|Role||Heavy Bomber design only|
|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.
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.
One fact that could have fostered the origin of the post-war aviation book storyline about the "He 177B"/He 277 controversy was 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.
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 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 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.
In total, there were three separate efforts 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, which only had a few airframe parts in the process of completion and no completed prototypes at any time, before or after the war.
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" 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 cockpit, with a fully glazed front section 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, and a deep, almost slab-sided fuselage, with lines 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 aft dorsal and ventral remote turret defensive weapons mounts, and a twin tail empennage assembly that added aerodynamic stability, and made mounting a defensive tail turret easier.
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.
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 Amerika Bomber program, 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, and five months after the Eighth Air Force had begun flying bomber missions against Nazi-occupied France.
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.This emerging fact was 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.
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.
By July of 1943, the only remaining competing design to the He 277's chance to get to the approval stage from the RLM, for prototype construction to begin, was Junkers' Ju 488 long-range bomber design, a four-engined, cobbled-together late war amalgam of a Ju 388's nose/cockpit unit, wing panels (for its own "outer" wings) and tail turret, a Ju 188E's fuselage midsection, the protruding bomb bay of a Ju 88A-15, and a twin tail from a Ju 288C, with only a new wing center section being designed especially for the Ju 488, to carry the two inner powerplants to complete the design, using two port and two starboard Ju 388 engine nacelle assemblies to house the engines and a four-strut main landing gear, all Ju 388 regular parts, with all components selected from different existing designs, to comprise the final design for the Ju 488 because their production tooling or design engineering had already been completed, theoretically saving valuable time in getting the Ju 488 design into production.
By early April of 1944, with the war situation in Germany deteriorating, and with the growing realization that defensive fighters of an advanced nature were becoming a higher priority than ever, the RLM shut down any further development of the He 277 design, which had only progressed to the manufacture of some components and parts, which were scrapped shortly thereafter.