Monday, January 30, 2012

Ruhrstahl SD 1400 X, Kramer X-1, PC 1400X, FX 1400 or commonly known as "Fritz X"

The Fritz X was a further development of the high-explosive bomb SD 1400 (Splitterbombe, dickwandig, 1400 kg; German for "fragmentation bomb, thick-walled, 1400 kg"). It was given a more aerodynamic nose, four stub wings, and a box shaped tail unit. The Luftwaffe recognized the difficulty of hitting moving ships during the Spanish Civil War. Dipl. engineer Max Kramer, who worked at the DVL, had been experimenting since 1938 with remote-controlled free-falling 250 kg bombs, and in 1939 fitted radio-controlled spoilers. In 1940, Ruhrstahl was invited to join the development, since they already had experience in the development and production of unguided bombs.

The dual-axis joystick-equipped Kehl series of radio-control transmitter sets onboard the deploying aircraft were used to send the control signals to the Fritz-X, with the ordnance itself picking up the signals through a Straßburg receiver within it to send the signals on to the movable surfaces in the Fritz-X's tail fin structure.

A Fritz X in the RAF Museum London

Another angle of the Fritz X also known as Ruhrstahl SD 1400 X

The only Luftwaffe unit to deploy the Fritz-X was Gruppe III of Kampfgeschwader 100, designated III./KG 100. This unit employed the medium range Dornier Do 217 K-2 bomber on almost all of its attack missions, though in a few cases toward the end of its deployment history, Do 217 K-3 and Do 217 M-11 variants were also used. The Fritz-X had been initially tested with a Heinkel He 111 bomber, although it was never taken into combat by this aircraft. A few special variants of the long-range Heinkel He 177 bomber were equipped to carry the Fritz-X but it appears this combination never saw combat.

Fritz-X was first deployed on 21 July 1943 in a raid on Augusta harbor in Sicily. A number of additional attacks around Sicily and Messina followed, though no confirmed hits were made and it appears the Allies were unaware that the large bombs being dropped were radio-guided weapons.

On 9 September, the Luftwaffe achieved their greatest success with the weapon. After the armistice with the Allies, the Italian fleet had steamed out from La Spezia and headed to Malta. To prevent the ships from falling into Allied hands, six Dornier Do 217 K-2s from the III. Gruppe of KG100 (III/KG100) took off, each carrying a single Fritz X. The Italian battleship Roma, flagship of the Italian fleet, received two hits and one near miss, and sank after her magazines exploded. 1,255 men, including Admiral Carlo Bergamini, died. Her sister ship, Italia, was also damaged but reached Malta.

USS Savannah (CL-42) is hit by a German radio-controlled glide bomb, while supporting Allied forces ashore during the Salerno operation, 11 September 1943. The bomb hit the top of the ship's number three 6"/47 gun turret and penetrated deep into her hull before exploding. The photograph shows the explosion venting through the top of the turret and also through Savannah's hull below the waterline. A motor torpedo boat (PT) is passing by in the foreground.

The light cruiser Savannah was hit by Fritz-Xs at 1000 on 11 September 1943 during the invasion of Salerno, and was forced to retire to the United States for repairs. A single Fritz-X passed through the roof of "C" turret and killed the turret crew and a damage control party when it exploded in the lower ammunition handling room. The blast tore a large hole in the ship's bottom, opened a seam in her side, and blew out all fires in her boiler rooms. Savannah lay dead in the water with the forecastle nearly awash and took eight hours to relight boilers and get underway for Malta.


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