Recently I have witnessed some total garbage written on the web about just how good some perceived the Boeing B-17 to be. I thought it time to drag out my analysis I used in my B-17 book for Pen & Sword...
Assessing the worth of a bomber aircraft by comparison with
its contemporaries is not easy, for different operating parameters, along with
the fast pace of change, especially during the war years, makes any form of
correlation particularly difficult.
Different
national requirements and varying operational methods of achieving the desired
goal resulted in great variation in bomber design. Weapons or stores carried -
‘size’ - became the yardstick and bombers were classified into light, medium,
heavy and very heavy categories. However, tactical needs brought about
different roles and design developments also blurred these basic
classifications.
The
Model 299 B-17 was originally designed as a long-range maritime reconnaissance
bomber of medium capacity during a period when the US government was actively
pursuing an isolationist policy and when any form of military expenditure was
only acceptable if it was for defence purposes.
With
a change of administration, and faced with the expansionist policies of Germany
and Japan, the B-17 became the prime aircraft design around which the USAAC's
doctrine of daylight precision bombing was developed.
A
key figure in this was Harold Lee George. An American aviation pioneer and an
outspoken proponent of the industrial web theory, George taught at the Air
Corps Tactical School (ACTS) and through his teachings, influenced a
significant group of airmen passing through it - who were to have powerful
influences during and after World War Two. He has been described as the leader
of the so-called ‘Bomber Mafia’, a group of men who advocated an independent
military arm composed of heavy bombers.
George
studied aeronautics at Princeton University and learned to fly at Love Field,
Texas, receiving his wings on 29 March 1918. He went to France that September
with an initial assignment to the 7th Aviation Instruction Center at Clermont.
Two months later he was posted to the Meuse-Argonne front, piloting a bomber
with the 163rd Bomb Squadron, 2nd Day Bombardment Group. In the one week that
it saw action, the 163rd flew 69 sorties. George observed that massed bombers,
flying in formation, swamped enemy defences and so reduced the attacker's
casualties.
In France, George met William
‘Billy’ Mitchell and became convinced that Mitchell's vision of an independent
Air Force was the best future direction for the American military.
After the war, George was assigned to the 49th Bombardment Squadron at
Kelly Field, Texas, where he was promoted to First Lieutenant in April 1921. He
next served with the 14th Bombardment Squadron at Langley Field, Virginia, and
with the Aberdeen Proving Ground, Maryland. From 1921 to 1923, George assisted
Mitchell in his bombing demonstration against old battleships, and helped
develop air-to-ship tactics. In August 1925, George went to Washington as chief
of the Bombardment Section in the United States Army Air Corps Operations
Division.
In
July 1929, George was ordered to Hawaii for two years with the 5th Composite
Group at Luke Field serving Pearl Harbor. In September 1931, he went to Maxwell
Field, Alabama, to study at the ACTS where he helped refine the precision
daylight bomber doctrine taught there. Following graduation, George became an
instructor at ACTS, teaching air tactics and precision bombing doctrine and
became de facto leader of the ‘Bomber Mafia’. With Haywood S Hansell, Laurence
S Kuter and Donald Wilson, George researched, debated and finally codified what
the men believed would be a war-winning strategy that Wilson had termed as the
‘industrial web theory’. This was a military concept which stated that an
enemy's industrial power could be attacked at nodes of vulnerability, and thus
the enemy's ability to wage a lengthy war could be severely limited, as well as
bring down his morale - his will to resist.
In
1934, George was made director of the Department of Air Tactics and Strategy,
and vigorously promoted the doctrine of precision bombing. It was through his
directorship of ACTS, that George became known as the unofficial leader of the men
in the USAAC who closed ranks and pushed exclusively toward the concept of
daylight precision bombing as a strategic, war-winning doctrine using massed
air fleets of heavy bombers commanded independently of naval or ground warfare
needs. This concept was to influence more than a generation of thinkers within
the USAAC, USAAF and even the USAF and, apart from a period when the USAAC
adopted the RAF-style area bombing tactics using B-29s over Japan that
cumulated in the dropping of the two atomic bombs in August 1945, continued
right through to the 1970s and Linebacker II missions over Vietnam. It was also
to strongly influence the designers and manufacturers of bomber aircraft.
George
was promoted to major in July 1936. He graduated from the Command and General
Staff School at Fort Leavenworth, Kansas, the following year and returned to
Langley as commanding officer of the General Headquarters (GHQ) Air Corps 96th
Bombardment Squadron. George flew to South America as a part of a series of
USAAC goodwill flights in February 1938 and November 1939. In 1940, George took
command of the 2nd Bombardment Group.
