In 1936 a prototype heavy bomber was in the middle of a complex, and problem-riddled development,
but it held great promise. It had smooth, modern lines; it was driven by four powerful
engines; it had a numerous crew; it was bristling with defensive guns that were set in modern,
powered turrets; and its manufacturer had built it on principles learned from the development
of large domestic aircraft. If this summary makes you think of the Boeing
299, the ill-fated precursor to the famous B-17 flying fortress, I wouldn’t blame you;
but I was instead referring to another four-engine heavy bomber that was being developed in the
Soviet Union, a bomber that would eventually be known as the Petlyakov PE-8.
Its story begins in 1931, when the Soviet Air Force (or VVS) was contemplating the idea
of a new heavy bomber to replace the Tupolev TB-3. Now this was a somewhat far-reaching
exercise in contemplation as the TB-3 had yet to even enter frontline service, but with
aviation technology advancing with every year it was accepted that the TB-3 could become
obsolete rather quickly. Because of this the VVS penned a tentative specification for a
replacement bomber, and approached the various design bureaus of the Soviet aircraft industry
to see what they could do. Initially they wanted a bomber that could
carry a 10 ton bombload over a 2,000km range, cruising at 250kmh and at an altitude of 7,000
meters. In essence it was a huge upgrade over the TB-3 in terms of overall bombload, but
only a slight upgrade when you look at speed, range, and service ceiling. It also made no
considerations for things such as enclosed cockpits to deal with the higher altitude,
nor did it allow much in the way of equipment or defensive armament. Unsurprisingly, Over
the next two years, and after collaborating with various aircraft designers, Tupolev in
particular, and after a keener appreciation of just how fast fighter aircraft were becoming,
(and how outdated their requirements were) the specification for the heavy bomber was
gradually revised. On the 29th of July 1934 Andrei Tupolev officially
began working on a new bomber design to meet the somewhat nebulous requirements of the
VVS. He proposed a four-engine, cantilever monoplane with a smooth stressed-skin, as
opposed to the corrugated skin of his earlier designs. He offered three variants of this
new design, a heavy bomber, an escort gunship (with enough defensive guns to even make the
Americans envious), and a unarmed troop transport. Tupolev’s submission was good enough to
warrant official interest, and in December of that year funding was released for the
development of a prototype. Along with this came a revised specification to which the
bomber was to be built, which, unlike the original, actually took into account the rapid
progress being made in aircraft development. The bomber was now to carry a 2-tonne bomb
load across a range of 4500km, at speeds of up to 440kmh, and at an altitude of no less
than 10,000m. Because of the high speed and altitude performance, the requirement for
the escort version of the aircraft was dropped, though there remained a lingering demand for
a transport version – but in the end this was never to be built.
Work on the bomber did not begin proper until 1935. This was due to some ‘re-arrangements’
that were being made in the Soviet Aircraft Industry, partly to help improve its collaborative
effectiveness, and partly because the NKVD were organising so-called ‘factory prisons’
for designers who had lost Stalin’s favour. Following this period of re-arrangement, a
special design bureau was formed that was to manage the development of the new heavy
bomber from start to finish. Tupolev and his team would manage the project from an administrative
perspective (along with several others), and dictate its overall direction, but a team
led by Vladimir Petlyakov would handle the actual design and construction of the prototype
and subsequent production models. To add to this slightly confusing arrangement, the internal
designation of the aircraft would be known as the ANT-42, which would suggest that the
whole thing was designed by Tupolev, when in-fact Petlyakov did most of the major design
work. That being said, the design of the bomber
inherited much from an earlier Tupolev design, the ANT-40 or more commonly known as the Tupolev
SB; perhaps the Bureau’s most successful design, and one that will definitely get its
own video in the future. The aerodynamics and stressing of the prototype airframe closely
resembled that of SB, albeit scaled up by a factor of 2, and like the SB much of the
airframe material was made up of D16-grade Duraluminiun. One of the few exceptions was
within the wings. Due to the size of the aircraft, with a projected wingspan to exceed 38 meters,
a heavier, but high-strength steel was used for the two main spars. The other exception
was the four main longerons of the complex fuselage, which were also made of this same
steel, but the rest of its complex framework was made from duraluminiun.
In terms of technology the ANT-42 was a huge leap forward over the old TB-3. The latest
types of electrical, radio and navigational equipment were provided to enable the bomber
to operate by night or in bad weather, and a large number of electrical drives were used
in the aircraft’s various systems. The aircraft was also far more streamlined, something which
was absolutely necessary if it were to achieve the required top speed. It would carry almost
all of its bombs internally, the various crew stations were all enclosed, and the defensive
guns were installed in much more sensible positions as opposed to the somewhat terrifying
dustbin turrets that were found on the TB-3. The desire for the most streamlined airframe
possible was probably the main cause for the prototype’s strange fuselage cross-section.
