number built	14

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 in 1940, 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request for a much more capable second generation heavy fighter to replace the Messerschmitt Bf 110, which was becoming outdated. Both Arado and Messerschmitt responded. Messerschmitt's response, the Me 210, was a totally new design, but thanks to Messerschmitt's experience with the Zerstörer ("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 Reichsluftfahrtministerium (German Aviation Ministry, RLM) was nevertheless interested enough to order prototypes of both designs.^[1]

Prior to this point, Arado had invested heavily in several lines of basic research. One was the development of the "Arado travelling flap" which offered excellent low-speed lift performance. Another was ongoing work into the design and construction of pressurized cockpits, which dramatically lowered pilot 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 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 parasite drag (at the expense of greater lift-induced drag). Normally this would make the plane have "impossibly high" landing speeds, but this was offset by the use of a huge travelling flap and 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.

The Daimler-Benz DB 601 inline engines were conventionally installed and equipped with a three-blade fully adjustable propeller. The radiators were somewhat unique however, quite similar to those fitted to the Junkers Ju 88 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 cowl flaps. As with the Jumo inline-powered versions of the Ju 88, this made the plane look as if it was mounting a radial engine, 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 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 wasn't suitable for piercing for conventional dive brakes, so a "petal"-type brake was installed at the extreme rear of the fuselage which opened to the sides 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 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 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, and it also tended 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 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 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.^[1]

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 reconnaissance aircraft over England, where no other two-seater could venture by 1942.

Variants

Ar 240 A-0: Four pre-production aircraft.
Ar 240B: Proposed version
Ar 240 C-1: Heavy fighter version.
Ar 240 C-2: Night fighter version.
Ar 240 C-3: Light bomber 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 1,900 hp (1,417 kW) DB 603G, the production aircraft would have had two 2,000 hp (1,491 kW) 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-01)

Data from ^[2]

General characteristics

Crew: 2
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)
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)
Cruising speed: 555 km/h (345 mph; 300 kn)
Range: 2,000 km (1,243 mi; 1,080 nmi)
Service ceiling: 10,500 m (34,449 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

Armament

Guns: * 2 × fixed 7.92 mm (.312 in) MG 17 machine guns
Two remote-control barbettes with 2 × 7.92 mm (.312 in) MG 81 machine guns
Bombs: * 1,800 kg (4,000 lb) bombs

References

1 2 Gunston 1989, p. 157.
↑ Green, William (2010). Aircraft of the Third Reich. Vol.1 (1st ed.). London: Aerospace Publishing Limited. pp. 85–90. ISBN 978 1 900732 06 2.

Bibliography

Green, William. Warplanes of the Third Reich. London: Macdonald and Jane's Publishers Ltd., Fourth impression 1979, First edition 1970. ISBN 0-356-02382-6.
Gunston, Bill. Jane's Fighting Aircraft of World War II. New York: Jane's Publishing/Random House, 1989, First edition 1945. ISBN 1-85170-493-0.
Lang, Gerhard. Arado Ar 240 (Luftwaffe Profile Series No.8). Atglen, PA: Schiffer Military History, 1997. ISBN 0-88740-923-7.
Smith, J.R. and Anthony L. Kay. German Aircraft of the Second World War. London: Putnam & Company Ltd., 1972. ISBN 0-370-00024-2.

External links

Wikimedia Commons has media related to Arado Ar 240.

Aircraft produced by Arado Flugzeugwerke

Ar 64 Ar 65 Ar 66 Ar 67 Ar 68 Ar 69 Ar 76 Ar 79 Ar 80 Ar 81 Ar 95 Ar 96 Ar 195 Ar 196 Ar 197 Ar 198 Ar 199 Ar 231 Ar 232 Ar 233 Ar 234 Ar 240 Ar 296 Ar 396 Ar 432 Ar 440 Ar 532 E.340 E.377 E.380 E.381 E.500 E.530 E.555 E.560 E.561 E.580 E.581 E.583 L I L II S I SC I SC II SD I SD II SD III SSD I V I W 2

