Junkers Ju 288

Ju 288
Ju 288
	Sole Ju 288A prototype (Ju 288V5) with Junkers Jumo 222 engines and ducted spinners
General information
Type	Medium bomber
National origin	Germany
Manufacturer	Junkers
Number built	22
History
First flight	29 November 1940
Developed from	Junkers Ju 88

Junkers 288B (Ju 288 V13, DB 606 engines) prototype

The Junkers Ju 288, originally known within the Junkers firm as the EF 074, was a German bomber project designed during World War II, which only ever flew in prototype form. The first aircraft flew on 29 November 1940; 22 development aircraft were eventually produced.

The Ju 288 was the winner of the Bomber B contest, although the contest was started by the Junkers firm's submission of the EF 074 and their selection was never really in doubt. The Bomber B concept of a Schnellbomber was originally intended to replace the Junkers Ju 88. The Ju 288 offered a design that was larger, offered cabin pressurization for high altitude missions, had longer range, a much greater bomb payload, was even faster, and had improved defensive firepower. The design was intended to replace all the bombers then in Luftwaffe service.

Delivering all of these requirements in a single airframe demanded much more powerful engines; all of the Bomber B concepts, at one time or another, relied on the Junkers Jumo 222 engine to deliver this power. Ultimately, the Jumo 222 was a failure in spite of massive effort and several redesigns over a period of several years, with nearly 300 development prototypes produced. No suitable replacement was ever forthcoming, dooming the Ju 288 program, and leaving the Luftwaffe with older bomber designs during the second half of World War II.

Design and development

Prior to the opening of World War II, the Luftwaffe bomber force included three major types, the Dornier Do 17 and Ju 88, both classed as schnellbomber, and the slower but somewhat larger Heinkel He 111. Although the Ju 88 outperformed the other designs in service, it however possessed adverse characteristics, including its very small internal bomb bay that forced it to carry some of its load externally, degrading performance.

Junkers had been outlining a variety of improved models of the Ju 88 since 1937, powered by the planned Jumo 222 multibank engine, or Jumo 223 inline multibank diesel of greatly increased power meant to achieve a 2,000 horsepower (1,500 kW) output level, a serious challenge for Germany's aviation engine industry of the time. The EF 074 was essentially a scaled-up Ju 88, sharing its general layout and most of its fuselage and wings with extensions in various places. The nose was redesigned with a more streamlined "stepless cockpit", having no separate windscreen panels for the pilot and co-pilot. This layout allowed cabin pressurization to be more easily implemented. This design approach had been growing in favour, subsequently appearing in various German types, notably the He 111P and -H's.

All of the defensive armament was meant to be remotely controlled ^[1] comprising a remotely operated rear-facing dorsal turret at the rearmost end of the cockpit glazing, and two remotely operated "flank" turrets on the rearwards sides of the fuselage just forward of the empennage, otherwise each resembling the FDSL 131 units of the Me 210. The exclusive use of remotely operated turrets for the Ju 288's defensive firepower allowed them to be positioned more efficiently, as well as eliminating "breaks" in the fuselage pressurization.

The fuselage was expanded along its length to allow for a much longer bomb bay – somewhat as had been done with the Dornier Do 217 then in development itself – that would allow for a 3,630 kg (8,000 lb) payload to be carried internally, eliminating the need to carry ordnance on outside hardpoints.

Bomber B Competition

No serious work was undertaken on these versions, but after Heinrich Hertel left Heinkel and joined Junkers in 1939, the EF 074 design was submitted to the RLM in May 1939. Accordingly, the RLM sent out the specifications for the Bomber B design competition in July, the Ju 88 retroactively becoming the second aircraft to be designated Bomber A, as the 3 June 1936 specification for the He 177 also had that name. The Bomber B program aimed at replacing all of the medium bombers in the Luftwaffe inventory with a new design based on the EF.74 or something with equal performance. Bomber B was intended to have even better speed than the Ju 88, high-altitude cruising with a pressurized cockpit, heavier defensive armament, range allowing it to cover any point in the British Isles, and a 4,000 kg (8,820 lb) warload, double that of the earlier generation bombers. A number of companies returned proposals, but these were to some extent a formality, the EF.74 had already been selected as the winner, and of the rest of the designs submitted, only the Focke-Wulf Fw 191 and Dornier Do 317 progressed even as far as prototypes, and the Henschel Hs 130 coming under consideration as a late entrant.

