Heinkel He 277

He 277

Manufacturer: Heinkel
Status: Cancelled
Primary user: Luftwaffe
Number built: none completed, only parts built
Developed from: Heinkel He 177
Variants: Heinkel He 274

The Heinkel He 277 was a four-engine, long range heavy bomber design, a derivative of the He 177, intended for production and use by the German Luftwaffe during World War II. The main difference was in engine configuration. Rather than using two fire-prone Daimler-Benz DB 606 "power system" engines, each of which consisted of side-by-side paired Daimler-Benz DB 601s, the He 277 was meant from the outset to use four BMW 801E 14-cylinder radial engines., each mounted in an individual nacelle. The design was never produced, due both to the deteriorating condition of the German aviation industry late in the war, and its chance for existence challenged by other long-range bomber designs from other firms, competing for Germany's increasingly scarce aviation production capacity. Although not specifically built for it at first, partially due to the timeframe in the spring of 1942 in which its ultimate niche was requested for by the RLM, the He 277 essentially became Heinkel's entry in the important Amerika Bomber competition, struggling to compete against both several other designs from rival firms in the competition for a truly trans-oceanic ranged bomber for the Luftwaffe, and Germany's own rapidly degrading ability, from Allied bombing damage to its aviation plants, to produce military aircraft of any sort.

The "He 177B" versus He 277 controversy

For many years after the war, a substantial number of aviation history books and magazine articles that dealt with late World War II German military aviation developments consistently stated that Reichsmarschall Hermann Goering, early in World War II, was becoming so frustrated by the 177A's ongoing engine problems, caused by the twin DB 606 "coupled" powerplants selected for the He 177A design in the pre-war years, that he forbade Ernst Heinkel from doing any work on a separately four-engined version of the 177 airframe, or even mentioning a new "He 277" design with four separate engines, until Heinkel brought the disagreement directly to Adolf Hitler, who supposedly not only approved of calling the new, separately engined version of the 177 the "He 277", but overruled Goering's prohibition on working on the design, previously called the "He 177B" by Heinkel as a "cover designation" to hide its existence from Goering, and the RLM, to bring it into production.

Statements by Goering himself in August of 1942, however, seem to directly contradict elements of the oft-repeated story, as those statements seem to show that Goering thought that the He 177A actually had four separate engines, and derisively labeled the coupled engine arrangements as "welded-together engines", in his complaints about the He 177A's ongoing engine difficulties, and was anxious to see a truly four-engined version of Heinkel's heavy bomber fully developed and in production.

Facts that could have fostered the origin of the post-war aviation book storyline about the "He 177B"/He 277 controversy were that the RLM, in listing the He 177 development projects that they approved of the Heinkel firm doing work on as of February 1943 (six months after Goering's recorded engine complaint statements), only included the He 177 A-5 heavy bomber, A-6 high-altitude bomber, A-7 long-range version, and the "He 277" itself, with the RLM also expecting, during the late spring of 1943 (about one year after the mid-Spring 1942 Amerika Bomber proposal first arrived in Goering's offices) that a trio of He 277 V-series prototype aircraft, and construction of ten pre-production A-0 series machines were to be completed, as well as "progressive development" of the still-unbuilt and unfinalized design, were anticipated as coming from Heinkel's Schwechat southern plant complex in Austria. The initial starting place for the He 277's fuselage design had been meant to originate with the last "coupled-engine" proposed variant of the He 177 itself, the long-range A-7, which itself was to be the basis for a four-engined variant of the Greif as the He 177A-10, then redesignated the He 177B-7 in the late summer of 1943. The changes in the He 277's overall design evolved after the Amerika Bomber proposal's emergence, from the changes in the He 277's general arrangement proposal drawings during that time period, from using the A-7's fuselage as the starting point into designing a dedicated, new He 219-general pattern fuselage layout for the 277 from the Spring 1943 timeframe onward, more capable of using a tricycle undercarriage then gaining favor with a few German aviation designers, even with the 277 not known to have been specifically considered by the RLM in the earlier timeframe for the Amerika Bomber proposal.