With
intelligence gained from the early months of air fighting in Europe, the B-17
was re-designed to improve its defensive firepower and to give it improved high
altitude stability to provide a better bomb sighting platform. It received a
further re-design following the experiences of the RAF operating a small number
of B-17Cs in actual, not simulated, combat.
From
concept and through the re-designs, the B-17 was tailored to operate in the
sub-stratosphere altitudes of between 20,000 to 30,000 ft, and in daylight. The
effective turbo-supercharging of engines, an excellent crew oxygen supply
system and an accurate high altitude bombsight - without doubt for which
extreme preference was given to the Norden version - were crucial elements in
this development. The thinking behind this was that the higher the altitude,
the less effective anti-aircraft artillery would be against the bomber, and any
intercepting fighters would suffer a heavy drain on fuel in climbing to reach
these heights, severely limiting their endurance.
Bombardiers
liked to boast that with the Norden bombsight they could drop a bomb into a
pickle barrel from 20,000 feet. When asked if that was true, inventor Carl
Norden is supposed to have responded, ‘Which pickle would you like to hit?’
Norden’s President, Theordore H Barth is said to have postulated ‘We do not
regard a fifteen foot square...as being a 'very difficult' target to hit from an
altitude of 30,000 feet, provided the new Army M-4 bombsight together with
Stabilized Bombing Approach Equipment is used’.
Postwar
evaluation of this battle between Norden and Sperry showed that precision
high-altitude bombing was much less effective than believed during the war.
Although the visual bombsights worked, the generally poor weather over Europe
interfered with their success. By the end of the war, both radar-guided and
television guided bombs were under development.
Although
based on technology from the early part of the century, the Norden sight was
important because of its popularity and its role as a morale booster and
ultimately because it did equip three quarters of US bombers. Although less
well known, the Sperry sight was based on later technology that ultimately
facilitated the development of avionics for all-weather flying. Its legacy
lasts to this day, in electronic autopilots and in the gyro-syn compass that is
still the standard heading reference on most commercial and military aircraft.
How
much of what has been quoted about the Norden was factual, and just how much
was hyperbole depended much on where the aircraft was being flown. In the
clear, peaceful skies over the deserts of the south-western USA performance
figures were considerably different to the cold, wet combat-filled air of
northern Europe.
B-17 vs B-24
The only operational bomber that stands a direct comparison
to the B-17 was its running mate in the strategic bombing campaign over Europe,
the Consolidated B-24 Liberator. A later design by four years, the Liberator
understandably embodied some of the new developments in aircraft engineering
and equipment that was not available when the B-17 first appeared.
Inevitably
the virtues and vices of the two aircraft have been endlessly discussed over
the ensuing years, but nowhere more avidly than among those who flew or
serviced them. Basically the two bombers had similar specifications and
performances, being designed and developed for the same purpose. On the other
hand each had distinctive handling qualities and operational characteristics.
For the men who entrusted their lives to one or the other there was no debate:
if you flew a ‘Fort’ then the ‘Lib’ was the inferior aircraft, and vice versa.
Reason just did not enter into it. Verbal antagonism was common. To the
Fortress men the B-17 was the 'Queen of the Sky' and the B-24 '...that Banana Boat'.
To the Liberator adherents the Fort was 'that heavy bombardment training plane'
while their own charge was 'a real man's ship'.
Many
of the derogatory remarks were aimed at the B-24; ‘..it having been designed as
a flying boat but leaked so badly they decided to put wheels on it instead’.
Then there was ‘...the B-24 was the packing case they sent the B-17 over in'.
A
more truthful jibe, supposedly originating from a B-17 Group Commander: 'Who
needs escorts when there are B-24s around?' - a statement referring to the
lower altitude at which B-24s were forced to operate, thus making them inviting
targets for both flak and fighters.
This
battle was known to be expressed in more dangerous ways. Performing some aerial
manoeuvre for which a B-17 or B-24 was not designed in the presence of
operators of the other type was a not infrequent occurrence, although liable to
get the rogue pilot grounded if witnessed by authority. Reports exist of a B-17
formation ploughing across an overcast at 150 mph during a training mission who
were amazed to see an old B-24 go sailing past at apparently twice their speed
with a pair of naked backsides framed in the waist window in a vulgar gesture.
The Liberator pilot apparently attained this turn of speed in a dive from higher
altitude.
