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.
Thirty five of the pre-production A-0 series were built, of which at least twenty five were destroyed in a variety of accidents. They were used for development and training.
The A-1 was still not a combat ready aircraft, although Arado produced 130 between March 1942 and June 1943. It was powered by the DB 606 engine, and could carry up to 6000kg/ 13,230lb of bombs, but was still prone to the more disastrous of the aircraft’s flaws.
The A-3 was the first version to see combat. It was a significant step up from the A-1, and featured many of the improvements suggested by the development work. The engines were moved forward, given an improved cowling and better exhausts, much reducing the danger of unexpected fires. The A-3 was also the first version of the aircraft capable of carrying the Hs 293 radio controlled glider. 177 were built before production switched to the A-5.
The A-4 was a proposed high altitude four engined version of the He 177 that was never produced.
The A-5 was the most important version of the He 177. It was powered by the DB 610, a more powerful engine producing by pairing two DB 605s, and capable of providing 3,100hp at 7000 feet or 2,950hp at take-off. The new engine improved the general performance of the aircraft, raising the service ceiling to 26,245 feet. The new model could carry three Hs 293s, two Hs 294s, one FX 1400s or one LT 50 glider bomb as well as a conventional bomb load that put it on a par with most Allied heavy bombers. A total of 565 were produced before production stopped in 1944.
The A-6 featured a pressurised cabin and an electrically powered tail turret. Only six were built.
The A-7 was the final type to see production, although in small numbers. It featured a new wider wing, with a span of 120 feet, but retained the DB 610 engine after the DB 613 failed to appear in time.
One of the more intriguing prototype versions of the He 177 was the A-5/V38, said to be the German atomic bomber. The main feature of this version was the replacement of the three small bomb bays of the standard aircraft with one massive bomb bay, of just the type needed to carry the massive atomic bombs then under development.
The B series was the designation originally used for the four engined He 277 before it received RLM approval.
Likewise the H series was the original designation for the He 274 high altitude bomber.
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.
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.