The main factor that seemingly required the lower-drag "coupled" powerplant format for the He 177A, the diving attack mandate by the RLM, which Heinkel himself vehemently disagreed with, was rescinded by Goering himself some five months before the "He 277"'s earliest-known February 1943 RLM approval date, and Heinkel started work on the He 177B as a straightforward, separately four-engined development of the 177A under the B-series designation at least as early as the late summer of 1943, when official Heinkel documents began referring to the He 177B, evidenced from an August 1943-dated, Heinkel factory-created general arrangement drawing of the He 177 V101 being labeled with the 8-177 RLM designation for the entire line of Greif airframes, and "B-5" elsewhere in the drawing's title block, as a fully RLM approved development of the original He 177 aircraft line, and not in any way directly related to the entirely separate He 277 advanced bomber design project, which by the summer of 1943 was considered to be Heinkel's Amerika Bomber aviation contract contender.

In total, there were three separate efforts, the movement toward which had been initiated by Herr Heinkel himself as early as November 1938, to develop "true four-engined versions" of the A-series Greif: the He 177B, which culminated in four prototype examples being built, with three getting airborne before the war's end; the He 274, of which only two prototypes were started before the end of World War II and completed and flown in France after the war's end; and the He 277, for which only had a few airframe parts had been in the process of completion, with no completed prototypes at any time, before or after the end of the war.

The He 277 design's features

The general arrangement "Typenblatt" drawings that Heinkel's firm was developing for the He 277 show an advanced design of heavy bomber, with a 133 square meter area (1.431.6 sq. ft.) "shoulder mount", 40 meter (131 ft 3 in) span wing design, four separate BMW 801E powerplants of 1,471 kW (2,000 PS, 1,973 hp) output each at take-off, a fully-retracting conventional or nosewheel landing gear, with main gear assemblies that possessed twinned main wheels on each unit, retracting forward (for the nosewheel version, rearwards for a conventional gear arrangement) into the inner engine nacelles, and a heavily-glazed and "greenhouse"-framed clear view "stepless" cockpit. Its fully glazed front section somewhat resembled a blended combination of a refined, rounded-off well-framed version of the Bristol Blenheim Mk.I's fully glazed nose shape, and pilot accommodation-enclosing upper section somewhat resembling what was used on the British Avro Lancaster heavy bomber, with a rearward extension atop the fuselage to just forward of the inner engine cowls. The fuselage outlines themselves were deep, and almost slab-sided in cross-section, with its general sideview profile lines being strongly reminiscent of the smaller He 219 night fighter, in a sort-of "Heinkel-familial" manner with the smaller aircraft. This similarity with the 219 even extended to the depictions of the He 277's fuselage-mounted defensive armament emplacements as proposed by Heinkel, with one forward and two aft-facing "steps" along the slightly rounded dorsal and ventral surfaces of the fuselage, much like the smaller night fighter's earliest prototypes had, for the 277's manned aft dorsal and remote aft ventral turret defensive weapons mounts, and a twin tail empennage assembly that added aerodynamic stability, and made mounting a traversable defensive tail turret easier.

In a May 1943 Heinkel factory document showing possible offensive bombload configurations and flight consumable (fuel, etc) weights for the He 277, two differing bomb bay sizes (interior dimensions of 1.5 x 7.5 meters for the He 277's tailwheel version, and 1.75 x 7.0 meters for the tricycle undercarriage version) were considered. The lightest warload of six 500 kg (1,100 lb) SC 500 bombs for each bomb bay configuration, gave the tricycle-geared wide-fuselage version, considering a larger load (12,200 kg/26,895 lb) of fuel, a possible stated maximum range of 11,100 km (6,900 miles), equalling the potential range capability of the earlier-designed Me 261, an indicator of what could have been achieved had the 277 been in full consideration from its beginnings, for the Amerika Bomber design competition.

