ramp catapult was powered by the Dampferzeuger trolley. The pulse-jet engine was started by the Anlassgerät, which provided compressed air for the engine intake, and electrical connection to the engine spark plug, and autopilot. The Bosch spark plug was only needed to start the engine, while residual flame ignited further mixtures of gasoline and air, and the engine would be at full power after 7 seconds. The catapult would then accelerate the bomb above its stall speed of , ensuring sufficient ram air. Operation Eisbär Mass production of the FZG-76 did not start until the spring of 1944, and FR 155(W) was not equipped until late May 1944. Operation Eisbär, the missile attacks on London, commenced on 12 June. However, the four launch battalions could only operate from the Pas-de-Calais area, amounting to only 72 launchers. They had been supplied with missiles, Walter catapults, fuel, and other associated equipment since D-Day. None of the nine missiles launched on the 12th reached England, while only four did so on the 13th. The next attempt to start the attack occurred on the night of 15/16 June, when 144 missiles reached England, of which 73 struck London, while 53 struck Portsmouth and Southampton. Damage was widespread and Eisenhower ordered attacks on the V-1 sites as a priority. Operation Cobra forced a retreat from the French launch sites in August, with the last battalion leaving on 29 August. Operation Donnerschlag began from Germany on 21 October 1944. Operation and effectiveness The first complete V-1 airframe was delivered on 30 August 1942, and after the first complete As.109-014 was delivered in September, the first glide test flight was on 28 October 1942 at Peenemünde, from under a Focke-Wulf Fw 200. The first powered trial was on 10 December, launched from beneath an He 111. The LXV Armeekorps z.b.V. ("65th Army Corps for special deployment) formed during the last days of November 1943 in France commanded by General der Artillerie z.V. Erich Heinemann was responsible for the operational use of V-1. The conventional launch sites could theoretically launch about 15 V-1s per day, but this rate was difficult to achieve on a consistent basis; the maximum rate achieved was 18. Overall, only about 25% of the V-1s hit their targets, the majority being lost because of a combination of defensive measures, mechanical unreliability or guidance errors. With the capture or destruction of the launch facilities used