Work began on building prototypes soon after, and the first example was completed by mid-1940. Power was supposed to be supplied by two 24-cylinder Jumo 222 six-bank, four cylinders per bank, over-1,500 kW output class powerplants, but problems with the Jumo 222's development – as with almost every new concept for over-1,500 kW output, reciprocating aircraft engines then underway in the Third Reich – meant the first prototypes flew with BMW 801 radial engines, instead. The first flight-quality 222s did not arrive until October 1941, and even then it was clear they were nowhere near ready for full-scale production. When it became apparent the 222 was not likely to become a viable powerplant, in May 1942, Junkers proposed replacing them, for their projected Ju 288C version, with the much heavier Daimler Benz DB 606s instead; the same 1.5 tonne, twin-crankcase "welded-together engines" that Reichsmarschall Hermann Göring complained about some three months later, regarding the He 177's own endless powerplant troubles.

Undercarriage difficulties

The Ju 288's intricate main landing gear system's design proved to be troublesome, possessing twin vertical members comprising the main "Y-shaped" retraction strut unit, directly behind a single oleo strut,^[2] for each pair of twinned wheels mounted through a forward-projecting lever-action arm, to the lower end of the uniquely attached main oleo strut unit. This single-tube oleo strut was pivoted off the lower end of the twin-member, "Y-shaped" retraction strut unit, and was rotated in the vertical plane about this single attachment in a rearwards direction during retraction of the main-gear unit, separate from the twin-member unit to help "shorten" its stowed length within the engine nacelle.

This distinctive type of design required the oleo strut's freely moving top end to physically rotate downwards and aftwards during the rear-swinging retraction of the main "Y-shaped" member, operated by a lever and gear-sector system mounted on the portside of each main gear assembly, operated with a long lever that had its upper end pivoted from a fixed bracket, anchored to the firewall's rear surface.^[3] The lever/sector gear system swiveled the oleo strut about its attachment point during the retract cycle, through an arc of roughly 180º from its position when the main gear was fully extended. The stowed position of the oleo strut ended up orienting it aftwards within the rear of the engine nacelle, and placing the wheels' axle location just ahead of and above the oleo strut's pivot point when fully retracted.^[4]

Such a complex main gear design, with only the single pivoting retraction point for its oleo struts taking the primary stress of touchdown, was likely only one of the many potential sources of trouble causing the Ju 288's main gear units to repeatedly collapse on touchdown.^[5]

Operational history

Although the 288 never even reached production status, let alone official operational service, the aircraft did see limited combat duty.^{[citation needed]} In 1944, following the cancellation of the 288 program, the surviving A and C series prototypes were hurriedly fitted with defensive armament and equipment and deployed as reconnaissance bombers on the Western Front. Very few missions were flown, owing to the scarcity of aviation fuel, spare parts and the unresolved problems with the aircraft's powerplant and undercarriage. It is believed^{[by whom?]} that the 288s were attached to the same unit operating the small number of Ju 388 reconnaissance planes that saw service.

Variants

Ju 288A – first seven prototypes with BMW engines
Ju 288B – seven prototypes with slightly enlarged airframes and better defensive armament
Ju 288C – final eight prototypes (of which only four were completed) with two Daimler-Benz DB 606 or 610 "power system" engines. This version was selected for serial production in 1944, but the program was abandoned before this could take place.
Ju 288D – mock-up of a Ju-288C with improved tail armament
Ju 288G – design for an anti-ship version armed with a 355.6 mm (14 in) recoilless cannon

Specifications (Ju 288C-1)

Data from Junkers aircraft and engines, 1913-1945,^[6] German aircraft of the Second World War^[7]

General characteristics

Crew: 4 (C-2 5)
Length: 18.15 m (59 ft 7 in)
Wingspan: 22.657 m (74 ft 4 in)
Height: 5 m (16 ft 5 in)
Wing area: 64.7 m² (696 sq ft)
Empty weight: 13,400 kg (29,542 lb)
Gross weight: 21,390 kg (47,157 lb)
Fuel capacity: 5,360 L (1,420 US gal; 1,180 imp gal) maximum internal fuel (4,915 kg (10,836 lb))
Powerplant: 2 × Daimler-Benz DB 610 24-cylinder coupled V-12 liquid-cooled piston engines, 2,200 kW (2,950 hp) each
Propellers: 4-bladed constant-speed propellers

