What is the difference between ASR and PAR?

• A. PAR provides azimuth guidance only
• B. ASR provides azimuth guidance only
• C. ASR provides azimuth and elevation
• D. PAR provides elevation guidance only

Answer: (B)

The key idea is how much guidance the radar system gives the pilot along the approach path. ASR, or Airport Surveillance Radar, mainly provides position information to the controller in terms of bearing (azimuth) and distance. The controller uses that to vector the aircraft toward the approach, but the radar does not supply vertical guidance to the pilot. So ASR offers azimuth guidance only.

PAR, or Precision Approach Radar, is designed to give two-axis guidance to the pilot: lateral (azimuth) and vertical (elevation) guidance. The controller provides instructions that guide the aircraft along both the horizontal path and the vertical descent, giving a more precise approach.

Therefore, the difference is that ASR provides azimuth guidance only, while PAR provides both azimuth and elevation guidance.