As it was more pear-shaped than spherical the two pilots had to be seated in a pair
of narrow, tandem cockpits, rather than the side-by-side arrangement that was more common
for bombers of this class. These cockpits were also set quite far back, which meant
that the pilot would have to sometimes rely on the crew members in the nose for instructions
when the bomber was taxiing on the ground. As initially planned, the bomber had a large
crew of 9 or 10: two pilots, a navigator and bomb aimer, a radio operator, an engineer,
and the rest were gunners. The defensive armament used by said gunners
was not inconsiderable, though it would chop and change a lot throughout the aircraft’s
development. Initially there was a 20mm ShVAK cannon mounted in a nose turret commanding
a 120 degree cone of fire; there were 7.62mm ShKAS machine guns mounted in dorsal and ventral
positions; the tail was equipped with another 20mm ShVAK cannon, and if that wasn’t enough
there were also two more 20mm cannons mounted in the rear of the two inner engine nacelles.
These could either be accessed internally through a small passage in the wing, or externally
through a hatchway on the upper surface, though the idea of using the latter during flight
was probably considered a last resort – if that.
Carrying a multi-tonne bombload, plus all of the modern equipment, and enough automatic
cannon to classify the bomber as a flying tank, presented a challenge when it came to
high-altitude performance. There had been a lack of development in the USSR when it
came to turbocharging or supercharging aero engines. And as time was pressing, and as
Tupolev preferred to not test the patience of his chiefs, the decision was made to install
a fifth engine in the fuselage that would drive a giant supercharger. Housed in a fireproof
compartment aft of the engineer station, this engine -using a step up gearbox- drove a centrifugal
blower at an astonishing 25,000 rpm, and this drove compressed air through aluminium pipes
to the four main propulsion engines.
These four engines were the 950HP Mikulin M-34FRN, one of the most successful Soviet
engines of the 1930s, but due to the unique shape of the upper fuselage, the super-charging
engine was the smaller 750HP Klimov M-100. This was not ideal, as it meant that two different
supplies of engine parts would be needed for maintenance and repairs, but there wasn’t
really any alternative. The M-100 was too weak to be considered for the four propulsion
engines, and re-designing the fuselage to accommodate the M-34 engine was out of the
question. As it turned out, this would be the least of the ANT-42s problems as design
and construction of the prototype got underway for a myriad of things immediately went wrong.
Firstly, a different aircraft, the gigantic ANT-20, known as the Maxim Gorky, was lost
in a demonstration flight over Moscow on the 18th of May 1935. As it had been a brilliant
demonstration of the capabilities of the Soviet aircraft industry, a flying propaganda tool
of the highest calibre, a replacement was immediately demanded, which took up a lot
of Tupolev’s time and resources. Secondly, the Lenin steelworks was failing
to supply the high-strength steel needed to keep the ANT-42s wings suitably attached to
its fuselage. Thirdly, the VVS kept sticking its nose in
and making numerous alterations to the specifications that dictated the bomber’s design.
And, finally, there were numerous delays in the production of the M-34 engines, which
were somewhat needed if the ANT-42 wanted to be anything other than a glorified full-scale
model, or perhaps the world’s heaviest glider. In fact, when the prototype was rolled out
of the factory on November the 9th 1936, it was still without any of its engines, and
they would not arrive for another five weeks. Finally, on the 27th of December the aircraft
completed its first flight, however the M-100 engine for the supercharger had not yet arrived,
and so this flight was done with a considerable power deficit. Despite this, the chief test
pilot, Mikhail Gromov, reviewed the prototype favourably, praising its stability and responsive
ailerons. After fourteen test flights his only major complaints came from the rudder,
which he felt was not suitably effective at lower speeds, and the installation of the
engines, which presented overheating problems. Both problems were solved within a few months.
The rudder was re-designed with a slightly greater area, with the corrugated skin giving
way to a stressed metal skin, it was reinstalled on more deeply recessed hinges, and its trim
tab was completely changed. The engines required a more radical change, as evidenced by various
wind tunnel tests. The eventual solution to the cooling problem was to place all four
radiators in deep ducts under the inner pair of engines. Airflow was controlled by curved
inlet doors that hinged on a vertical axis and opened like a clamshell; not only did
this improve cooling dramatically, But it also allowed airflow to be re-directed if
an engine were lost, or if one engine in particular was having cooling difficulties.