Performance

Maximum speed: 655 km/h (407 mph, 354 kn) at 6,800 m (22,300 ft) (estimated)
Cruise speed: 518 km/h (322 mph, 280 kn) (estimated)
Landing speed: 150 km/h (93 mph; 81 kn) (estimated)
Range: 2,600 km (1,600 mi, 1,400 nmi) (estimated)
Service ceiling: 10,400 m (34,100 ft) (estimated)
Rate of climb: 8.167 m/s (1,607.7 ft/min) (estimated)

Armament

Guns:
- 4 × 13 mm (0.51 in) MG 131 machine guns
- 1 × 15 mm (0.59 in) MG 151 cannon or 20 mm (0.79 in) MG 151/20 cannon
Bombs: 3,000 kg (6,600 lb) bomb load

References

^ in one proposal Archived 13 April 2014 at the Wayback Machine
^ "Archive photo of Ju 288 starboard main landing gear". Archived from the original on 13 April 2014. Retrieved 11 July 2014.
^ Junkers Ju 288 (Bomber B) (YouTube) (YouTube). History of the Third Reich. Event occurs at 1:28 to 1:33. Retrieved 18 November 2016.
^ Animation of Ju 288 maingear retraction cycle
^ Sengfelder, Günther (1993). German Aircraft Landing Gear. Atglen, PA USA: Schiffer Publishing. pp. 175–177. ISBN 0-88740-470-7. The Ju 288's landing gear was most innovative in its design. A Y-shaped bearer was mounted in the engine nacelle with its upper arms hinged. At the bottom end of this bearer was the shock absorber leg, which was likewise hinged. Two double-brake wheels, with (metric) size 1015 x 380 tires, were mounted on the cross-axle. During the retraction cycle a folding strut was raised by a hydraulic jack. The bottom part of the folding strut drew the Y-bearer upwards. Functioning via a lever-and-gear arrangement, a pushrod positioned parallel to the Y-bearer acted upon another gear segment mounted to the oleo leg's hinge pin and rotated it about this as the Y-bearer was drawn upwards.
^ Kay, Anthony L. (2004). Junkers aircraft and engines, 1913-1945 (1st ed.). London: Putnam Aeronautical Books. pp. 190–197. ISBN 0851779859.
^ Smith, J.R.; Kay, Anthony L. (1990). German aircraft of the Second World War (7th impression ed.). London: Putnam. pp. 211–2202. ISBN 0851778364.

Sources

Hitchcock, Thomas H. Junkers 288 (Monogram Close-Up 2). Acton, MA: Monogram Aviation Publications, 1974. ISBN 0-914144-02-2.

External links

"Flugzeug Lorenz" Ju 288 page Archived 14 May 2012 at the Wayback Machine (in German)
YouTube photo montage of Ju 288 prototypes and production details

[1] roposal Archived 13 April 2014 at the Wayback Machine

[2] "Archive photo of Ju 288 starboard main landing gear". Archived from the original on 13 April 2014. Retrieved 11 July 2014.

[3] Junkers Ju 288 (Bomber B) (YouTube) (YouTube). History of the Third Reich. Event occurs at 1:28 to 1:33. Retrieved 18 November 2016.

[4] Animation of Ju 288 maingear retraction cycle

[5] Sengfelder, Günther (1993). German Aircraft Landing Gear. Atglen, PA USA: Schiffer Publishing. pp. 175–177. ISBN 0-88740-470-7. The Ju 288's landing gear was most innovative in its design. A Y-shaped bearer was mounted in the engine nacelle with its upper arms hinged. At the bottom end of this bearer was the shock absorber leg, which was likewise hinged. Two double-brake wheels, with (metric) size 1015 x 380 tires, were mounted on the cross-axle. During the retraction cycle a folding strut was raised by a hydraulic jack. The bottom part of the folding strut drew the Y-bearer upwards. Functioning via a lever-and-gear arrangement, a pushrod positioned parallel to the Y-bearer acted upon another gear segment mounted to the oleo leg's hinge pin and rotated it about this as the Y-bearer was drawn upwards.

