THE 456th FIGHTER INTERCEPTOR SQUADRON

THE PROTECTORS OF  S. A. C.

 

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Heinkel He 177 "Greif" ("Griffon")

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Heinkel He 177
He 177 A-02 production prototype with broad bladed propellers
Role Long range heavy bomber
Manufacturer Heinkel Flugzeugwerke
Designed by Siegfried Gunter
First flight November 1939
Introduced 1942
Retired 1945
Primary user Luftwaffe
Number built 1,169[1]
Variants Heinkel He 274
Heinkel He 277

The Heinkel He 177 Greif (Griffin) was a long-range bomber of the Luftwaffe. This troubled aircraft was the only heavy bomber built in large numbers by Germany during World War II. Luftwaffe aircrew nicknamed it the Luftwaffenfeuerzeug (Luftwaffe's lighter) or the "Flaming Coffin" due to serious engine problems on the initial versions of the aircraft.[2] When these problems were later rectified the type was successful, but could not be deployed in numbers due to Germany's deteriorating situation in the war.

 

Aircraft Design

In 1936 the company of Heinkel Flugzeugwerke received details of the new Bomber A specification from the Reichsluftfahrtministerium (RLM). This specification, first proposed by the RLM on June 3, 1936, called for an aircraft more advanced than the Dornier Do 19 or Junkers Ju 89 Ural bomber prototypes. The aircraft was to be capable of carrying a bombload of at least 1,000 kg (2,204 lb) over a range of 5,000 km (3,107 mi), possess a maximum speed of not less than 500 km/h (311 mph) at altitude,.[3] This was a formidable specification, calling as it did for an aircraft able to outrun any modern fighter and outperform, by a considerable margin, any bomber then in service. On June 2, 1937 Heinkel Flugzeugwerke received instructions to proceed with construction of a full scale mock-up of its Projekt 1041 Bomber A. The mock-up was completed in November 1937, and on November 5, 1937 allocated the official RLM type number "8-177", the same day that the OKL first stipulated the requirement for the new design to possess sufficient structural strength to enable it to undertake medium degree diving attacks.[4] Heinkel Flugzeugwerke's estimated performance figures for Projekt 1041 included a top speed of 550 km/h (341.7 mph) at 5,500 m (18,045 ft) and a loaded weight of 27,000 kg (59,525 lb). In order to achieve these estimates, Heinkel's chief designer, Siegfried Gunter, employed several revolutionary features.

 

The Aircraft Engines

The He 177 required at least a pair of 2,000 PS (1,973 hp, 1,471 kW) engines to meet performance requirements. However, no engine at the time developed such power. To overcome this problem without resorting to four smaller engines and their attendant drag and maneuverability penalty, Gunter decided to employ two of the complex Daimler-Benz DB 606 "power system" setups for propulsion. This "power system", which was first introduced on the record breaking Heinkel He 119, consisted of a pair of Daimler-Benz DB 601 liquid-cooled 12-cylinder inverted-vee inline engines mounted side by side in a single nacelle driving a single propeller. The two component engines in each "system" were mounted side by side in each nacelle and inclined inwards by 30° in the vertical axis of each component engine's crankcase, so that the inner cylinder banks were disposed almost vertically, a single gear casing connecting the front ends of the two crankcases, with the two crankshaft pinions driving a single airscrew shaft gear.[5] This engine configuration stemmed directly from the RLM's, and the OKL's determination that the He 177 should be capable of dive bombing. The use of only two propellers on a heavy bomber offered many advantages such as a substantial reduction in drag, reduction of dive instability, and a marked improvement in maneuverability. Indeed, the initial prototypes and pre-production models of the He 177 displayed an airspeed and maneuverability comparable to many heavy fighters of the time. Two of the DB 606s, each of which initially developed 2,600 PS (2,564 hp, 1,912 kW) for take-off, were to power the He 177.

 

Surface Evaporation Cooling

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The Heinkel He 119 was an experimental single-engine monoplane developed in Germany. A private venture by Heinkel to test radical ideas by the Günter brothers,

In order to refine aerodynamic cleanliness, Gunter decided to dispense with the usual system of heavy drag producing engine radiators and to instead employ an evaporative cooling system. In the evaporative cooling system the coolant water is pressurized; thus, it is possible to heat the water to a higher temperature than its boiling point, in this case about 110° C (230° F), before steam began to form in the engine. The superheated water was then ducted away and depressurized, at which point steam formed. The water was then separated from the steam and returned to the engine. At the same time residual steam was fed through pipes in the wing and cooled by the airflow. After resultant condensation had taken place, the water from the wing pipes was also returned to the engine. During flight tests, this evaporative cooling system worked relatively well on a modified Heinkel He 100 fighter. However, even before the design of the He 177 was finalized, it was clear that such a system would be incapable of dealing with the vast amount of heat generated by the DB 606 engine. As a result, the evaporative cooling system had to be abandoned in favor of conventional annular radiators fitted directly behind each propeller, which resembled but were larger than those fitted to the Junkers Ju 88 A bomber. The addition of these radiators added significantly to the He 177's weight and drag.

 

Defensive Armament

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A 7.92 mm MG 81 machine gun was fitted in the nose to defend against head on attacks - this aircraft has the two lower rows of nose glazing panels painted over.
He 177A in a shallow dive. The He 177 was meant to have dive-bombing capabilities
He 177 A-5 tail gun position, with MG 151 cannon
He 177, 1944. Note the flaps cover the entire trailing edge.

The undercarriage well covers/hatches have been deployed showing the interior wing structure. Just beyond the outer wheel door is an external rack which could carry conventional bombs, Fritz X or Henschel Hs 293 precision-guided warheads under the wing.

The fifth prototype He 177, the V5, with Stammkennzeichen code "PM+OD" and early cockpit design used on the first eight prototypes.
A He 177s outline in flight, heading away from the camera.

A He 177 having an engine maintenance overhaul
He 177 comes in for a low flypast, January 1944
Closeup of the "fishbowl" nose glazing of an A-series Greif - the B-series prototypes (V101-V104) used it as well
A He 177 taking off for a sortie, 1944
A He 177 during refueling and engine-run up, 1943. Note the four-bladed propeller. The He 177 is painted in a night camouflage scheme.

Gunter's original intention had been to equip the He 177 with three cockpit-controlled remote gun turrets, with two of them intended to come from the Junkers Ju 288 program,[6] and only a single manned position in the tail. Compared with the manned turret, the idea of remotely controlled, turreted defensive armament traded technical complexity for reduction of size, weight, and drag. Furthermore, it held the advantage that the gunner could be installed in a protected position where he would have the best possible view, and where he would be less likely to be blinded by the flash from his own guns. Although work on remotely controlled aircraft defensive systems had reached a relatively advanced stage in Germany in the late 1930s, progress in this field was to prove insufficient to keep pace with the He 177. As a result the He 177 had to be modified to accommodate larger and heavier manned positions, such as the rear dorsal turret usually fitted to almost all examples of the Greif, armed with a single 13 mm MG 131 machine gun, this installation requiring that the fuselage receive structural strengthing in several locations. Eventually, most of the later production aircraft did receive a single remote forward dorsal turret, the Fernbedienbare Drehlafette (abbreviated "FDL") 131Z, armed with two MG 131 machine guns, located at a point on the fuselage directly above the wing root's leading edge, with its hemispherical sighting station's dome located slightly offset to starboard, just behind the forward cabin area.

A compact tail gun position was fitted from the beginning for rearward defense, and armed with a single MG 131 machine gun, but its streamlined glazing severely restricted the gunner's comfort, so a revised tail gun position with a bulged upper glazing design, requiring a reduction of the lower end of the rudder surface for clearance, was fitted to the He 177 A-3 and later models, the initial MG 131 being often replaced with a 20 mm MG 151 cannon.

Usually, a single 7.92 mm MG 81 machine gun in a flexible mount was mounted in the upper starboard side of the cockpit nose glazing, for defense from a direct frontal fighter attack.

The undernose Bola gondola, which was the full width of the fuselage where it emerged from under the nose, and centered under the forward cabin, usually had a flexibly-mounted 20 mm MG FF cannon at the front end, and a flexibly-mounted MG 81 machine gun in the rear for the initial A-1 version. A MG 151 cannon would replace the forward MG FF cannon in later production models, with a single MG 131 replacing the MG 81 for rearwards ventral defense.

