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PC 1400 FX "Fritz X" Guided Bomb
Over-All Length: 130 in.
Length Of The Control Unit Housing: 16 in.
Length Of Fins At The Root: 31 5/8 in.
Length Of Fins At Outer Edge: 18 1/4 in.
Length Of Fin At Leading Edge: 18 5/8 in.
Max. Width Of Tail Width: 48 in.
Min. Width Of Tail Width: 33 3/4 in.
Span Of The Fins: 58 3/4 in.
Weight Of Filling: 270 kg.
Total Weight (Approximate): 1,650 kg.
DESCRIPTION: The PC 1400 FX is a radio controlled glider bomb designed for attacks against capital ships or similar targets. The complete missile consists of three distinct units, the H.E. armour piercing warhead, the control unit housing, and the tail assembly. There are four aluminum alloy fins secured to the missile at approximately the center of gravity. The purpose of these fins is to give the bomb sufficient lift so that the control surfaces in the tail unit can exercise adequate influence.
WARHEAD: The warhead is an ordinary PC 1400 kg bomb to which the four above mentioned fins have been attached. It has one transverse fuze pocket located aft the H-type suspension lug. Two horizontal exploder tubes are centered in the warhead to insure high order detonation on impact. The usual filling for the warhead is 50/50 amatol.
FUZING: The type fuzing generally used has the El. A. Z. 38B electrical impact fuze set to operate with a very short delay. The fuze is sometimes fitted with an extension cap. Alternative fuzes have been found in the missile are the El. A. Z. 28A and the El. A. Z. 35. The wiring diagrams and the operation of each of these fuzes can be found in the bomb fuze section.
CONTROL UNIT HOUSING: The control unit housing, made of cast magnesium alloy,
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The Ruhrstahl SD 1400 'Fritz X' : Air-to-Ship, Wireless Guided, Gliding Bomb
In 1938, Dr. Max Kramer of Ruhrstahl A.G., Westfalen, tested methods of correcting errors in falling bombs, using radio-controlled spoilers located in the tails of 550 pound bombs. In 1940, the RLM adopted Kramer's control system utilizing the SD 1400X armor-piercing bomb. The German 100 kilogram bomb had always been known as "Fritz" so its code name became "Fritz X" and its code designation, "FX" or "FX 1400." Ruhrstahl continued with its manufacturer's designation of "X-1" which led to Fritz X variants, X-1 through X-7. The "X" was a classification used by Ruhrstahl to denote all their missiles with cruciform tails. The operational missile was later referred to as "Korper" or body by security-conscious personnel.
In early tests, bomb-aimers had difficulty following the bomb in flight due to its high velocity. Also, the electromagnetically activated spoilers tended to jam. Pneumatic power was tested but was found to develop problems in low temperatures causing the electromagnetic system to be retained. It was not until early 1942, when a high-speed wind tunnel had been constructed, that Dr. Kramer's control spoilers were modified and that a velocity-reducing tail-mounted air brake was perfected.
Tests, beginning in February 1942 at Karlshagen and Peenemünde-West, showed that the bomb had to be dropped from a minimum height of 13,000 feet if there was to be enough time for the bomb aimer to correct the flight of the bomb. The need for more favorable weather conditions to conduct tests from this height caused the program to be transferred to Erprobungsstelle Sud at Foggia, Italy. Here, Dr. Kramer was able to complete developmental tests in an amazing time of only a month. At 23,000 feet, half of the test bombs hit within a 50-foot radius while 90 percent hit within a 100-foot radius when controlled by experienced bomb aimers.
As issued the Fritz X was the standard SD 100X armor-piercing (AP) bomb with four centrally-mounted standard cruciform wings giving the bomb aerodynamic pivotal points for control. The total span across the wings was 4 feet 5 inches. The tail assembly consisted of four fins similar to those of an orthodox bomb, but were surrounded by the air brake ring which contained the control spoilers and operating solenoids. The dive brake was fitted around the tail fins to limit the terminal velocity of the bomb to 600 miles per hour. The dive brake was fabricated of metal but a section was electrically insulated to serve as a radio antenna. The fuselage and tail measured 10 feet 8* inches and had a diameter of 1 foot 10 inches.
A bright flare unit ("Leuchtstaz") was contained in the tail unit to assist the bomb aimer in following the course of the falling, rapidly diminishing bomb. Early flares left a smoke trail which was so dense as to obscure the target. The red tracer was tried but it was sometimes lost in anti-aircraft red tracer. Green was tried next with a blue-white smokeless type finally settled on. An alternative tracking aid was a blue electric lamp, but since it required an additional battery it was not commonly used. In early tests it was found that half of the flares failed. It was found that the plastic base of the flare deteriorated in storage.
