The Arado Ar 240, manufactured by Arado Flugzeugwerke, was a twin-engine heavy fighter aircraft that served multiple roles for the Luftwaffe during World War II.
It took its maiden flight on May 10, 1940, but encountered numerous design issues that hindered its progress. As a result, the prototype phase was plagued by marginal stability. Eventually, the project was abandoned, and the available airframes were repurposed for various testing endeavours. The Ar 240 was developed in response to a 1938 request for a more advanced second-generation heavy fighter to replace the outdated Messerschmitt Bf 110.
Arado and Messerschmitt both submitted designs.
Messerschmitt’s design, the Me 210, was a completely new concept, benefiting from their experience with the Zerstörer (“Destroyer”) concept, allowing for a quick entry into service.
On the other hand, Arado’s design was a more ambitious project, reflecting the vision of Arado’s chief designer, Walter Blume, dating back to the mid-1930s.
Despite the longer timeline for Arado’s design to be ready for delivery, the German Aviation Ministry showed interest by ordering prototypes for both designs.
Arado had made significant investments in various areas of basic research prior to this stage.
One area of focus was the development of the “Arado travelling flap,” which demonstrated exceptional lift performance at low speeds.
Additionally, they were actively engaged in designing and constructing pressurised cockpits to alleviate pilot fatigue during flights above approximately 4,500 m (14,760 ft).
Furthermore, they had also dedicated resources to the advancement of a technologically advanced remote-control defensive gun system, which had been under experimentation for several years.
This system incorporated a gunsight positioned in the rear cockpit, operated by the navigator/gunner, equipped with optics on both the top and bottom of the aircraft, enabling aiming in any direction.
The gunsight was hydraulically linked to streamlined pancake-shaped turrets located on the top and bottom of the aircraft.
In the design of the Ar 240, the engineers at Arado amalgamated all of this research into a single airframe.
To optimise its performance, they employed a relatively small wing size, effectively reducing parasite drag (although at the cost of increased lift-induced drag).
This approach would typically result in excessively high landing speeds, but this was counterbalanced by incorporating a large movable flap and leading-edge slats to generate substantial lift at low speeds.
When the flaps were deployed, the upper section of the ailerons would remain stationary while the lower section extended backwards, effectively augmenting the wing’s surface area.
The Daimler-Benz DB 601 inline engines were conventionally installed and equipped with three-blade, fully adjustable propellers.
The radiators had a unique design, similar to those found on the Junkers Ju 88, but with a closer resemblance to the intended installation of the radiators for the Junkers Ju 288.
These radiators consisted of an annular block located in front of each engine, partially covered by the Ar 240.
Additionally, each radiator unit had an oversized, ducted flow-through propeller spinner positioned in front, allowing air to enter through a large hole in the spinner and exit through the cowl flaps.
This design was inspired by the Jumo 222-powered Ju 288, which was intended to have this configuration.
Similar to the Jumo inline-powered versions of the Ju 88, the Ar 240 appeared to have a radial engine, giving it a distinctive look.
The Focke-Wulf firm also adopted this simpler setup of an annular radiator just forward of the engine for their later Jumo inline-powered fighter aircraft, such as the Fw 190D, Ta 152, and the twin-engined Ta 154.1.
The wings’ fuel cells were equipped with an innovative self-sealing system that utilised thinner tank liners, enabling increased fuel capacity.
Due to the liners adhering to the tank’s outer surface, they were not easily detachable, necessitating the removal of the wing panelling for maintenance.
This resulted in the development of a sophisticated system to provide sturdy skinning that could be managed in the field, adding complexity to the construction process and increasing the overall weight of the aircraft.
Like other German multi-use aircraft designs from that time, the plane had to serve as a dive bomber.
Due to the thick wing panelling, traditional dive brakes couldn’t be used.
Instead, a “petal”-type brake was installed at the rear of the fuselage, similar to the Dornier Do 217 but opening to the sides when activated.
When closed, the brake resembled a stinger extending beyond the horizontal stabiliser and twin fins. Moreover, the cockpit was pressurised fully.
This would have been challenging if the gunner had to manually operate the armament, requiring the guns to penetrate the rear of the cockpit canopy.
However, the remote-control system allowed the guns to be placed in turrets in the unpressurized rear of the fuselage.
All these modifications, along with the small wing, resulted in a high wing loading of 330 kg/m2 (221 lb/ft2), significantly higher than the average of about 100 for a single-seat fighter.
Specifications 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) Empty weight 6,200 kg (13,669 lb) Gross weight 9,450 kg (20,834 lb) Max take-off 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 Armament Guns 2 × fixed 7.92 mm (.312 in) MG 17 machine guns Two remote control turrets with 2 × 7.92 mm (.312 in) MG 81 machine guns Bombs 1,800 kg (4,000 lb) bombs. Sources Arado Geschichte Eines Flugzeugwerks-Jorg Armin Kranzhoff. Aircraft of the Luftwaffe 1935-1945, An Illustrated Guide-Jean-Denis GG LaPage. The Official Monogram Painting Guide to German Aircraft, 1935-1945-Kenneth A Merrick & Thomas H Hitchcock.
