Hawker Typhoon airplane model. Responding to 1937 RAF specifications requiring a substitute for the "Hurricane" fighter, the Hawker Aircraft Company built 2 prototypes, one for each type of engine indicated in the specifications. Thus the "Tornado" was fitted with the Rolls Royce Vulture engine, and the "Typhoon" with the RR Napier Sabre engine. While the first project was abandoned, the second continued its development despite structural and power problems. Entered into service in 1941, the "Typhoon" was nearly retired from service due to a number of fatal accidents resulting from failure of the aircraft structure. After these and other problems were resolved, in 1943 the plane began to play an important role mainly as a fighter-bomber since its performance at low level was outstanding. In 1944, with the introduction of 8 air-to-ground rockets fitted on rails under the wings, the "Typhoons" began to hit sea and land targets and this primary tactical role was of utmost importance after D-Day in Normandy. Some of these aircraft were transformed into night-interceptors (NF) and others into tactical reconnaissance aircraft (FR).