In this new guise, and with a working supercharger at last, flight testing of the prototype resumed
in July, but by this point construction on the second prototype was well underway, which
incorporated much of the lessons learned with the first. This new aircraft was powered by
uprated engines, each producing 1,200HP, and the engine driving the supercharger was also
beefed up from 750 to 850HP. As its high-altitude performance was now expected to be better
than ever, the defensive armament was scaled down. All but one of the 20mm ShVAK cannons
were removed, being replaced by either single or twin mounted machine guns. Along with this
change, numerous others were also found all across the design. The fuselage was 100mm
wider, an improved AP-42 autopilot system was installed, the already huge 1.6 meter
diameter main wheels were further enlarged, the electrical system was revised to be less
spark-inducing, more armour was installed, fuel capacity was increased by 2,000-ish litres,
and the bomb-carrying provision for the various racks were further improved.
This last improvement is what makes the bomber quite famous in certain circles. It could
now carry either: forty FAB-100 bombs, twelve FAB-250s, six FAB-500s, four FAB-1000ss, or
one FAB-2000, and later during the second world war- it would carry the massive FAB-5000.
This bomb was the largest used by Soviet air forces during the war, and it would not be
exceeded until the development of the FAB-9000 demolition bomb during the Cold War.
Sadly, few photos of the aircraft carrying this bomb into action seem to exist, but thankfully
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today’s video, and now lets get back to the troubled development of the PE-8.
The improvements developed with the second prototype should have launched it into a long
and successful production run, but before this aircraft had even flown the entire bomber
program encountered a major problem, one that would cause untold damage to Soviet military
enterprises: the Great Purge. Both Tupolev and Petlyakov, the driving forces
behind the whole project, were arrested in 1937. This was then further compounded by
the arrest and execution of thousands of Army and Air Force officers, along with key members
of the aviation industry. One of those arrested was the director of the V M Frunze engine
factory, where the AM-34 engines for the ANT-42 were being produced, and to make matters worse
the director was arrested before the newest versions of the engine had been cleared for
production. Though the bomber was officially accepted
for service as the TB-7 in April 1938, the chaos caused by the arrest of countless key
individuals meant that the second prototype did not fly for another three months. Additionally,
the factory that was meant to produce the TB-7, GAZ #124, couldn’t even start production
of the bomber as 1) the factory itself had almost no resources, 2) half the production
engineers were still incarcerated (or dead), and 3) the engine supply situation was becoming
so complicated that it was almost comical. The end result was a highly chaotic beginning
to the bomber’s career. The first production model flew for the first time in late 1939,
taking off on skis which promptly broke when it came in for landing. After this it was
discovered the huge mainwheels were safe enough for use on ice, and the aircraft became one
of the few soviet aircraft to ditch skis for winter use altogether. Then, only a few months
later at the end of the year, after only a handful of airframes had been built, production
was halted as the factory was told that production of the M-34 engine had been completely terminated.
Not only was the bomber without its main engine, but the smaller engine that drove the super-sized
supercharger was also incredibly difficult to source. Because of this, the decision was
made somewhere in the upper echelons of the design team to drop the fifth engine and supercharger
altogether. This meant that the TB-7 had to undergo a rapid and major design change at
the 11th hour, which, of course, brought even more complications.
As the team tried to rapidly evaluate potential replacements for the M-34 engine, no doubt
privately weeping as they did so, the TB-7s airframe was redesigned. The gondola-style
chin under the nose was deleted, crew compliment was increased to 11 with the addition of a
commander’s station in place of the internal engine, a retractable dorsal turret was installed
with a 20mm cannon, tandem radio masts were fitted, and the navigation and communication
equipment was updated. All of this came at no major cost to performance thanks to the
removal of the internal engine and supercharging pipes – so you were basically trading one
weight for another, but the question of the main engines was still a cause for concern.
A potential solution was explored with the use of diesel engines. In May 1940, Commissar
Kaganovich was appointed to the project to replace I.F. Nezval, who in turn had previously
replaced Petlyakov after his incarceration. Kaganovich wanted to reinstate production
of the bomber using the Charomskii M-30 or M-40 diesel engines, which were large water-cooled
V-12s. Equipped with four turbochargers, the M-30 was rated at 1,400 HP, the M-40 at 1,500,
and it was found that little changes were required to install the engines onto the TB-7,
so it all looked rather promising. Altogether, five aircraft would be built with
the M-40 engines, and eleven more with the M-30s. Due to the efficiency of diesel engines,
their range was significantly increased (reaching almost 5,500 km), but most other aspects of
the aircraft’s performance were negatively affected. Reliability was poor, power and
general behaviour were described as unacceptable at high altitudes, starting the engines was
often difficult (especially in winter), and its oil consumption was enormous. Though Charomskii
would eventually solve most of the engines difficulties, the outbreak of war with Germany
led to the surviving bombers having their diesel engines swapped out for the Mikulin
M-35A by the end of 1941. Producing 1,350hp, this was the dominant engine that powered
the bomber during its early wartime service. However, for a time both petrol and diesel
powered bombers would see some action. Due to the litany of problems that dogged
its development and early production run, only one squadron (the 2nd of the 14th Heavy
Bomber Regiment) was equipped with TB-7s when Operation Barbarossa began, and even then
they were not deemed combat ready due to a lack of aircraft. This was then further hampered
by the loss of two aircraft on the ground, and the rest were promptly pulled back. They
were then re-organised as part of the new Long-Range aviation branch of the VVS.