The total operational weight of Fritz X was 3,454 pounds. The missile was usually painted a light blue to match the underside of the Do 217, which generally carried the bomb operationally.
Dr. Kramer, from his previous aerodynamic investigations, choose from the beginning of the Fritz X project the then little-known oscillator principle of aerodynamic control. He did so because it promised a simple method of transmitting steady control movement in conjunction with remote control. The principle major disadvantage of increased drag and long delay in control transmission at low speed would not be vital in the project.
There were three pairs of tail-mounted spoilers, each of the six was located between boundary layer fences and was operated by an electromagnet located in the largest section of that particular tail fin. Unlike the Wagner spoilers found on the Henschel missiles the Fritz X spoilers passed through the electromagnetic coils and were operated by them. The drag of the tail fins was altered by the spoilers, which were small metal plates projecting on command into the air stream. No control command had both spoilers projecting equally into the air stream. When a control command was given one spoiler projected into the air stream to cause a directional response. Pitch and yaw commands, directed by the bomb aimer, were performed by the spoilers of the horizontal and vertical tail fins respectively.
The third set of spoilers were connected to the gyroscope so as to operate in opposition giving roll stabilization. These spoilers were located in the horizontal fin. The disadvantage of drag and disrupted air flow caused by the spoilers was compensated for by their ease and low expense of manufacture, use of existing electrical power, and their adaptation to a simple radio control system.
The 24 volt battery supplied power for the gyroscope and radio receiver generator along with direct current to the spoiler electromagnetics. The FuG 203/230 radio control unit used a 203a Kehl I transmitter on the aircraft and 230a Strassburg receiver on the Fritz X. Later transmissions beginning with Kehl IV were interchangeable with those used on the Hs 293.
The Duran/Detmold FuG 208/238 wire control system was also developed for Fritz X use. A direct current to the spoiler electromagnets flowed through two .22 mm transmission wires which unwound to a five mile maximum from tail bobbins. An air raid on development facilities caused the wire transmission project's abandonment.
The bomb aimer had two control panels to direct. The first panel contained two switches. One switch started the gyroscope and activated the radio receiver in the bomb while the other switch activated the radio transmitter in the aircraft. The second panel contained four gauges. A voltmeter and ammeter gave battery readings on the bomb. The "H" ("Hitze" = heat) gauge gave the temperature in the bomb's rear fuselage "nerve center."
Due to the cold outside temperatures at the high altitudes the bomb was released from the control components needed to be heated to 86 degrees Fahrenheit (30 degrees Centigrade). Hot air from the aircraft's deicing system was fed into the bomb prior to launching.
The "G" ("Geradlaufapparat") gauge gave gyroscopic function readings. Below the gauges on this panel was a switch to activate the control apparatus at least two minutes before release.
The bomb aimer took the normal kneeling position over a standard Lofte 7D bomb sight. To the left of the sight was the bomb release control with the overriding button ("Kursgeber") in front of it. The Kursgeber allowed the bomb aimer to control the aircraft's approach to the target and the run in procedure was similar to that on a normal bomb run.
The Fritz X was tactically designed to do everything an armor-piercing bomb of the same weight could do. The bomb aimer needed a well-defined target which could be readily discerned from its surroundings. Since the mother aircraft was required to slow down to allow the bomb aimer to track the bomb it was even more vulnerable to anti-aircraft fire than the Hs 293 mother aircraft which launched from further away. Therefore, sea targets not heavily defended by anti-aircraft fire were ideal.
The Ruhrstahl SD 1400 'Fritz X' : Air-to-Ship, Wireless Guided, Gliding Bomb
The sudden but arranged capitulation of the Italian fleet to the Allies on 9 September 1943 spurred the Germans to take quick actions against their former ally. The battleship Italia was damaged and Roma sunk as victims of a new type of air-to-surface weapon, the Ruhrstahl/Kramer X-1 or Fritz X. It was a free-falling bomb guided by the parent aircraft. Usually it was dropped at an altitude of about 6,000m (19,685ft); by the time of detonation it would have had gained a velocity close to that of sound.
