Definition
A non-precision instrument approach in which an air traffic controller, watching the aircraft on Airport Surveillance Radar, provides verbal heading instructions to guide the pilot to the runway. The controller issues headings to keep the aircraft aligned with the final approach course and advises when to begin descent, when the aircraft reaches the missed approach point, and (on request) recommended altitudes during descent. Because ASR provides only horizontal guidance, no electronic glideslope is involved.
Plain English
An approach where the controller watches you on radar and tells you what headings to fly so you line up with the runway. The controller does not give you vertical guidance down a glide path -- you fly the published step-down altitudes yourself.
Context Anchor
Used during instrument flying, especially when a pilot needs radar assistance to get lined up with a runway or when other approach equipment is unavailable.
Derivation
ASR stands for Airport Surveillance Radar. "Surveillance" comes from French, meaning "watching over." The controller is literally watching the aircraft on a radar scope and talking it down to the runway.
Why Pilots Care
It provides a safe backup landing option when precision approaches are unavailable, reducing the chance of a missed approach or diversion.
Intuition Check
An ASR Approach is not an approach flown using the airplane’s own radar. It is flown using instructions from ATC, based on ground radar.
Example Sentence 1
With the GPS unreliable, the pilot requested an ASR approach and followed the controller's heading instructions to the runway.
Example Sentence 2
During the ASR approach the controller instructed a left turn to heading 240 and descent to 1,200 feet.