Another
story relates to what could be called the ultimate in B-17 one-upmanship, a prank performed by a pilot assigned
to the ‘Aphrodite’ unit at Fersfield. Gremlin Gus II as already described was
sometimes called ‘The Roadster’ and this unique machine caused considerable
interest wherever it appeared. Being some three tons lighter than an empty
combat Fortress due to its gutted state, Gremlin Gus II had a considerable turn
of speed. A Liberator could normally out-pace a Fortress so that every B-24
pilot knew he was unlikely to be overtaken by the Boeing. The operators of
Gremlin Gus II delighted in exploiting this situation. A story is told about
how Major Hayes of the Aphrodite unit would allegedly stalk a B-24 formation,
amble alongside and then smartly advance all throttles to full power, whereupon
Gremlin Gus II would speed by. As the head of the formation was passed, Hayes
would stand up in the open cockpit and salute!
What
is clear from the facts and figures is that the B-17 was more suited to the
type of operations undertaken by the USAAF, primarily because it had better
high altitude performance. A loaded B-17G was a relatively stable aircraft,
even at 25,000 ft, and was not difficult to control at 30,000 ft. A fully
loaded B-24J required constant pilot attention to maintain position in
formation at 20,000 ft, at 25,000 ft it was floundering around the sky.
The
characteristics of the B-24's high aspect ratio wing, the so-called ‘Davis’
wing, named after designer David R Davis, were not suited for flight in thin
air while supporting a heavy load. Above 18,000 ft the B-24 became
progressively demanding of the pilot on the controls as altitude increased,
while the Fortress presented no detrimental change until over 30,000 ft.
However, at lower altitude most pilots with experience of both bombers
considered the B-24 easier to handle.
Both
types of aircraft had turbo-supercharged engines but the B-24 used the Pratt
& Whitney 1830 whereas the B-17 had the longer stroked Wright 1820. The 1830
demonstrated better reliability and did not use, or disgorge, oil to the same
extent as the Wright. The take-off horsepower rating of 1,200 was the same for
the two makes so the B-24's slightly better performance can be attributed to
cleaner aerodynamic design.
Both
the B-17 and the B-24 had bomb bays the full depth of the fuselage. The B-24's
bay was divided into a front and rear section which together provided almost
double the space of that in the B-17. However, the design of the bay and racks
limited the largest size of individual bomb to 2,000 lb, of which the Fortress
could carry two and the Liberator four. With combinations of smaller bombs the
load could be substantially increased, particularly with the slim 1,600 lb
armour piercing bombs, of which the B-17 could accommodate six totalling 9,600
lb and the B-24 eight with a total of 12,800 lb.
If
the under-wing racks were used then heavier bombs could be lifted, but these
very heavy loads brought flight stability problems. In practice, tactical considerations
- of range and altitude - were the influencing factors and average bomb loads
for the B-17 and B-24 in the USAAF high altitude daylight operations were 5,000
lb and 6,000 lb respectively. In operations over Europe, to reach more distant
targets, loads were often l,000 lb less than the average. The heaviest
operational load known lifted by a B-17 was two 4,500 lb Disney rocket bombs on
under-wing racks and this demanded caution at the flight controls. The racks
were used to supplement bomb bay loads when attacking short range targets, but
the effect upon high altitude climb through the increased fuel consumption at
high engine temperatures limited their use.
At
similar loadings and at the same altitude the maximum speeds of the B-17G and
the B-24J were much alike, 280 mph and 290 mph at 25,000 ft. The difference in
combat cruise speed was more marked; 208 mph true airspeed for the B-17G as
against 220 mph for the B-24J at 20,000 ft, due to the slightly higher power
settings required by the B-24. This difference in airspeed was enough for it to
be undesirable to fly the two types in adjacent formations.
When
it came to range with the same amount of fuel and the same altitude, the B-24
could achieve up to 100 miles more than the B-17. Both aircraft had provision
for additional fuel tanks in the bomb bay which would add an additional 1,000
miles to range. The larger bomb bay of the B-24 still allowed for a reasonable
bomb load, whereas in the B-17 this was seriously curtailed. It was for this reason
that the B-24 was the preferred type for maritime patrols or in the Pacific war
zones, where much greater distances than in Europe had to be flown on combat
missions.
Range
considerations were the principal reason for the B-24 replacing B-17s in the Pacific.