 

The Wings

Among the He 177's noteworthy features were its Fowler-type extensible trailing edge flaps which occupied the entire wing trailing edges, including those portions covered by the ailerons. Each aileron comprised upper and lower portions, the latter arranged to slide rearwards with flap extension while the upper part retained its function of providing lateral control for takeoff and landing. Unfortunately, the original wing design did not take into full account the stresses resulting from the operation of the fowler flaps. A Rechlin report dated October 9, 1942 stated:

The examination has shown that the strength of the He 177's wings is one-third below that estimated by Heinkel. The reason for this is the uneven rigidity of the individual members with consequent deformation under load. This condition was not recognized by Heinkel at the proper time, the failure tests having been undertaken too late in view of the size of the structure.

Tests on the fortieth production A-1 aircraft in September 1942 revealed serious outer wing panel component damage after only some twenty flights due to the aerodynamic stress from diving attack exercises, and very costly and extensive strengthening was needed to solve the problem.[7] This significantly increasing the aircraft's weight. Starting with the later versions of the He 177 A-3, the Fowler flaps along the outboard wing sections were deactivated and removed and an additionally strengthened wing design was introduced on the He 177 A-5.

 

Dive Bombing

Accuracy with horizontal bombing during the years of the Ural bomber program demonstrated the weaknesses in existing German bombsights. This in itself called into question the effectiveness of horizontal bombing, whether by a medium or heavy bomber force. Some in the Luftwaffe believed that dive bombing was a more effective way to destroy targets. Technical data supported the accuracy of Stuka strikes achieving greater target destruction over Dornier Do 17s or Heinkel He 111s. The experience of the Condor Legion in Spain supported the theories of dive bombing and led some to believe that pinpoint accuracy was possible, consequently diverting them away from the idea of horizontal bombing in favor of dive bombing.

During the final inspection of the Projekt 1041 mock-up on November 5, 1937, Ernst Udet stated OKL's new divebombing requirement to Ernst Heinkel, who replied that the aircraft would never be capable of it.[4] The He 177 had to be strengthened to support the stresses imposed by the pull-out from a dive. Unfortunately, the dive bombing requirement was later increased to 60° attacks rather than the medium angle dives originally called for, resulting in further structural strengthening and an alarming increase in weight. Nevertheless, the requirement to dive bomb up to 60° was never satisfactorily solved, due to the constant increases in loaded weight. Despite the specially strengthened airframe, it was still possible to overstress the airframe during a dive attack maneuver. While the German bombsights of the 1930’s were in fact quite lacking, the follow-on versions of the Lotfernrohr 7 proved to be arguably as accurate as the American Norden bombsight. With the introduction of the Lotfe 7, which offered an average error of 20 m to 30 m (65 ft to 98 ft) from a release altitude of 3,000 m to 4,000 m (9,842 ft to 13,123 ft), and Hermann Goering's rescindment of the dive attack requirement in September of 1942, the barred-gate type dive brakes were omitted from all He 177 built after the initial pre production batch.

 

Its Undercarriage

In the end, the anticipated weight of the He 177 had increased so alarmingly that the provision of an undercarriage of sufficient strength began to pose a major problem. Neither the engine nacelles or the wings provided much stowage space for the main undercarriage members, and after several extremely complex arrangements had been considered during the aircraft's initial design stages, a rather novel, but complex, system was adopted. Instead of the originally projected single wheel leg under each engine nacelle, two massive single wheel legs were attached to the main spar at each engine nacelle, the outboard legs retracting upward and outward into shallow wing wells, the inboard legs swinging upward and inward into similar wells in the wing roots, all units being completely enclosed by flush fitting doors, and almost "meeting" under each engine nacelle when fully extended. A more conventional single-leg twin wheel arrangement for each main gear was actually used on the two examples (one during the war, one post-war) of the He 274 in France, and a few developments that only existed as drawings actually had tricycle gear setups being fitted to the paper-only He 277.[8] The two hour time that it could take to change just one damaged main gear tire, using special Heinkel-provided 12-tonne capacity main gear jackstand blocks, which were in short supply, was just one of the myriad of problems that the He 177 A's complex main gear format brought about.[9]

 

Prototypes

On November 9, 1939, the first prototype, the He 177 V1 was flown for the first time with Dipl. Ing. Leutnant Carl Francke, chief of the Rechlin flight test center, at the controls. The initial flight terminated abruptly after only twelve minutes as a result of overheating engines. Francke referred favorably to the general handling and landing characteristics of the prototype but complained of some vibration in the airscrew shafts, the inadequacy of the tail surfaces under certain conditions, and some flutter which accompanied any vigorous movement of the elevators.[10]. The He 177 V2 made its first flight soon afterwards. Following Francke's initial flight, the He 177 V1 received several modifications suggested by the initial trials, including a 20% increase in the tail surface area. These modifications were not applied to the He 177 V2 when another test pilot undertook the first diving trials. During the diving trials, the V2 developed severe control flutter and broke-up in the air. Following this incident, the tail surfaces of the V3, V4, and V5 prototypes were modified in a similar fashion to those of the He 177 V1. The He 177 V3 was allocated the task of power plant development. The V1 through V3 prototype airframes were all equipped with two counterclockwise rotating DB 606 A powerplants, while the V4 prototype and all later aircraft, throughout the production run of the A-series, used a DB 606 A or DB 610 A engine on the starboard wing and one clockwise rotating B-version of the same powerplant on the port wing, so that the propellers rotated "away" from each other at the tops of the propeller arcs..[11] The He 177 V4 was retained at Heinkel's test field where it undertook diving trials. While flying over the Baltic, the He 177 V4 failed to recover from a moderate dive, crashing into the sea near Ribnitz. It was later discovered that the accident had resulted from the malfunctioning of an airscrew pitch control mechanism.

The He 177 V5 incorporated a number of changes which were principally concerned with defensive armament installations. Early in 1941, during a simulated low-level attack, both DB 606 engines burst into flames, the V5 hitting the ground and exploding. The He 177 V6 was the first aircraft equipped with main production type DB 606 A/B engines instead of the pre-production units which offered a slight increase in takeoff power by 100 PS to 2700 PS (2,663 hp, 1,986 kW). The He 177 V7 featured a revised nose section which, while generally following the contours of the nose sections employed by the previous prototypes, was considerably reinforced and embodied fewer glazed panels. In September 1941, the He 177 V8, the last of the aircraft to be built as prototypes from the outset with a different, almost "bulletlike" cockpit construction from the production He 177A series aircraft, was made available for engine tests, but owing to the urgency of other development work it was returned to Heinkel after only forty days, and it was not possible to resume engine tests in the air until February 1942. The He 177 V1 to V8 and the A-0 production prototypes are notable for having a broad-bladed set of four-bladed propellers, with blade shapes and profiles similar to those used on the Junkers Ju 88 medium bomber, which were not used on the production He 177A series aircraft.

Photos of the first eight prototypes show a largely circular fuselage cross-section, especially forward of the wing root, with the A-0 series possessing flatter sides, dorsal and ventral surfaces of the main A-series production aircraft. The choice of what was called the "Cabin 3" cockpit design on September 20, 1939 for the production A-series run,[12] placed a well-framed hemispherical "fishbowl" nose onto the He 177 A-0, giving it the generic "stepless cockpit", without a separate windshield for the pilot and co-pilot, that almost all German bomber aircraft had in World War II. The He 177A's "stepless" cockpit's forward glazing had its characteristic framing of four supporting frame members running in each orthogonal direction, running as the parallels and meridians on a globe would. Two sets of four roughly square windows, themselves arranged in a square of four windows each, on each side of the upper cockpit, just behind the "fishbowl's" rear edge, provided sideways vision from the cockpit for the pilot and crew. Often, the two lower rows of the "fishbowl's" windows in the lower nose were made opaque, with the exception of the bombardier's projecting bombsight window, either by painting them over or replacement with metal panels that performed the same function.