Due to the small number of TB-7s available, they were not expected to bring decisive results,
but the ability to strike right into the heart of German territory was a morale-boosting
advantage that could not be ingored. Unfortunately, these particular aircraft were
the ones powered by the M-30 and M-40 diesel engines, and their unreliability was more
dangerous than the enemy. Eight took off from Leningrad for a strike on the 1st of October
1941, only four reached Berlin (their intended target), and just two of them managed to return
safely to base. Of the six casualties, one crashed on take-off due to an engine failure,
at least three more had engine failures during flight, and one had the deep misfortune to
be attacked by friendly fighters, then enemy flak, and then suffered an engine failure
as well. Following a hasty switch to the more reliable
M-35 engines, the aircraft’s luck improved when it came to attrition, but its slow production
at the factory hampered its wartime effectiveness. By the start of October 1941 only fourteen
aircraft were ready for frontline operations, and although the bombing regiment had received
a further 17 by the spring of 1942, their total number had only grown by one, for 16
had been lost during that period. 1942 would not only see a change of fortune,
but a change of title for the bomber as well. Vladimir Petlyakov, who had been responsible
for many of the positive design changes that improved the TB-7, was killed in a plane crash
in January 1942. Though he was no longer on the project, the bomber was renamed as the
PE-8 in his honour later in the year. In general, 1942 would be a much more successful
year for the PE-8, despite its small production run. Bombers of the 746th and the newly formed
890th Long-Range aviation regiments would conduct various strikes on German targets
throughout the year. Unlike the heavy bombers of the British and American air forces, who
would arrive in huge numbers in the latter half of the war, the PE-8s were used differently.
Rather than broad raids on industrial centres, they were used in so-called pinpoint strikes
against airfields, supply lines and transportation hubs deep within enemy territory, often doing
so at night, and dropping the heaviest bombs possible to make up for any lack of accuracy.
For the most part this would consist of the FAB-1000 or 2000 bombs, but in 1943 the 5-Tonne
FAB-5000 was added to the arsenal as well, being dropped for the fist time during a raid
over Konigsberg. The effectiveness of the PE-8s in these strikes
is difficult to tell, mostly due to a lack of documentation from either side of the conflict.
For the most part, as mentioned earlier, these missions were conducted mostly to boost morale.
Additionally, Soviet strategic bombing really wasn’t much of a thing during the second
world war, as most of its aviation industry was geared towards close air support in the
massive ground battles. But these sporadic attacks, which eventually resulted in a few
thousand tonnes being dropped on German targets (not bad at all seeing as less than 100 PE-8s
were ever built), were at least a good demonstration of the aircrafts long-range endurance…when
the engines weren’t failing. This range was also demonstrated by series
of long-distance flights, specifically those intended to get the Soviet Foreign Minister,
Molotov, from Moscow to London, and then on to New York – where discussions would be
had about opening a second front in Western Europe. Before these flights had taken place,
the PE-8 had been almost unknown to western observers, and when it arrived in Scotland
for the first leg of its journey it surprised many members of the Royal Air Force. It had
been known that the Soviets had fairly modern twin-engine aircraft at their disposal, but
many had assumed that their new heavy bomber was more of a continuation from the box-like
TB-3. After Molotov had conducted his various visits
to US and British leaders, the bomber program was running into yet another engine problem:
The excellent M-35 was now in short supply. This time, it was decided to try fitting a
radial engine to the aircraft instead. For this the fourteen-cylinder Shvestov Ash-82
was selected, the same engine that would power the famous Lavochkin series of fighters. The
first radial-engine PE-8 flew in the Autumn of 1942, and it was deemed to be immediately
successful, with 34 aircraft eventually being built.
