The Junkers Ju 252 was a German cargo aircraft that made its first flight in late October 1941.
Only a small number were built as cargo aircraft for the Luftwaffe.
The original Ju 252 came about after talks between Junkers and Deutsche Lufthansa in December 1938.
Lufthansa requested a new design that would replace the Ju 52, but offer much greater loads, seating, range and performance.
Junkers responded with the EF.77 design with a pressurized fuselage with seating for up to 35, making it one of the larger airliners in the world at that time.
It was powered by three Junkers Jumo 211F engines, in nacelles almost identical in appearance, each complete with annular radiator and possibly as Kraftei unitized “power-egg” modular engine installations, to those on Jumo 211-powered versions of the Junkers Ju 88, replacing the BMW 132 of the Ju 52, which dramatically improved performance.
Compared to the Ju 52, the Ju 252 was twice as heavy (13,100 kg vs. 5,600), was over 100 km/h faster (440 km/h vs. 305) and had dramatically improved range (3980 km vs. 1300) when fully loaded. Design was headed by Konrad Eicholtz.
By the time the prototype was ready to fly in October 1941, the war was already in progress and the Luftwaffe took over development.
Like earlier tail-dragger designs, the Ju 252 would normally be difficult to load when parked, owing to the sloping floor.
Junkers had already pioneered with the earlier Junkers Ju 90’s fifth and sixth prototype airframes during 1939 a unique solution to this problem, the Trapoklappe, a hydraulically powered ventral rear loading ramp that possessed powerful enough operating mechanisms to lift the plane off its tailwheel, leveling the floor and allowing oversized cargo to be loaded directly forward into the fuselage.
Even though all cargo aircraft since World War II have used tricycle landing gear undercarriage designs, the Trapoklappe concept of a rear loading ramp that forms the opening rear ventral panel of the fuselage of a cargo aircraft, is a ubiquitous feature of most military airlift cargo aircraft to the present day.
Although the Ju 252 was a vast improvement over the Junkers Ju 52/3m, the situation at that time did not permit any disruption of the existing production lines, and the Reich Air Ministry (RLM) was of the opinion that any replacement for the Junkers Ju 52/3m must make minimum demands on supplies of strategic materials and use power plants not required by combat aircraft.
Junkers was then instructed to investigate the possibility of redesigning the Ju 252 in order that a considerable portion of wood could be included in its structure, simultaneously replacing the Junkers Jumo 211F engine with the BMW Bramo 323R engine of which surplus stocks existed.
The result was the Junkers Ju 352.
Production of the Ju 252 was restricted to already completed prototypes plus those for which major assemblies had already been semi-completed, thus only fifteen transports of this type were completed before production was switched to the Junkers Ju 352.
During the late spring of 1942, the Junkers-Dessau project office was instructed by the Reich Air Ministry (RLM) to investigate the possibility of redesigning the structure of the Junkers Ju 252 transport to make maximum use of non-strategic materials, replacing the Junkers Jumo 211F engines of the Ju 252 with Bramo 323R radial engines.
The result followed closely the aerodynamic design of the Ju 252 but was an entirely new aircraft.
The wing of the Ju 352 was similar in outline to that of the Ju 252 but, mounted further aft on the fuselage, was entirely of wooden construction.
The Ju 352 also had a similar Trapoklappe (“Transportklappe”, rear loading ramp) to that of the Ju 252.
The ramp allowed the loading of vehicles or freight into the cargo hold while holding the fuselage level.
In general, the Ju 352 was considered a major improvement over the original Junkers Ju 52 but noticeably inferior to the Junkers Ju 252.
Deliveries of the Ju 352 had only just begun to get into their stride when, during the summer of 1944, the worsening war situation resulted in the decision to abandon further production of transport aircraft.
In September the last two Ju 352As rolled off the assembly line, 10 pre-production Ju 352s and 33 production Ju 352s having been manufactured.
Several developments of the basic design were proposed before production was halted, these including the Ju 352B with more powerful engines and increased defensive armament.
Variants
Ju 252
Initial variant.
15 built.
Ju 352
Redesign of the Ju 252 constructed of non-strategic materials and powered by Bramo 323R radial engines.
50 built.
Ju 452
Derivative of the Ju 252 to be constructed from wood.
Specifications
Ju 252A
Crew
3-4
Length
25.11 m (82 ft 5 in)
Wingspan
34.1 m (111 ft 11 in)
Height
5.75 m (18 ft 10 in)
Wing area
122.6 m2 (1,320 sq ft)
Empty weight
13,127 kg (28,940 lb)
Gross weight
22,257 kg (49,068 lb)
Max take-off weight
24,050 kg (53,021 lb)
Powerplant
3 × Junkers Jumo 211F,
V-12 inverted liquid-cooled piston engines,
1,007 kW (1,350 hp) each
Propellers
3-bladed constant-speed propellers
Performance
Maximum speed
438 km/h (272 mph, 237 kn) at 5,800 m (19,029 ft)
Cruise speed
335 km/h (208 mph, 181 kn) (econ. cruise)
Range
3,981 km (2,474 mi, 2,150 nmi) with maximum payload
6,600 km (4,100 mi; 3,600 nmi) with 2,000 kg (4,409 lb) payload
