actually took their radio equipment to the two closest ROC operations rooms at Horsham and Maidstone, and vectored fighters direct from the ROC's plotting tables. The critics who had said that the Corps would be unable to handle the fast-flying jet aircraft were answered when these aircraft on their first operation were actually controlled entirely by using ROC information both on the coast and at inland. The average speed of V-1s was and their average altitude was to . Fighter aircraft required excellent low altitude performance to intercept them and enough firepower to ensure that they were destroyed in the air (ideally, also from a sufficient distance, to avoid being damaged by the strong blast) rather than the V-1 crashing to earth and detonating. Most aircraft were too slow to catch a V-1 unless they had a height advantage, allowing them to gain speed by diving on their target. When V-1 attacks began in mid-June 1944, the only aircraft with the low-altitude speed to be effective against it was the Hawker Tempest. Fewer than 30 Tempests were available. They were assigned to No. 150 Wing RAF. Early attempts to intercept and destroy V-1s often failed, but improved techniques soon emerged. These included using the airflow over an interceptor's wing to raise one wing of the V-1, by sliding the wingtip to within of the lower surface of the V-1's wing. If properly executed, this manoeuvre would tip the V-1's wing up, over-riding the gyro and sending the V-1 into an out-of-control dive. At least sixteen V-1s were destroyed this way (the first by a P-51 piloted by Major R. E. Turner of 356th Fighter Squadron on 18 June). The Tempest fleet was built up to over 100 aircraft by September, and during the short summer nights the Tempests shared defensive duty with twin-engined de Havilland Mosquitos. Specially modified Republic P-47M Thunderbolts were also pressed into service against the V-1s; they had boosted engines () and had half their .50 calibre (12.5 mm) machine guns and half their fuel tanks, all external fittings and all their armour plate removed to reduce weight. In addition, North American P-51 Mustangs and Griffon-engined Supermarine Spitfire Mk XIVs were tuned to make them fast enough, At night airborne radar was not needed, as the V-1 engine could be heard from away or more and the exhaust plume was visible from a long distance. Wing Commander