Hello, and welcome to Aviation Deep Dive In today’s video we’ll be taking a look
at the flagship of Germans often forgotten heavy bomber fleet. The Luftwaffe’s bomber
force - often remembered solely in terms of medium bombers such as the Heinkel He 111
- was admittedly far too slow and hesitant to accept the importance of heavy bombers
and strategic bombing of enemy industry, but what not many people realise is that they
didn’t shun this class of aircraft entirely. A four-engined bomber driving two enormous 4 metre
(13 foot) propellers, weighing 32 tons and longer than a Lancaster - The Heinkel He 177 ‘Greif’
was a bizarre aircraft - borne of a mishmash of conflicting requirements, strange design ideas
and technological limitations. Nevertheless, over 1,000 of these giants would be produced
- but to better understand the fascinating, and at times frustrating, story of this
aircraft, we must first harken back to 1936. I want to take a moment to thank the sponsors
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Warships for sponsoring this video. At this time the idea of strategic bombing,
courtesy of some strong proponents of it in the Luftwaffe, was still considered worth exploring
- although this would change fairly quickly in the coming years. Alongside some other projects
intended to bear the fruit of a new generation of Luftwaffe bombers, the RLM issued ‘Bomber A’
a specification that called for a pure, strategic bomber, capable of carrying a bomb load of 1,000
kg over a range of 5,000 km. Not disimiliar to the requirements of the Dornier Do 19 (which we’ve
also covered on this channel). The aircraft was also, unusually, directed to have only two
engines - it was believed that this would lower drag and allow the aircraft to be faster - and the
Luftwaffe really liked the ideas of fast bombers. Issued on the 3rd June 1936, in a
stroke of very unfortunate luck, the biggest proponent of German strategic bombing
- General Walther Wever - was killed in an air crash on the very same day. In a single
blow, the future of any aircraft to come from the specification looked significantly
less promising than it had the day before, but nevertheless Heinkel opted to take it on and
start development. Straight of the bat, there were a few design considerations that made work on a
bomber to this specification difficult. First, the RLM wanted it to reach at least 500 km/h (310
mph) at it’s service altitude - a speed that was not only faster than all contemporary bombers,
but of virtually all contemporary fighters. Not only this, but a strict two-engine limitation
had been imposed on the project - meaning that the engines would have to be enormously
powerful to propel a heavy bomber faster than anything else in the sky. It was decided that the
aircraft needed a pair of engines that produced at least 2,000 horsepower to meet the design
requirement, there was just one small issue. There was no powerplant available in Germany
at the time that could meet that power output. The reason the RLM was deadset on a twin-engine
design was because of drag. It was believed that with a traditional four engine design, and all
the drag associated with it, a large amount of the power produced by the extra engines is countered
by the extra drag caused by the extra engine nacelles and propellors. Having just two engines
with contra-rotating propellors, allows far less drag with a theoretically similar power output -
whilst also negating torque. As such, to achieve the needed power levels, as well as the design
requirements, it was decided by Heinkel to mate together two DB 601s, driving a single crankshaft
- to produce what would be dubbed the DB 606. A 24-cylinder 2,500 horsepower engine, that weighed
some 1.5 tons - the DB 606 would be one of only two German engines throughout the entire
war to break the 2,000 horsepower threshold. At this point, with a significant amount
of the design finished, the RLM stepped in. Having watched eagerly as their Stukas showed
their excellent combat effectiveness in the Spanish Civil War, they had a reinvigorated
enthusiasm for dive bombing. Now of course, they wouldn’t be so stupid as to try and turn a
strategic bomber into a dive bomber except… well, yep that’s actually exactly what they did.