 

Production

Eight prototypes were completed, followed by 35 pre-production He 177 A-0s (built by Arado and Heinkel) and 130 Arado-built He 177 A-1s. The early aircraft in this batch were used for further trials, and after a brief and unhappy operational debut the remainder were also withdrawn from service. From late 1942 they were replaced by 170 He 177 A-3s and 826 A-5s, which had longer fuselages and repositioned engine nacelles.[13]

 

Engine Difficulties
Daimler-Benz DB 610

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Specifications:
Model: DB 610
Cylinders: 24
Configuration: Inverted W, Liquid cooled
Horsepower: 2,450 hp
(0,000 kw)
RPM: 2,800
Bore and Stroke: 6.1 in. (154 mm) x
6.3 in. (160 mm)
Displacement: 5,438 cu. in.
(71.4 liters)
Weight: 3,476 lbs.
(1,580 kg)

The tendency of the DB 606 engine to ignite became increasingly serious as the test program progressed and many of the He 177 A-0s were destroyed in accidents or engine related causes. The DB 606 engine had first been introduced on the Heinkel He 119 and later used on other aircraft such as the Messerschmitt Me 261 where they functioned as intended, but the extremely tight cowlings on the He 177 led to considerable problems, the most common being in-flight engine fires and engine overheating. There were several reasons for the flammability of the DB 606 engine, one of which was the common "central" exhaust manifold, serving a total of twelve cylinders, on the two inner cylinder banks of the engines, which became excessively hot and caused the usual accumulation of oil and grease in the bottom of the engine cowling to catch fire. When the pilot throttled back there was a tendency for the injection pump to deliver more fuel than was required by the engine, in addition to which the injection pump connections leaked. In order to restrict the aircraft's weight, no firewall had been provided, and the DB 606 was fitted so close to the main spar that there was insufficient space for the fuel/oil pipelines and electrical leads. The engine was frequently saturated by fuel and oil from leaking connections. At high altitude, the oil tended to foam due to a badly designed oil pump,[14] and in this condition it circulated in the engines, its lubricative qualities being severely reduced. The lack of adequate lubrication resulted in the disintegration of the connecting rod bearings which burst through the engine crankcase, puncturing the oil tanks which poured their contents on to the hot exhaust pipe collector. The tightly-packed nature of the engine installations also led to very poor access to the engines as well as very poor ventilation. As a result of these factors, as well as a lack of routine maintenance in the field, the DB 606 easily caught fire in flight. The effort to create an adequately powerful engine for the He 177 by mechanically coupling pairs of lower-power engines, while theoretically sound, proved to be difficult and time consuming to perfect, leading to numerous engine complications especially on the initial production models.

Reichsmarschall Hermann Goering, angered at the apparent slowness with which the He 177 was having its powerplant problems researched and solved late in August 1942, responded thusly to one Oberst Petersen's report on the He 177's powerplant troubles, remarking on the unusual engine configuration, and the difficulty of maintenance access, of the DB 606"s:

“ Why has this silly engine suddenly turned up, which is so idiotically welded together? They told me then, there would be two engines connected behind each other, and suddenly there appears this misbegotten monster of welded-together engines one cannot get at! ”

Starting with the He 177 A-3/R2, a modified engine nacelle with a new engine, the Daimler-Benz DB 610 which consisted of a pair of Daimler-Benz DB 605's, was used to eliminate the tendency for engine fires. With the introduction of the DB 610 came several improvements including the relocation of the engine oil tank, the lengthening of the engine mountings by 20 cm (8 in), the complete redesign of the exhaust system which also facilitated the installation of exhaust dampers for night missions, and the setting of a power limitation on the engines which resulted in greater reliability. These modifications were successful as far as engine fires were concerned but other minor problems with the transfer gearbox between the two engines and their shared propeller remained.

 

Experimental weapon loads

In addition to carrying a variety of bombs, torpedoes, and guided weapons the He 177 was tested with a number of unorthodox armaments. The first of these experimental weapon schemes known to have been tested were the twelve examples of the He 177 A-1/U2 Zerstörer variant, which was armed with a pair of limited-traverse 30 mm MK 101 cannons in the extreme front of a dramatically enlarged Bola ventral gondola, and intended for ground attack, train busting, and possibly long-range anti-ship raids.[17] Later, when assigned to flak-suppression sorties in the area of Stalingrad during the winter of 1942, Luftwaffe forward maintenance units modified a small number of He 177s, fitting a 50 mm Bordkanone BK 5 cannon to the aircraft's ventral gondola. This variant was unofficially dubbed the Stalingradtyp. Although a small number of He 177 A-3/R5 models were to be built from scratch, with the larger 75 mm Bordkanone BK 7.5 ventral cannon, structural problems caused by the weapon's recoil meant that the Stalingradtyp did not see combat use outside of the original, BK 5-armed improvised handful. Five He 177 A-5s were experimentally equipped in January 1944 with batteries of thirty-three obliquely-mounted rocket mortar tubes, likely derived from components of the Nebelwerfer infantry barrage rocket system, to create the Grosszerstorer (Big Destroyer) flying battleship, meant to break up and destroy the tight combat box defensive formations used by enemy bombers over Germany. The mission of these specialized aircraft was to stalk and destroy Allied bomber formations. The bomb bays and fuselage-housed auxiliary fuel tanks were deleted on these aircraft in order to provide space for the spin-stabilized 21 cm (8 in) rockets and their firing tubes. The tubes were inclined to fire upward at an angle of 60° to the horizontal axis of the aircraft and slightly to starboard. The tubes could be fired individually, simultaneously, or in two salvoes of fifteen and eighteen. Tests with fixed balloon targets showed the potential of this system, and limited operational trials against US Eighth Air Force bomber streams were authorized. The aircraft were operated by Erprobungskommando 25, flying out of Tarnewitz. The intended mode of operation called for the He 177s to follow the enemy bomber formations, passing below and to port of the target, maintaining a difference of altitude of 2,000 m (6,562 ft) at the time of the attack from below. A few trial daylight operations were flown but no contact was made with Allied bomber formations, and as the escort fighters were becoming ever more numerous the entire scheme was abandoned.

 

He 177 components in other aircraft

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As part of the Junkers Ju 287 program, the fuselage of an He 177 A-5 was used as the core component. Mated to a revolutionary forward-swept wing, the tail of a Junkers Ju 388, its fixed main undercarriage from a Junkers Ju 352, and twinned nosewheels from captured B-24 Liberators, the Ju 287 V1 first took to the air from Brandis airfield on August 16, 1944.

The nosegear units of the first three prototypes of the turbojet-powered Horten Ho 229 flying wing fighter were obtained from He 177 landing gear components. The first two prototypes used complete tail gear lower units (oleo strut and wheelfork), complete with wheel, for their nosegear, while the unflown V3 used a Greif's main gear wheel and tire assembly for its nosewheel, as some 40% of the Ho 229's entire weight was meant to be placed on the nosegear and wheel.

 

Airworthiness and handling

The initial production version of the Greif, the He 177 A-1, demonstrated a tendency for instability in the yaw and pitch axes during August 1942, during flight tests, that would have led to poor bombing accuracy in action. Shortly after these tests, the third production A-1 example (factory serial number 15153, with Stammkennzeichen of GI + BN) had its fuselage lengthened by 160 cm (63 in) just aft of the trailing edge of the wing, and tests of the modified aircraft, from the longer distance of the "tail moment" that resulted, gave a marked degree of improvement in the yaw and pitch axis stability, enough to mandate the construction of the He 177 A-3 and all later models of the He 177 with the lengthened fuselage.[18]

British Royal Navy test pilot Eric Brown related in his book, Wings of the Luftwaffe, about the visual appearance and in-flight handling characteristics of the He 177 A-5 version, one of which he flew as a captured aircraft late in the war:

Its ground stance reminded me vividly of a Short Stirling which had sunk to its knees. In fact if there had been a choice between the Stirling and the He 177 as aesthetically the least appealling of bombers then I think the German contender would have won by a short head. A check of stability showed the aircraft to be positive about all axes, but the controls were all remarkably light for such a large aircraft. Indeed I had the feeling that the elevator was dangerously light and I was all too aware of the intelligence reports of He 177s breaking up in the air so I decided to treat this control very gently. I began a cautious exploration of the aircraft's diving characteristics since the permissible acceleration was 2.3 g with a flying weight of 27 tonnes it was vital to know the exact weight of the He 177 at all times. The aircraft had an automatic pull-out device and an acceleration warning apparatus fitted, but it really was nailbiting to have to treat a giant like this immense Heinkel bomber as if it was made of glass. The stalling characteristics with flaps and undercarriage lowered the aircraft buffeted violently at 140 km/h (87 mph) before the nose dropped at 135 km/h (84 mph). The buffet experienced was so violent that I had some concerns over structural damage. Somehow the He 177 always conveyed an impression of fragility despite its size.

