 Mk . III went into extensive testing at No. 25 Sqn in May 1940 and another troubling problem was found . As the target aircraft moved to the sides of the fighter , the error in the horizontal angle grew . Eventually , at about 60 degrees to the side , the target was indicated as being on the other side of the fighter . Hanbury Brown concluded that the problem was due to reflections between the fuselage and engine nacelles , due to the change to the long @-@ nose IVF from the short @-@ nose IF and IIF . In previous examples they had used the fuselage of the aircraft as the reflector , positioning and angling the antennas to run along the nose or wing leading edges . 