In Europe the reverse was the case. The Fortress's better high altitude
behaviour found it the more favoured type with USAAF commanders. The B-17's
excellent flight characteristics, the foremost being directional stability with
little requirement for trim, made it far more suited to survive damage than the
B-24. Several Fortresses were landed successfully with complete tail
stabilisers shot off and major damage to wings. B-24s were in general less able
to keep flying with comparable damage to flight surfaces.
B-17 vs the Soviets
The Russians were mainly interested in air support for their
ground forces, although a few four-engined bombers were produced. One was the
Petlyakov Pe-8, which was originally known by the Soviet bomber designation T-7
until that system was dropped in favour of acknowledging the leader of the
design team responsible for an aircraft. Most of the total of 79 Pe-8s reputed
to have been completed were on hand before the German invasion of the USSR in
August 1941, but the type remained in service until the end of hostilities.
During the war years many Pe-8s were extensively modified and re-engined, once
with diesels to enable these bombers to attack Berlin.
In
comparison with the B-17G, the Pe-8 was a slightly larger and more powerful
aircraft. An auxiliary engine in the fuselage provided supercharging that
enabled the Pe-8 to be operated at between 20,000ft and 25,000ft. At this
altitude its maximum speed was some 20 mph below the B-17G's. Maximum range
with a 4,408 lb bomb load was 2,900 miles at a speed of 174 mph with fuel
overload amounting to a massive 4,120 US gallons. Bomb load could be doubled
but this severely curtailed range and altitude performance. The B-17 could only
equal or better this range by using bomb bay fuel tanks which then reduced its
payload to 2,000 lb.
The
armament of the Pe-8 featured a 20mm cannon in the nose, tail and dorsal
turrets, all manually manipulated, and a single machine gun in manned
emplacements at the rear of each engine nacelle. Although heavier weapons were
employed, the Pe-8 was less well defended than the B-17, particularly as the US
type's power turrets were far superior in operation to those on the Russian
aircraft. The Pe-8, like the other non-US bombers, operated chiefly at night
with a view to improving its chances of survival in hostile airspace.
B-17 vs the Axis
The Luftwaffe
was created to support land forces and was in reality a tactical air arm.
German interest in long range heavy bombers was limited and only one model in
this classification entered service, but others were under design and
development before the end of hostilities. Luftwaffe bombers of the early war
years were in the twin-engined light or medium classification. There were no
plans for strategic bombing forces prior to hostilities, air power being
centred on support of army and navy operations. The Luftwaffe's sole heavy
bomber to go into service was the Heinkel He. 177 Greif. Of similar dimensions
to the B-17 and the other Allied four-engined bombers, it had the novel feature
of using two coupled liquid cooled engines in each nacelle, thus driving a
single large propeller on each wing in order to minimise drag. This proved to
be the weak feature of the design, as the He.177 was plagued with recurrent
engine overheating problems that took the best part of three years to resolve.
In
comparison with the B-17G, a much older design, the He.177A had a lower
operational altitude — around 15,000 ft — against the B-17's 25,000 ft. The
service ceiling of the Heinkel was 25,250 ft against the Fortress's 35,600 ft.
The He.177's maximum speed was 314 mph at 20,000ft, some 25 mph higher than the
B-17G at the same altitude, chiefly due to far more powerful engines. The
Heinkel could lift ordnance loads as heavy as the British bombers, but much of
this had to be carried externally. The normal operational load was only 4,480lb
although this corresponded with that of the Fortress on very long range
flights; but even so it was able to haul this load some 500 miles further than
the Fortress could at 20,000ft. The He.177 flew at night during its limited
bomber operations over Britain and the USSR but was also used in a long-range
anti-shipping role. The defensive armament was good, albeit nowhere as
extensive as the B-17Gs, but on some versions it included two 20mm cannon.
The
Japanese, like their Axis partners, concentrated on employing air power in
support of army and navy operations. A solitary four-engine heavy bomber design
was produced and first flown in 1936, but never reached quantity production.
They did not produce a modern four-engined heavy bomber until 1944 and this
type never entered service.
The
only other four-engined heavy bomber to be employed operationally by the Axis
air arms was the Italian Piaggio P.108B. First flown in November 1939, this
type was of similar configuration to the early B-17 and is said to have had
excellent handling characteristics. However, the aircraft proved to be
mechanically unreliable and production was curtailed after only 26 had been
completed. Nevertheless, during 1942 and 1943 the only unit of the Italian Air
Force - the Regia Aeronautica - equipped with the P.108B did undertake 29
operational sorties. During these operations five of the bombers were shot down
and three lost through mechanical failure or accident.
