Heinkel He 177 Greif (Griffin) Heavy Bomber
The advanced Heinkel He 177 Greif as a heavy bomber for the Luftwaffe of World War 2 was limited in production due to ongoing engine reliability and structural issues.
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The Heinkel concern of World War 2 Germany became one of the largest and most prolific aircraft makers of the period. Its primary claim was its medium bomber, the He 111, which was used throughout the grand war over every front that the German military operated in. Along the way there were many other designs put forth by the company which proved serviceable - others groundbreaking- and still others forgettable. The He 177 "Greif" (or "Griffin") became one of the company's failed offerings that was doomed through a variety of issues - a complex engine arrangement led to many-a-technical problem and structural deficiencies plagued the line for the duration of its short-lived career. Had its list of problems been remedied at some point, the He 177 may have very well become an excellent heavy bomber for the German Luftwaffe in search of such a type - the service was forced to continue use of its medium bomber types for the duration of the war.
Origins of the He 177 lay in a 1936 RLM requirement calling for a new, all-modern bomber with a minimum maximum speed of 310 miles per hour and able to travel out to ranges of 3,100 miles with a 2,200 pound bomb load which resulted in the "Bomber A". Its primary defense was initially thought to be sheer speed as it would be able to simply outrun any trailing interceptor. The Heinkel concern received the go-ahead to build its "Projekt 1041 Bomber A" submission and a full-scale mockup appeared in 1937 (receiving the RLM designator of "8-177"). Because dive-bombing offered better accuracy during this period of military aviation (and German bombsight technology was limited heading into the war), it was written into the new bomber requirement that the type should possess an inherent dive-bombing capability - meaning that its structure would have to be constructed and arranged for the appropriate tolerances due to the forces at work in a diving action.
While appearing very conventional with what looked like a twin-engined configuration, the 8-177 utilized a unique "quad-engine" arrangement in which the wing-mounted nacelles paired engines to combine the power of two within a more streamlined shape. This was required to maintain the aerodynamics of the aircraft during its proposed diving attacks but, realistically, served only to complicate the design during its protracted development phase. No one engine then in existence could provide the needed power in a two-engine arrangement and thus this unique four-engine setup was used.
Heinkel engineers elected for the Diamler-Benz DB606 engine which coupled two DB601 12-cylinder inlines in a side-by-side format to drive a single propeller unit by way of a shared gearbox. Each engine developed 2,600 horsepower and drove a large-diameter propeller blade unit. To gain speed in other areas, Heinkel employed various technologies into the airframe learned from prewar high-speed racers.
A mid-wing monoplane form was used which held the complex engine arrangement. The mainplanes were seated just ahead of midships along the fuselage which was of a rounded-rectangle shape. The nose was well-contoured and heavily-glazed, containing the key crew positions such as pilot and bombardier. The fuselage then tapered at the rear to produce a tunnel to reach the extreme tail end. The empennage employed a single, cut-off vertical tailfin and low-set horizontal planes. A "tail-dragger" undercarriage was used though reinforced for the weight of the aircraft, each main leg carrying a twin wheel arrangement. An internal bomb bay would carry largely conventional drop stores into combat.
When it became clear that the latest fighters would be able to catch modern prop-driven bombers, the bomber was given an appropriate defensive gun network. At least one position would be remote-controlled to save on weight and keep the design streamlined (it was initially envisioned that the aircraft would carry three RC turrets). The tail gun position at the extreme rear of the fuselage would be manned. There were eventually guns featured at dorsal positions, the nose proper, a "chin" mounting and a ventral, aft-facing position held in a gondola type fairing. No "beam", or waist, positions were used.