It’s unclear exactly what about the 32 ton, 70 foot long bomber on the drawing board
screamed ‘future dive bomber’ to the RLM, but inexplicably - it did. Heinkel was ordered
to introduce various design changes such as strengthened wings to make the aircraft - now
dubbed the He 177 - capable of undertaking 30 degree dive bombing. The RLM had begun to
look upon the aircraft not as a strategic bomber, but as effectively a long-range Stuka - a
role its design was completely at odds with. Still, regardless of Heinkels concerns, a
mock-up was constructed of the aircraft in November 1937 - which was showcased to the
Luftwaffe High Command on the 5th of that month. The significant strengthening of the
structure to make the aircraft capable of undertaking dive bombing had increased the
weight significantly. So what comes next perhaps resembles a comedy sketch more than
real life. Luftwaffe Colonel-General Ernst Udet - upon being showcased the mockup
of the aircraft - mentioned to Heinkel that the requirements had been changed once
again. Now, the He 177 - larger and heavier than a B-17 - should be capable of undertaking
dive bombing attacks at angle of 60 degrees. So once again the wing and fuselage section was
strengthened, to the point where the aircraft was so heavy that its original undercarriage could no
longer support it. And despite all of this work, the airframe was still susceptible to overstress
during dive bombing attacks. To rub salt in the wound, a big part of the reason that the
Luftwaffe was more interested in dive bombing, was the fact that through the 1930s
their bomb sights had been broadly inferior and less accurate than similar
types fielded in the UK or US. However, promising development of the Lotfernrohr 7
bomb sight - which was broadly on parr with the American Norden bomb sight - negated
this issue, and ultimately Hermann Göring would remove all of the dive bombing requirements
placed on the He 177 - by which time the aircraft was already in full-scale production and the
rolling back all of the reinforcements and extra weight would mean retooling a significant part of
the wing production line. Heinkel opted not to. Further development of the aircraft was slow.
The constant insane design requirements had had negative effects on numerous facets of the
aircraft, which were constantly redesigned. And this was on an aircraft that was already
fairly technically difficult to work on anyway, owing to the numerous technological innovations it
introduced. Aside from it’s unique engine layout, Heinkel also intended to make use
of evaporative cooling elements in the wings to further reduce drag, as well as
to deck out the aircraft with remote control defensive turrets - a technology which
promised higher accuracy as well as the potential to fit guns where crew
members couldn’t physically fit. Indeed, the 177 would not be a slacker in
the armament department - it would be an exceptionally well defended aircraft, sporting no
less than 3 20mm MG 151s in the frontal gondola, dorsal, and tail turret, 3 13mm MG 131 in
a dorsal turret and gondola, as well as a forward facing 7.92 mm MG 81 machine gun. The
aircrafts enormous bomb bay could also carry up to 7,000 kg (15,000 lbs) of bombs, as well as
underwing racks which - among other things - could mount 3 Fritz X guided anti-shipping bomb (each
one containing 320 kg/700 lbs of explosives) By the summer of 1939, as War with England and
France was looking increasingly likely - the Luftwaffe expressed further interest in a
long-range bomber for upcoming conflicts with these two superpowers. In July an order for
20 pre-production Heinkel He 177 A-0s was drafted, which would later be increased to 30 - just
in time for the aircrafts maiden flight in November of that year. In a flight lasting
12 minutes, the aircrafts performance was considered overall favourable - nothing short
of a miracle after everything the design team had been put through - although the flight
had to be abandoned after just 12 minutes due to a sharp rise in engine temperatures. This
would be a recurring pattern with the He 177. The initial dream of evaporative cooling had
been just that, a dream - as the heat output of the DB 606s was truly extraordinary, and far
more than the optimistic evaporative cooling system could deal with. Indeed, even with the
enormous annular radiators, supplemented by two further wing radiators outboard of the nacelles
, the heat could barely be kept at bay - and high engine temperatures would be a hallmark of
the 177 throughout it’s entire service life. Continuing flight testing, this pre-production
prototype was 20.6 metres in length, and 31.4 metres in span - weighing in
at 13,700 kg empty and just over 23,000 fully loaded. The weight, impressively
low all things considered - would rise by an astonishing 10,000 kg (22,000
lbs) by the time it entered service. By 1940, 4 further prototypes had been constructed
and were undergoing testing - and were subject to continuous minor improvements - a process
that continued until early 1941 - when another hallmark weakness of the design showed itself.