[Kay-6] Kay, Anthony L. (2004). Junkers aircraft and engines, 1913-1945 (1st ed.). London: Putnam Aeronautical Books. pp. 190–197. ISBN 0851779859.

[Smith-7] Smith, J.R.; Kay, Anthony L. (1990). German aircraft of the Second World War (7th impression ed.). London: Putnam. pp. 211–2202. ISBN 0851778364.

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v t e Junkers aircraft
Company designations	J 1 J 2 J 3 J 4 J 5 J 6 J 7 J 8 J 9 J 10 J 11 J 12 F 13 J 15 K 16 K 17 J 18 T 19 A 20 H 21 / J 21 / T 21 J 22 T 23 G 23 F 24 / G 24 A 25 T 26 T 27 J 28 T 29 K 30 G 31 A 32 W 33 W 34 A 35 S 36 K 37 G 38 K 39 K 47 A 48 J 49 A 50 K 51 K 53 K 85
Company EF designations (experimental aircraft)	EF 29 EF 31 EF 52 EF 61 EF 72 EF 73 EF 74 EF 77 EF 94 EF 126 EF 127 EF 128 EF 130 EF 131 EF 132 EF 140 EF 150
Idflieg designations	CL.I CLS.I D.I E.I E.I (2) J.I
RLM designations	Ju 46 Ju 49 Ju 52 Ju 60 Ju 85 Ju 86 Ju 87 Ju 88 Ju 89 Ju 90 Ju 160 Ju 187 Ju 188 Ju 248 Ju 252 Ju 268 Ju 287 Ju 288 Ju 290 Ju 322 Ju 352 Ju 388 Ju 390 Ju 452 Ju 488 Ju 635