Defensive armament comprised, as envisioned, a forward, remotely operated "chin turret" under the extreme nose with twin MG 151/20 cannon much as the 177B-series was intended to use, twin dorsal turrets each armed with a pair of MG 151/20 cannon, a ventral turret for lower rearwards defense, just behind the bomb bay's rear edge with another pair of MG 151/20 cannon, and a manned HL 131V tail turret with a quartet of MG 131 heavy machine guns.

Competing bomber designs

Throughout the time that the He 277 design was being worked on, Ernst Heinkel was facing competition from other developing heavy bomber designs, and large four-engined aircraft proposals that showed promise as heavy bombers, from Focke Wulf (the Fw 300, and later, the Ta 400), Junkers (the Ju 390), from Messerschmitt AG (the Me 264), and from his own firm's He 274 four engined, high-altitude development of the He 177.

The first of these designs that the He 277 was pitted against, mostly to determine the "most producible" bomber that could also be license-built, given Germany's limited aircraft production capacity to arm the Luftwaffe with, and partially to determine the best long-range bomber design to fulfill the needs of the spring 1942-issued Amerika Bomber program documents, the Messerschmitt Me 264 ended up being the first design to challenge the He 277's chance for production. The Me 264 was a purpose-built long range bomber that was already flying in prototype form with four engines as early as late December of 1942, a full year after Nazi Germany had declared war on the United States, five months after the Eighth Air Force had begun flying bomber missions against Nazi-occupied France, and two months before the earliest-known mention of RLM approval of the 277 itself.

The four-engined Me 264's development, because of the need to use scarce strategic materials in its construction, and because of the better performance estimates that the Focke-Wulf Ta 400 and He 277 possessed, was stopped in May 1943.

Because of the US involvement in the European Theater, the Luftwaffe now found that it had a serious need for a well-armed, long range bomber, which the Luftwaffe found could not be achieved with the 1,120 kW (1,500 hp) class engines it had for such a four-engined bomber, and that six engines of that same class would be needed on a strategic bomber design for a successful mission from Europe to attack the US and safely return to base, with enough of an offensive bombload to be effective, and to have enough defensive firepower for protection for a safe return. The Blohm & Voss firm's aviation division had already settled on six engines with success, as early as 1940, on the prototypes of the Bv 222 Wiking flying boat maritime patrol aircraft. This emerging need for six engines for such an aircraft was also recognized by Messerschmitt AG, when that firm fielded a paper project for a six-engined "Me 264B", that had a stretched wingspan outwards to 47.5 meters (155 ft 10 in), with two additional BMW 801 radial engines outboard of the existing four powerplants.

In March 1943, Focke-Wulf came up with a six-engined version of their proposed Fw 300 bomber, originally powered with just four BMW 801E radials. Their more advanced Ta 400 design, first proposed in October 1943 and meant to be powered with a half-dozen of the same engines as the 277 was meant to use, was joined by the Ju 390, a Junkers six engined version of the developed version of their early-war Junkers Ju 90 airliner, the operational Junkers Ju 290 maritime patrol bomber, and also using six of the same BMW radials as the 277.

By October 1943, Ernst Heinkel had compared the Messerschmitt and Junkers four-engined designs, and the six-engined Bv 222, Ju 390 and Ta 400 designs to his own He 277 project, with the following conclusions:

"In our opinion, the Me 264 is a record-breaking aircraft, and does not come up to service requirements for operations in large numbers. The Bv 222 and Ju 290 are far too big and are not bombers, in addition to which the Ju 290 has to be altered to Ju 390 (six engines). This would make the construction effort bigger still. Thus, only the Ta 400 and the He 277 remain as useful operational aircraft".