Compared
with the B-17G, the P.108B had a much lower operational altitude range,
15,000ft being the optimum with a service ceiling of 20,000ft. Its top speed
was also some 20 mph slower than that of the B-17G at 15,000ft despite higher
rated engines. With a normal bomb load of 2,2051b the Piaggio's range was
approximately the same as the Fortress's. The Piaggio had a greater maximum
internal load capacity amounting to 7,716 lb for short range flight but engine
difficulties precluded such heavy lifts on operations. An advanced feature of
the P.108B was the two remote controlled twin machine gun barbettes mounted at
the rear of each outboard engine nacelle and sighted from stations on the
fuselage. A single machine gun in a retractable 'dustbin' type turret provided
underside defence but this was both cumbersome and considered ineffective.
Overall the seven or eight machine gun defensive armament was vastly inferior
to the B-17G's but, in fairness, this bomber was more the contemporary of the
B-17F model than the G, even though in the matter of comparison the same
judgements apply.
B-17 vs British designs
In contrast to the USAAF, the heavy bombers developed for
the Royal Air Force were expected to operate mainly under cover of darkness and
at much lower altitudes. When comparing the B-17 with the three major British
four-engined bombers, there are two major differences - the amount of defensive
armamant carried and the maximum bomb loads.
The
Short Stirling, earliest of the British designs, could accommodate and lift
14,000 lb, the Handley Page Halifax 13,000 lb, and the Avro Lancaster 14,000 lb
in standard, unmodified form. The more extensive bomb bays in the British
aircraft, in contrast to the B-17 and B-24, only occupied the fuselage area
below the wing spar and were not encumbered by walkways. This allowed the
carriage of more bombs and, in the case of the Halifax and Lancaster, larger
bombs, with single 4,000 lb bombs being dropped regularly by Lancasters in
amongst other munitions carried. Much larger single bombs were also carried and
modified Lancasters were quite capable of carrying and dropping 22,000 lb deep
penetration missiles.
The
normal maximum loads of the British bombers could only be carried some 750
miles at operational altitude by the Stirling, 1,000 miles by the Halifax and
1,500 miles by the Lancaster. Loads were substantially reduced for long ranges
but Lancasters and Halifaxes regularly hauled 10,000 to 12,000 lb loads to the
Ruhr and 8,000 lb loads to Berlin.
Unlike
the USAAF day bombers, RAF heavies operating at night did not circle to gain
altitude before setting course to penetrate enemy airspace. Normally the
British heavies made their ascent during the run up to the enemy coast. The
Stirling could not operate with a combat load at much above 15,000ft and the
Halifax Mks I and II above 18,000ft. The radial engined Halifax Mk II did
operate successfully at 20,000ft, which was also the optimum level for
Lancaster sorties. The B-17G had better range than the Stirling and Halifax and
marginally better than the Lancaster while flying at similar altitudes. All the
British bombers had, on average, double the pay load for similar ranges but the
Lancaster's larger fuel load allowed it, even with a 10,000 lb load, to match
the B-17 on radius of action.
In
the matter of armament differences the B-17G had far superior firepower to the
British bombers: thirteen .50in calibre machine guns to the usual eight .303in
machine guns in three power turrets of British bombers. Moreover, the US .50
weapon had a higher muzzle velocity and much more destructive power than the
rifle calibre weapons which defended the RAF bombers. To improve matters
Lancasters of one Bomber Command Group had two .50s as tail turret armament
during the final months of hostilities. The British bombers did not have
underside defences and were very vulnerable to attack from that quarter, albeit
that in any event, an approach from below by an interceptor could rarely be
seen at night until it was too late. In fact, the difficulty of being alerted
to an enemy fighter's presence in any quarter during the times of darkness was
the greatest problem of bomber defence. Given the technology available at the
time, there was almost a fatalistic inevitability amongst RAF bomber aircrews
that not much could be done.
Instead
the RAF turned to different tactics - by making use of the small, fast, highly
maneouverable De Havilland Mosquito twin-engined night fighter flying within
the bomber stream to act as ‘bait’ to German night-fighters. When spotted on
the tail warning radar in the Mosquito, the pilot would quickly loop around,
picking up the German machine on his main radar and then bring his four 20 mm
cannon to bear on the rapidly closing target.
The
wooden composite De Havilland Mosquito - originally designed as an unarmed
high-speed bomber but also produced in Photo-Reconnaissance, Fighter and
Figher-Bomber variants - sacrificed the weight of excessive armament for the
safety gained from performance could uplift the same bombload internally as
that of a B-17. The two-man crew could also theoretically make two trips to
Berlin from England in the same time it took a 10-man B-17 to make one!
