Improvement Practice of Aircraft Altimeter Antenna Installation Step Difference

To decrease the step difference between the outer plane of the mounting frame and the outer surface of the belly skin,the causes are analyzed from the aspects of the antenna structure,mounting bracket,aircraft skin shape,assembly process,etc.,and three methods are proposed（ polishing the antenna mounting frame of the altimeter,installing with stress,and improving the mounting bracket）. According to the advantages and disadvantages of the methods,the best is to improve the mounting bracket. The new mounting bracket is produced and tested. The result shows that installation step difference is reduced from 2. 5 mm to 1 mm,and the step is effectively improved.