Arado Ar 240 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for a much more capable second generation heavy fighter to replace the Messerschmitt Me 110 , which was becoming outdated .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 . 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 turret s 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 brake s , 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 gun s 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 reconnaissance aircraft over England , where no other two - seater could venture by 1942 .