Fortresses
were experimentally employed on night operations, but the limitations on bomb
load made such sorties uneconomical. By daylight the precision that could be
achieved and the mass formation drops employed were regarded as the proven
means of using the type successfully.
Lancasters
and Halifaxes frequently took part in daylight bombing of Ruhr targets during
the final year of the war, by which time the Luftwaffe was in demise and
fighter escort was provided to and from the target. Formations flown were much
looser than those of the USAAF and target sighting was performed from
individual aircraft. Attack altitudes - 15,000 ft to 18,000 ft - were generally
lower than those of the US heavies. Each of the British bombers delivered a
more destructive load but post mission reconnaissance showed that this was more
scattered than the formation drops of the B-17s and the B-24s. However, the
USAAF did use exactly the same area bombing techniques over Japan.
The B-17 munitons
When one tries to compare the B-17 with other aircraft, one
needs to consider the munitions available for use. As the B-17 was used more in
the ETO than in any other theatre then this area is a good one to study.
Munitions
fell into a number of categories: General Purpose (GP) High Explosive (HE)
bombs, Incendiary bombs, and then a whole swathe of what could be called
‘Special Use’ bombs.
The
glide bombs, the GB-1 and GB-4s, are covered elsewhere, as are the Disney
rocket weapons. The B-17 could carry chemical weapons, by far the worst being
the poison gas bombs, which were in two types - the 400 lb mustard gas bomb
codenamed Flying Cow and the 500 lb phosgene bomb. In 1942 several thousand
M47A2 HS unfilled incendiary bombs were set aside for use with mustard gas and
held ready in muntion stores. Storage levels appear to have been 40,000 M47 100
lb mustard bombs and 50,000 phosgene bombs. There is no record of any being
used.
Another
chemical weapon became available to the USAAF in the second half of 1944, when
a refined petroleum jelly known as napalm became available. Handled in bulk it
was intended for filling as required. Tested in various containers, the
preferred type was the paper composition fighter fuel tank of 108 US gallon capacity.
Known as Class C-Fire Bombs, napalm tanks were used on a few special missions
where blanket fire cover was required, notably against German strong-points on
the French coast in April 1945. Usually four napalm tanks were carried in a
B-17; small incendiary igniter units were fixed to each tank.
Fragmentation
bombs, which were basically anti-personnel munitions, were used mostly in
tactical attacks in support of ground forces. The 20 lb M41 was common to both
the M1 and M1A1 - which were differing in attachment arrangement - clusters of
120 lb and the M26 clusters of 500 lb. The M1A1 was employed extensively in
heavy bomber loads. To enable fragmentation bombs to be used in conjunction
with the Norden sight it was necessary for special computation tables to be
used as the maximum trail angle of the sight was not great enough for the light
bombs.
When
they began operations, the 8th Air Force were using the old type of GP bombs of
100, 300, 500 and 1000 lb size ratings. It was not long before supplies of
these were exhausted and the new AN (Army/Navy) bombs were used, these being
categorised as the M30/100 lb, M31/300 lb, M43/500 lb, M44/1000 lb and M34/2000
lb.
In
general terms, the 500, 1000 and 2000 lb muntions were used against industrial
targets while the smaller sizes were used against airfields. In practice,
little use was made of the M30s. Likewise, use of 1000 and 2000 lb GP bombs
were found to be of little use against the submarine pens themselves, for they
either just bounced off or barely chipped the concrete, although significant
damage was done to adjacent structures.
At
one time the 8th considered operating in two waves, the first dropping 1600 lb
US Navy Mk 1 armour-piercing bombs which were expected to crack the concrete,
and then to follow up with a second wave dropping 2000 lb GPs to blast through.
Two attempts to achieve this were made at Lorient, but the only successful
drop, on 30 December 1942, gave disappointing results, basically because it was
not possible to obtain successive strikes with the two types of bombs.
An
intelligence report on the December 1942 Lille mission showed that 30% of bombs
dropped failed to detonate. There were indications that the mechanical arming
mechanisms of the fuses had frozen. Trials showed that things could be improved
if the bombs were not fused until shortly before take-off, thus reducing the
time the fuses were exposed to damp. Even so, a high percentage of detonation
failures persisted, even in warmer weather. British fuses were adapted for American
bombs and in the spring of 1943 US chemical action long delay fuses were
received for service tests. These had an anti-withdrawal device to prevent
defusing by the enemy. Fortunately a method was devised in the UK for removing
these fuses safely, sometimes necessary with aircraft that crashed on take-off.
