The radar set AN/FPN-40 has four separate functions:
height finder, final approach, and taxi (Figure 2).
Functions of radar set AN/FPN-40.
a. The surveillance function detects small aircraft within a radius of
25 miles and large aircraft within a radius of 40 miles.
b. The height finder function determines the height of an aircraft if
the aircraft is within 30 miles of the airfield and between 500 and 50,000
feet in altitude.
c. The final approach function guides the aircraft along the proper
glidepath and courseline to the touchdown point.