The He 177A's physical dimensions and empty weight were close to that of the best known American heavy bomber of WW II, the B-17, which made Eric Brown's perceived "lightness" of the Greif's control forces potentially all the more unusual.

 

Further Development-The He 177B prototypes

Due to continuing problems with the DB 606's configuration, much development work was being done in order to rectify engine complications, including a complete redesign of the original He 177 intended towards the creation of a four engined version of the Greif's airframe. Ernst Udet was critical of the coupled DB 606 powerplant choice for the He 177 from before the war's start, with Goering adding his input from his own frustrations with the seemingly interminable engine problems delaying the introduction of the He 177A into service. Goering was reported as stating in August 1942:

“ I had told Udet from the start that I wanted this beast with four engines. This crate must have had four engines at some time! Nobody had told me anything about this hocus-pocus with welded-together engines. ”

The RLM's requirement for the He 177 to perform diving attacks was finally rescinded in September 1942 by Goering himself, and with that decision finally rendered, Heinkel's design work on four engined versions of the He 177A, collectively named the He 177B, were then able to progress, all to be powered with four individual Daimler-Benz DB 603 engines, with each liquid-cooled DB 603 fitted with a Heinkel He 219-style annular radiator right behind the propeller for engine cooling. This task was accomplished in a considerably later timeframe than British aircraft designer Roy Chadwick had done in similarly converting the Avro Manchester. The initial design of the Manchester, like the A-series Greif with its coupled DB 606s and 610s, had similarly depended on only two very powerful and quite troublesome 24-cylinder powerplants, the British Rolls-Royce Vulture, which by 1941 had evolved under Chadwick's work into the Rolls-Royce Merlin powered, truly four-engined Avro Lancaster.

By August 1943 much of the detail work for the He 177B series aircraft was well on its way to completion, and Erhard Milch approved the creation[19] of three He 177B prototypes, designated He 177 V101 to V103. The V101 was converted from a mid-production He 177 A-3 airframe (number 535550, with Stammkennzeichen of NN + QQ), the V102 being converted from the eighth He 177 A-0 production prototype aircraft, and the V103 being converted from an existing, early production He 177 A-5 airframe, and all three of which initially retained the 177A-style tail surfaces. Because of the 177A-style single-tailed V101 prototype having increasingly serious stability problems with higher airspeeds in its flight testing, the second prototype, the V102, was the first to be fitted with an empennage of twin tail configuration that, when tested, gave the V102 significantly better in-flight handling when compared to the original He 177A's single tail design, except during the landing approach when the Fowler flaps were extended, when flown in November 1943.[20] The only photograph that exists today of any of these He 177B prototypes is one of the V101, parked outdoors on a foggy German airfield.[21][1]

The He 177B was also intended to introduce a slightly enlarged, somewhat more aerodynamic fully-glazed nose[19] that could incorporate a remotely controlled power chin turret for forward ventral defense, mounting either a pair of MG 131 machine guns or MG 151 cannon, but the nose was only tested on the fifteenth He 177 A-0 production prototype, without the chin turret, and was never fitted on any of the He 177B prototypes, which used the standard "Cabin 3" He 177A's well-framed nose. No photographs of this new nose design are known to have survived the war and only drawings exist of it in modern archives. The remaining defensive armament generally remained similar to the He 177A, particularly the twin dorsal gun turrets for the He 177 B-5, with the aft manned dorsal turret being deleted on the planned He 177 B-7 (as on the He 177 A-7) to reduce weight, and a fully powered manned Hecklafette HL 131V tail turret, carrying a quartet of MG 131 machine guns, was intended for installation on the prototypes and would have been standardized on the production aircraft, but never went beyond the mockup and working prototype stage. The cumbersome four-strut main landing gear of the A-series was retained intact for the B-series prototypes, even though their height, meant to allow clearance for the A-series' pair of large four-blade propellers, was not changed - the outer edge of the DB 603's inner engine nacelle/wing surface juncture was located right at the "centerline" of each of the twin pairs of A-series main gear strut locations, on all four of the B-series prototypes.

The first flights of the He 177B prototypes occurred between late December 1943 and early January 1944 in the vicinity of the Vienna-Schwechat airfield, at the firm's Heinkel-Sud southern production facility, where an additional prototype, the V104, whose purpose was to be the "finalized" production prototype for the He 177 B-5, and also meant to be a twin tailed prototype like the earlier V102, was being completed by order from the RLM, converted from an early production He 177 A-5.

However, from late April through July 1944, repeated Fifteenth Air Force bombing raids on German aircraft production facilities in Vienna destroyed the airworthy V103 and the incomplete V104, setting back any plans of producing He 177 B-5, with the V101 and V102 prototypes surviving until at least February of 1945 before they were scrapped. The adoption of the Emergency Fighter Program dealt the final blow to the entire He 177B development program, with the Heinkel He 162 jet fighter being the only new Heinkel aircraft design that would be allowed into production.[22]

 

Operational history

Beset by technical difficulties in development and service, the He 177 had a troubled life. This was in part due to the overly optimistic design requirements of long range, high speed, heavy bombload, and dive bombing. Although the He 177 entered service in 1942 it was still far from operational. In an assessment of the aircraft on April 9, 1942 the newly activated Erprobungsstaffel 177 reported that the Greif had good flying characteristics, but had unacceptable engine troubles and deficits with the airframe strength. As an emergency measure it was used to supply the encircled 6th Armee at Stalingrad where it was determined that it was totally unsuited for the transport role, carrying a little more cargo than the appreciably smaller and infinitely more reliable Heinkel He 111, and was useless for the evacuation of wounded troops. As a result the He 177s reverted to bombing and flak-suppression missions in support of the Wehrmacht in the vicinity of Stalingrad. Only thirteen missions were flown and seven of the He 177s crashed in flames without any action attributable to the enemy.

As the war progressed, He 177 operations became increasingly desultory. Fuel and personnel shortages presented insurmountable difficulties, and He 177s were sitting on airfields all over Europe awaiting the replacement of engines or engine related modifications. Serviceability also was invariably low as a result of last-minute mishaps before operations. On the night of February 13, 1944 as part of Operation Steinbock, fourteen He 177 taxied out on a bombing mission, thirteen took off, one suffering a burst tire, eight promptly returned to base with overheating or burning engines. Of the four He 177s which did reach London one was shot down by night fighters. It is not always clarified that these aircraft were brand new, delivered about a week before the operation and not properly flown-in, as the air unit had moved to a new airfield the day before and lacked sufficient maintenance personnel and material. The constant attacks of Allied bombers against the Luftwaffe's long range combat units in France made continuous operations on these airfields quite difficult. Many aircraft could not be maintained properly due to destroyed hangars or were simply unserviceable due to damages caused by Allied strafing attacks.

While Steinbock could be considered as an unsuccessful operation, the He 177 did achieve some successes. The more experienced crews typically carried two 1,800 kg (3,968 lb) and two 1,000 kg (2,204 lb) bombs. Climbing to 7,000 m (22,965 ft) while still over German territory, the He 177s approached the target in a shallow dive, each aircraft throttled back, the pilot putting his aircraft into a gliding descent to take it across the bomb release-point at about 4,500 m (14,763 ft). After releasing the bombs the pilot re-opened the throttles, but continued the descent at approximately 200 m (656 ft) per minute. The bombers typically re-entered German airspace at an altitude of 750 m (2,460 ft), and headed back to base. By such means, the He 177s were able to keep up speeds of about 600 km/h (373 mph) to 700 km/h (435 mph) during their withdrawal phase. The higher speed and constant change of altitude made the aircraft harder to intercept, increasing the survivability of the aircraft, but unfortunately decreased bombing effectiveness. In fact, with an average loss rate of 60% for every type of bomber used in Operation Steinbock, the He 177s had a loss rate well below 10%, making them the most survivable bomber used in this campaign.