Along with the change in powerplant, a few other modifications were made to this later
model. The nose turret was replaced by a hand-aimed machine gun in a flexible mount; this enabled
the tip of the nose to be narrowed, reducing weight and drag at the same time. This, combined
with a small increase in overall fuel tankage, resulted in this version of the PE-8 having
a range that actually exceeded that of the ones that had been powered by diesel engines.
Speaking of which. Charomskii, embarrassed by the failure of
their earlier attempts, had developed the far more reliable ACH-30 engine, and this
was to go into the final four PE-8s that were to be built. These aircraft were delivered
in 1944, but they were not intended to be bombers, instead they were built as long-range
VIP transports, instantly identified by the addition of a curved dorsal fin.
By this point, the loss-rate of PE-8s in frontline operations were becoming unsustainable, and
with the introduction of lend-lease American bombers, the aircraft was gradually removed
from frontline service. Records do show that the PE-8 remained with active units until
the end of the war, but it is not fully known if they were used for anything major after
the end of 1944. After the war, the PE-8 saw over a decade
of very varied use – indeed it could be said that its postwar service was actually
more successful. Some bombers were converted over to a similar
specification to that of the VIP transports, except they kept their original engines and
didn’t convert to the diesels. Some of these, now carrying 12-14 passengers, flew on various
transport routes for Aeroflot, but some were used for polar exploration. Early polar aircraft
had the original radial engines, were painted orange, and had special raidio and navigational
equipment installed. Later on they were upgraded to the 1,900hp -82FN version of the engine,
driving four-bladed propellers. One single example, operated between 1949 and 1957 was
equipped with even more powerful engines, eventually receiving 2,600 hp Ash-73’s,
and this aircraft was used to carry a Mi-1 helicopter, slung under its belly, to a remote
polar station. Along with exploring the frigid polar regions,
several PE-8s would also serve out the early years of the Cold War as testbeds for up to
nine different types of engines, with them being mounted on the wings, in the nose, or
even under the fuselage. One PE-8 was used as a carrier for the experimental Bisnovat
high-speed, air-launched research aircraft. And others were used, after heavy modifications,
to test the 10kh, 14kh and 16kh air-to-surface cruise missiles -which were based on captured
German V1 flying bombs. Ultimately, the PE-8s postwar life could be
considered more successful than its wartime service, especially when its effectiveness
is considered against other aircraft of its class. That being said, when the PE-8 made
its first public appearance to the allies, when it landed in Scotland on a brisk spring
day, it still surprised those who saw it. This was mostly due the to numerous reports,
often provided by various intelligence agents, that the Soviets did not have the infrastructure
or resources on hand to produce something like the PE-8 en masse.
Technically, they were right. By the time that production of the PE-8 had ceased, only
93 examples had been built (some sources claim 149 but I wasn’t able to find enough evidence
to support this). Either way, this was not much at all when compared to the 7,377 Lancasters,
12,731 B-17s, and 18,188 B-24s built by Britain and the United States. But even if the biggest
problems that had hampered the PE-8s development, political turmoil and a lack of parts supply,
had not occurred, its unlikely that its production run would have been anywhere near as large
as those of its western rivals. In the lead up to war, it had not been clear
who the eventual enemy would ultimately be; would the Soviet Union be facing off against
a united western bloc, or just the axis powers, or maybe just the democratic powers? This
on its own would influence the path taken with bomber design, but the size and potential
speed of a war front was another matter as well.
Britain and the United States had the advantage of a sea barrier, whereas Germany and the
Soviet Union did not. This naturally influenced aircraft design to have more of an emphasis
on supporting ground battles, rather than pummelling far flung enemy cities. Of course,
the ideal situation would involve bombers that could do both, but for various reasons
that are outside the scope of this video the focus was given to lighter bombers instead.
In the end, the PE-8 could not be described as a glowing success. In fact, its history
reads somewhat like the plot to some sort of black comedy.
It was dogged by development problems, delayed by the paranoid machinations of Soviet leadership,
and produced in numbers so small that its effectiveness was doomed from the start. But,
when looked at individually, especially with the later models. The PE-8 represented a functional,
long-range, heavy bomber, and one that probably would have done itself credit, had Soviet
air doctrine preferred the heavy bomber and had it been produced in large enough numbers.
The PE-8s failure as a heavy bomber contrasts sharply with the success of another of Petlyakov’s
designs, the twin-engine PE-2 which was perhaps the most important, and successful Soviet
bomber that was built during the second world war. But the story of the PE-2 is one for
another day. Once again thank you to war thunder for sponsoring
today’s video, don’t forget to click on the link below to sign up for free and claim
premium benefits, and who knows. Maybe you’ll see me flying about dropping 5-tonne bombs
from a horribly mismanaged soviet heavyweight.