The control apparatus comprised of electromagnetically operated spoilers activated in sympathy with radio signals from the parent aircraft (often a Dornier Do 217). After dropping the Fritz X, the airplane would have its motors throttled back and be flown to a higher altitude directly above the target, thus enabling the observer to guide the missile with a conventional Lofte 7 bombsight. Direct wire-link control using transmission lines that were 8km (4.97 miles) long was also possible. However, it was later abandoned for economic reasons.
The first tests were conducted in Germany in 1942, and were moved to Italy later. In Italy, pneumatic power was tested to substitute for the electromagnetic actuation of the spoilers. However, variations in temperature in different parts of the atmosphere posed obstacles and the idea had to be dropped. The Allied advance to Italy forced the Germans to press the Fritz X into increased use. The cruiser USS Savannah was attacked successfully alongside several naval transports. During a night attack two British cruisers collided in utmost confusion. Seven days later the Germans scored hits on the battleship HMS Warspite, which had to be towed to Malta.
Each month about 66 of these guided bombs were manufactured, far less than the projected figure. About half of the bombs were consumed by tests done during 1943 and 1944. The real obstacle to the success of the Fritz X program was not the low production rate, but the substantial loss suffered by the deliverer aircraft. The parent planes were very vulnerable because fairly slow speed was needed over the target area.
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* Luftwaffe aircraft armed with these glide bombs went into combat at the end of August 1943, attacking Allied shipping in the Bay of Biscay. On 25 August 1943, they sank the escort sloop HMS EGRET and badly damaged the destroyer HMCS ATHABASCAN. These attacks were among the first recorded instances of operational use of guided weapons. The British Admiralty ordered their warships to stay at least 320 kilometers (200 miles) from the French coast until countermeasures could be devised.
The glide bombs were used more intensively in the Mediterranean, with spectacular results at first. Late on 8 September 1943, the terms of Italy's armistice with the Allies went into effect, and the Italian fleet left their anchorage on the Italian mainland, bound for Malta, where the ships would be surrendered. The Italians told the Germans that the fleet was going to sea to help fight the Allies, but the Germans were suspicious, and Luftwaffe aircraft shadowed the warships to see where they were going.
The next day, as the fleet passed through the Straits of Bonafacio, which separate Corsica from Sardinia, it was attacked by 11 Do-217s carrying Fritz-X glide bombs. The bombers concentrated their attacks on the large modern battleships ROMA and ITALIA. The ROMA was hit twice, bringing it dead in the water while fires raged below decks. Twenty minutes after the first hit, the fires reached the ROMA's magazines, the resulting explosion breaking the ship in half. It folded up and sank with most of her crew. The ITALIA was hit by a single Fritz-X, but although the battleship took on water, it managed to limp to Malta.
That same day, the Allies landed on the beach at Salerno to begin their movement into Italy. The Luftwaffe responded with a week of glide bomb attacks, badly damaging the battleship HMS WARSPITE, the cruisers HMS UGANDA and the USS SAVANNAH, and sinking or damaging several other lesser vessels. The WARSPITE was hit by three Fritz-X bombs, one of which penetrated six decks and blew a hole in the ship's bottom. The ship took on a good deal of water and was completely disabled, but fires didn't break out and casualties were only 9 dead and 14 wounded, blessedly light for so devastating an attack. The battleship was towed away and did not return to action until June 1944.
* The Luftwaffe also mounted a number of raids in October and November 1943 against Allied convoys in the Mediterranean, using Hs-293As to attack escort vessels so the merchantmen could be struck by torpedo-carrying Ju-88 bombers. However, the days of the Luftwaffe's success with the glide bombs were short-lived. Allied air superiority was steadily growing, and when the Allies landed at Anzio in January 1944, German bombers encountered fierce fighter opposition and suffered badly, though they did sink the cruiser HMS SPARTAN.
The Allies also introduced electronic countermeasures against the Kehl-Strassburg control system. One system was a broadband jamming transmitter that simply disrupted the control transmission with radio noise. Another system was more subtle, "spoofing" the bomb by sending false control signals to the Strassburg controller that slammed the weapon's control surfaces to an extreme position, causing it to stall and tumble, or descend in an aimless spiral. When the Luftwaffe attempted to attack the Allied fleet during the Normandy landings in June 1944, they were unable to overcome Allied fighter defenses. What few glide bombs they dropped were ineffective due to jamming and spoofing. The Hs-293A and Fritz-X were no longer useful weapons.
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I just found it very interesting that the Luftwaffe had such capable weapon at that time, early 1940’s! Like an early JADAM.
Originally Posted by Mastermind