During operations on the Eastern Front in early 1944, often carried out in daylight at about 6,000 m (19,685 ft) or higher, losses were relatively light. The Soviet Air Force, equipped mainly for low-level interception and ground-attack roles, was able to do little to hinder the high-flying bombers. Individual pilots did make interceptions but, unaccustomed to engaging such comparatively large targets and disconcerted by the effective defensive armament, they rarely pressed home their attacks.

In common with most German bombers, the He 177 was grounded from the summer of 1944 as the Allied bombing campaign began to seriously affect German fuel production. By this time the He 177 had proved itself to be the most technically advanced bomber of the Luftwaffe. This was confirmed by postwar tests on the He 177 A-5 and the single long-range He 177 A-7, which the Royal Air Force found impressive. The He 177 can be compared with the B-29 Superfortress which also took about two years to have its problems ironed out, after which it became one of the most successful bombers of aviation history. However, due to the Emergency Fighter Program, fuel shortages, and the deteriorating war situation in Germany the He 177 was never able to achieve its full potential.

 

Production

Production of the He 177 until 30 November 1944:

Version EHF [24] HWO [25] ArB [26] Total Production period
Prototypes 8     8  
He 177 A-0 15 15 5 35  
He 177 A-1   88 42 130 January 1942 - January 1943
He 177 A-3   217 398 615 November 1942 - June 1944
He 177 A-5   71 278 349 December 1943 - August 1944
Total 23 391 723 1,137  

Note - One A-0, one A-3, and two A-5 rebuilt as He 177B prototypes from before December 1943 to July 1944. Source: Bundesarchiv/Militärarchiv Freiburg

 France
  • French Air Force operated at least two He 177 A-3s left behind by the Germans and rebuilt by SNCASE at Blagnac.
 United Kingdom
  • Royal Air Force

Click on Picture to enlarge

He 177 A-5 captured by RAF

 

 

RAE (Farnborough) tested one He 177 A-5. An aircraft with the Geschwaderkennung code of F8 + AP from 6./KG 40 was captured by the Allies on September 1944 at Toulouse-Blagnac airfield. Transferred to the UK and was repainted with British roundels and serialled TS439.[27]

 

 

 

 

Specifications (He 177 A-5/R2)
 

Click on Picture to enlarge

General characteristics

  • Crew: 6
  • Length: 22 m (72 ft 2 in)
  • Wingspan: 31.44 m (103 ft 1¾ in)
  • Height: 6.40 m (20 ft 11¾ in)
  • Wing area: 101.99 m² (1,097.918 ft²)
  • Empty weight: 16,800 kg (37,038 lb)
  • Loaded weight: 27,200 kg (59,966 lb)
  • Max takeoff weight: 31,000 kg (68,343 lb)
  • Powerplant: 2× Daimler-Benz DB 610 24-cylinder liquid-cooled inline piston engines, 2,900 PS (2,133 kW) each

Performance

  • Maximum speed: 565 km/h at 6,000 m (351 mph at 19,685 ft)
  • Stall speed: 135 km/h (84 mph)
  • Combat radius: 1,540 km (957 mi)
  • Ferry range: 5,600 km (3,480 mi)
  • Service ceiling: 9,400 m (30,840 ft)
  • Rate of climb: 190 m/min (623 ft/min)
  • Wing loading: 303.9 kg/m² (62.247 lb/ft²)

Armament


 

  • 1 × 7.92 mm MG 81 machine gun in nose
  • 1 × 20 mm MG 151 cannon in forward ventral gondola position
  • 2 × 7.92 mm MG 81 machine guns in rear ventral gondola position
  • 2 × 13 mm MG 131 machine guns in FDL 131Z remotely-operated forward dorsal turret, full 360º traverse
  • 1 × 13 mm MG 131 machine gun in manned aft dorsal turret
  • 1 × 20 mm MG 151 cannon in tail position

Up to 6,000 kg (13,227 lb) of disposable stores internally or 7,200 kg (15,873 lb) externally or up to 3 Fritz X or Henschel Hs 293 radio-guided munitions

  • 48 × 50 kg (110 lb) bombs (2,400 kg/5,291 lb total)
  • 1 × 2,500 kg (5,511 lb) bomb (2,500 kg/5,511 lb total)
  • 12 × 250 kg (551 lb) bombs (3,000 kg/6,613 lb total)
  • 6 × 500 kg (1,102 lb) bombs (3,000 kg/6,613 lb total)
  • 2 × 1,800 kg (3,968 lb) bombs (3,600 kg/7,936 lb total)
  • 2 × 1,800 kg (3,968 lb) bombs + 2 × LMA III mines (4,600 kg/10,141 lb total)
  • 10 × 500 kg (1,102 lb) bombs (5,000 kg/11,023 lb total)
  • 2 × 1,000 kg (2,204 lb) bombs + 2 × 1,800 kg (3,968 lb) bombs (5,600 kg/12,345 lb total)
  • 6 × 1,000 kg (2,204 lb) bombs (6,000 kg/13,227 lb total)
  • 2 × FX 1400 Fritz X + 1 × FX 1400 Fritz X under the wings and fuselage
  • 2 × Hs 293 or 294 + 1 × Hs 293 or 294 under the wings and fuselage
  • 2 × 500 kg (1,102 lb) bombs internally + 2 × Hs 293 under the wings
  • 2 × LT 50 torpedoes under the wing

 

References

Notes

  1.  Munson 1983, p. 292.
  2.  Price 2004, p.162.
  3.  Griehl & Dressel 1998, pg.8
  4.  Griehl & Dressel 1998, pg.9
  5.  Griehl & Dressel 1998, pgs.92-94
  6.  Griehl & Dressel 1998, pg.33
  7.  Griehl & Dressel 1998, p.53
  8.  Griehl & Dressel 1998, pgs. 159 & 195
  9.  Griehl & Dressel 1998, pg. 218
  10.  Griehl & Dressel 1998, pg.17
  11.  Griehl & Dressel 1998, pg.22
  12.  Griehl & Dressel 1998, p.16
  13.  Munson 1983, pp. 292-293.
  14.  Price 2004, p.162
  15.  Griehl & Dressel 1998, p.52
  16.  Griehl & Dressel 1998, pg.94
  17.  Griehl & Dressel 1998, pgs.106-111
  18.  Griehl & Dressel 1998, p.46 & 54
  19.  Griehl & Dressel 1998, p.162
  20.  Griehl & Dressel 1998, p.163
  21.  Griehl & Dressel 1998, p.165
  22.  Griehl & Dressel 1998, pgs.170-172
  23.  Griehl & Dressel 1998, p.160-161
  24.  Ernst Heinkel Flugzeugwerke
  25.  Heinkel Werke Oranienburg
  26.  Arado Brandenburg
  27.  Flight International May 1945
  28.  

Bibliography

  • Chant, Christopher. Aircraft of World war II. Grange Books, 2000. ISBN 1-84013-336-8.
  • Darling, Kev. Heinkel He 177 (Warpaint Series No. 33). Milton Keynes, Buckinghamshire, UK: Hall Park Books Ltd., 2000.
  • Griehl, Manfred and Dressel, Joachim. Heinkel He 177 - 277 - 274. Shrewsbury, UK: Airlife Publishing. ISBN 1-85310-364-0.
  • Hirsch, R.S.; Feist, Uwe and Nowarra, Heinz J. Heinkel 177 "Greif" (Aero Series 13). Fallbrook, CA: Auro Publishers Inc., 1967. ISBN 0-8168-0548-2.
  • Mondey, David. The Hamlyn Concise Guide to Axis Aircraft of World War II. London, UK: Chancellor Press, 2004. ISBN 1-85152-966-7.
  • Munson, Kenneth. Bombers 1939 - 45. London, UK: Bounty Books, 2004. ISBN 0-7537-0919-8.
  • Price, Alfred. "Heinkel He 177 Greif (Griffon)". Aircraft in Profile, Volume 11. Windsor, Berkshire, UK: Profile Publications Ltd., 1972. p. 265-288.
  • Price, Alfred. "He 177 Greif: The Luftwaffe's Lighter". International Air Power Review, Volume 11. Norwalk, Connecticut, USA: AirTime Publishing, 2004. ISBN 1-880588-60-9.
  • Smith, J.R. and Kay, E.L. German Aircraft of the Second World War. London, UK: Putnam, 1972. ISBN 85177 836 4.