During a simulation of a low level attack run, both engines simultaneously caught fire,
causing the aircraft to crash - a complete write off. The fire, naturally linked to
the temperature issues of the DB 606s, would certainly not be a first - and in fact
the aircraft would go on to become infamous for this very shortcoming, being nicknamed ‘Reich’s
Lighter’ after it’s proclivity to catch fire. Nevertheless, a production line was setup - and
by 1942 He 177 A-1s began rolling out of their factories to operational units. However,
of the 130 A-1s produced between January 1942 and January 1943 - the vast majority
were very quickly withdrawn from service. The aircraft were simply not ready, and engine
issues continued to be a serious achilles heel of the project. The exact reason why the DB 606s
were so very unreliable is a multifaceted issue. The engines had been trialled
before with reasonable reliability, but the tight-fitting cowl on the 177 (originally
a weight-saving measure) had birthed a whole host of other issues. One issue was the fact that the
exhaust from the 24-cylinders generated immense heat - and due to the side-by-side coupling of
the engines, the central cylinder banks had to share all exhausted a single port on the underside
of the nacelle to exhaust from. This port would often become excessively hot, and heat the usual
accumulation of oil and grease on the bottom of the nacelle to catch fire. Further, the lack of
a firewall (a weight saving measure) meant that there was virtually no seperation between
the engines and the wings main spar - from which came the oil and fluid lines - which were
packed extremely close to the engines exterior and would frequently saturate it with hot oil
and fuel. Not content with just these issues, a badly designed oil pump meant that at
higher altitudes the oil would often foam, vastly reducing its lubricating qualities.
This would often lead to disintegration of the connecting rod bearings, which could
result in the conrods bursting through either one of the component engine crankcases
and puncturing the oil tanks. The oil would then spill out onto the central exhaust
port, which was usually extremely hot. All this to say, the coupling of two engines
in a single nacelle had been a novel idea, but the execution had left it being far less
desirable than a normal four-engine layout, or even just a standard twin-engined
bomber. In absolutely ideal circumstances, the He 177 could outperform either - but the
crux of the issue is that it could virtually never operate in its ideal circumstances
due to its cataclysmically bad reliability. Amongst other things, the initial A-1 type - which
had entered and then quickly been removed from service, had demonstrated poor lateral stability
in normal flight - meaning that the bomb accuracy from the aircraft was exceedingly inaccurate.
Work to remedy this resulted in the A-3, with a lengthened fuselage, of which over
300 were built, entering service in 1943. The operational history of the aircraft
had been, thus far, very little to write home about. ad seen use as an emergency measure
to supply the encircled 6th army at Stalingrad, but it carried comparable cargo to the much
smaller and much more reliable He 111. Indeed, although it had been delivered
to units in reasonable numbers, it originally simply wasn’t flown operationally
because it was considered unfit for combat duty. An attempt to use it as a light bomber
and flak suppressor around Stalingrad had resulted in 7 of the 13 aircraft being lost.
None to enemy action, all to engines fires. Although the large amounts of He 177s
being produced suggested that they would be being used in some capacity,
in reality - the vast majority were sat around airfields around Europe awaiting engine
modifications or sufficient fuel to fly them. Operation Steinbock, a reinvigorated strategic
bombing offensive against South-England in early 1944, represented another chance for the now
fairly mature 177 to come into it’s own, but of the 14 aircraft ready for the mission - eight
returned with overheating engines, one suffered a burst tire on takeoff, one was shot-down
en-route, and only four made it to England. The aircraft was not a total failure though, in
the rare instance that the crews who flew it were able to make effective use of it. A technique was
developed that involved climbing to an altitude of 7,000 metres (22,000 ft) over German territory,
and then throttling back and going into a shallow dive towards England, arriving over the target at
around 4,500 metres (15,000 feet). At this point, the crew would release their bomb load, open
up the the engines (which would hopefully be fairly cool after running at lower
settings and at such high altitude), and continue their powered shallow dive back
towards Germany. With this technique, the crews would maintain an astonishing speed of around 650
km/h (400 mph) back towards France. The average loss rate for German bombers during Operation
Steinbock was 60%, in stark contrast the He 177s suffered only a 10% loss rate, making it by
far the most survivable bomber of the campaign. However, this would really be the last
significant operational use of the aircraft, as huge fuel shortages grounded the He 177 (as
well as most other bomber types) in favour of fighter production and upkeep - a desperate
attempt to counter the allied bombing raids. With over 1,000 airframes built, and sporting an
extremely unglamorous combat career, the He 177 went down in history as an aircraft more
dangerous to itself than to the enemy. However, despite its shortcomings, it was undoubtedly
a technologically interesting aircraft, that was the first to adopt numerous innovations
which became more common on bomber aircraft later in the war. The Heinkel engineers had done
all they could to come to terms with the requirements of the RLM, but in the end it just
wasn’t good enough. Sadly, no 177s survive today, despite numerous examples falling into the
hands of both the British and the French. A huge thanks to my Patrons, on screen now,
for supporting the channel and Thankyou so much for watching this video of Aviation
Deep Dive. Consider liking and subscribing for more weekly content, and please also consider
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