A
new range of GP bombs became available late in 1943, the M57/250 lb replaced
the M31, then there were the M64/500 lb, M65/1000 lb and M.66/2000 lb. These
munitions made up the greater part of the tonnage delivered by the 8th during
the final year of operations. A small number of M56/4000 lb bombs were received
in 1944 but could not be carried internally by either B-17 or B-24. Experiments
to use them on under-wing racks of B-17s were not successful and no record has
been discovered to suggest that M56s were delivered on combat missions. While
the large 1000 and 2000 lb bombs continued to be used on industrial targets, by
January 1945 analysts were recommending 250 lb GP to be used against synthetic
oil plants, refineries and storage tanks as well as against ammunition supply
and dump targets. The 100 lb GP bomb was advised for attacking marshalling
yards and for cratering airfields.
The
first incendiary bombs used by the 8th Air Force were British, either 250 lb or
500 lb. Both were filled with a rubber/gasoline mixture. It was not long before
the American M50A1 4 lb magnesium incendiary in 100 lb clusters became
available for use, along with a 500 lb cluster version and an 100 lb M47 type.
However, these clusters proved unsatisfactory as they opened quickly, causing
excessive dispersion, some aircraft in the formation being damaged by
clustering material, so use was suspended. The 8th then began trial missions
with the M47, and discovered that a full load only amounted to 24 due to the
limited number of shackle points in a B-17 bomb-bay. It was not until July 1943
that a successful method of clustering M47s together was achieved. Wire cables
with snap hooks were used to hold three or four bombs together, but in such a
way that after release there was separation, the cables being carried down with
one bomb. This not only allowed three or four M47s to be shackled to one
station in the bomb-bay, increasing the total load to 42, but also avoided
damage to other aircraft. This ‘shackling’ became standard operating proceedure
for use with various other small bombs.
Other
incendiary munitions were the M52, a 2 lb magnesium type, and the M69, which
weighed 6 lb and was filled with petroleum gel. The M69 was later packed in the
M12 cluster. In January 1944 8th Air Force started to use the 500 lb M17
aimable cluster containing 110 M50A1s with better ballistics than the earlier
M11 cluster; it had a primacord release that could be set to give the desired
scatter. A larger petroleum gel filled bomb, the M76/500 lb, was introduced in
1944 and used with some effect during the rest of the 8th's campaign.
The
M50A1 which made up magnesium incendiary clusters had a hexagonal, cored
magnesium alloy body with-hollow steel sheet fins containing thermite with an
igniting charge and fuse. On ignition, the M50 burned for six to eight minutes
at a temperature of 2300 degrees F. The preferred jellied-oil incendiary, the
M47A2, had a thin-walled steel cylindrical body weighing 26 lb empty and on
impact gave a 120 feet fire spread.
All
of this gave the B-17 a wide range of small-to-medium munitions that could be
carried.
The failure of the industrial web theory.
American bombing leaders maintained that precision attacks
were being carried out by B-17s and B-24s, but in early 1944 poor weather over
Europe prevented visual sighting, and bombs were dropped indiscriminately by
inaccurate radar methods through cloud cover, resulting in general population
destruction. By September 1944, all pretence to precision was abandoned when
General Dwight D Eisenhower ordered the area bombing of Berlin. By that time,
bombing was not so much strategic as it was tactical, to soften Germany for
invasion by ground troops. Thousand-bomber raids were not able to diminish
industrial production of war materiel in time to prevent invasion. When arms
production in Germany finally faltered in the third quarter of 1944, only 30%
of the total of eventual bomb tonnage had been dropped on the country - this
was after the French-German border had been reached and the war on the ground
had seen its decisive breakthrough. It must be said that Germany was conquered
by invasion; it did not surrender as a result of bombing. The morale of the
enemy was not significantly affected; no population that was bombed in World
War Two lost their will to resist, and it was the Emperor, not the people, who
decided Japan must surrender.
The problem with the B-17...
The ‘designed in’ problem with the B-17 was the bomb-bay.
From the outset the B-17 was a medium bomber and, because of the way the
bomb-bay was designed and positioned, there was absolutely nothing that could
be done to allow the internal carriage of the larger weaponry as it became
available or was required.
The
B-17 bomb-bay was eight foot nine inches long by seven feet wide, but this had
to be divided in two down its length and then subtract the nine inch wide
walkway that formed part of the keel of the aircraft. This gives two ‘holes’
105 inches long by 37.5 inches wide.
