Self-Defending Bomber Concept--Could It Have Worked?
during World War Two, American bombers used as standard
defensive armament Browning .50 machine guns...and nothing
else. As a result, unescorted bomber crews became relatively
easy "pickings" by German fighters, which possessed much
more powerful, long-range weaponry...meaning the Germans
could stay out of range of American firepower with the
.5's...and fire cannon at will, bringing down many American
bombers and their crews to their deaths.
question: would it have been possible for the self-defending
bomber concept to have worked in the War if the B-17's and
the stage, and get the broad picture, we have to go back in
time to the latter part of World War I, when a multitude of
nations were working to perfect heavy guns. In "Rapid Fire"
by Anthony G. Williams, this statement is made on page 86:
"A line of development came from the need to produce a
hard-hitting but still compact and lightweight weapons for
Once again it was German firms who led the way with the development of the first 20mm cannon, the Becker. It was mainly used, as intended, as a defensive weapon in aircraft...." (Publisher: Motorbooks International)
Already it was clear that even early military aviation
pioneers realized that defending an aircraft would take
something bigger than a regular machine gun. Strangely
enough--and yet at the same time quite logically--the need
for big guns aboard aircraft was "learned" from
"Olive-drab.com" comes this comment from an article about
the .50 machine gun. "Experience in
The evolution of machine guns seems to have had a tortured history. Page 98 of "Rapid Fire" says this: "The evaluation of heavy machine guns was rather confused. They had proved largely ineffective in the AA (antiaircraft) role. An American analysis based on the last year of the war (WW II) showed that over 50,000 .50 rounds were fired for every aircraft brought down, compared with 500 (40 mm) Bofors rounds--that is, almost two hours of continuous firing per gun, compared with four minutes."
All well and good for end-of-war studies, but didn't the Allies know all this much earlier? This time, the lesson comes from naval guns used during WW II. "War experience soon justified the concerns of both the British and the Americans about the .5" machine gun's lack of range and hitting power. Their high rate of fire means that they had some effect against strafing aircraft which came too close, but they were of little use against torpedo and dive bombers.
"The smallest calibre to prove its worth was the 20 mm. In Allied navies, this calibre became virtually synonymous with the Oerlikon S, the most powerful of a family of API blowback 20 mm weapons developed by the Swiss firm between the wars. It was introduced by the RN (Royal Navy) in 1939 and by the USN (US Navy) in 1941.
"The USN rated the Oerlikon as between eight and ten times more effective in the AA role than the .5" and estimated that it accounted for 32% of Japanese aircraft destroyed by naval AA fire between Pearl Harbor and 1944, after which the figure dropped to 25%." (Page 124, "Rapid Fire")
OK--so the armed services realized the value of big guns in anti-aircraft guns starting back in WW I, but now where do the air corps come in?
"By far the most significant of the wartime automatic guns was the first 20 mm automatic cannon in the modern sequences of development, the German Becker. Development started even before the war but significant use was not made until 1917, when it was first primarily used for the defence of heavy bombers and airships."
A pivotal point is now within reach here, as we show that cannon for bombers was viewed as viable well before WW II.
"Bomber aircraft logically needed defensive armament capable of defeating fighters, and therefore should have possessed weapons at leat equal in range and hitting power. In fact, a British inter-war study concluded that bombers needed more powerful weapons in order to destroy the engines of fighters as they attacked head-on." (Page 146, Ibid)
And speaking of studies, get this!
"Before the war (WW II) an attempt to transform bomber defensive armament had been made. An RAF study into air-to-air fighting concluded that a single hit from a 2 lb (0.9kg) shell would be sufficient to destroy most aircraft and in 1938 a specification was issued which led to the production of the Vickers Class S 40 mm gun....
first example of the Class S was produced in 1939. Initial
plans were to fit the gun into a large turret, complete with
a rangefinder and predictor gear, to enable bombers to
engage attacking fighters at long range. A turret was duly
produced and fitted to a much-modified
this very day, one of the closest-held secrets of the U.S.
Army Air Forces of WW II is that of the death rate of the
bomber crews during combat. Despite horrible mounting losses
throughout the war, which totalled 88,000 airmen dead by V-E
day, AAF top command refused to arm the B-17s and B-24's
operating over Europe with any defensive armament more
powerful and with longer range than the Browning .50 caliber
This enabled German fighters and bombers to simply cruise alongside the bomber formations outside .50 caliber range and fire their longer-range and much harder hitting 20 mm (.79 caliber) automatic cannon and fire rockets into our bombers with, of course, deadly results.
From "Clash of Wings" by Walter J. Boyne, Page 314-315, comes this reality check: "So equipped, they (the Germans) would linger outside the range of the American bombers's guns and lob rockets into the formation. It was a terrifying sight, for the USAAF crews could watch the smoke trail from the launch of the big 250 lb. mortar shells from invulnerable aircraft sitting out of range. A hit from the 21 lb. warhead was fatal and usually broke up the tight formation, allowing single-engine fighters (carrying 20 mm cannons) to close with the survivors.
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