Wikipedia

 

 

Heinkel He 177A-5 of II Gruppe, Kampfgeschwader 1 'Hindenburg' based at Prowehren, East Prussia, mid-1944. KG 1 assembled about 90 of these bombers for attacks on Soviet communications and military installations, but unreliability dogged operations.

 

Click on Picture to enlarge

Both the most important heavy bomber projects - the Heinkel He 177 'Greif ('Griffon') and the Junkers Ju 288C - had pairs of siamesed engines as their powerplant. They were designed to carry both conventional bombloads in internal bays and external racks but also guided glider bombs such as the 'Fritz- X' or the Henschel Hs 293. The only one built in significant numbers was the He 177, over 1000 of which were produced. Many were fitted with forward-firing 5cm and 7.5cm anti-tank guns to be deployed on the Eastern Front. However, it was never entirely successful, even after five years of development. A high-altitude reconnaissance version of the He 177 was developed, powered by four (separate) DB 610 engines of 1750hp and with a new high aspect ratio wing and a new twin fin tail. Known as the He 274, the prototype was built in Paris at the old Farman works, which were overrun in July 1944 before it could be completed. It was finished by the French and flown from December 1945. An improved version of the bomber, also with four separate engines and a twin fin tail, was built as the He 277, but only eight were completed before the Emergency Fighter Programme was put into effect on 3 July 1944.

The Heinkel He 177 Greif (Griffon) was a long-range bomber of the Luftwaffe. The troubled aircraft was the only heavy bomber built in large numbers by Germany during World War II. Aircrews nicknamed it the Luftwaffenfeuerzeug (Luftwaffe's lighter) or the 'Flaming Coffin' due to the engines' tendency to catch fire on the early versions of the aircraft.[1]

 

Design

The He 177 was conceived as a result of an Reichsluftfahrtministerium (RLM) requirement called the Bomber A specification which called for a bomber aircraft more advanced than the Dornier Do 19 or Junkers Ju 89, capable of carrying a bombload of at least 1,000 kg (2,204 lb) over a range of 6,695 km (4,160 miles). The aircraft had to possess a maximum speed of about 540 km/h (335 mph) at altitude and it had to embody sufficient structural strength to enable it to undertake medium degree (later changed to 60 degree) diving attacks. In order to meet these specifications the He 177 embodied many advanced features including coupled engines with surface evaporation cooling and small remotely controlled defensive gun barbettes.

 

Engines

An unusual feature of the aircraft was the use of twin engines in each nacelle driving a single propeller, as the components of a "power system". Siegfried Günther, chief designer of Heinkel, chose to use the Daimler-Benz DB 606, which consisted of two Daimler-Benz DB 601 engines coupled together to use a common propeller, in order to minimise drag. The two engines were coupled side by side in each nacelle and inclined inwards at the crankcases' upper surfaces, so that the inner cylinder banks were disposed almost vertically, a single gear casing connecting the two crankcases, and the two crankshaft pinions driving a single airscrew shaft gear. The insistence of this engine configuration stemmed directly from the RLM's determination that the He 177 should be capable of dive bombing. The use of only two propellers on a heavy bomber also offered a substantial reduction in drag and a marked improvement in maneuverability. Indeed, the initial prototypes and pre-production models of the bomber had an airspeed and maneuverability comparable to many heavy fighters of the time.

The paired engines had first been introduced on the single-propeller equipped Heinkel He 119 prototype reconnaissance bomber aircraft to reduce drag where they worked well, but their extremely tight installation on the He 177 led to considerable problems, the most common being in flight engine fires and overheating. There were several reasons for the flammability of the DB 606 engine, one of which was the common exhaust manifold on the two inner cylinder blocks, which became excessively hot and caused the usual accumulation of oil and grease in the bottom of the engine cowling to catch fire. When the pilot throttled back there was a tendency for the injection pump to deliver more fuel than was required by the engine, in addition to which the injection pump connections leaked. In order to restrict the aircraft's weight, no firewall had been provided, and the DB 606 was fitted so close to the main spar that there was insufficient space for the fuel/oil pipelines and electrical leads. The engine was frequently saturated by fuel and oil from leaking connections. At altitude, the oil tended to foam partly as a result of the oil pump being overly effective, and in this condition it circulated in the engines, its lubricative qualities being severely reduced. The lack of adequate lubrication resulted in the disintegration of the connecting rod bearings which burst through the engine crankcase, puncturing the oil tanks which poured their contents on to the hot exhaust pipe collector. The tightly-packed nature of the engine installations also led to very poor access to the engines. As a result of these factors, as well as a lack of routine maintenance in the field, the DB 606 easily caught fire in flight. Thus the effort to create an adequate engine to power the He 177 (such as the Junkers Jumo 222 produced too late in the war), by mechanically coupling pairs of lower-power engines, while theoretically sound, proved to be difficult and time consuming to perfect, leading to engine complications especially on the initial production models.

Starting with later versions of the He 177A-3, a modified engine nacelle with a new engine, the Daimler-Benz DB 610, was used to attempt to eliminate tendency for the engines to catch fire. Several improvements concerning cooling issues for the engines by setting a power limitation resulted in greater reliability. This modification was successful as far as engine fires were concerned but there were other minor problems with the transfer gearbox between the two engines and their shared propeller and other difficulties involving the installation of flame damper tubes for night missions.

 

Surface evaporation cooling

Originally, the He 177 design called for evaporative cooling in order to eliminate radiator weight and drag, but despite the immense amount of research undertaken by Heinkel into the problems of surface evaporation cooling, this feature was soon abandoned in 1939 in favor of annular radiators, one fitted directly behind each propeller, which resembled those fitted to the Junkers Jumo 211-powered versions of the Ju 88. The addition of large radiators added significantly to the aircraft's weight and drag.

 

Armament

Another design innovation featured by the He 177 as originally conceived was the use of three remotely controlled defensive gun turrets, which offered substantially less drag than manned turrets. Unfortunately, the perfection of these turrets was slow, and the He 177 had to be modified to accommodate larger manned positions, this requiring the fuselage to be strengthened in several locations, further increasing the aircraft's weight and drag. Most of the He 177As produced did have a single, twin MG 131 gun remote dorsal turret, located forward of the aft-located, manned dorsal turret, and sighted from a transparent dome just behind the forward cabin area.

 

Experimental weapon loads

In addition to carrying a variety of torpedoes, and guided missiles such as the Hs 293 anti-shipping missile, the 177 was tested with a number of unorthodox armaments. The first of these experimental weapon schemes known to have been attempted were the twelve examples of the He 177 A-1/U2 Grosszerstörer variant, which was armed with a pair of limited-traverse 30mm MK 101 autocannons in the extreme front of the under-nose gondola, and intended, variously, for "train-busting" ground attacks and possibly long-range anti-ship raids. Later, when assigned to flak-suppression sorties in the area of Stalingrad during the winter of 1942, Luftwaffe forward maintenance units modified a small number of 177s, fitting a massive 50mm cannon to the planes' nose gondolas. This variant was unofficially dubbed the Stalingradtyp. Although a small number of later A-3/R5 models were to be built from scratch, with an even larger Bordkanone BK 7.5, 75mm ventral cannon, structural stress problems caused by the gun's recoil meant that the Stalingradtyp did not see combat use outside of the original improvised handful. Three later-model 177s were experimentally equipped in June 1944 with batteries of obliquely-mounted rocket mortar tubes (thirty-three in all) to create the Pulkzerstorer (Formation Destroyer) flying battleship, a term also used for the Werfer-Granate 21 rocket-firing Luftwaffe single engined fighters. The mission of these specialised aircraft was to stalk and destroy Allied bomber formations. Bomb bays and auxiliary fuel tanks were deleted on these aircraft in order to house the spin-stabilized rockets and their firing mechanisms. The tubes could be fired individually, simultaneously, or in two salvoes of fifteen and eighteen. Tests with fixed balloon targets showed the potential of this system, and limited operational trials against US Eighth Air Force bomber streams were authorised. These trials yielded no results, however - each time an attack was attempted the Pulkzerstorer 177s were unable to close to firing range with their targets. It is also believed that a single heavily modified He 177 was prepared as a prototype for a projected nuclear bomber variant, the Greif being deemed the best compromise choice for the role until the arrival in operational service of more suitable carriers, such as the Junkers Ju 488 or Ju 287. [1]

 

Wings and undercarriage

The insistence on the ability to dive-bomb also led to the need to strengthen the wing structure, leading to the classic "vicious circle" in military aviation design, starting with an increase in unloaded weight, producing the need to enlarge the undercarriage, in turn increasing further the weight and causing a decrease in speed, range and carrying capacity. The requirement to dive-bomb was never satisfactorily solved and the later versions of the aircraft were produced without dive brakes.