"In our opinion, the Me 264 is a record-breaking aircraft, and does not come up to service requirements for operations in large numbers. The Bv 222 and Ju 290 are far too big and are not bombers, in addition to which the Ju 290 has to be altered to Ju 390 (six engines). This would make the construction effort bigger still. Thus, only the Ta 400 and the He 277 remain as useful operational aircraft".

Of these competing types, only three each of the Me 264 and Ju 390 aircraft were ever built, solely as flyable prototypes, and none of these aircraft saw any action against the Allies.

The He 274, because of its own intended high-altitude role, was only a potential competitor with the He 277 for Heinkel's own company engineering and production staff, and the He 274's production had already been outsourced by the end of 1941 to the French Societe Anonyme des Usines Farman, or "SAUF" firm in Suresnes to partially allow Heinkel to work on other projects, like the He 277.

End of the He 277 project

The last competing aircraft design that threatened the He 277's chance for increasingly scarce production capacity was the Junkers Ju 488, a composite of earlier developments of the Junkers Ju 88 twin-engined fast medium bomber design, with a few core components being purpose-designed solely for it, that were brought together to create a four-engined heavy bomber while using already-available components.

In April 1944, simultaneously with the four He 177B prototypes either flying (He 177 V101 to V103) or nearing completion (V104) at the Heinkel-Sud facility at Schwechat, the RLM ordered Heinkel to cease any further work on the He 277 project, and all components were also ordered to be scrapped, without any complete examples of the 277 ever having been completed by Heinkel.

Specifications (He 277 basic configuration)

General characteristics

Crew: 7
Length: 23.00 m (75 ft 5 in)
Wingspan: 40.00 m (131 ft 3 in)
Height: 6.66 m (21 ft 10½ in)
Wing area: 133.00 m² (1,431.60 ft²)
Empty weight: 21,800 kg (48,060 lb)
Max takeoff weight: 44,500 kg (98,105 lb)
Powerplant: 4x— BMW 801E 14-cylinder, twin row-radial engine, 1,492 kW (1,973 hp for takeoff) each
maximum of 16,950 litre/4,478 US gallon fuel capacity for Amerika Bomber mission profile

Performance

Maximum speed: 570 km/h at 5,700 m (354 mph at 18,700 ft)
Cruise speed: 460 km/h (286 mph)
Range: 6,000 km (3,728 mi, up to 11,100 km/6,900 mi in Amerika Bomber role)
Service ceiling: 15,000 m (49,210 ft)

Armament

2 x— 20 mm (0.79 in) MG 151/20 autocannon in remotely operated, undernose Fernbedienbare Drehlafette FDL 151 Z "chin" turret
4 x— 20 mm (0.79 in) MG 151/20 autocannon in twin dorsal turrets, one FDL-type remotely operated forward and one aft manned turret
2 x— 20 mm (0.79 in) MG 151/20 autocannon in FDL-style remotely operated, ventral turret facing aft, behind bomb bay
4 x 13 mm (0.51 in) MG 131 machine guns in Hecklafette HL 131 V "quadmount", manned tail turret
up to 3,000 kg (6,612 lb) of disposable stores for Amerika Bomber trans-Atlantic missions.

Amerika Bomber

Related development

Heinkel He 177

Comparable aircraft

Heinkel He 274
B-29 Superfortress
Nakajima G10N

Bibliography

Green, William. Warplanes of the Third Reich. London: Macdonald and Jane's Publishers Ltd., 1970 (4th Impression 1979). ISBN 0-356-02382-6.
Griehl, Manfred and Dressel, Joachim. Heinkel He 177-277-274, Airlife Publishing, Shrewsbury, England 1998. ISBN 1-85310-364-0.
Gunston, Bill & Wood, Tony. Hitler's Luftwaffe. London: Salamander Books Ltd., 1977. ISBN 0-86101-005-1.

Heinkel He 277 Pictures and Heinkel He 277 for Sale.

Living Warbirds: The best warbirds DVD series.

Source: WikiPedia