U-Boats’ Anti-Aircraft Weapons
March 5th 2010
Much as they did towards the
end of the Great War, in the early years of World War II
German’s U-Bootwaffes roamed, almost with impunity, the sea
trade routes of the Western Allies, engaging and sinking
vital shipping at an alarming rate. It wasn’t until the
Allies began to implement a sophisticated system of long
rage, air patrol over the Atlantic that the tide of the
submarine war finally began to turn in their favour.
Because most of Germany’s U-boat force was incapable of
prolonged, submerge patrol time, they became easy targets
for predatory allied medium and heavy bombers covering the
Engaging and hitting allied patrol airplanes became the
sub’s main objective from late 1943 to the end of the war in
May ’45. In an attempt to achieve this task, each boat was
fitted with a vast array of defensive weapon systems.
The submarine’s main anti-aircraft weapon was the 2CM Flak
Gun. Two basic designs of this uninspired looking, but
tremendously effective flak system were employed. The first
operating 2CM was the No. 30. The thirty was a single barrel
weapon with a 360 degree traverse and capable of a two
degree depression and 90 degree elevation. It fired a 0.32kg
shell capable of reaching distances of up to 12,350 meters.
What made this weapon so effective was it impressive cycle
rate of 480 rounds per minute.
The second, improved version of the 2CM was Flak 38th.
Similar to the 30th, but capable of reaching a cycle rate of
960 rounds per minute, the 38th was arguably the best
German, light attack weapon of World War II.
Another light weapon use by U-Boats to fend-off attackers
was the 3.7CM M/42 Flak Gun. In the bottom half of the war,
most German submarines were fitted with the 42nd platform.
It fired a .73Kg shell up to a distance of 15,350m. Maximum
firing cycle was 50 rounds per minute.
Those two weapon systems accounted for almost 85 percentage
of all hit allied aircraft. Official numbers regarding hit
aircraft varies from source to source, but the most reliable
figure (coming from British-generated documents released in
the mid 1950s) puts the amount at 247 from the spring of
1944 to April 1945.
Although it was not a intended as a primary anti-aircraft
weapon, the 8.8CM Schiffskanone Deck Gun was also used in
that role, especially towards the end. This remarkable 8.8
gun employed by the German navy was not directly related to
the more famous, 8.8 Acht-Acht flack gun utilized by the
army as an anti-tank weapon. The CM was purely a naval gun
develop in the waning days of World War One.
The gun was mounted on a low box forward of the conning
tower. It could traverse through a field of 360 degrees. Its
-4 degrees depressed parameter and 30 degree elevation
capacity were two of the most impressive features of this
remarkable weapon. The gun fired a 13.7kg high explosive
shell at a 700m/sec muzzle velocity. It had a solid impact
range of up to 12,350m.
Manned by a three men crew, the CM was a powerful,
horizontal weapon that when use against sea-based platforms,
it caused heavy damage. As the U-Boats began to sustain
alarming losses to Allies praying bombers, German crews
commenced utilizing their main armament on incoming enemy
aircraft. Although their use in that type of environment
wasn’t tested before the war, the gun performed well.
Data on the numbers of downed allied aircraft hit by the
8.8CM is not reliable. But unofficial accounts put the
numbers in the low 50s. Much of that was accounted for
between the autumn of 1944 and the spring of 1945.
Aside from those three defensive weapons, German submarines
carried a limited amount of small calibre fire arms
including 9mm and 7.62mm hand guns. Nine millimetre machine
guns and some 7.92mm rapid fire rifles. No data on hit
aircraft by these weapons are available.
Of course, no weapon can be effective if the enemy isn’t
spotted. For long range detection, the U-boats employed the
Funkmessorungsgerat (Fu) MO-29 Radar. The MO-29 was use
primarily on Type IV boats as well as some Type VIIs. The 29
was simple to utilize thanks to its twin horizontal rows of
eight dipoles on the upper front part of the conning tower.
On the top row laid the transmitters and in the lower one,
the receivers. An improved version of the 29 was introduced
in the summer of 1942. In that version, known as No. 30, the
diploes were replaced by a retractable antenna which was
housed in a slot in the tower.
Although relative powerful for the times, this system barely
was able to detect surface vessels because of the low
position of it’s mounting in respect to the horizon.
A more complex system, FuMB1 or the ‘Metox’ was introduced
in the fall of 1942. This system was utilized in conjunction
with a raw, wooden cross antenna strung with copper wire
know as the ‘Biscay Cross’. But as with the early Fus
platforms, this unit wasn’t that reliable. In fact, a case
could be mad that their use was highly detrimental to the
sub’s survival thanks to the Metox’s volatile emissions
which were easy detectable by Allied radars.
By November 1943, the Germans had finally develop what would
become the world’s first true, all around naval radar. Born
out of desperation, FuMB7 combined Metox and Naxos emissions
to give U-boat commanders a first rate, long range detection
system. Further enhancements were undertaken (the FuMB24 and
25) to the base MB7 giving it an extended operational
Aside the radar, maybe the
most ingenious defensive measure used by German submarines
was the Focke-Achgelis. The ‘Focke’ was basically a manned
unpowered autogyro with a triple blade rotor. It was as
simple to operate as it was to assemble. Housed in a storage
cylinder on the afterdeck, the Focke was quickly armed and
launched. It remained connected to the U-boat by an
umbilical cord. From its advantageous position high above
the sub (10-12,000 feet), the pilot could spot any target
approaching the boat. Unfortunately for the Focke, if the
U-boat came under direct attack, there was no time to reel
it in, thus the sub cut the cord and left the pilot to
defend himself until all was cleared to surface back again.
More effective than the Focke-Achgelis was the Aphrodite. It
was a basic devise consisting of a large (one meter
diameter) hydrogen-filled balloon from which dangled small
strips of metal foil. It was attached to the sub by way of
an anchor weight. Its main purpose was to confuse allied
aircraft utilizing radar navigational systems.