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STEVEN J. ZALOGA, illustrated by JIM LAURIER
This chart shows the pace of missile launches by Flak Regiment 155 (W) against London In the initial phase of the campaign from June 12th to September 1st, 1944. The lower band shows the number of missiles which landed in England, the middle band shows the missiles brought down by air defense, and the upper band shows the missiles which crashed after launch or otherwise disappeared due to technical problems. Due to discrepancies in accounting between German and British records, the data are based on three-day averages which tends to level the extremes. (Author)
Due to shortages of the standard Amatol 39A+ explosive, substitutes such as 52A+ were used in some missiles. On June 25th, 1944. Hitler ordered thai 250 V-1 warheads per month be filled with Trialen, an enhanced blast explosive, and these were first used on July 18th, 1944. Other types of explosive such as Myrol were planned but not employed. By 1945 shortage of explosives led to the substitution of low-grade commercial Donarit explosive in many warheads.
During the 1944 summer campaign against London, about seven percent of the missiles were fitted with FuG-23 transmitters to help triangulate the location of the impacts. In later campaigns, the percentage fitted with this device increased substantially, and during the final actions of March 1945, more than half the missiles had this feature.
Due to steel shortages, a number of efforts were made to conserve material including the design of a wooden wing. The wooden wings had a slightly greater span than those of the original metal-wing A-1, and they reduced the wing weight by about 38kg (851bs). The first of the wooden-wing versions was the Fi-103B-1 which also substituted plywood for steel in some of the nose construction and had some other changes such as the location of the fuze pockets. The first wooden-wing Pi-103 missiles were launched in late February 1945. There was some change to the wooden wing late in the production run. A wooden-wing Fi-103 currently preserved at the Ordnance Museum at the US Army's Aberdeen Proving Ground shows that the internal framing of the wing was wood, but that a thin sheet-metal cover was added over the wood. The Fi-103B-2 was similar to the B-1 but substituted Trialen explosive and improved fuzing. The Fi-103C-1 used a lighter SC 800 aircraft fragmentation bomb inside the fuselage instead of the normal warhead to extend the range. The Fi-103D-1 was designed to carry chemical warfare agents; so far as is known there was no series production.
In the fall of 1944, intensive work was undertaken to extend the range of the Fi-103 so that it could be launched against London from sites in Holland. The initial version was the FH03E-1 which was fitted with a wooden wing, an enlarged fuel tank with a capacity of 810 liters (214 US gallons; 178 Imperial gal) instead of the usual 690 liters (182/152 gal), and a smaller plywood-encased warhead. The definitive long-range version was the FH03F-1 with 1,025 liters (271/225 gal) of fuel and the warhead reduced to 530kg (l,1681bs). A final type with the fuel tank increased to 1,180 liters (312/260 gal) was found at the Mittelwerke by Allied troops, hut does not appear to have entered serial production.
One of the lingering problems with the Fi-103 design was the inefficiency of its pulse-jet engine. Design studies for a jet-powered Fi-103 using the Porsche 109-005 turbojet engine were begun, but these did not progress very far before the war ended.
These original German plans show the warhead configurations of the main types of Fi-103. Externally, the Fi-103 variants can be distinguished by the location of the fuze pockets; otherwise, most of the warhead shapes were similar.
FR155W managed to extract about three-quarters of its troops from France, but all of the heavy launch equipment except that from III Abteilung was lost. The regiment was reorganized around two launch battalions and the other two were converted to flak units. New launch sites were scouted along the Rhine in Sauerland and northern Westerwald, but there was some anxiety about launching near heavily urbanized regions of Germany due to the large numbers of missile crashes. Since some launch sites had already been scouted in the Eifel forests along the Belgian frontier, these were the first sites to become active. The Eifel region was in range of the port of Antwerp, and the border area had only scattered German villages that were less likely to be hit by wayward missiles. By mid- October, one battery from III/FR155W was ready to begin launching missiles from the Eifel near Mayen. but examination of the 329 missiles in inventory found 226 to be defective, and repairs delayed the launches.
Starting in late June 1944, some of the V-1 missiles launched against London were fitted with a Kuto cable cutter to deal with the threat of barrage balloons. This illustration from the manual shows how the cutter was contained within the leading edge of the wing with the blade (A) attached by metal clips (B).
The first launches of Operation Donnerschlag ("Thunderclap") began from Germany at 07231ns on October 21st, 1944. Of the 410 missiles launched in late October, 55 were aimed at Brussels and the remainder at Antwerp. The improved autopilot permitted a new "oblique firing" (Winkelschuss) tactic. The launcher no longer had to be directly aimed at the target since the missile could make one course correction after launch to align itself to the target. The main advantage of this feature was that it made it difficult for the Allies to track the missile launch path back to the launch site. The disadvantage was that it caused a higher rate of crashes. By the end of the month, eight launch sites were operational in the Eifel, none of which was discovered by Allied aircraft due to the forest cover in the region. In spite of the best efforts of FR155W to avoid hitting German towns, V-1 and V-2 missiles often crashed after launch, and so the V-weapons were grimly dubbed the Eifelschreck ("Horror of the Eifel").