Much
has been made by those promulgating the abilities of the B-17 about the fact
that there were 42 internal ‘positions’ on four racks that bombs could be hung
on. This was certainly true, and indeed there were also two external racks as
well. However, they also convienently forget to mention that depending on the
size of the bombs carried and the distance from the operating airfield to the target, virtually all of these
positions were completely unusable mainly because of whatever was hung on them
had to be ‘stacked’ one above the other and they had to pass through two
‘holes’ filled in by the bomb bay doors. Indeed, the pair of ferry fuel tanks
were conformal in shape in order to maximise the possible uplift. Everything
had to be fitted into two areas deliniated by the front and rear bulkheads of
the bomb bay, the sides of the fuselage and the edges of the walkway. No matter
what the volume of the bomb bay, this simple area restriction gave two
apertures each slightly over twenty nine square feet in area for bombs to drop
through, thus limiting the aircraft weaponry uplift.
The
British Avro Lancaster, on the other hand, did not have that problem. The bomb
bay in this machine was thirty three feet six inches long and sixty-two inches
wide, with three ‘racks’ running the entire length. That is slightly over one
hundred and seventy three square feet of completely unobstructed, usable bomb
bay. If a bomb could fit in that area, it could be carried - and if it could
not fit inside the bomb-bay with the doors closed, there was no problem -
either bulge the doors or remove them all together!
In
the immediate post-war years a number of studies by the Allies were conducted,
to coldly calculate losses and the so-called ‘efficiency’ of different aircraft
designs.
Overall,
it was stated that as the ‘ultimate’ B-17, the B-17G had a superior
high-altitude performance to all other Allied and Axis bombers. In maximum
speed the only notably faster bomber was the He 177. In tactical speeds the
Fortress was similar to its contemporaries except when flying in formation
where uniformity demanded lower power settings and therefore lower speed. The
B-17G's range was better than that of the British heavies, equal to the Piaggio
but less than the Pe-8 and the He177 with similar bomb loads. In the matter of
maximum loads it was at the bottom of the scale, particularly in comparison with the British bombers.
In the case of defensive armament the B-17 justified the name Fortress, for in
number of guns, calibre and effectiveness it was the best armed, with the B-24
running a close second.
If
cautiously loaded, the B-17G had no really undesirable flight characteristics
and was a pilot-forgiving aircraft, easy to fly. While it is extremely doubtful
if any one pilot had experience of all the types reviewed it appears that, with
the exception of the Lancaster and Liberator, the other types left something to
be desired in mechanical ability or operation. Opinions from those who have
flown Lancaster, Liberator and Fortress single out the last named as the least
demanding, even at low and medium altitudes.
Of
all the ‘efficiency studies’ located, one is of particular interest, for it
broke the figures down in a similar manner to how airlines of today
cross-compare their statistics in load-factors and seat cost per mile to
generate a common denominator. However, the originators of the study were
somewhat selective in their choice of aircraft to compare.
The
first calculation it used was to divide the bombload by the number of crew on
board - this gives a figure that describes the destructive weight uplifted per
man on board the machine. The second was to state a nominal mission distance,
in this case 600 miles, 1200 miles round trip, which happened to be an average
distance from the UK to Berlin and to work out an average point-to-point time
taken by each aircraft to cover that distance at the quoted combat speed.
The
original study compared the B-17G to the Stirling, Halifax and Lancaster.
Missing from the table was the Lancaster (Special) and the Mosquito, which was
considered a light bomber anyway. It also did not take into account the
different styles of operation between the RAF and USAAF in that the RAF did not
require formation assembly, which could add at least an hour to the time. Both
of these omissions create a somewhat slewed view. Today, inserting those two
aircraft into the table gives a far better perspective.
In conclusion...
To try to make a comparison and then to say that one design
is ‘better’ than another is too simplistic and just exhibits what today would
be termed ‘blind brand loyalty’. Each design served, and in many ways met and
exceeded, the purpose of its creation. Sometimes the urgent needs of combat -
or political expediency - meant that this was outside the design parameters.
This worked at times, failed at others, and in this the B-17 was no different
than all the others.
The
passing of time and a number of over-active publicity machines have meant that
many legends and myths have grown up surrounding both the B-17 and the Norden
bombsight. Does the ‘Flying Fortress’ deserve it? That is for the individual to
decide. Was it fit for purpose? Undoubtedly.