 

The He 177's main gear arrangement can best be described as complex. There were four main gear struts, each with one large wheel, with the inboard and outboard retracting sets almost "meeting" under the nacelle of each of the engines when fully extended. A more conventional single-leg twin wheel arrangement for each main gear was actually used on the sole example of the He 274, and a few developments that only existed as drawings actually had tricycle landing gear setups being fitted to the He 277.

 

Airworthiness and Handling

British Royal Navy test pilot Eric Brown related in his book, Wings of the Luftwaffe, about the amazingly "light" handling of the He 177 A-5 version, one of which he flew as a captured aircraft late in the war. His remarks also seemed to indicate that the He 177's elevator control forces, in particular, were all too "exceptionally" light for a plane, which was no more than two feet different in wingspan and fuselage length, and with a similar empty weight, than the American USAAF's famous B-17 heavy bomber, and that reports of He 177's breaking up in flight could have been partially due to such light elevator control forces fooling He 177 pilots into thinking that they could "horseplay" with the control yoke in the pitch axis, over-stressing the Greif's fuselage to the point of structural failure.

 

Operational history

Beset by many other technical difficulties in development and service, the plane had a troubled life. This was in part due to overly optimistic design requirements of long range, high speed, a large bombload, and dive bomber. Though Goering forbade Heinkel to develop a version with four separate nacelles, Heinkel nevertheless produced prototypes of the Heinkel He 177B (later renamed into the Heinkel He 277) which was produced in limited numbers.

Although the He 177 entered service in 1942 it was still far from operational. As an emergency measure it was used to supply the encircled 6th Armee at Stalingrad where it was determined that it could carry a comparable payload to the appreciably smaller Heinkel He 111, and being virtually useless for the evacuation of wounded troops. As a result the He 177's reverted to bombing and flak-suppression missions in support of the Wehrmacht in the vicinity of Stalingrad. Only thirteen missions were flown and seven of the He 177's crashed in flames without any action attributable to the enemy. Another example of problems most resources cite a special situation regarding a night attack on England during Operation Steinbock (early 1944): 13 aircraft took off, 1 failed to take off due to a burst tire, 8 returned with burning or overheating engines and of the remaining few that got to their target two were destroyed by enemy night fighters. What most resources neglect to cite is that these aircraft were brand new, just delivered about one week before and not even properly flown-in, the air unit just moved to a new airfield the day before and was missing great amounts of maintenance personnel and material.

During later operations such as the aforementioned Operation Steinbock ("The Little Blitz") with an average loss rate of 60% for each type used (Do 217, He 111, Ju 88, Ju 188), the participating He 177A-5s had a loss rate well below 10%, making them the best bomber used in this campaign. According to sources experienced crews were able to carry a 5,600 kg (12,345 lb) payload on these missions. Standard tactics for the He 177 was to climb to its service ceiling before crossing the French coast, then carry out the rest of the mission in a shallow full power dive, which allowed the aircraft to reach a speed of over 690 km/h (428 mph). The higher speed and constant change of altitude made the aircraft harder to intercept, increasing the survivability of the aircraft, but greatly decreased bombing accuracy and effectiveness.

The final end for the He 177 came in late 1944 when high grade fuel wasn't available in the quantity needed to operate a whole Geschwader and the implementation of the Emergency Fighter Program. At this point the He 177 proved to be the most reliable, rugged and technically advanced bomber of the Luftwaffe. This seems to be confirmed by post war tests on the He 177A-5 and the single long-range He 177A-7, which turned out to be impressive for the RAF. As such, the He 177 can be compared with the Boeing B-29 bomber which also took about two years to have its problems ironed out, after which it became one of the most successful bombers of aviation history. Due to the war situation in Germany the He 177 was never able to prove itself and the designs used within.

 

 

 

Click on Picture to enlarge
 

The He 177 was the nearest the Luftwaffe came to possessing a long range heavy bomber during the Second World War, although it was not originally designed with that role in mind. The young Luftwaffe, inspired by Generalleutnant Wever, the head of the Air Force General Staff, had been interested in strategic bombers, and had produced the Do 19 and Ju 89, both of which first flew in 1936. Work on these potential heavy bombers ended after Wever was killed in an air crash. He was replaced by Generalleutnant Kesselring, who shared the more common Luftwaffe view of the heavy bomber as an inflexible waste of resources. Both projects were cancelled.

In their place came the Bomber A long range bomber and Bomber B twin engined medium bomber projects. The Bomber A specifications, issued in June 1936, called for an aircraft with a top speed of 335mph, an operational radius of 1,000 miles with a 4,400lb payload and 1,800 miles with a 2,200lb payload. The original specifications asked for an aircraft capable of acting as a shallow dive bomber. Only later on was this specification altered to add steep dive bombing capacity.

The main problem faced by anyone attempting to respond to the Bomber A specification was the known preference of the RLM for twin engined designs. Unfortunately, in 1936 no German aircraft engines were capable of providing the amount of power that a twin engined Bomber A would require. Heinkel’s response was the use of the Daimler Benz DB 606 twin engine. This took two DB 601 inverted V inline engines and placed them side by side, with the inner cylinders almost vertical, producing a inverted W engine. The two engines powered a single propeller through a complex gearing mechanism. In theory this would produce a single engine with double the power of the original unit. It would not safe any weight and the frontal area of the combined engine was also double that of the single engine, but the reduction in the number of engine nacelles would reduce drag.

Daimler Benz and Heinkel were not the only people working on twinned engines in 1936. The Rolls Royce Vulture was a remarkably similar twinned engine, which developed many of the same problems as the DB 606. It was also installed in a twin engined heavy bomber, the Avro Manchester, which then suffered from unreliable engines. The German mistake was to persist with the twinned engines long after Rolls Royce had abandoned the Vulture and Avro had turned to four Merlin engines, turning the unsuccessful Manchester in the famous Avro Lancaster. The fault for this must be placed with the RLM, which turned down repeated requests from Heinkel for permission to work on four engined versions of the He 177, before eventually allowing work on the four engined He 277 to officially start in 1943.

The main problem with the DB 606 would be heat. The DB 601 was already a hot engine. For the He 177 Heinkel designed a wing based evaporative cooling system, using pressurised water as the coolant, with pipes in the wing used to cool the resulting steam. This system proved incapable of providing enough cooling for the He 177 and had to be abandoned. In its place Heinkel had to use a standard radiator system, which increased drag.

This was one of many technical problems and specification changes that soon dragged the He 177 into a vicious circle. Drag would increase, reducing fuel efficiency and forcing Heinkel to add more fuel to maintain range. This would increase weight, forcing increases in the strength of the design, and thus the weight, again requiring more fuel.

The biggest increase in weight came from the requirement for the He 177 to be able to act as a dive bomber. The steep dive, sharp pull-out and steep climb put the fuselage of any aircraft under serious stress, and so the aircraft had to be strengthened yet again. The eventual aircraft would have the required range, a better bomb load than had been specified, but would fall short on maximum speed. It would also be have very high wing loading (wing area divided by weight), making it very hard to handle. It would never be able to act as a dive bomber.

The lengthy design process eventually ironed out most of the major problems with the aircraft. However, the first flight, on 19 November 1939, would reveal the main unsolved problem with the He 177. The flight had to be aborted after only twelve minutes when the engines began to overheat.

The test program was costly in aircraft. Of the initial eight prototypes, the second was destroyed in a dive test, the fourth crashed into the Baltic, the fifth was destroyed after both engines caught fire and the eight after a collision. The pre-production aircraft would also suffer heavily, with at least 25 of the 35 built destroyed.

Engine fires would remain the main weakness of the He 177 throughout its service career. The causes of these fires varied in detail, including amongst them oil leaking onto the hottest parts of the engine, oil and fuel leaking into the bottom of the engine cowling and then igniting and fuel vaporising as the engine overheated. One of the first British combat reports to feature the He 177 included a sighting of one aircraft with an engine that burst into flame for no obvious reason. The crews of the Avro Manchester would have sympathised. The number of fires was slowly reduced by improving cooling, the use of a larger engine cowling, and improvements made to the later DB 610 engine, but they were never eliminated.