Reich Air Ministry aircraft designations

1 to 100	B 9 Gö 9 Do 10 Do 11 Wn 11 Do 12 Do 13 Do 14 Do 15 Wn 15 Do 16 Wn 16 Do 17 Do 18 Do 19 Do 20 Do 22 Do 23 Do 24 Kl 25 Do 26 Kl 26 M 27 Do 29 Kl 31 Kl 32 W 33 L 33 W 34 Kl 35 Kl 36 HD 37 HD 38 G 38 DFS 39 BV 40 DFS 40 A 40 Fw 42 He 42 Fw 43 HD 43 Fw 44 He 45 He 46 Ju 46 Fw 47 Ju 47 K 47 A 48 He 49 Ju 49 He 50 A 50 He 51 K 51 Ju 52 K 53 NR 54 Fw 55 NR 55 Fw 56 Fw 57 Fw 58 He 58 He 59 He 60 Ju 60 Fw 61 He 61 Fw 62 He 62 He 63 Ar 64 He 64 Ar 65 He 65 Ar 66 He 66 Ar 67 Ar 68 Ar 69 He 70 He 71 He 72 He 74 Ar 76 Ar 77 Ar 79 Ar 80 Ar 81 Ju 85 Ju 86 Ju 87 Ju 88 Ju 89 Ju 90 Ar 95 Ar 96 Fi 97 Fi 98 Fi 99 He 100

101 to 200	Al 101 Al 102 Al 103 Fi 103 Fh 104 Kl 105 Kl 106 Kl 107 Bf 108 Bf 109 Bf 110 He 111 He 112 He 113 He 114 He 115 He 116 Hs 117 He 118 He 119 He 120 Hs 121 Hs 122 Hs 123 Hs 124 Hs 125 Hs 126 Hs 127 Hs 128 Hs 129 Hs 130 Bü 131 Hs 132 Bü 133 Bü 134 Ha 135 Ha 136 Hü 136 Ha 137 BV 138 Ha 139 Ha 140 BV 141 BV 142 BV 143 BV 144 Go 145 Go 146 Go 147 Ju 147 Go 149 Go 150 Kl 151 Ta 152 Kl 152 Ta 153 Ta 154 BV 155 Fi 156 Fi 157 Fi 158 Fw 159 Ju 160 Bf 161 He 162 Bf 162 Bf 163 Me 163 Me 164 Fi 166 FK 166 Fi 167 Fi 168 He 170 He 172 He 176 He 177 He 178 Bü 180 Bü 181 Bü 182 Ta 183 Fl 184 Fl 185 Fw 186 Ju 186 Fw 187 Ju 187 Ju 188 Fw 189 Fw 190 Fw 191 Ao 192 DFS 193 DFS 194 Ar 195 Ar 196 Ar 197 Ar 198 Ar 199 Fw 200

201 to 300	Si 201 Si 202 DFS 203 Si 204 Fw 206 Me 208 Me 209 Me 209 (1943) Me 210 Hü 211 Do 212 Do 214 Do 215 Do 216 Do 217 Hs 217 He 219 He 220 BV 222 Fa 223 Fa 224 Ao 225 Fa 225 BV 226 Ho 226 FGP 227 DFS 228 Ho 229 DFS 230 Ar 231 Ar 232 Ar 233 Ar 234 Do 235 BV 237 BV 238 Fw 238 Ar 239 Ar 240 Go 241 Go 242 Go 244 BV 246 Ju 248 BV 250 Fw 250 Ho 250 Ho 251 Ho 252 Ju 252 Fi 253 Ho 253 Ta 254 Ho 254 Fi 256 Sk 257 Fw 261 Me 261 Me 262 Me 263 Me 264 Fl 265 Me 265 Fa 266 Ho 267 Ju 268 Fa 269 He 270 We 271 Fw 272 He 274 He 275 He 277 He 278 He 280 Fl 282 Fa 283 Ta 283 Fa 284 Fl 285 Ju 286 Ju 287 Ju 288 Ju 290 Me 290 As 292 Hs 293 Hs 294 Hs 295 Ar 296 Hs 296 Hs 297 Hs 298 Fw 300

301-	Me 309 Me 310 Do 317 Do 318 He 319 Me 321 Ju 322 Me 323 Me 328 Me 329 Fa 330 DFS 331 DFS 332 Fi 333 Me 334 Do 335 Fa 336 Fl 339 E.340 WNF 342 He 343 Rk 344 So 344 Go 345 DFS 346 Rk 347 Ba 349 Ju 352 Me 362 Me 364 Ju 388 Ju 390 Fw 391 Ar 396 Ta 400 Me 409 Me 410 Do 417 He 419 ZMe 423 Ar 430 Ka 430 Ar 432 Do 435 Ar 440 Ju 452 Me 462 Ju 488 Fw 491 Me 509 Me 510 He 519 ZSO 523 Ar 532 Do 535 E.555 Me 609 Ar 632 Do 635

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