EFFICACY OF AN S-SHAPED AIR INLET ON THE REDUCTION OF FRONT BISTATIC RADAR CROSS SECTION OF A FIGHTER ENGINE

The engine of a fighter plane is one of the largest scattering centers of the entire aircraft.One possible way of reducing the radar cross section (RCS) of the engine is to use an S-shaped bending air inlet to avoid direct radar wave illumination and reflection.We evaluate the efficacy of an S-shaped air inlet on RCS reduction by simulating the boresight and ±15 • bistatic RCS for a digital model of an engine located behind an S-shaped inlet, using a multi-level fast multipole method (MLFMM) code in the S and X bands.The results show that a curved S-type air inlet can reduce the engine boresight bistatic RCS by ∼ 10-12 dBsm at 3 GHz, and ∼ 16 dBsm at 10 GHz when radar wave is incident from boresight, but not to the level required by RF stealth standards.When the radar waves are incident from θ = 105 • ϕ = 90 • or θ = 90 • ϕ = 345 • , the RCS reduction is less effective, which is the results of the bend direction of the S-type air inlet.