The He 177 finally entered service in the summer of 1943. Around 1,000 aircraft were eventually produced, but the majority of them never saw combat and were captured intact and unused at the end of the war. The aircraft arrived too late to make any impact of the war, despite some useful service in the anti-shipping role. It played a minor role in the last German bombing campaign over Britain, Operation Steinbock, in January-April 1944 and saw some desperate use on the eastern front, but in common with most German bombers the He 177 was grounded from the summer of 1944 as the Allied heavy bombing campaign began to cripple German fuel production.

Combat

The He 177 had a short combat career that lasted from the winter of 1942 until the summer of 1944. It first saw action on the eastern front, when a number of A-3s were pressed into service as part of the desperate air-lift of supplies to Stalingrad. The He 177 made a poor transport plane, with limited space for supplies, and was not well suited for use from the rough airstrips in use in Russia. This was quickly realised, and the surviving A-3s were used to attack the Russian positions around Stalingrad, either as a conventional bomber or with a 50mm BK 5 anti-tank gun under the nose. Once again it was not a great success, with engine fires causing several losses.

The He 177 was then withdrawn from the front line until the A-5 was ready. This aircraft was issued to KG 40 in the summer of 1943, to be used in combination with the Henschel Hs 293 glider-bomb. This was a small radio controlled powered glider designed for use against merchant ships. The He 177 could carry one under each wing, and in theory the Hs 293 could hit a target from a range of up to five miles.

KG 40 began operations with the He 177 in November 1943. Their first major operation came on 21 November and was an attack on a British convoy in the Bay of Biscay. Twenty five aircraft took off, two had to return to base early, one crashed thirty miles away, one was lost in the attack, and two more on the return journey. In return one small merchant ship was sunk, although the crew escaped. One successful aspect of the He 177 was its range. Five days later the same unit launched an attack on an allied convoy off the coast of Algeria, with 21 aircraft. This time they ran into fighters, and six aircraft were lost, although a German troop ship was sunk.

The heavy losses suffered on these two missions forced KG 40 to abandon daylight attacks. Night attacks, with the target ships illuminated by flares, took their place, with even less success, although losses to enemy activity were reduced.  

Two He 177 units took part in Operation Steinbock, the last Luftwaffe bombing campaign over Britain. Experienced crews were able to carry a 5600kg/ 12346lb payload on these missions, which took place between January and April 1944. Standard tactics for the He 177 was to climb to its service ceiling before crossing the British coast, then carry out the rest of the mission in a shallow full power dive, which allowed the aircraft to reach a diving speed of over 400mph. The dive would continue all the way to the French coast, by which time the aircraft would have dropped down to 2,500 feet. The higher speed and constant change of altitude made the aircraft harder to intercept, increasing the survivability of the aircraft, but the operation was generally unsuccessful.

Operation Steinbock trailed off in the spring of 1944 as the Luftwaffe began to husband its strength in preparation for the allied invasion of Western Europe, which was clearly going imminent. In the days after D-Day, II./KG 40 took part in the desperate attempts to attack in the invasion fleet. In ten days the unit lost half of its 26 aircraft, before being withdrawn to rest.

Over the summer of 1944 the Allied attack on the German oil industry finally took hold. For the rest of the war Luftwaffe operations would be severely limited by a shortage of aviation fuel, which had to be careful horded before any major operations. One victim of the fuel shortage was the He 177, which in common with the majority of German bombers was grounded for the rest of the war. It had absorbed a great deal of effort, had arrived late and had never really overcome the problems imposed by its engines.

Stats (A-5/R2)
Engine: 2 x Daimler Benz DB 610
Horsepower: 2,950hp at take-off
Crew: 6 (pilot, co-pilot/nose gunner/bomb aimer, observer/ wireless operator/ ventral gunner, two dorsal gunners, rear gunner
Span: 103ft 1in
Length: 72ft 1in
Max Speed: 303 mph at 20,000ft, 270 mph with full load
Cruising Speed: 210 mph at 20,000ft
Ceiling: 26,246 feet
Range: 3417 miles
Time to 10,000 feet: 10 minutes
Full weight: 68,342lb

Armament: One 7.9mm MG 81J in nose, one 20mm MG 151 in front ventral gondola, two 7.9mm MG 81 in rear ventral gondola, two 13mm MG 131 in dorsal barbette, one 20mm MG 151 in dorsal turret, one 20mm MG 151 in tail turret.

Bomb load: Normally retained internal bomb bay for 1000kg of bombs (2205lbs) plus under wing pylons for a variety of advanced munitions. Could carry 5000kg/ 11,000lb of conventional bombs if required.

 

 

 

Heinkel He-177 "Greif" (Griffin)

 

Perhaps no other aircraft of the German Luftwaffe was so potentially useful, but so troublesome as the Heinkel He-177 Greif. The Greif was detested by its crews, and by its mechanics. It is a fine example of the unrealized possibilities of the German Air Arm in the Second World War.

 

 

The He177 only made it to production through dogged courage and perseverance, and those two factors were the only thing that allowed it to reach large production numbers. In defense of the aircraft however, it could be said that all its troubles originated from a (absolutely asinine) 1938 requirement for a proposed heavy bomber/anti-shipping aircraft, that should also be capable of dive-bombing! So, the main problem of the He-177 was created: In an effort to reduce drag, the engineers decided that they would use coupled engines. (basically four engines, stuck together into two nacelles) These coupled engines would enter record books as being the most fire-prone engines in normal cruising flight. Out of the eight prototypes, six crashed. And of the 35 pre-production A-0s, (built for the most part by Arado Handelsgesellschaft, Warnemunde) a large number had to be written off due to take-off swings or in-flight fires.

Arado built 130 A-1s, followed by 170 Heinkel built A-3s, and 826 A-5s, which had repositioned engines and a longer fuselage. About 700 Greifs served on the Eastern Front, many of these having 50mm and 75mm guns for tank-busting duties. A few even (nervously) bombed England in 400mph shallow dives, without any proper aiming for their bombs. The aircraft proved so bothersome that Goering had to forbid Heinkel to pester him any more with plans to use four separate engines! But Heinkel secretly flew the He277 with four 1-750hp DB 603A at Vienna, as the first of a major production programme. The almost completly redesigned He274 was a high-altitude bomber developed at the Farman factory at Suresnes, with four 1,850hp engines, a 145ft wing and twin fins. After the liberation, it was readied for flight, and flown at Orleans-Bricy.

Perhaps the scariest fact about the He177 was the fact that one was secretely being readied in Czechoslovakia to carry the planned German Atomic bomb. It is quite possible that, if it weren't for a few brave Norwegian saboteurs, Adolf Hitler would have had a prepared Atomic bomb towards the war's end. I have no further information on that special He177, and I would like anyone with any to please send it to me.

 

Charles Bain

Technical Data

Origin: Ernst Heinkel AG, also built by Arado Flugzeugwerke.
Type: He177, six seat heavy-bomber and missle carrier
Engines: Two 2,950hp Daimler-Benz DB 610A-1/B-1, each comprising two inverted-vee-12 liquid-cooled engines geared to one propellor.
Dimensions: Span 103ft 1 3/4 in (31.44m); length 72ft 2in (22m); height 21ft (6.4m)
Weights: Empty 37,038lb (16,800kg); loaded (A-5) 68,343lb (31,000kg)
Performance: Maximum speed (at 41,000lb) 295mph (472 km/h); initial climb 853ft (260m)/min; service ceiling 26,500ft (7080m); range with FX or Hs293 missles (no bombs) about 3,107 miles (5000km)
Armament: (A-5/R-2) one 7.92mm MG 81J manually aimed in nose, one MG131 in forward dorsal turret, one MG 131 in rear dorsal turret, one MG 151 manually aimed in the tail and two MG 81 or one MG 131 manually aimed at rear of gondola; maximum internal bombload 13,200lb (6000kg), seldom carried. External load: two Hs293 guided missiles, FX 1400 guided bombs, mines or torpedoes (more if internal bay blanked off and racks added below it.)
Users: Germany (Luftwaffe)

 

 

 

Last Updated

07/17/2010

 

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