v t e Reich Air Ministry (RLM) aircraft designations (list)
1 to 100	8-1¹ Fi 2 8-3¹ 8-4¹ Fi 5 DFS 6 8-7¹ Gö 8 Gö 9 Do 10 Do 11/Wn 11 8-12⁴/Do 12 Do 13 Do 14 Do 15 Do 16/Wn 16 Do 17 Do 18 Do 19 Do 20 8-21¹ Do 22 Do 23 Do 24 Do 25³/Kl 25 Do 26/Kl 26 8-27/Do 27³/Kl 27⁵ 8-28¹ 8-29/Do 29 Fw 30 Kl 31 Kl 32 Ju 33 Ju 34 Kl 35 Kl 36 He 37³ He 38/Ju 38 DFS 39 BV 40/DFS 40 He 41³ Fw 42/He 42 Fw 43 Fw 44 He 45 He 46/Ju 46 Fw 47/He 47 Ju 48 He 49/Ju 49 He 50/Ju 50 He 51 He 52/Ju 52 Ju 53 DFS 54/NR 54 Fw 55/NR 55 Fw 56 8-57⁴/Fw 57 Fw 58/He 58 He 59 He 60/Ju 60 Fa 61/Fw 61/He 61 Fw 62/He 62 8-63⁴/He 63 Ar 64/He 64 Ar 65/He 65 Ar 66/He 66 Ar 67 Ar 68 Ar 69 He 70 8-71⁴/He 71 He 72 He 73³ He 74 Al 75 Ar 76/FZG 76⁶ Ar 77 Ar 78³ Ar 79 Ar 80 Ar 81 8-82⁴ 8-83¹ Al 84 Ju 85 Ju 86 Ju 87 Ju 88 Ju 89 Ju 90 Ju 91³ Ju 92 Ju 93³ Ju 94³ Ar 95 Ar 96 Fi 97 Fi 98 Fi 99 Fi 100³/He 100
101 to 200	Al 101 Al 102 Al 103/Fi 103 R Fh 104 Kl 105 Kl 106 Kl 107 Bf 108 Bf 109/Bf 109R⁶ Bf 110 He 111/He 111U⁶ He 112 He 113⁶ He 114 He 115 He 116 He 117³/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 Bü 132³/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 148³ Go 149 Go 150 Kl 151 Kl 152/Ta 152 Kl 153³/Ta 153 Kl 154³/Ta 154 BV 155/Kl 155³/Me 155 Fi 156 Fi 157 Fi 158 Fw 159 Ju 160 Bf 161 Bf 162/He 162 Bf 163/Li 163/Me 163 Me 164/MeC 164 Bf 165 Fi 166/FK 166 Fi 167 Fi 168 Fi 169³ He 170 He 171³ He 172 He 173³ He 174³ 8-175⁴ He 176 He 177 He 178 He 179⁵ Bü 180/He 180 Bü 181 Bü 182 Bü 183³/Ta 183 Fl 184 Fl 185 Fw 186/Ju 186 Fw 187/Ju 187² Fw 188³/Ju 188 Fw 189 Fw 190 Fw 191 Ao 192 Ao 193³/DFS 193 DFS 194/Me 194 Ar 195 Ar 196 Ar 197 Ar 198 Ar 199 Do 200^4,6/Fw 200
201 to 300	Si 201 Si 202 DFS 203 Si 204 8-205¹ Fw 206 8-207¹ Me 208 Me 209 (I)/Me 209 (II) Me 210 Hü 211 8-212⁴/Do 212 8-213¹ Do 214 Do 215 Do 216 Do 217/Hs 217 Do 218³ He 219 He 220 Do 221³ BV 222 Fa 223 Fa 224 Ao 225/Fa 225 BV 226/Ho 226 FGP 227 DFS 228 Go 229/Ho 229 8-230/DFS 230 Ar 231 Ar 232 Ar 233 Ar 234 Do 235⁵ Fa 236³ BV 237 BV 238 8-239¹ Ar 240 Go 241 Go 242 Me 243³ Go 244 Go 245³ BV 246 8-247¹ Ju 248 BV 250/Ho 250 Ho 251 Ho 252 Ju 252 Fi 253/Ho 253 Ho 254/Ta 254 8-255¹ Fi 256 SK 257 8-258¹ Fw 259 8-260¹ Me 261/Me 261w Me 262 Me 263 (1941)/Me 263 (1942)/Me 263 (1945) Me 264 Fl 265/Me 265 Fa 266/Go 266³ Ho 267 Ju 268 Fa 269 He 270 We 271 He 272³ He 273³ He 274 He 275⁵ He 276³ He 277 He 278 He 279³ He 280 He 281³ Fl 282 Fa 283 Fa 284 Fl 285 Ju 286 Ju 287 Do 288^4,6/Ju 288 Ju 289³ Ju 290 Hs 291 As 292/Hs 292³ Hs 293 Hs 294 Hs 295 Ar 296/Hs 296 Hs 297 Hs 298 Ju 299³ Fw 300
301 to 349	DFS 301 8-302¹ 8-303¹ 8-304¹ 8-305¹ 8-306¹ 8-307¹ 8-308¹ Me 309 Zwilling Me 310 8-311¹ 8-312¹ 8-313⁴ 8-314¹ Hs 315 8-316¹ Do 317 Do 318 He 319 Me 320³ Me 321 Ju 322 Me 323/ZMe 323 8-324¹ Fa 325/Fw 325³ 8-326¹ Me 327 Me 328 Me 329 Fa 330 DFS 331 DFS 332 Fi 333 Ar 334³/Me 334 Do 335 Fa 336 Ju 337³ 8-338¹ Fl 339 Ar 340 8-341 WNF 342 He 343 Rk 344/So 344⁵ Go 345 DFS 346 Rk 347 8-348¹ Ba 349
Post-349 (non-sequential)	Ju 352 Fi 356/Ju 356 Me 362 Me 364² Me 368³ Ju 388 Ju 390 Fw 391 Ar 393³ Ar 396 Ta 400 Me 409 Me 410 Do 417 He 419 ZMe 423 Ar 430/Ka 430 Ar 432 Do 435 Ar 440 8-445⁴ DFS 446 Ju 452 Me 462² DFS 468 Ju 488 Fw 491 He 500 Me 509 Me 510 He 519 8-520⁴ ZSO 523 Ar 532 8-534⁴ Do 535/He 535 Me 600² Me 609 Ar 632 Do 635/He 635/Ju 635
¹ Not assigned ² Unofficial/proposed ³ Assigned, but not used before RLM was dissolved ⁴ Assigned to captured aircraft ⁵ Unconfirmed ⁶ Propaganda/cover designation Note: Official RLM designations had the prefix "8-", but this was usually dropped and replaced with the manufacturer's prefix.