Heinkel He 177 Totally Explained

Everything about Heinkel He 177 totally explained

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

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.
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 mainspar 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 somewhat 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 flame damper tubes.

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.

Wings and undercarriage

The insistence on the ability to dive-bomb also led to the need to strengthen the wing structure, leading to 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.

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 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: 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 lots of maintenance personnel and material.
   During later operations such as Operation Steinbock (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.

Variants

He 177 V1 � First prototype, 8 prototypes built in total.

;He 177 A-0 � Pre-production series, 35 built.

He 177 A-1 � First production series, 130 built.

;;He 177 A-1/R1

;He 177 A-4/R4 ;He 177 A-3 � Second production series, 170 built. Sixteenth and subsequent aircraft powered by DB-610 engines.

;He 177 A-3/R1 � :Powered by two Daimler-Benz DB 606A/B piston engines.

;;He 177 A-3/R2 � :Modified defensive armament - MG-151 replacing MG FF cannon in nose.

;He 177 A-3/R3 � :Anti-shipping version capable of using Henschel Hs 293 glide bomb.

;;He 177 A-3/R4 � :Fitted with FuG 203 missile-control equipment.

;He 177 A-3/R5 � :Version armed with BK 7.5 75 mm gun in ventral gondola, five built.

;;He 177 A-3/R7 � :Torpedo bomber version abandoned in favor of the He 177 A-5, three built.

He 177 A-4 � Proposed high altitude version later developed into the Heinkel He 274.

;He 177 A-5 � Main production version with increased maximum external bombload, 826 built.

;He 177 A-5/R1 ;;He 177 A-5/R4

;He 177 A-5/R5 ;;He 177 A-5/R6

;He 177 A-5/R7 � :Fitted with pressurized cockpit.

;;He 177 A-5/R8

He 177 A-6 � Long range, high altitude bomber with increased bombload and defensive armament. Six built as the He-177 A-6/R1. This version also had a tail turret and the capability to carry Henshel 293 missiles

;He 177 A-7 � Conversion of six He 177A-5 airframes which were modified with a 36 m wing, and with DB 610 engines instead of the intended 3,600 hp DB 613 engines.

Production

Production of the He 177 till 30 November 1944:
He 177 A-0He 177 A-1He 177 A-3He 177 A-5Total

Prototypes	8			8
15	15	5	35
	88	42	130	January 1942 - January 1943
	217	398	615	November 1942 - June 1944
	71	278	349	December 1943 - August 1944
23	391	723	1,137

Source: Bundesarchiv/Militärarchiv Freiburg

Operators

Luftwaffe

French Air Force operated at least two He 177A-3 abandoned by Germans and rebuilt by SNCASE at Blagnac.

Royal Air Force

RAE (Farnborough) tested one He 177A-5. Aircraft (formerly F8+AP from 6./KG 40) was captured by French Resistance in September 1944 at Toulouse-Blagnac airfield. Transferred to the UK was repainted with British roundels and serialled TS439.

Possible survivors

During the period of the war when He 177s were based in the occupied Soviet Union, a small number of Griffins were known to have force landed on frozen lakes within that territory, which then could have sunk to those lakes' bottoms when spring thaws melted the lake ice. As no He 177s were to survive intact well past the end of the war (all known captured He 177 example aircraft, as well as the sole prototype He 274 in France, had been scrapped by the end of the 1950s) those possible sunken Griffins would be the only known surviving examples of the He 177 but none have yet been discovered as of 2007.

Specifications (He 177 A-5)

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